Current Sharing Experiment: 25kWh LiFePO4 w/ Diagonal Wire Configuration

[@WillProwse]

Some are saying that this configuration should allow for equal charge and discharge. Not true. One of our forum members did the math! Check it out here. It shows why I got the results I got: diysolarforum.com/threads/some-modeling-to-go-with-wills-current-sharing-videos.35121/#post-439794 Beginners should check out the free PDF from Victron called Wiring Unlimited. It is a fantastic resource if you do not understand what is going on in this video: diysolarforum.com/resources/wiring-unlimited.2/ Part 1 of this current sharing series: kzbin.info/www/bejne/pYmlhWuiiKhla68 Server rack batteries: www.mobile-solarpower.com/server-rack-lifepo4.html All in one systems: www.mobile-solarpower.com/all-in-one-122448v-packages.html ~~~~~~~~~~~~~~~~~~~~~~~~~~ Does off-grid solar confuse you? Check out my DIY friendly website for solar system packages and product recommendations, and so much more! www.mobile-solarpower.com Join our DIY solar community! #1 largest solar forum on the internet for beginners and professionals alike: www.diysolarforum.com Check out my best-selling, beginner-friendly 12V off-grid solar book (affiliate link): amzn.to/2Aj4dX4 If DIY is not for you, but you love solar and need an offgrid system, check out Tesla Solar. Low prices and great warranty, and they can take your entire house offgrid with their new Powerwalls: ts.la/william57509 ~~~~~~~~~~~~~~~~~~~~~~~~~ My solar equipment recommendations (Constantly updated! Check here first): 12V/48V Lithium Batteries: www.mobile-solarpower.com/solar-batteries.html Solar System Component Directory: www.mobile-solarpower.com/solarcomponents.html Plug-N-Play Systems: www.mobile-solarpower.com/full-size-systems.html Complete 48V System Kits: www.mobile-solarpower.com/complete-48v-solar-kits.html DIY Friendly Air Conditioner/ Heat Pumps: www.mobile-solarpower.com/solar-friendly-air-conditioners.html Complete 48V System Blueprint: www.mobile-solarpower.com/48v-complete-system-blueprint.html ~~~~~~~~~~~~~~~~~~~~~~~~~~ My Favorite Online Stores for DIY Solar and Coupon Codes: -Current Connected: SOK, Victron and High Quality Components. Best prices and warranty around: currentconnected.com/?ref=wp -Signature Solar: Cheap Server Rack Batteries and Large Solar Panels: www.signaturesolar.com/?ref=h-cvbzfahsek -Ecoflow Delta Official Site: My favorite plug-n-play solar generator: us.ecoflow.com/?aff=7 -AmpereTime: Cheapest 12V batteries around: amperetime.com/products/ampere-time-12v-100ah-lithium-lifepo4-battery?ref=h-cvbzfahsek -Rich Solar: Mega site and cheaper prices than renogy! Check them out: richsolar.com/?ref=h-cvbzfahsek -Shop Solar Kits: Huge site with every solar kit you can imagine! Check it out: shopsolarkits.com/?ref=will-p -Battery Hookup: Cheap cell deals bit.ly/2mIxSqt 10% off code: diysolar -Watts 24/7: Best deals on all-in-one solar power systems, with customer support and distribution here in the USA: watts247.com/?wpam_id=3 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Contact Information: I am NOT available for personal solar system consult! If you wish to contact me, this is my direct email: [e-mail] Join the forum at diysolarforum.com/ if you wish to hang out with myself and others and talk about solar FTC Disclosure Statement and Disclaimers: Every video includes some form of paid promotion or sponsorship. Some links on this youtube channel may be affiliate links. We may get paid if you buy something or take an action after clicking one of these. My videos are for educational purposes only. Information is subject to change/update at any time. Electricity is DANGEROUS and can kill. Be smart and use common sense :) DIY Solar Power with Will Prowse is a participant in the Amazon Services LLC Associates Program, An affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com

[@wanderingzythophile9083]

Could you cut/drill some small copper bars, very short, that fit the width of terminals, then bolt your larger lugs onto on the other end? Sufficient thickness to handle the currents involved? Sort of like an extension.

[@jimsjacob]

I have the hard copy of Victron's "Wiring Unlimited", so I recognized your diagrams. But again, the conductors are different lengths in that example. I'm thinking the important lengths are the jumpers connecting battery to battery and not the lengths to the load. Would you agree?

[@MYCHANNELWITHMYSTUFF]

Can you do a video on how to size bus bars?

[@geepeerces]

@@jimsjacob yes, exactly.

[@geepeerces]

@@MYCHANNELWITHMYSTUFF find a table of wire gauges and resistance for pure copper wire, pick the gauge you want, then calculate the cross section of that gauge (pi*R^2). a bus bar thats X wide and Y thick has X*Y cross section. example, 2/0 is 0.365" diameter, so thats R=0.1825, pi*R^2 is 0.10 square inches. so if your bus bar was made from 1/4 inch thick copper it would need to be 0.4 wide (0.10 square inches / 0.25 inch thick == 0.4 inches wide) to have the same cross section and DC resistance as 2/0 wire.

[@jamesboulton2722]

Would be interesting to a thermal camera to your tool kit. Would be cool to ‘see’ the cables warming up. It would also be handy to help identify bad crimps or bad connections too.

[@tammyhalcomb6440]

Hi Will I'm 56 single female and at 55 because of watching your videos I felt confident enough to design and build a off grid solar system. It worked perfectly from the very beginning and has worked since... its going on 2 years. Your videos are so informative and you are such a good teacher...Thank you for all of the thrilling opportunities. Tammy Halcomb

[@psychopitt1982]

I absolutely love these battery tests! I spend do much time wondering about the best ways to wire batteries like I going to reinvent the wheel, then will not only does the tests but explains everything in great detail.. thank you @DIY Solar with Will Prowse

[@ronjuliannerobertson5243]

You talked about the wires coming from the inverter needing to be equal links going to your distributing block. What about the wires from the distributor box to each battery bank do they need to be the same length as well.

[@cinemaparts]

Hello Will. I just want to say thanks for all of your videos. You have the coolest job and I really appreciate the information and tutorials. Keep it going! You’ve inspired me to put together a 12V 600Ah system for my RV and I’m in the midst of building it now. This battery test video reassures me that I should be okay to use 4/0 cable and hookup my six 100Ah Lithium batteries in the same diagonal wiring configuration you have demonstrated here. I hope to be finished with it in a few weeks.

[@ranig2848]

It’s actually quite simple. When the batteries are at the top or bottom of the curve, the large batteries will supply more power (amps) as they’ll stay in the steep curve longer than smaller ones (they’ll be both supplying the power and pulling up/charging the smaller batteries). Once they are in the flat curve all will contribute the same as all will be around the same voltage. Once they reach the bottom curve, the large batteries will supply more power again as they will still be in the flat area - they will “prohibit” the small batteries from dropping - keeping the voltage at the flat area. Bottom line, if you want to use this type of setup, especially with LiFePo4, just keep the voltages very close to the flat area. Then 99% of the time, all batteries will be contributing the same as they will have limited voltage differences.

[@WillProwse]

Exactly!

[@robert4027]

@@WillProwse in future can you do some ebike battery testing and budget ebike testing please PLEASE

[@robert4027]

@@richardhobbs7107 I just received a Ancheer Hummer model ebike and I want to modify . I do love it so far but 22 mph in full electric mode is to slow and replacement battery packs just have me scratching my head I can't tell good ones from ripoff junk

[@ralphbell1786]

It would be useful to know how much of these SOC differences are due to their curve characteristics and how much is actually due to voltage drop.

[@kswis]

Watching this again because as I mentioned elsewhere I'm playing with a lithion and lifepo4 parallel packs connected to the same inverter. It really I testing how the two act differently but the major item I'm noticing is how they share current. It is really I trusting. I've got a pile of wire from changing lengths, guage, and I've ven recently changed the connection location. The lifepo4 likes to dump current but the lithion shines on low current constant load situations. Best way to thoroughly learn is with your hands. Personally anyway

[@trx4treats]

In the Army we wired the batteries diagonally. This was something I learned in AIT Electrical Engineering, to balance the charge and the load and get longer battery life. Those were lead acid batteries on trucks though. Glad to know it works even on LiPO batteries for when I convert over from lead acid. Right now, living alone they work for me and are less expensive up front.

[@geepeerces]

sadly, the dual batteries on virtually all diesel pickups like my ford f250 are NOT wired diagonally. each has its own chassis ground wire, and the loads are all connected to one, which has a fat wire over to the other.

[@dennisdunbar2340]

Can't wait to see the busbar version of this experiment. nice video

[@magnum164]

Mechanical Designer, but also do electrical and when I passed my Ham lic we learned about common grounds and it applies to pos, neg as well. So my guess is your common bus bar would be equivalent to a common ground. Each battery would have a cable that could handle the 40amps per battery, but the Bus bar and the cables to the device device (car) would handle the combined amps, so the individual batt cables would not get as hot. That gives you a common voltage ref point and reduces noise and interference as well to surrounding electronics. Good video, gives me some ideas even on a smaller scale, but I am sure you have clarified more in later videos. I just found your channel a few days ago and they pop in now and then:).

[@MiketheMeister]

I have read (and heard of) all the different things that were demonstrated in this video, but this is the 1st time I've actually seen it. Outstanding video, Will!

[@williammeek4078]

Will, I really liked this hands on example of a practical system. This is the best of the internet.

[@wideawaketotruth5301]

Awesome video as always Will. One of the things I really appreciate, is the fact that you stay on real world topic. And Don't drift off into minutiae that nobody really cares about. Not to mention the fact it over complicates. I consider myself a novice at best. Please keep them coming big guy!

[@Jim.D]

I use a bussbar with opposite connections and have no issues and highly recommend it, well worth the investment

[@JamesJ-85]

@willprowse I can't remember what video started me on the youtube rabbit hole but when I cam across your's (looking for opinion videos on RV batteries) your information, presentation, detail, proper procedures,etc , the first 2-3 seconds I thought you were a high schooler but then quickly realized no way could someone that young be this knowledgable. I'm a micosoft sys eng... but your channel got me binging and finind a new hobby Batteries!.

[@AdemirDeMirandaJunior]

Good to see it working well. I have 12x 100A lofepo4 connected the way you showed at the video!

[@mxbadboy263]

As long as the conductors are large enough to avoid voltage drop across the batteries it doesn't mater which way you wire it.

[@emilhwilkins3275]

Will it would be nice to do a video using copper buss bars and comparing the results to your other videos and seeing the different numbers.

[@ncplantdoctor]

Excellent demonstration. My system uses equal length conductor paths which I prefer although in a larger system that would entail buying a lot of copper. Your diagram called it Post pattern.

[@tomduffy6911]

Question: Do the positive and negative wire lengths from the battery to the system need to be the same length? I see in the diagram, and also in the video, that they appear to be different lengths. I'm asking since it seems to be important for the cables connecting the batteries together to be the same length. Why not so in connecting batteries to the system?

[@Sanwizard1]

Awesome and useful test and proof points. It also shows how well the MPP LV6548's handle large loads!

[@2008mjb]

You need 5 rack units of the exact same brand put in an actual rack. Then do the following tests. Wire it 3 ways: Bus bar, same side, opposite side. Cycle each method and record each battery for % of total amp draw at 100/75/50/25% state of charge. This is a lot of work but would fully prove how each one performs. I agree that it will most likely level out once you pass the first 10-15% of a battery charge.

[@WillProwse]

Yes I plan to do that soon. I don't have that many packs but will soon.

[@WillProwse]

Bus bar is only method I've found to work every time.

[@wilsonluilui]

consider use one DC current clamp to capture the current as each battery and make consumption calculation be good.because each battery inside meter not the same reading sir.

[@WWarthog798]

Heh...in grad school I had a high-current, low voltage experimental rig that used 5000 watts at 12 volts. 0000 cables, brass connections, and they still got hot enough to melt lead solder. Had to use silver solder. Rig was, of course, water cooled, even near the connections...but that was a LOTTA current. Of course, we were heating carbon tubes up to 2500 C.

[@jasonmorgan4108]

I think using large gauge wire with the correct size lugs for your terminals and figuring out the best order for the packs would work great. If the lugs are too wide trim problem side or sides and hook it up.

[@fishhuntadventure]

@Jason Morgan Exactly- I’d have just trimmed the terminals on the grinder.

[@5400bowen]

I tried that and it still pulls more from batteries closer to the load. As Will mentioned in the first video on this, it’s when you start pushing towards the output limits of the batteries that this issue arises. In that case the cost/size of the wires needed gets excessive. I’m going with the Victron image (third one) with the “posts” configuration, as I don’t have rack mount batteries. I’m using small free standing bus bars from Amazon to hook the batteries to the inverter, and the same for the charge controller. The bus bars are going where the big dots are where the four leads come together in the diagram. And of course, a much larger cable between the bus bars and the inverter and charge controller.

[@Infinion]

Hey man, this was a pretty cool experiment. I noticed you didn't measure the voltage drop across each length. That would've really helped explain the variation and show how much the diagonal configuration is normalizing C rate along the chemistry's discharge curve compared to the daisy-chained configuration. Then, when you mention how bigger batteries have lower internal resistance, it will actually provide context towards the experiment you're running. In addition to calling out current and SoC, please call out the pack voltage and if it isn't too much trouble, the voltage drop across the cable segments. Thanks for the vid.

[@chrissweisberger7509]

i bought the book -mobile solar power - made easy thank you for writing this - very easy to understand

[@NeverTakeNoCut-offs]

Is the "post" configuration with equal length cable the same as using a busbar?

[@bdr518]

I was thinking this last night when watching your video on top balancing lifepo batteries.

[@Sylvan_dB]

Fascinating results, thanks for the additional testing!

[@honesty_-no9he]

If you look at the charging curve on a TESLA MODEL 3 with LFP what was called the SR+ especially in colder weather, it starts out building the kW quite slowly then ramps up later but for longer than NCM etc on an LR or Performance.

[@SuperBrainAK]

Wow that is what I thought would happen, but it is always awesome to see it in action! I think the best way to connect the batteries is Posts or functionally identical short Bussbars, what I mean is that you have equal lengths wires either stacked directly on top of each other in the Posts configuration (but that would require alot of torque) or alternatively use the exact same wires to connect everything to a copper bussbar that is only spaced apart enough to fit the lugs next to each other. That way you have the advantage of Posts but you have much more surface area touching each lug, because a lug to lug connection is never perfect.

[@leopoldpoppenberger8692]

that is why I have a copper pipe 1/2" flattened and drilled hole to equally distanced batteries. There is only one screw in point. And opposite take off +ve and-ve 3x200 ah 12vdc in parallel

[@SuperBrainAK]

@@leopoldpoppenberger8692 copper pipe is a good cheap way to get started. May I ask how you attach your lugs to the pipe? Is it bolts and nuts sandwiching the lug to the pipe or is the pipe threaded and you are tightening down to that? If you were to ever upgrade your inverter you should definitely increase your system's voltage. Get a 4th battery and wire them all in series to get 48v that would certainly increase your efficiency. If you are also using 12v appliances then just use a 48v to 12v DC-DC converter.

[@robbehr8806]

Will, how about doing a video on specific bus bars?

[@scothunter3221]

These last two videos have a dress questions that I have had for a long time. I’m still re-watching them to make sure I understand everything and I just ordered some appropriately sized fuses so that I have my batteries properly protected. I keep learning from you but like someone else said earlier I am especially admirable of your focus on safety. I have a neighbor who is trying to learn about solar and he is putting one into his RV. He’s been watching your videos but I don’t think he’s listening closely as he had four 100watt panels in 2s2p connected to a controller with a 50 foot piece of extension cord with the ends cut off, all feeding into a 3000 W inverter. Think it was 16 gauge. The inverter came with cables which were intended to be paired but he only had single cables on them. His components were correct per your plans but the wiring itself was downright scary. I think I’ve got them straightened out. A bit more focus on correct and appropriate wire size would be helpful for the newbies. Otherwise I’m always really loving your videos.

[@danielatbasementtech]

Nice video … would have loved to see you measure the voltage drop across the conductors to make your point with numbers.

[@timguishard4641]

Try using the diagonal configuration, take the power leads to the inverters out of the batteries 1 battery from each end. This will reduce the current from the jumpers that got hot and may allow the batteries to discharge more equally.

[@a64738]

After what I can see and also what he is saying this IS diagonal configuration...

[@SkypowerwithKarl]

I’ve never had an issue with diagonal as long as all the capacities are the same. I just ran a test on a 2P X 16 620ah battery. Did you know that 175 amps on 2/0 cable for a few hours makes a nice hand warmer?

[@wagmiorngmi]

I love how excited this guy gets by some batteries.

[@captainobvious9188]

Bus-bars are the same as a diagonal configuration but essentially with a larger conductor. At some point a battery bank grows large enough that you would need really thick and long bus bars, so it becomes more economical just to have equal length conductors from each battery to much smaller bars (length wise).

[@WillProwse]

Yes very true!

[@kswis]

Pulling current like that in an experiment is just fun. thankyou for the real world example

[@SylwerDragon]

Interesting results. It looks like it depend on battery itself. I didn't expect it will be like that.. It might be good lesson for ppl who got a lot of parallels cells or systems..

[@jayjonah2762]

only thing left to do is show us the bus bar setup with these packs! :D great video Will

[@adiq13]

Grat video. I think that the size of the wires in between the packs is important. In here we have thicker cables on each end of the string but thinker cables between the individual banks. If all the wiring was done with the thicker cables we would have more balanced results ( proportional to the capacity) as the resistance on the hotter thin wires would be smaller.

[@WillProwse]

But we cant. Did you see the video? The max you can add on this terminal is 2 gauge. These batteries come with 6 gauge wires. That's a huge reason I made this video.

[@adiq13]

@@WillProwse yes I've seen it and I understand why you have done it this way. You can do this by filing the connectors so it fits. I didn't see the surface too close so can't calculate exactly how big the connection surface is there and whether enough for 230 amps of current but I think it was worth asking. I know that it is never good to tamper with the connections but you are wire enough to do it safely ;)

[@wesleyofficer1237]

Oh my word that load test was just insane!!!

[@WillProwse]

Right!! So fun 😁

[@rickyroaster]

A nice wee torque wrench is needed for uniform tightening of the terminals, takes out the guess work. Split bus bars are the way to go for high current discharge/charge. Nice copper 3/8" thick from the BMS would sort out any resistance issues. With the energy prices going through the roof in the UK 50% INCREASE in April, I think the return of investment would pay for itself in half the time.

[@unkillablespirits8582]

You have alot of effort put into this channel , you are the boss on this topic !

[@centerrightproudamerican5727]

Another good video will!! I particularly liked the discovery that the imbalance is much less when the batteries are in the flat part of the charge curve. A few points: 1) If there are only 2 batteries in parallel, they will stay balanced if you hook them up diagonal. Each additional battery above 2 will create more imbalance even with the diagonal hook-up. 2) If you use long bus bars as shown in the picture in the video, they need to be sized fairly large in order to minimize the voltage drop across the bus bar, otherwise you will get the same problem you are trying to avoid. 3) When making the cables for the battery hook-ups, each crimp is important. If one of the crimps is not perfect, it can throw off any attempt to arrange the batteries for balance. Along these lines, server rack batteries should be designed so that when they are racked up you can bolt busbars directly on the battery terminals to interconnect them. The Jakiper batteries in the video would not handle this well because the bus bar would have to be narrow and one of the busbars would cover the controls. The un-named batteries look like they might handle direct connection to the busbars better but I would prefer to be able to put wider bars on. If you used two thick bars on the un-named batteries it might work well. 4) When doing busbars, it is important that they be covered for fire safety reasons and electrocution safety on 48V systems. I like putting heat-shrink over everything except the connections, but there are other techniques like mounting plastic covers that can be removed when servicing....... Hmmmmm that would be an interesting feature on a server-rack battery: Snap-on Plastic bus-bar covers that are the height of the batteries. 1) Rack up the batteries 2) Bolt on the busbars 3) Snap on the covers *** Done ***

[@stefanvanzyl9090]

That's exactly what I did at my last battery install, got 400A flexible insulated busbar, drilled holes, cut the insulation and bolted them in - 5 batteries connected to 3 inverters, no hassle. "CFX1045" from electromechanica

[@WillProwse]

Agreed!! Good points

[@geepeerces]

um, even with 4 or more in parallel diagonally, if the inter-battery wires are the same gauge and length on both plus and ground, each battery sees the same total wire resistance on + and - combined. say each jumper is 10 milliohms, and your plus feed cable goes to B1, with the - ground cable to B4, then B1 sees 0 extra milliohms on + but 3*10 on ground, B2 sees 10mOhm on + and 20 on -, B3 sees 20 on + and 10 on -, and B4 sees 30 on + and 0 on -... so each battery has the same 30 milliohm in series with it. I definitely agree re crimps, but with proper fine strand pure copper welding cable and a decent hex crimper and using the same pure copper ring fasteners, the crimps should be very consistent.

[@centerrightproudamerican5727]

@@geepeercesYes, diagonal is better than nothing but it is *not* balanced beyond 2. If you have more than 2 batteries in parallel and use diagonal to hook them up to the system, the outer 2 will carry more load than the next ones in and so on. That is what will just demonstrated in his video. The higher the load, the worse it will be. This was worked out years ago with lead-acid and holds true with LiFePo4. It is interesting that in the flat part of the SOC curve the effect is less pronounced than when the batties are fully charged, but the effect is there nonetheless.

[@OhRonaldo]

@@centerrightproudamerican5727 That's how the entire US grid works, higher voltage flows to lower voltage. Higher internal resistance lowers output voltage under equal load, etc.

[@EspHack]

put the terminals on the two middle packs surrounding the center pack for peak cheap balancing :P I've done just that before, now I see its actually beneficial somehow, all I cared about was symmetry, turns out its also functional! I'd put the two newer packs between the 3 old ones also

[@mostrogolf22]

I might be a little late in the game but I've been watching your videos for about two years now. At the 5:24 minute mark you show a great diagram of 4 types of connections. I have the "Halfway" setup curently with all cables cut to the same length with the exception of the cables going to the inverter which are longer. My question is, can I add a battery on each end of the "halfway" setup making it with six batteries and continue to be a "balanced" load? Please let me know. Thank you for what you do 😊 Good day😊

[@andrewakrause]

Years ago when I worked in car audio, a common problem was large stereo systems that would call for 200 to 300 amps of sustained current draw, but working with 2/0 wires wasn't always practical. We would instead use 2 2-gauge wires in parallel. Looking at these server rack batterys' terminals, it would seem that if you can stack terminals, this would do the trick. That being said, by the time you bought, cut, and crimped all those cable, it probably would have been cheaper to buy copper bars and drill/file them to fit.

[@badactor3440]

Instead of using a busbar, I use thicker cables as needed to equalize the batteries. Seems to be working well for my installation.

[@carlosencarnacion9667]

Well, thank God for Will Prowse and his NBS (No BullShit) Channel. Here in Puerto Rico the neoliberals are privatizing the grid with LUMA Energy, and we need to migrate, not out of the islands, but to Solar. This is good, practical info. ¡FUERA LUMA!

[@sia3540]

It would be nice to see you do the same test with the bus bars.

[@OhRonaldo]

Eliminate your variables, experiment with same batteries to start. But you still have a busbar with 0 resistance connectors, so "busbar" and "diagonal" to the posts is the same setup, electrically, assuming more consistent conductors than you're using. You want equal resistance from your load to the individual packs. As I mentioned yesterday, the diagonal setup is just the "reverse" of connecting your load to the middle pack. Same issues. In your setup specifically your positive load conductor is very different from your negative load conductor as well as between the packs. Get out your Fluke and have fun getting it properly balanced. It'll be instructive for all

[@WillProwse]

Once a company sends out 6X of one type of battery, I will. And I bet I can pull within 1% of each other once I have that set up. Will do so in the next few months

[@OhRonaldo]

@@WillProwse It should be fun, and great to watch.

[@WillProwse]

I will make a pack with 6X matched server racks with equal length conductors. Should work great.

[@OhRonaldo]

@@WillProwse Equal resistance conductors, yes

[@geezenslaw]

I have to get my electrian to watch this vid before the install of my batteries on my boat. Thanks Will...!

[@stizzywomizzy5322]

Love how detailed your vid's are great job as always. I can't stop looking at the screwdriver sitting on top of the batteries tho lol

[@setag54321]

Will...you need a bench grinder, so you can fit your cables in narrower terminals when needed.

[@brucemccreary769]

Well done, Will. A very clear picture of the issues of parallel battery design. Someday, we'll get away from these ridiculous low voltage batteries for home power. I think 120V should be the practical minimum, with 350VDC for larger applications per many server farm power/battery systems (230VAC switching supplies work at that DC voltage). My own custom off grid system is 120 VDC; no need for parallel batteries or big wire. It's been serving me well for over 12 years now.

[@TschingisTube]

Dc voltage above 60v is considered dangerous, and then you need protection for the build which makes it harder in other regards, but yes you also could simply not care.

[@brucemccreary769]

My comment was about the future of higher voltages for battery banks, but really that is already here. The Tesla powerwall is already 350-450V. So are their car batteries. I assume they care about safety, as do I. So do Server Farms, who use 350V battery/DC distribution systems. Many people has been seriously injured by accidental shorts of batteries even at low voltages. There is no magic voltage where safety is assured in spite of unsafe practices and ignorance. 120VAC kills people but is in common use. DC has 4x the shock safety of the same AC voltage; this is a well proven fact. I suggest that 120VDC is a good next step for off grid battery voltage because I use it myself, and 110VDC has a long history of relative safety for home power from back in the Edison days, with bare uninsulated wires on ceramic posts and tubes. As I write this, my computer and rear projection display system with stock power supplies are running directly off of my unregulated battery bank DC voltage; 133V at present. My lighting and daytime cooking are also direct 120VDC, zero conversion loss. The same safety concern should apply is your typical high voltage PV array, even if feeding a 48V system. Someone with less power safety training than an electrician should not work with higher voltages. I was commenting about the obvious technical future for off grid battery bank voltages. 120VDC is a good, relatively safe next step, in my experience of over 12 years with it. I'm a retired EE and designed and built my own power system. I should probably avoid commenting on public forums for the obvious reasons as illustrated here. Will does a good job of mentioning safety, and perhaps he should do a separate safety training video. I'm very impressed with the quality of his technical content and presentations. Bravo, Will.

[@TschingisTube]

@@brucemccreary769 Anything above 60V is considered dangerous in most countries. DC is not less dangerous than AC, actually it is more dangerous because if you get hit by it, the chance that you muscle keep contracted is much higher than with 50Hz AC where you can still let loose the connection you grabbed, as it is not constantly flowing current but alternating. There are for sure ready build powerbanks which have much higher voltages because of efficency but then they are closed products and not like on this channel, DIY solutions. So if you are talking about finished products, yes there will be higher voltages. If you are talking about DIY you will not get much more than now, this is voltage of 48V LiFePO4 which fully charged is nearly 60V is not just an accident. It easy to raise the voltage, put more cells in series, but the danger of serious injury also raises. This does not mean that you cannot simply do it if you feel yourself comfortable with, but i think you should not expect a public youtube channel which has thousends of viewers present possible dangerous solutions.

[@brucemccreary769]

Alas, your information on the ""can't release"" safety of AC vs DC is absolutely wrong. You can easily confirm this at any reputable engineering or physics web site. Try AC vs DC safety in google. DC is 3-5 times safer at any given voltage, and the "can't release" voltage is higher with DC, not lower. You might want to actually learn something about electrical safety before further posting.

[@jacquesvermaak373]

Did I miss it somewhere? Did you mention the capacity size of the last two batteries? I can on the videos that the first three are 48V 100Ah, but what is the rating for the last two batteries? I will be connecting two 150Ah and one 100Ah batteries to my 2 x 5KVA Solar Inverters. Glad to see that it can be done.

[@neccron9956]

Please note the the current is additive, so the interconnect wires closest to the output is pulling all the current. That is why they are hotter then the other upstream wires. If you connect the output wires in the middle of the pack, then no single interconnect will take the full current.

[@WillProwse]

Yep that's right

[@teotwawki_je]

How about a test with rings - like UK mains does. I.e. like earlier where bank all connected at one end, but *also* connected to the bus junctions with long cabled from the other end. A sort of double-diagonal.

[@williecai]

Can you change it in different ways from time to time? Also, swap battery banks in different positions to see what happens?!

[@michiganengineer8621]

With those batteries (or similar ones with the same type terminals) would it make sense to run two cables to each bus-bar? Yes, you'd have to be very careful on your cable lengths and crimps, but it seems like that should help with the wire heating.

[@torecrash6493]

Man, this is top notch. Nothings like a visual demonstration like this

[@MrEvadmullek]

Thank You Will, every one of your videos are a learning experience of eminence value. Amazing you give it away. You are a good man.

[@jbaker8871]

Are you adding current draw? Batteries closest to charger would only draw faster if wire size is to small or your resistance values off from weak ,different size, different type of batteries. if your mixing batteries you can order the batteries by resistance . Diagonal is great idea tho as cost of wire thru the roof. Thank you brandon.

[@MrFredsDIY]

Please tell us that you are now doing the same experiment with buss bars for us to see!?!? Great video!

[@flemmingdjensen]

The difference in currents between the rack batteries in parallel are because of the difference in capacity. The larger the batteri the more amps needed to get same SOC . Discharge same pattern where the larger ones deliver more amps becuase of the larger capacity

[@killykilroy]

It might be a stupid question, but why not use a think copper bar directly on the battery connections? I mean a sort of home made copper bar. Buy the copper bar, drill some holes in in, connect. Would't this work, and also be cheaper then a 'seperate' bussbar with short cables to every battery connection?

[@booterone1]

You would get more stable charging/discharge with connecting main wiring to the center battery versus an end one.

[@fishhuntadventure]

Not necessarily- the length of equal gage conductors is the factor in play

[@DingleFlop]

Do the "Posts" configuration you showed in the image regarding alternative configurations.

[@geepeerces]

you could always grind or file the sides down slightly on the ring terminals to fit on the battery terminal strips...

[@HippocratesGarden]

At the 6 min mark, when feeling the cables. Visual thermal imager would be cool screenshot of the pack and cables.

[@WillProwse]

Yeah that would have been awesome. Should have used my thermal camera.

[@vincentmolloy5660]

Great test example Will. Well done 👏

[@tammietimmion6994]

Appreciate your analytics. Ever consider explaining high output alternator charging of lifepo4? I’m considering installing a Nations secondary alternator for my Battleborn bank. But the internal BMS seems to be an issue allowing a complete charge even with a Wakespeed regulator.

[@emilhwilkins3275]

Nice video Will. In the long run it would be best to use a copper buss bars using a bar that is 3/8" x 2 1/2"?(the width of the terminal block) this will balance out all five batteries outputs. Also you can eliminate the cables just by mounting the buss bar to the top of the batteries using some copper spacers larger O.D. the best, you can also use both terminals to connect to the buss bar to increase the DOD and charging capacity.

[@emilhwilkins3275]

Should have mentioned you should use heat shrink on the buss bars between the batteries terminals, then use a liquid rubber paste to cover the exposed terminals or install a hinged plexiglass cover for safety.

[@DEADB33F]

With five packs would you not be even better off connecting +ve at pack 2, and -ve at pack 4? ...likewise if you had four packs you'd probably get a better spread of electrons if you connected at 2 & 3 (this is how I connected the Pb leisure batteries on the boat I used to live on).

[@stefanvanzyl9090]

You calculate the total resistance that the battery "sees" from the cells to the inverter and back, and then compare that total with the other batteries, to know how the spread would be. in your example wiring method, the "outside" batteries will have a greater cable distance, and thus greater total resistance. Battery 1 will "see" four jumps (pos+neg+neg+neg) battery 2 will "see" two jumps (neg+neg), battery 3 will "see" two jumps (pos+neg), battery 4 will "see" two jumps (pos+pos) and battery 5 will "see" four jumps again, (pos+pos+pos+neg) I attribute the current sharing differences in the video solely to internal impedance differences between each pack's true SoC - the 100% mark is a calibrated point, not an absolute point. You'll still also need to make each jump cable the exact same length, so all short black and red cables must be the same, otherwise it'll favor some batteries over other.

[@_loki]

It's all a trade-off. If connected in the middle, the outer packs will always lag behind as the resistance is higher because of the extra cable (out + back). So on charge, they will be the last to charge, and on discharge they will be the last to discharge. Thus the middle cells will wear out first. It's electrically similar to the "connect all at the same end approach", but harder to visualize. That said, it's slightly better than the "connect all at the same end approach" because the current will be far less through the outer wires (~1/4 with four batteries), so less voltage drop assuming you use similar wires.

[@rogerkahrau3168]

I have 6 48v battery's in a cabinet designed for them. It has buss bars in the cabinet for the battery's. Worried about the possibility of bad current sharing, I came up with a different solution. My battery cables are connected at the top of the buss bars. I then took a heavy duty battery cable and connected it onto the buss bars input then connected the other end to the bottom of the buss bar. In this way I am feeding from top & bottom at the same time.

[@tiloalo]

You could have 2 wire between each battery just as you did on the first one. And add some conductive paste on the conductor to improve the connection.

[@CaptBill69]

Appreciate the lesson on options. I wonder how the battery balance would turn out if the main cables were connected to the middle (lower volt reading) battery. ... That might be worth a test on that specific battery set. ... just some thoughts

[@jstaffordii]

@DIY Solar Power with Will Prowse I'm questioning having the batteries daisy chained the way you are showing. You said the wire on battery 1 was getting hot. That would be obvious that without the use of parallel buss bars that cable was carrying the current of all 5 batteries added together. Even though each battery was providing ~30-35 amps the single cable was carrying the entire 200 Amp load.

[@WillProwse]

Yep, that's why I said to use busbars and equal conductors instead

[@shameelali2549]

Can you pls do a video with fully charged same capacity batteries and also do charge test as well cheers.

[@dang6832]

I think that answered my question perfectly. Better, but not best.

[@jodywood]

I would like to see a test with the bus bars.

[@haydnwilde]

Hi Will, you talk of using buzz bars to connect multi batteries. If you were to replace the interconnect cables with oversized cables (eg. equivalent to a buzz bar), would that be the same as buzz bars?

[@tigeroll]

You could put those eye connectors against a bench grinder to make them slightly narrower with no problem.

[@francmauer4473]

A very interesting episode. Maybe next time you will show experiments with connecting batteries in series ...

[@glencooke494]

Do we just take for granted that the wires inside the battery are of equal length or resistance? If we go to all the trouble of doing it correctly outside of the battery and inside your two different types of batteries are different lengths it may cause a bit of imbalance. Just asking?

[@WillProwse]

Yes that's a problem. Hopefully they are.

[@richdobbs6595]

I like the argument, bus bars with equal length conductors are the best solution, even though bus bars might be cheap or expensive. It seems like for keeping things simple, you should just use a better configuration of jumpers, unless you have so many jumpers that you can't install them on the battery terminals, or that the jumpers end up more expensive than the bus bars.

[@IrishSouthPaw]

thanks for these examples, will you be doing the same test with a bus bar so we can see the results there?

[@props-model-shop]

Thanks for sharing your results. Much to be considered...

[@Der_Hannes]

Hey will, i personally would change the order of the Batteries like this: 1 Jakiper | 2 "MyteryBrand" | 3 Jakiper | 4 "MyteryBrand" | 5 Jakiper or 1 "MyteryBrand" | 2 Jakiper | 3 Jakiper | 4 Jakiper | 5 "MyteryBrand" Connect Main Positive and Negative ALWAYS to 2 and 4 Made good exp at this way....would you test this on the neyt video? Have a good time!

[@Der_Hannes]

And please replace the longer wire on the positive side between the Battery packs!

[@marvinsauer8493]

Reverse return (ie your diagonal connection) is a very common designed used throughout the engineering world. If you constructed your wiring with reverse return buss bars or simply reverse return as depicted in this test, electrically there is zero difference. The differences in “supplied amperage” you are witnessing between these server rack batteries is actually minor internal electrical differences within each battery, and not caused by wiring. Do an experiment with reverse return on a buss bar and simple reverse return with absolute equal length cables, you will find there is no difference. But negative and positive cables must have as close to identical length as possible, just the same as your “buss bar” idea, total cable length does matter.

[@danielardelian2]

Exactly. Each battery is connected via a series of 4 cables to the diagonal points so each battery "sees" the same wire resistance. The battery closest to the camera sees 0 wires to the negative diagonal point and 4 red wires to the positive diagonal point. The next battery sees 1 black wire to the negative diag. point and 3 red wires to the positive diag. point. And so on... The battery furthest from the camera "sees" 4 black wires and 0 red wires.

[@michaelalbert8474]

I had the same comment.

[@bkuker]

Yeah I think you and Daniel are right, right? I could not see any way that there could be more draw from the batteries on the ends than the ones in the middle.

[@FullSendPrecision]

Agree. Adding bus bars to the "diagonal" config is the same thing. A diagonal config with bus bars.

[@jimsjacob]

I have questions on this topic. Since my positive conductor will have the 400Amp T-fuse and a battery Isolator switch and as a result, a slightly longer run, should I be adding more negative conductor length to my setup to try and equal that? I’d assume it’s resistance that’s most important and not exact length, but how to determine that? Do I just measure the ohm resistance on each conductor and then add more length to the negative cable if needed to match what I’m seeing on the positive? BTW, my two BattleBorn GC3 batteries will be connected with buss bars. Thanks in advance for any input!

[@fhorst02]

Great test, too bad you stopped at 60% (?) SOC. Draining them till the first low voltage protection kicked in will show how it would perform in a real setup. Charge with solar, discharge at night. Especially as it's a mix and match pack, that's useful information! Many of us upgrade their system as they discover to have not enough storage. Seldom the same configuration can be bought. Busbars work always best for me :-)

[@MrRossi1805]

May you use this configuration and show the effect of the bus bars?

[@jtr82369]

Love my EG4s except the 2gu cables I am using don’t allow the plastic guards to lock in place (I don’t have the rack yet)

[@ronbethmiller]

With the bus bar example would you fuse each Battery... If so, what size fuse for each one with 12v 304ah battery... Thank you

[@danielgrwaldphone2927]

Solar golf car pt4 wish4: Advanced Parallell battery chemistry experiment: Regenerative braking, LTO to LiFePo4 to Li Ion, for super long battery life, fire safety, and current efficiacy. Will it work?

[@RecarroJamesOfficial]

Awesome Content. These videos are very helpful learning material. Thanks!

[@danielchukwu5062]

It always good seeing you do your thing, great job. Thanks 👍