Lithium cells in Series with BMS - Battery Pack Considerations (MEHS) Episode 61

[@rahulpathania78]

The best video on passthrough charging.

[@ElijahAndrade01]

Dudeeeeee, I've had all these problems and had to solve it myself with barely any knowledge. Been watching videos and piecing knowledge and ideas together until I figured it out. Ofc after all that I find this video.

[@PedroFaria]

Really great explanation with comprehensive schematics!! Thank you very much for taking the time!! Keep up good work!! Best regards from Portugal!! :)

[@michaelsstuff4402]

- Thank you.

[@stormrazer121]

This is exactly what i am looking to do, i need to implement a 14.4v li-ion battery into my speaker dock and have it so i can just plug in a charger - just like a laptop!, just got yourself a new sub XD

[@michaelsstuff4402]

- Thank you.

[@Enoch-Gnosis]

Why does this module output stops supplying power ? Once I supply power into it , it starts to output voltage , but then the output shuts down ?

[@kampmedia7776]

Great Video! Thank you so much! I have been trying to get a better understanding of this.

[@michaelsstuff4402]

Thank you.

[@Eltechs]

Great Video! Was looking for stuff like that for a long time! Thumbs Up!

[@michaelsstuff4402]

- Thanks.

[@arn_abs8882]

What your're saying is exactly true, excluding few unintentional wrong schematics, like at 1:50. Making a proper UPS type DC power supply with Li-Ion batteries is complected, and pointless. I'll rather use a 12V-7Ah lead acid battery to power up an external monitor, with a c/5 float charger It's cheaper and safer.

[@michaelsstuff4402]

- Hi. Yes agree using Lead Acid batteries is a much easier and cheaper solution. Cheers.

[@sanjeebshrestha8636]

Arnab Satapathi @

[@hdagelic]

Maybe a BMS + a 12V supply & 1A PTC thermistor between the cells and the charge socket? Less parts... Thats the "A" case, but with current limiting built in. If it doesn't heat too much, don't know, didn't try... If it does, add an 1ohm 2w resistor in series with the PTC. You can also use just an 3.3ohm 5W resistor but then the charging current will vary, and it will charge slower... Also If you then connect a schottky diode between the batteries and the load, and another one between the supply and the load - the load will be powered by the supply when the batteries go below 12V.

[@irapashunnur8237]

I made a circuit, with (3 Batteries + 10A BMS & XL6009) - working fine. Buit, the battery voltage is dropping automatically even if the input voltage is ON and is 12V. Why the battery voltage should drop ?? Where could be the problem ??

[@nathanw851]

Excellent! I've been struggling with 3.7v using a TP4056, but it's to run a robot that needs 3v3, 5v, and 6v. With boosting to higher voltage it overloads the TP4056 BMS chip and cuts the power. I got around it by using the TP4056 - output to trigger the base of a large PNP transistor so I can pull much more current from the battery without losing the protection circuitry. It makes so much more sense to just use a higher voltage supply but I couldn't find any suitable modules - ebay is flooded with TP4056 on all the charger module keywords. I'll give this a go. Thanks.

[@michaelsstuff4402]

- Thanks for the post. Yes I agree its easier to start higher and use step down regs to get the voltages you need in your project(s). You also get better current control (less loss). Best of luck. Cheers.

[@astorm1774]

how do i know if a relais is necessary? So if my project draws little current a "pass through" functionality is given with my bms alone? But how do I know if its not enough? --> Just see if my project works and see if the batteries are actually charging up voltage? One can also always disconnect the project with a switch while charging up the batteries and only continue using the project once the batteries are charged and the charger is disconnected.... right? A lot of questions from me ik :D You answered quite a few here, but i am still left with these though ;D

[@jacka55six60]

I appreciate your warning of a mistake @ 1m 48s - but a still shot @ 2m 22s is lacking specifics.

[@chrislimck]

Great video, mate. I plan to build a 3S6P (19.2Ah) pack for a golf trolley. Do I need a balancer on top of the BMS? How much voltage & current do I need to charge this pack efficiently? What kind of charger should I have for auto cut-off when the pack is fully charged? Thanks in advance.

[@pleasecho2]

You could use a current sensing circuit that would disconnect the charger upon receiving a load, but aren't current chargers already doing this? Also this looks like it might be suitable in low power solar charging applications

[@huckfin1100]

I have this board on my 12v pack and it wont allow me to charge it power flows one way, not what i was told when bought !

[@robertwechsler6637]

I have had a similar problem and solved it as follows: I used two 18650 cells in parallel with a buck converter to deliver the 12 volts, I connected the charger directly to the cells to charge a 3.7v. This system was used to replace the battery pack in a surveyors total station and so has worked very well. I used the 3 cell and 3s circuit as you used by after charging I connected to 12 volt light for capacity test and destroyed the cells (zero volts and apparently internal short circuit - did it twice before adopting the solution above. Would appreciate your comment. Regards Robert W

[@john-sw1nu]

Do you know if I were to build up multiple BMS like you did at the 0:15 mark could I wire them in parallel to my load to get a longer battery life?

[@yucelsari4613]

Hello. I want to ask you about the bms on the video which i have got the same one. I am tryin to make a 12 v battery for my hand drill. I make the connections exactly true . I can get voltage from b1 and b2 but everytime there is no voltage on the outut. I tried it many times but always it ended fail... would you share me your opinion please.?

[@michaelsstuff4402]

- You have to reset your BMS. You can do this by applying a charging current to P+ and P-. It needs to be at least 12v and not more than 12.6v and you only need to connect that input power for a couple of seconds. After that your BMS will work as expected until it cuts off again because the connected batteries have dropped below the BMS cutoff voltage of approximately 8.5v. Cheers.

[@yucelsari4613]

@@michaelsstuff4402 I thank you man👏👏 it works. Great!! From Turkey what can i do, i will do for you..

[@PhG1961]

Interesting video !

[@devilninja907]

How to charger this

[@theransomgamer]

I am about to use this board in a project that only draws 1 AMP , is it suitable in this situation with a normal 12V power supply without voltage booster boards?

[@theAGanimators]

Have you tried a Hebang Li-Ion charger HB-120601 or HB-120603? Not sure if it's a good idea to use a charger like this while the light is in use, but I found they work great charging up a 3s pack with that BMS you're using. 3 amps is too much for some 18650's, check the datasheet to make sure.

[@michaelsstuff4402]

- It would be interesting to see how the charge is really applied to the cells. Not the cheapest solution either but not unrealistic. It does look like it has a termination point but the little info I've seen so far suggests its a raw 12.6v dump rather than a correct charge curve. If I get one I will test it for sure. Cheers.

[@Boz1211111]

I have the same prob building 12v li ion for drill. Bms cutoff is too high(4 27), balancing resistors only 42mA, no cc/cv charge... I guess i cant help those batteries can i

[@JamieDSilva1]

I'm been looking for a solution exactly the same way you describe in the beginning of this video! Multiple TP4056's seems to be one solution. But I'm eager to know what you suggest in the coming videos!

[@michaelsstuff4402]

- Hi. Yes they are coming. Cheers.

[@51im]

Why leave this video up if it's giving wrong information.

[@1over137]

So, this charges/discharges the battery via the balance leads, yes? So limited to around 1 amp output, unless you use much larger balance lead wires. Then there is the problem of the actual protection it offers. On AliExpress the minimum discharge disconnect is 2.35V which is too low for most batteries. The Maximum overcharge voltage disconnect is 4.3V which is too high for more cells. I have seen evidence to suggest that a LiPo pack can burst into flames with as little as 4.37V per cell charge voltage.

[@michaelsstuff4402]

- Hi. Yes current is limited by the wire you use. This one cuts off at 2.9V per cells so its fine. Over charge is 4.25V which is also fine but you are correct, you need to know the details and test the claims to make sure all is good. Cheers.

[@vincenttelfer4206]

good video, maybe the loop off balance could work off more current from the charger with its own balancer

[@vincenttelfer4206]

never mind, explained very well

[@____________________________.x]

I didn't understand why you were adding relays. Edit: OK after 20 odd rewinds I think I've got it, maybe I'm just tired today. Not sure why you are not using the other contact NC/NO to just select the appropriate power source and just use the one relay. The random wiring angles makes this hard to follow although the idea is good, the music while you are talking is a big distraction for older people, labelling the relays with Trig etc would have helped I feel.

[@getenlightened]

Your videos are great, thank you. I would love it if you could help explain how a BMS works when used on larger packs, such as those used for ebikes, or for a power wall. Also, what happens if you were charging multiple packs, each with their own bms, from a single charge controller? Would this even work? Could it be dangerous? Thanks so much.

[@michaelsstuff4402]

- Hi. There is a video idea for later on, thanks. Yes you can charge multiple packs from the same charger but the more packs, the less current goes to each of them so you would need to keep that in mind as you typically want to supply each cell at least 300ma. Cheers.

[@getenlightened]

Cheers. So essentially, I'd want to make sure a solar setup, with controller, could provide enough amps for the total number of packs / cells? With two packs, I'd want to send double the recommended amps/current for charging a single pack, and the BMS would, in theory, protect the pack from too much current if one finished first? Thanks again, I look forward to your future videos.

[@michaelsstuff4402]

- Hi. Yes basically. You just need to make sure that the solar power source has sufficient current (and the correct voltage) for the X number of packs. If the packs are 3S then you would be feeding the pack no more than 12.6V at a min of 1A and a max of 3A. If you are just allowing the current to flow to the BMS boards and letting the BMS board do all the work for charging the cells then that not a good approach. You need to have a regulator between the solar panel and the BMS(s). Cheers.

[@sayantan9409]

I wanted to build a 18ah 36v battery pack using lifepo4 6000mah 3.2v (32650/32700) cells. I wanted to make 6ah 36v pack of 3.. And I wanted to charge faster... What should I do? Please help me out

[@rndm9087]

question, if i use the bms to connect my 3 battery's, how will i charge them? and how will i know they are fully charged? would i need to add a charging module to know this information? as i have a TP4056 Micro USB 5V 1A 18650 Lithium Battery Charger Module and i was going to connect 3 battery's to it but i think using the bms bored would be a safer option but would i be able to introduce this? as this little bored is perfect for what i need.

[@motobacktoconstitution4138]

Thank you thank you kind of explaining but this is too difficult I just want to make 18 volts safe

[@ailijic]

Please also cover usage efficiency and charging efficiency.

[@coenraadloubser5768]

This is ridiculous... surely there's a comparable BMS that does alll of this? ... Why is the charging directly through the BMS suboptimal? Will the batteries not last as long, or not hold as much charge?

[@garycotz563]

Ok... so now what if you want to add in a big ol Solar Panel to the project? Do you need a solar controller... and it needs to be 12v or perhaps a bit more?

[@michaelsstuff4402]

- It depends on what the solar controller is actually doing. The one I had was a regulator that would either block the unwanted voltages or boost or lower them. Like a SEPIC power regulator. This is because your solar panel will produce low voltage when there's little sun and up to 20v when full sun. The batteries and devices connected to the panel only want a 12v supply. In this case the solar regulator is more useful than a BMS by itself. You could do it all yourself and run a battery pack with a BMS and between the BMS and solar panel run a regulator, but the PWM or MPPT solar regulators are going to do a better job of it. Cheers.

[@batangenyodotcom]

hi, what is the cut-off voltage when using that charging board (SY6912) with 3 cells in series connected with the BMS? I was looking at 2:44 the details of charging board, is that the correct configuration( the position of 0 ohm resistor)? Thank you.

[@michaelsstuff4402]

Hi. From memory it was 12.6v or very close to it. I moved away from this board and started using the MAX745. Look at my other vids on this. Cheers.

[@unionse7en]

Also need a method to stop/restrict charging current when nearing freezing temps.

[@chandachoudhary3189]

i m using phone batteries to make 12 v battery do i need to use this protective module as phone battery already has this inside please reply

[@arpadprp1778]

Hi. Great video. I've got a question about these protectn boards, donno who to ask maybe you know. So if I install a prot board on a toy car rather than on the battery, will I need to kick off the system with a charger every time when connecting the LiPo? Most specs say that output is closed initially. Would not be a problem if I glued and soldered the prot board to the battery not the car, but this is not what I want. I want to disconnect the batt completely when just storing it. No daily use. Thanks for experting it.

[@michaelsstuff4402]

- Hi. No I don't think that will work. The BMS needs to connect to the cells as it brings them together to provide a higher unified battery. If you want to isolate the battery for storage, just install a switch between the BMS and the motor. The BMS becomes part of the battery and won't draw any current when stored. Cheers.

[@arpadprp1778]

@@michaelsstuff4402 --- thanks a lot. Nevertheless I got to do something like that. The LiPo is normally uded in quadcopter where an addtnl BMS is not desired. Occasionally I put the same batt in a car, where I do need over-discharge protection. Stopping and weight not an issue there, but would be an issue with the copter. Basically I only need an occasional over discharge protection. Charging is controlled differently.

[@Ziplock9000]

I've just done some tests on this board. If I have 3 cells, 4.1v, 3.33v, 4.18v and start charging, as soon as one of the cells (the last one) hits ~4.26ish it cuts off charging for ALL of them. While I understand this is not a balance BMS, I thought the behaviour was that it only cut off the charging on the individual cells that are already at max and continues with the ones that are not (the 3.33v one)? Is this the experience you're having?

[@michaelsstuff4402]

Hi. No its not. Unfortunately not all BMS are created equal, even ones with the same look and published feature set. All you can really do is test for yourself as you're doing. The BMS I tested in this video, and a couple of others, would keep going as long as the total voltage was under 12.6, so 4.2v per cell. Remember, these BMS aren't chargers, just a way to combine cells to make a higher voltage battery. If you can, try some other boards with different configurations and components. Ones with the green PCB are set up differently and seem to work. The only thing I've found with those is the rated current handling is about half the real current rating. Cheers.

[@Ziplock9000]

@@michaelsstuff4402 Ok thanks mate, I might order a green one then. Is it the ones that look identical to these blue ones that I've seen?

[@michaelsstuff4402]

@@Ziplock9000 - Hi. No, the green ones are more square and are laid out differently.

[@voyagertechnologies]

Isn't 4.25v a bit higher for what each cell should be charged to? i have a typical good quality charger that cuts off at 4.16 and these circuits go way past that and stop at 4.24-4.26 ,so why are these bms like this? everybody advises going above 4.20

[@michaelsstuff4402]

- Hi. The peak voltage is often rated at 4.2v. There is some safety margin but its commonly understood that you can damage cells if you go over 4.25v. Most BMS will cut in around 4.23v - 4.25v which is the max upper limit. If you're charging your cells correctly the BMS won't need to step in at all. You can also charge your cells to 4 or 4.1v. This slightly reduces the max possible capacity of your cells but extends the cell life. I have charged a few unprotected cells to 4.3v without issue but I can't tell you what that does to their life expectancy. Cheers.

[@voyagertechnologies]

Thanks, really great and elaborate comment. Although my question was more towards if everybody knows this, why do they design these BMS to keep the cells at their toes, I have charged some cells even above 4.3v and they seem to work (at that time)

[@ZonaALG]

I have some questions about the components used, specially about the bms: First of all: the bms basically prevents the cells from overcharging and over discharging, doesn't it? Then: For example; tp4056 charger, it automatically charges the cells preventing them from overcharging, right? So there's no need to connect the tp4056 to the bms, you can just use it directly on the cells. Another question is if the bms boosts the cells voltages? Because when cells discharge they lose voltage, so does the bms boost it to keep it constant or not? If not, you will need a buck converter to boost it to a constant load. So...bms will only work to prevent batteries from over discharging. Am I right?

[@michaelsstuff4402]

- Hi. Yes mostly correct. A TP4056 will correctly charge the cell and not exceed the safe voltage (4.25v) but it wont stop the project draining the cell past the unsafe low voltage point (2.5v on average). A BMS does stop this from happening as you mentioned. Note you can get TP4056 boards with a real BMS built in. Also if you use protected cells the BMS function is built into the cell. A TP4056 is only for a single cell. If you use multiple cells in series you will need a BMS. No a BMS does not have a voltage reg on board. You will need a DC-DC converter for constant voltage output. The BMS just combines the cell voltage. Depending on the type of BMS and the IC used some BMS also monitor current and will step in if the current is too high going to the cells. Additionally you can get BMS that have balancing on board too (not the one I used in the video though). Cheers.

[@ZonaALG]

Oh, thanks, i spent some time searching for info and concepts and i know understand pretty good all this, but i still have a question. will the bms make some current limiting like the one done by the tp4056? So for example if i conect tp4056 directly to bms, will the current and voltage it outputs will remain the same as the one provided by the tp4056?

[@michaelsstuff4402]

- Ok. Most BMS include a current cut off. This means that the power flowing through the BMS to the cells will be cut if the current is excessive. The actual limits vary depending on the IC on the BMS board. The TP4056 without integrated BMS does not limit current but is mostly safe as a single TP4056 can only charge at up to 1A. You don't need to monitor or limit the current going to the cell as virtually every lithium battery can handle 1A. This is different to a BMS current limiting function as the BMS might be receiving up to 10A at any one time as an example. The BMS will temporarily cut the supply of power to a cell of the current at that time is over the set limit (around 2 -3A depending on the board). You would not connect a TP4056 to a multi cell BMS as the TP4056 is only for a single cell. Also you can't use multiple TP4056 boards to feed a multi cell BMS as there is a common ground plane. If you are asking whether a BMS takes external power and provides a CC mode to the cells (e.g. take 12.6v input at 3A and charge the cells at a constant 1A each), the answer is no. Cheers.

[@starforce224]

Hi, the charging current must be greater than 12v? Can I use a simple DC charger >12v? or a multifunction rc lipo charger set to "3s"? or a pc + 12v power supply? Thank you and sorry for my english

[@michaelsstuff4402]

- Hi. Do you mean charging voltage? If you use a BMS to charge cells then you need to feed the BMS 4.2V times the number of cells. So a 3S BMS will need 12.6V. Remember, a BMS keeps voltages in a safe range for cell operation but its not a real LION charger. Take a look at my other videos for more info.

[@justsoyouknow1196]

Please answer this. My need is 30amps at between 12.5 and 14.8 volts to power a portable transceiver. Im considerimg a 4s and short charging the to 14.8v. I would still use a BMS for safty. Its not reasionable for the weight and complexity to us a 3s and a boost board mainly because of the 30a needed at transmit. Thanks and Im currently watching all your videos trying to learn.

[@michaelsstuff4402]

- Hi. You're talking about a LOT of power there. How accurate is the voltage range? Yes you can stop the charge per cell at 3.7V for your 14.8V but that can be tricky and you wont get anywhere near the potential capacity of the pack. I would go with a 5S3P pack and a 5S BMS rated at 60 to 100 amps. That would give you all the power you need and you could use a robust step down regulator to get a solid and constant suitable voltage. Might cost a bit but should last a good while. Cheers.

[@rosekreuze]

i knew somethings wrong with my 12.6v ups. i thought the bms will be enough to protect my batteries from over discharge. i guess i should also learn how to use relays too

[@michaelsstuff4402]

Yeah, the BMS alone won't completely manage cells but it should have protected your lithium cells from over discharge. Maybe a couple\of things wrong in UPS land.

[@MCsCreations]

Really nice! Looking forward to se what you came up with. :) BTW, I tried using 2 18650 cells and 2 TP4056 with protection circuit, to connect the output in series. Didn't worked. :/

[@michaelsstuff4402]

- Thanks. No, 2 x TP4056 boards connected in series wont work as there is a common ground which basically shunts all the current through one chip and acts like a single cell. You need to use a similar approach as I did in this video. Still not very elegant. Cheers.

[@MCsCreations]

My Electronics & Hacking Show Yeah, I already ordered a few BMS from AliExpress (in around 4 to 6 months they should get gere. LOL). And I'm going to use a step up/down in the output to regulate it to 12v. BTW, a good solution to the relay would be a simply DPDT switch. I'm going to explain in the next comment.

[@MCsCreations]

My Electronics & Hacking Show The DPDT would select "internal/outside power", let's say. If it's outside power, the energy from the adapter would power the LEDs and charge the batteries at the same time. Other way, the LEDs would be powered from the batteries. In that case, if you connect the adapter, it would connect only to the BMS.

[@michaelsstuff4402]

- I intentionally avoided talking about switches as the main objective was to get as close to a laptop power arrangement as possible. A manual switch is a very easy option but I'm certain at some point I will forget to flick the switch so I wanted to approach this with as much automation as possible. Hope your order doesnt take forever. Cheers.

[@swimwithcoachraven1532]

I short circuited the battery. Think I blew the fuse in the bms

[@burnikellj]

hello, I bought the SY6912 board but it comes set as 2s as default. the instructions are sketchy. the 0 ohm resistor or link in the red box in the diagram is not there on my board. which other ones do I remove to make it 3s. TIA

[@michaelsstuff4402]

- Hi. I received your email and I have replied with a couple of medium res photos that clearly show the resistor you need to remove. Cheers.

[@valmonta3647]

Can i have your suggestion on what BMS is the best to use for my 9.6V drill Li ion swap ?

[@ravikrishna.1997]

Can we use 12v 5A adaptor for this, input supply

[@Ziplock9000]

I need something like this too, maybe more capacity to run several different small electronic devices on like a camcorder, a IR LED array etc. The latter uses 12v, so that can be tapped directly off and the camcorder needs 3.7v, so i could use a voltage regulator in series with that or something. I'd rather not use a seperate pack.

[@michaelsstuff4402]

- Yes that could work. Cheers.

[@KennethTanFotografie]

Could you please post an electronic schematic of your circuit. I can't find the wiring @2:22 and @5:22 I can't make any sense of the wiring. Could you please post a technical sketch?!?

[@ReExplorer]

Did u experiment using multiple tp-4056 as u said at the end of the video??

[@paulrichards2860]

impressed with your vids, ive been looking at power supply options for a gimbal i'm building/modifying. Looked at several options, especially like the BMS option. I'm hoping you can give me some advice, I had a thought today regarding powerbanks. is there any way to combine two of the single ones, and provide 7.4v? I have figured out linking the charging circuit as its similar to the TP4056 micro usb connection, but how can I use the output in series to up the output V? obviously as they only contain the one battery they are currently wired in a parallel style. thanks for ya help ;)

[@michaelsstuff4402]

- Hi. If you are talking about 2 of those single cell battery banks that have a full size USB output and usually a micro charging input then its fairly easy. Option 1 - Grab a couple of basic USB cables, cut the ends off (dont cut the end that goes into the power bank) and join the ends together, red to red and back to black. Option 2 - Open up the battery bank and solder wires onto the positive output and ground on each battery bank. Just like using two USB cables but you can use bigger wire and its more secure. When charging you can use one 5V charger if you make the reverse of the cable I just mentioned (one full size USB from the power supply splitting into two micro USB plugs). Cheers.

[@paulrichards2860]

Ah thats brilliant pal thanks, I kinda had a similar thought process, but wasn't 100% on the physics of it all, gonna make something up and try it out :)

[@chongshenchang9367]

Sir, can I use three cells in parallel with 3 series 20 amps BMS ? Altogether it's nine cells. Three parallel cells in series.

[@mattivirta]

i have some different project, arduino etc, clock etc, need 12V battery and alltime in wall adapter to charge battery and if wall elelkrick cut off clock etc, all work good normal many hour. normal there cut elektric manytime off /day or onetime and 2-9hour..its problem all my little elektric, i need 12V and 5V 3 cell ,power bank/ups. what is better use ? bms or tp4056 chip modules charging if battery go low and keep battery alltime full, and clock etc other stuff use alltime battery. what is best way make this simple ?

[@michaelsstuff4402]

- Hi. You can't use TP4056 as it i s for single cells only. If you need 3 cells and make it easy I would buy a 3S lipo pack used in RC cars etc and use a MAX745 board in your project to continually charge the pack properly. I have a video on the MAX745. Cheers.

[@ddthames]

If you could provide links to the charging board and the boost board, that would be great. Thanks.

[@michaelsstuff4402]

- Done. Both in the video description. Cheers.

[@experimentswithmanay9519]

What is the charging time

[@azimalif266]

I want to charge a 3s battery and take out the power seperately from each cell. Any idea? I was wondering if there are some mosphet instant switching solutions that can switch between cells fast enough to not disrupt the power flow too much. Any suggestions. If there is a video would be very helpful.

[@michaelsstuff4402]

No video exactly but yes most mosfets will switch very quickly. can't say whether its fast enough to fool a charging IC but I worth testing. Why a 3S battery if draining 1 cell at a time. Just run a 3P pack and be done with it.

[@azimalif266]

@@michaelsstuff4402 to fast charge. Super vooc charging charges 2 cells at a time and drains 1 at a time. I was wondering it's possible with 3s 4s or even more, increasing the charging speed in the process with every segment added.(I don't care how bulky my phone gets 😀). What if I add a 3.7 or closer to 4 volt capacitor in line? Is there a 4 volt high capacity low discharge rate capacitor?

[@more_u-listen_more_u_love9543]

I need some suggestion like I am using this board ..and total voltage of my three battery is 8.36. but I am not getting this output voltage from board output?? can you please tell me what is the reason behind this?

[@michaelsstuff4402]

Sounds like one of the cells is faulty or has been connected incorrectly, e.g. a cold solder joint. Check everything.

[@theAGanimators]

Hi MEHS. Search ebay for "5A Lithium Charger CV CC buck Step Down". This ~$2 module is said to be usable as a Li-Ion charger and has three "charge status" LEDs. Have you tested it?For a couple bucks more there is one with two buttons and a display so you don't even have to break out your DVM to set the voltage and current.

[@michaelsstuff4402]

- Hi and thanks for the info. I haven't tested the exact one you mention (just took a look at a few) but they all seem to be similar. I have a couple of very similar board on their way to me. The issue I have with all these is that it will charge a lithium cell but it does so in an incorrect and uncontrolled way. The board sets a current limit not to be exceeded but ideally we need a current limit that the charge does not drop below. The CC stage of charging a lithium cell is supposed to be a constant Xamps (say 1A). These boards can be used to set a 1A upper limit but the cell will quickly reduce that draw and the constant current phase will be much less than 1A before its complete, not what we need. So in short they are better than nothing but it is not correct charging. Cheers.

[@africantwin173]

what should i buy for charging 4 x 18650 cells in total. i have 2 double 18650 battery holders that put the 2 18650 cells in serie. voltage of 2 cells in series between 7.4 volts - 8.4 volts.

[@michaelsstuff4402]

- Hi. If you're talking about an integrated solution use the MAX745 board i reviewed a few videos back. It can charge 1-4 cells in series. If you are going to remove the cells you could use a 4 cell charger like the Nitecore D4. Cheers.

[@theAGanimators]

Search for SY6912 and you can find it. Resistors need to be removed to limit charging current. Default current is 2A. Another resistor needs to be relocated to change from 2s to 3s. What a pain. There is a MAX745 board on ebay that is easier to use (has dip switches and pots), but almost twice the cost. I think a simple switched 2.1mm DC jack is easier than the relay(s) but then you can't run the light while charging.

[@michaelsstuff4402]

- Hi. Yes the ability to run the project (light) while charging is critical (in this instance anyway). Yes the board I used off Ebay is a multi cell charger meaning some tiny tiny resistors needed to be removed or relocated to make it a 3S charger. The board gave the desired voltage but the CC stage was not ideal. Cheers.

[@ACTlVISION]

I just bought the SY6912 board from China and planning to use it with 3S. I can't seem to find any reference for which modifications need to be made for 3S. Any chance you can provide a reference? Thanks. Also it's not too late to cancel and get the MAX745, is it really that much better for $10 over $5? I'm just going for a one-off project so I don't mind moving around a resistor or two to save half the cost.

[@michaelsstuff4402]

- Hi. I don't know of any reference. I used trial and error to determine which resistors needed to be removed or added for the desired number of cells. Many of the ebayers have a screen shot of what to do with their exact board. Take care with your selection as I asked for SY6912 IC boards and got AOC chips which I tested and I didn't like. I would go with the MAX745 only because the boards I tested did not work as expected. Cheers.

[@simonmerrett]

The MAx745 board looks quite handy - even appears to have a pair of plated through holes for header pins allowing you to break out the charging LED. Do you think that there's anything wrong with using a single one of those to charge multiple 3S BMS packs (as opposed to 3SXP parallel packs under a single BMS)? Apart from the overall charge time and acknowledgement that you wouldn't be hitting 1C. Grateful for anyone's feedback on the CC/CV performance of that module in 3S mode.

[@michaelsstuff4402]

- Yes I think I need to do some testing with that IC. Cheers.

[@otkare]

Something is up with my MAX745 charging board. no matter what combo on the dip switches I can't get it past 8.4V. the 3S setting only has 4.2 on the battery leads. I have no idea where to even begin finding out what's wrong.

[@michaelsstuff4402]

- Hi. Start by checking that you are feeding the board at least 15.6V so it can provide sufficient voltage for a 3S pack (up 12.6V). The MAX745 needs 3V above the charging voltage. If that doesn't help, take a close look across the board and make sure all the resistors are there (none missing) and they all test correctly. Then test individual components and traces. Hope that helps. Cheers.

[@otkare]

it might be the 100Kohm resistor. I'm reading 55.5K from it. But what I find weird is the dip switches seem off. all 4 settings yield nothing but 4.2V and 8.4V

[@millennium677]

all I want is a bms that will let me charge two 18650 as a 6v battery, I want to put in 2 18650 batteries into my lantern battery thats now flat and be able to recharge it whenever I need too

[@jj-jo6wr]

what if i charge with 19v power adapter.. will that charge?

[@daveh2938]

i have 7 cells in series so can i buy a bms that will suitable for 7 cells

[@ethanarquette3924]

Hello, I need to run a solar power camera during the day and when there is no daylight left I want to run my project from a 3p 18650 battery pack. Do you know of a proper board for this? Thanks!

[@michaelsstuff4402]

- Hi. It depends on the current draw of the camera. If its less that 500ma then I would use the Sparkfun Sunny Buddy part number 12885. Cheers.

[@ethanarquette3924]

the video transmitter is a 100mw. the camera is 5-12v and the transmitter also accepts 5-12v. The solar panel is 5volts 5watts.

[@conodigrom]

What happens if a cell dies with a short? Does the BMS shut the other two off?

[@michaelsstuff4402]

It will depend on the features of the BMS but in most cases the BMS will detect that minimum voltage has been reached by a cell or as a collection of cells. E.g. a 3S BMS is expecting to be able to provide a minimum of 9V and a peak of 12.6V. If a cell dies then the max a BMS can provide is 8.4V (2 fully charged cells). since this is less than the expected minimum of 9V the BMS should clamp down and stop any further drain from any of the cells. Easiest way to be sure with your BMS is to disconnect one cell and observe the result. Cheers.

[@conodigrom]

@@michaelsstuff4402 Thank you. I've been looking araound for this feature and it is never mentioned on cheaper BMS, where I guess you have to do your own test.

[@michaelsstuff4402]

@@conodigrom - For sure. So many different BMS and lack of documentation means you can't be certain of features and thresholds so always a good idea to do your own testing. Cheers.

[@cicovci]

2:59 the curves have nothing to do with the electronics it is only dependent on the battery internal resistance; the electronics do only the power supply limited by voltage (+sometimes current)

[@michaelsstuff4402]

- Hi. Yes that is correct. Is that not clear in the video?

[@RonaldWijermars-rohmega]

Couldn't you also just use a CC/CV dc-dc converter like the LM2596, this way you have the same type of charging characteristics but cheaper and in a single component. EDIT:LM2577 instead of LM2596

[@michaelsstuff4402]

- Hi. No, the 2596 is a step down reg which doesnt work in this situation and its not a CC/CV IC. Take a look at the characteristics available from the TI site and compare with the charging methodology needed for lithium batteries over at Battery University. There is a significant difference - and unfortunately, the 2596 isnt an improvement in this instance. Cheers.

[@RonaldWijermars-rohmega]

Sorry I meant the LM2577, it is a step up and step down converter with CC CV capabilities.

[@michaelsstuff4402]

- No worries. No sorry that one is just a more advanced converter. It doesnt have the CC/CV mode or a timer for correct lithium charging. There really is a big difference between a proper charging IC and a dc regulator. Cheers.

[@RonaldWijermars-rohmega]

I am not sure we are talking about the same converter. www.ebay.com/itm/262455953687 With a timer you mean that charging would be terminated after a certain time at constant voltage? That is indeed a weak point, but you could add a ampere meter to manually halt the charging process when a certain current is reached.

[@michaelsstuff4402]

- No we weren't. Thanks for the link. That board has more than just the LM on it which is why it can do more. It looks good. I am going to get one and start testing. Current output could be an issue but we will see. Thanks again. Cheers.

[@SuperDutchman59]

I do not give out voltage at output-P + and P-, by checking the oddnitelnosti and on balancing issues, what is the reason and how to repair, new boards from China

[@michaelsstuff4402]

Hi. You may need to activte your board by connecting a load to P+ and P- for at least 1 second. This has also been discussed in some detail in other posts for this video, on case you need more information. Cheers.

[@SuperDutchman59]

@@michaelsstuff4402 Yes, I have already done, activated and everything worked

[@tooljockey2777]

Hey there I have a question. If my BMS is rated for 15A and I have a 30A power supply, will my bms draw 15A and blow up my batteries that can only take 5A? or will the bms only draw 5A? Thanks

[@michaelsstuff4402]

- Hi. If you are just connecting the 30A power supply (such as a power brick or wall wart) to your 15A BMS, and you are just trying to charge the cells (not ideal by the way), then your cells will only charge at around 1A each, so 3A total and this will drop off quickly as you are not applying a CC charge. If you have a 30A CC supply then the BMS will be destroyed. The reason your cells will only charge at 1A or less each is because you're not using a proper lithium charger to provide CC then CV. The cells will just draw enough current to obtain a basic charge. The BMS is not charging the cells, just allowing current through to the cells that does not exceed the peak voltage of 4.25V. Cheers.

[@tooljockey2777]

Thank you so much, big help. Love your videos and your channel. You've got a loyal sub here!

[@micha5628]

Yeah thanks!, i have 1 more qqquestions i powered this bms by my step up board from usb 5v to 12,6V.Step up is veery hot. 1A used.Its normal??

[@michaelsstuff4402]

- Hi. You should use your meter to measure the output from the 5V supply going into the step up board and the current coming out of the step up board going into your BMS. The 5V source is probably capable of 2A output. Your BMS is likely needing between 1 to 3A. Most small step up boards are only capable of 600ma, some 1A but it will be working very hard. Might be best to make sure the 5V source can produce plenty of current and you use a solid step up board capable of 2A or so. Take a look at the Pololu step up boards. The U3V50F12 can give a solid 1.5A at 12V from a 5V supply. Link www.pololu.com/product/2568

[@qaisehayati9373]

About samsung SDI battery, how much is DOD, calender life and it's discharge cycle to discharged up 85%

[@michaelsstuff4402]

- Hi. I didn't specifically test Samsung cells so can't say accurately. Cheers.

[@Hardik-by2xr]

how to charge the batteries with this board?

[@MrBobWareham]

I am looking to make a battery powered 10" screen with a raspberry Pi 3 to make a portable tablet that I want to fit inside a book so when you open the front the unit comes to life and can be used for Linux then use with a small keyboard but will need a power supply and charging system both the display and the Pi will run on 5v so any suggestions for the best way to do the power supply so when it is powered it runs or if no power available it auto switches over to battery but don't want to use relays if you find an answer I will be most interested thanks, Bob

[@michaelsstuff4402]

- Hi. All 5V is good in this situation. The question is how many amps does your project draw? That will determine the way forward. Cheers.

[@MrBobWareham]

Thanks for your reply My 10-inch display runs at 3.3volts at 275ma and the pi at 5v 2.5 amps so I think I can run the display from the Pi output 3.3v

[@michaelsstuff4402]

- Ok. First check the max power output from the 3.3v pins on the Pi. I think your display is over what the Pi can deliver. In this case you could use a combination of a Sparkfun 12711 and a pololu U3V50F5. The Sparkfun board provides a barrel jack input and a mini USB input for charging the battery. It also has a lithium charger on board that can charge a battery at up to 1.5A. It feeds the U3V50F5 which is a boost regulator with reverse current protection that can boost a 3-4v lithium cell to 5V at up to 4A. What I have done before is use the barrel jack of the Sparkfun board to provide external power to both charge the battery and power the unit. When external power is disconnected, the unit runs from battery power. If you want to run the unit and charge it at the same time you need to run a couple of extra wires from the barrel jack of the 12711 to the OUTPUT of the regulator. I've used this on a couple of portables I built (in previous videos, mk3, mk4, mk5) and it works well. Cheers.

[@MrBobWareham]

Thank you for your suggestions yes I have not looked at current output on the Pi 3v3 but will make sure if it powerful to do the job

[@batangenyodotcom]

hi everybody, I've ordered one of this BMS board (still waiting to receive) to be used to a battery pack of three 18650. I just want to ask : is it necessary to charge with that specific "intelligent"charger/same type of charger or I can directly power it with any source provided that the voltage is in that range detailed on the specification. Thank you and sorry for this question maybe a stupid question but the more I search the more I become confused.

[@michaelsstuff4402]

- Hi. Its best to charge the cells in an intelligent charger as the BMS will allow charging current to pass to the cells but its not in the fashion that LION cells require for best, safe charging and long life. Cheers.

[@batangenyodotcom]

Thanks. Reading the comments, I found that better use Max745 for charging but can't understand if it also capable of those protections used by BMS. Is max745 BMS and charger in one board? Thanks.

[@abhishekkkuswaha231]

BMS Kanha milega 3battry kitna der chalega

[@faustsmith]

can a laptop 11.1volt battery be charged with a cellphone 3.7volt universal charger?

[@michaelsstuff4402]

- Hi and no you can't. Cheers.

[@kermdncer9981]

Please help. I see 0.15 V between P+ and P- . Why?

[@michaelsstuff4402]

Probably because your BMS is locked out. Apply 12V 1A input to the P+ P- of the BMS for 1 - 2 seconds. Cheers.

[@pearinnovation1419]

Can we connect only two battery in series using this module

[@michaelsstuff4402]

- There are 2S versions available. If you're just using 2 cells then use a 2S. Cheers.

[@HQHQHQHQHQHQHQHQHQHQHQHQHQHQHQ]

lol So you step up voltage and then step it back down... Yeah... That's one of the right ways of waste!

[@mp180170]

It’s because if you understand how these work the input voltage has to be 1 1/2 vaults higher than the output voltage hope that helps you understand how it works

[@electronic7979]

Nice video

[@michaelsstuff4402]

- Thank you.

[@ramkrisan1435]

sir please tell me which Rating of BMS i should use in 48 volt 33 ah lithium ion battery pack. I want us this battery in my 48 volt 15 Amp. 350 watt motor controller.

[@michaelsstuff4402]

- I don't know that you will find a 13 cell BMS so you may have to make a number of 4S and 3S packs and combine them to get your 48V output. Just make sure your BMS's are rated higher than the project current. A 30 Amp unit should be fine but I would go any lower just to be sure. Cheers.

[@miteshdhanani]

Want to make a 7.4v

[@Thundherstruck69]

Dear MEHS, I would like to create a big battery module for a small electric car. This car have got a 96 V nominal voltage feeding. I think to use the solution of relais. My battery pack have to 26 cells in series to create a nominal voltage of 96 V, but for a properly capacity, with a single cell of 2,6 Ah, I need to connect a 20 cells in parallel. So i Have a battery pack 26s 20p. If I use 26 TP4056 for charging and a Battery PROTECTION Board to control the discharging ( Balance function is not necessary, because we still look that don't charge properly my battery and main BMS have a "fake" balance function base on passive resistance, right?) with relais could I solve the problem? In what manner I can use a normal AC-DC wall feeder that provide, for example, 5 Vdc to feed my TP 4056? The cable for feed 26 TP4056 become too (very) big.... Then, if each TP 4056 provide 1,2 A for just one battery, It is possible to feed the 20parallel batteries? On each 20 parallel batteries I have got the SAME current of 0,06 Ampere? About Battery Protection board, when my pack is discharging the 20 parallel battery discharge with the same current? Thank you and sorry for not good english

[@michaelsstuff4402]

- Hi. I would not proceed the way you are suggesting. There are a couple of projects I have seen that are doing something similar to what you are doing. I suggest you take a look at the videos I link below. Watch the series of each and take a look at the comments too. I think it will help you a lot and help avoid some mistakes. Happy to help if you have further questions. Cheers. kzbin.info/www/bejne/mGTIg6mVe7-deMU kzbin.info/www/bejne/n5DNaWejopiahaM

[@Thundherstruck69]

Grazie. :-) Have a nice weekend.

[@MrBrymstond]

My Electronics & Hacking Show+ Have you ever used 4 TP4056's to charge a 4S 16.8v battery pack? Fast and efficiently @ 4amp balanced and charged??

[@michaelsstuff4402]

- Hi. If you mean one TP4056 per cell separately then yes a good solution. If you mean running 4 TP4056 boards into a BMS then no, that won't work as each IC is looking at the individual cell, you can't combine outputs into 8.4v, 12.6v or 16.8v and get the same results. If you connect each TP4056 to each cell and bypass the BMS then it can work. You need to watch out for common ground issues which is a typical problem when using multiple TP4056's where the batteries or pack are connected together in some way. Cheers.

[@MrBrymstond]

I mean 4 TP4056's connected as one TP4056 to each 18650 battery as you would normal directly on the terminal, but in a 4 cell holder with wires on each battery then you run the first battery wire negative to the next battery's positive and so on, These 2 wires 1 neg at one end and 1 pos at the other end is used for the DC inputs on the device. So it's wired in series while the TP4056 are all wired in parallel, the trick is you need isolation on the inputs, each TP4056 has to have isolation so it's easier to run 4 USB Phone Chargers then you can wire the AC in parallel, I stuck mine together in a clear project box using a extension cord. You will get 1 amp per cell so 4 amps for 4 when they turn green they're charged and balanced. I have a bunch of them working in my mini amplifiers. You can do this for 2S~ whatever you need. You can do 2P/4S, but the charging will be limited to .500mAh for each cell. This would make a great video if you'll try it. You can use 1 supply if you use a isolation chip but you're limited to .200mAh not good.

[@MrBrymstond]

I just subbed thanks.

[@aniketchauhan3276]

Hi buddy, i have the same 3s chip but it is not working. i don't know why. i did the same connections as you did. but still. Help me out.

[@michaelsstuff4402]

-Have you activated your BMS board? Have a read through the comments but basically you need to connect a 12v or 12.6v power supply to the P+ P- pads for a second or two. That will release the blocking relay and the board will work, as long as you connected everything up correctly. Cheers.

[@aniketchauhan3276]

I don't know how to activate BMS board.

[@kamran-ve7xc]

👍👍

[@gigstreamer6410]

Could you have used the circuit board in a laptop battery cell unit and substitute laptop batteries for multiple smartphone cells batteries. Cris crossing substitute

[@michaelsstuff4402]

- Hi. Not really as you would need to ensure the power going into the laptop is getting distributed correctly and not all laptops are the same. You could if you knew the specifics and number of cells etc but not straight forward. The principle however is correct because large lithium batteries (like a laptop battery) are just a number of 3.7v cells connected together with something like a BMS to make a bigger battery with more voltage. Cheers.

[@gigstreamer6410]

My Electronics & Hacking Show In the case of cellular phone liion battery, the cells inside this type are configured different than round 3.7v. Laptop? I see that 3.7 bank chargers via USB charge cellular phone locally. If I were to remove the cellular battery from phone is remotel charging same remotely? If so then how does the BMS know what type of battery its charging. Is it mha

[@michaelsstuff4402]

- There is no difference as far as voltage and how they are charged. The BMS doesn't know what type of cell its protecting because lipo or lion are the same nominal voltage and charge the same way. You only need to understand how much current or time you need for the pack you are charging. A 3S BMS is 11.1V nominally and will need a peak charge of 12.6v @ 1A for about 3 hours. A single 3.7V cell will be happy with a 4.2v charge at 1A for about the same time, depending on the capacity of the cells. Cheers.

[@kushalnarayangowda7955]

Can I get circuit diagram for this

[@MrBrymstond]

So where do you get the project supply?

[@michaelsstuff4402]

Hi. Do you mean the bench power supply? It was an Ebay purchase. Very cheap for what you get. Cheers.

[@cicovci]

1:48 is wrong. do not connect it this way

[@michaelsstuff4402]

- Hi. This is actually the manufacturers recommended connection. Why do you think its wrong?

[@cicovci]

Hi and thanks for the response. Well maybe I do not understand your drawing but battery should not be connected to the P+/P-. P+/P-. It is just to connect the load (output) and charging (input) in parallel. Battery has another points to be connected to. Btw - I doubt that this is the connection recommended by manufacturer. Maybe I just do not understand what you mean by the drawing (the blocks)...

[@kids123123123]

It looks wrong to me too - the whole purpose of BMS is to *disconnect* the battery during over/under voltage or overcurrent. But in the drawing, the battery is *always* connected (it is directly soldered to both the load and the charger). If your charger is unplugged, your load will eventually drain the cells to 0.0v and wreck them. If your load shorts, it'll be.... exciting. As shown, the BMS is not in the circuit :(

[@michaelsstuff4402]

-Hi. Ah yes now I see what you mean. Yes you are correct. I have drawn the BMS wiring connected to the P+ P- pads instead of the B+ B- pads around the BMS. I didn't even pick up on that. Thanks.

[@michaelsstuff4402]

- Hi. Yes you are correct. My mistake. They do happen especially when the hours blur together. I will write a correction and advise people to view the actual wiring example shown a little further in the video. Thanks.

[@rtoebak76]

Does the bms shut down when one cell reaches the low voltage or the total voltage?

[@michaelsstuff4402]

- Hi. The BMS monitors individual cells so it will shut down the pack if just one cell drops below the cutoff voltage. If its a BMS that doesn't have a different recovery voltage or timer, it will turn back on when the voltage of the cells recovers above the cutoff voltage. This means your project, say a light, will flicker quickly as the BMS turns the cell pack on and off as the low cell drops below the cutoff voltage (say 2.9v) and then recovers to be above the cutoff voltage. Better BMS will have a recovery voltage that is different to the cutoff voltage. The cut might be at 2.7v and the recovery might be at 2.9v. And some have a timer that will keep the cell cut off for x number of seconds. Hope that helps. Cheers.

[@rtoebak76]

My Electronics & Hacking Show. So a bad balanced pack will leave others in the high voltage range when the first cuts off.

[@michaelsstuff4402]

- Yes, correct. That's why its important to use a good charging methodology such as a good lithium charger and balanced cells (as well balanced as you can find), doesn't need to be perfect but the closer they are, the better the result.

[@davidbolha]

Hello, I have a really stupid question (so forgive me), but could the BMS be used as a substitute circuit for of that which is used in laptop batteries ? 🙄😏 So you would use this circuit to power your laptop (still using 3 18650 cells) instead of the original one. Because if you look up a video from Charlie Miller, titled "Battery Firmware Hacking" (almost 50 minutes long, but worth it)... then research either Smart Battery Worshop or Battery EEPROM Works program (for example), you see that if you want to just rebuild your laptop battery pack, it's not that easy just by removing depleted 18650 cells & adding in new ones. So I'm wishfully thinking that the BMS could be used to power a laptop & also it could charge the batteries connected onto it as well. But this is really crude thinking. 🤔😑😐

[@michaelsstuff4402]

- Hi. short answer is no. The laptop battery pack has a specific number of cells and the laptop is preconfigured to take the correct voltage and current from the charger that can power the laptop and charge the battery while in the laptop. You can replace the cells yourself but you need to match the voltage and number of cells. Anything attempt other than this should be done outside the laptop and you need to take care making yo, selecting the correct charge voltage and current and you would also need a step up regulator as 12V is unlikely to be enough to power a laptop. Cheers.

[@davidbolha]

My Electronics & Hacking Show Thank you for your detailed reply. ☺ Best Regards,

[@theAGanimators]

It would appear to me that the point of this little green board is to enable the use of a 19v laptop supply as a 3s lithium charger, yes?I can't find this board on ebay, can you share a link?

[@michaelsstuff4402]

- Hi. Not really. The little green board is supposed to be a 3S lithium charger meaning it can provide a proper CC then CV charge of up to 12.6V at up to 2A. The idea is that you can use it and a BMS to build a battery circuit that can be left in a project (like a laptop battery) and can be recharged when external power is available or can run the project from battery power when external power is not available. Yes I will post the link in the video description sometime today. Cheers.

[@JensRoland]

My Electronics & Hacking Show great video; if I understand you correctly then the green charging board outputs CC/CV on the pins which connect to the BMS, charging the 3S pack correctly; but with the load in parallel, wouldn't the charging board be delivering the wrong (low) voltage to the load during CC, and too little current to both load and BMS during CV?

[@michaelsstuff4402]

- Hi. Good point. It depends on the load and whether your project has external power going only through the battery pack and BMS to the project load (LED panel or whatever) or whether you run power to the battery pack and to the load (in parallel as you say). The charging board is capable of a 2amp output so if your project draws more you would run a parallel setup and avoid any CC/CV issues. If not then its possible that the supply from the charging board could be taxed and not able to supply the best charge to the cells. Not a perfect solution. Cheers.

[@JensRoland]

Ah, that's what I thought. While CV should work as long as the load doesn't need too much current, the constant-current phase seems like it would pretty much ensure that the BMS would be receiving less current than optimal since the load would be draining part of the current. As for the setup with relays at 5:00, don't you need a diode on the red wire between the output and the junction leading to the leftmost relay trigger? I tried sketching this and it looked like I would get a loop from the relay output to the trigger.

[@michaelsstuff4402]

- I tried a couple of different relays (a few actually) and I think I found one that was isolated meaning no loop problems which I was getting during some of the testing. If no inherited isolation then yes add another diode. Cheers.

[@jorn7629]

So im not planning on charging my project while using it so how would i have to worry about looping

[@michaelsstuff4402]

- Hi. If your aren't charging while using, then no worry at all. It's only an issue when your project draws 2A when running (as an example), and your charging module can only charge at 1A no matter how much power you could provide your project. If your project is sleeping then the charge module can charge the cells without the cells being drained faster than the charger can supply power. Cheers.

[@jorn7629]

Thanks for helping me understand liked and subbed

[@johnnybuoy9551]

What's the moral of the story? Can I charge a 3s 3p set of 18650s (total 9) with my regular 12V adapter (or 12V solar panel) using this 3s BMS or naa?

[@michaelsstuff4402]

Hi. The answer is a bit of yes and no. From a 12v supply you will put power back into your cells but it won't be an ideal charge (maybe 50%). This means the battery pack won't reach peak charge and the cells won't have as long a life as if they were well looked after. How long is a guess. By using the 12v supply or solar supply (which has other considerations) you are bypassing the CC CV charging method desirable for healthy lithium charging. A proper charger has this methodology baked in, but in a pinch your method will work. The Solar option is less desirable unless your are using a regulator to get a smooth (roughly) 12v from the solar. As you know, solar does not produce a constant supply. It peaks and troughs. This will upset the BMS and force it into under or over voltage protection, depending on the features of your BMS. It could be a situation where the BMS is switching on an off like flicking a light switch on and off as fast as you can. The BMS and the cells won't enjoy that and you could introduce a failure or excessive heat. If your Solar is regulated then the ups and downs will be much less and it becomes basically the same as using a standard 12v supply. Cheers.

[@johnnybuoy9551]

@@michaelsstuff4402 Thanks a lot for the detailed reply... I am planning to make my own "Solar Street Light". For that I am planning to use the 3s 3p set of 9 18650s. I will connect them to the 3s BMS and also connect the BMS to a 12V Solar Panel and the LEDs.. I hope it will work. I agree that using a Buck/Boost module to fix the power supply to 12.6 will be good but I have a feeling that it can still work without it. Since there's this 3s 25Amps BMS which should (kinda) help incase of under voltage. Any comments on that, if you'd like..