What is the Best and Safest Way to Connect Lithium Batteries in Parallel for RVs and Boats or Homes?

If you are looking to buy LiTime batteries please use this link. It does not increase your price and it give me a little pocket change. Get 6% off by using my Promo Code Ricketoff6
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I wrote an article about this a year ago and I am finally getting around to making it into a KZbin video. The written version is short but it has more details. Please give me feedback if you have it. Wiring batteries in my Method A is not a disaster but, the more batteries you have in parallel, the harder the batteries will work and the shorter their life will be.
For more RV Power support articles see my website www.TravelingLightReflections.com
This video was made from article # 7
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Here is my current list of informative RV articles on my website.
List of Articles
1. Choosing How to Power Your RV An Analysis of What You Really Need
2. What is an Amp Hour Ah and How Does it Apply to Your RV?
3. What is a Watt Hour Wh and how it applies Amp Hours and to your RV? Also a short summary of RV batteries
4. Why You Need a Shunt Battery Monitor in Your RV
5. Evaluating How Long Your RV Battery Will Last Off Grid
6. Stock Solar with 12V RV Refrigerator Not Charging Battery
7. The Best Way to Connect Batteries In Parallel
8. Interactive Tool to Evaluate How Long Your Battery Will Last During Certain Weather, Battery Sizes, Loads and Panel Wattages
9. A Simple Way to Add Extra Solar Panels to the Existing Furrion Solar Controller
10. Using Water Columns to Represent Charging a Battery
11. How Does a 50 Amp RV Service Compare to a 30 Amp RV Service?
I also have a growing list of Ukulele articles and Videos.
"See 10 Reasons Why You Need a Traveling Ukulele in Your RV" As well as other related stuff!!!
www.travelingl...
/ 769783158357242

[@offgridwanabe]

What about Method C, all cables the same length go to a bus bar then a large cable goes to the charge / discharge apparatus.

[@TravelingLightReflections]

An advantage to your suggestion on method C is that you could use smaller wires to each battery. The disadvantage it that there would be more connections. Connection failures are the most common failure in a working system. This usually comes from a failed wire terminal or lug crimp. Limiting the number of connections is a high priority in my personal opinion. But your method C would serve the same purpose. There are applications where your method C is a better choice, for example when the batteries can not be installed next to each other due to space constraints.

[@richardstott7777]

Option c also means any problem with a connection affects only one battery and will be easier to detect.

[@bigKDL]

@offgridwanabe is spot on the way he describes is the only way to perfectly balance all the batteries traveling light is wrong

[@JFSmith-nb8hf]

My batteries are connected with 1/8 in. x 5/8 in. copper buss bars, I think the resistance would be negligible. On the other hand, it would take very little effort to move one cable to the other battery. Good advice, thanks.👍👍

[@malk6277]

I came to make the same comment. Seems to also lend itself to safer isolation of one battery or the other: if for instance you want to work on one battery bank while the other continues to provide power.

[@davidrogers-b1r]

use a bus bar with two or more batters.

[@TravelingLightReflections]

If done by a professional who can guarantee twice as many crimps will all be done perfect. For the small gain in similarity I would rather see beginners do it with less crimps. Pro do not need this video.

[@titusllewelyn]

I am a retired electrical engineer. I designed a numer of devices that used large industrial batteries. Your suggested method would help a little. The danger in connecting batteries in parallel is that if one cell in one battery develops an internal short that heat will be generated and a massive amounty of current will flow from the the other batteries. A fire could result.

[@hansonic2938]

Thanks for the warning. What about placing a fuse on each battery terminal directly to prevent this worst case?

[@titusllewelyn]

@@hansonic2938 - Good Question. You Tube is full of ideas. No matter what you do, remember that no two batteries are the same. Also remembeer that the battery is part of the charging system. All batteries have an unwanted internal resitance. Lithium Ion batteries have a low internal resistance. You connect batteries in series to up the voltage. When connected in parallel the current is upped. A fuse would add to the resistance and lower the power delivered by a small amount. It would also become part of the charging system. I have a 48 volt golf cart with 4 12 volt lead acid batteries. I use a BatteryMINDer Model 483CEC1 48 V 3 Amp charger that pulsates the batteries. It is temperaturre limited and can stay on the cart charging 24/7 if I wanted. It charges overnight. The original charging system was left intact. I personally do not like paralleling at all.

[@balsmit1]

​@@titusllewelynhow about using a terminal block sir?

[@titusllewelyn]

@@balsmit1 - It is not the type of connection. It is just not recommended to parallel batteries. To get more current batteries are connected in parallel. To get more voltage batteries are connected in series. That is in use. If they are charged in parallel the charger can not determine what is happening with each battery. Perhaps in a model plane or something it might be OK to use, but for charging the batteries need to be seperated.

[@mytubing101]

That is when a balancer comes in to play

[@leapnlarry]

This is one of the first things i learned when i designed my solar system 4 years ago, very true. I should make a short about it. Larry

[@TravelingLightReflections]

Yes, you should. So many DIYers just to method A, because I do not realize there is a difference.

[@aaronsmith593]

That is an excellent idea, it will cut down on cable or buss bars resistance. 😊

[@prepparig144]

Great video, very helpful. Also viewed that video link you put in one of your responses of the person testing the 3 setups. It's all black and white now. Thank you!!

[@TravelingLightReflections]

I am glad it was helpful for you. Thank you, I appreciate the feedback!

[@Ed19601]

I have a very hard time to believe this. Any regular wire will have a negligentv esistance. Are you using meters of resistance wire to connect your batteries.?

[@TravelingLightReflections]

I do not have a video recording of this but if you do not believe this watch this video. He recorded the currents for each battery. Ohms Law, V=IR or I=V/R. At a constant voltage, current is inversely proportional to resistance. kzbin.info/www/bejne/laG0YYqgpbh4l5Isi=VJ-nIWsvUDvWNpU5

[@whochecksthis]

It is more about voltage drop, from load vs cable length, don’t forget contact resistance as well… When two identical batteries are connected together, the shortest path has the least resistance, coupled with voltage drop and load drop, the closest short cable battery drains faster than the further ones. Forcing round trip through both batteries equally, the batteries experience equal resistance, and equal voltage drop, resulting in more even discharge.

[@Ed19601]

@@whochecksthis voltage drop is the result of resistance. Not sure what connectors you are using but those also should not have any relevant resistance

[@whochecksthis]

@@Ed19601 … everything except a superconductor has resistance, and when you connect to the closest side of the closest battery, the further lengths have resistance. It adds up, resulting in uneven discharge.

[@starcruiser9325]

@@whochecksthis Spot on. When there’s hundredths of a volt between 90% and 100% charged, every micro ohm matters. Connecting in the way shown is the correct way to negate any differences and is so easy to do.

[@makantahi3731]

ok, do you have any physical reason why you claim that the faulty method is faulty, for example the resistance of the wire, are we talking about the distance between the batteries in cm or km, if it is in cm then the voltage drop through the wire in the further battery is negligible, that's how I charged several batteries at the same time and the farthest battery had a difference of maybe 0.02v on a total of 5m of cable. your correct method is correct only because it equalizes the currents of both batteries, regardless of how good the connection is, for example if the clamps are connected to an oxidized contact, it can happen that only half the current flows through the wires that would otherwise flow if the connection was good, this way how much as long as this current flows equally from both batteries

[@falcorthewonderdog2758]

No mention of any lithium battery monitoring device. You can't just hook lithium batteries to a system designed for lead acid you need a charging controller to isolate the lithium battery for the lead acid battery.

[@TravelingLightReflections]

If you are building a lithium battery from lithium cells you need a Battery Management System (BMS) for each battery. This BMS will manage the cells contained in each battery, as a unit. This video is about batteries. All lithium batteries already have BMSs managing the current and voltage of the cells. No large lithium batteries are sold without BMSs. You can get small lithium batteries for model aircraft that do not have BMSs. The ones that do not have BMSs will have balancing leads with a JST connector. However, this video is about power system batteries.

[@davidbuchanan327]

Good info for me as Im currently designing my system in my Lance truck camper. Space is limited and the camper came with only one battery. I have removed the microwave and added 2 lithium batterys, solar charge controller and some fuses and buss bars in that space. From the buss bars in that space I will connect to the camper battery. So I will have 3 100ah batterys and 400 watts of solar and a 2000 watt inverter. The camper also has a propane generator which connects to a transfer switch. I hope it all works when Im done.

[@TravelingLightReflections]

Check out this power system interactive I created. It may help you predict how well you planned system will work. kzbin.info/www/bejne/o3qulGtnhriSfNk

[@bivideo7]

This is absurd. The only cause of the problem you're trying to solve is corrosion in the cables. If the cables are correctly sized and remain clean this is pure fantasy. It's about charge voltage.

[@TravelingLightReflections]

@@bivideo7 The problem is getting DIYers to understand how to arrange their parallel batteries so that the resistance is distributed better and each battery gets equally discharged under heavy loads. I see the first method too often. I looked at your videos, you are a smart guys so I am guessing you did not actually watch the video. Corrosion is not mentioned or a concern. You know enough about electricity to know that the first battery will get worked harder than the one with longer wires.

[@Bilskirnir030]

Can you define/elaborate on “a period of time”. Days, weeks years? Running time/idle time etc. thanks in advance

[@TravelingLightReflections]

I do not have a definitive or data based answer for you. I can give the best science or physics based answer though. It takes the batteries a long time depending on how hard you are using them. You will not see an effect within days or weeks but over months and years. However, the harder that batteries are worked, the greater the in use difference, in each batteries discharge you will get. Let me explain that. Think of it like this, In example method A, if you pull a high current from the batteries, battery 1 has slightly less resistant than battery 2. Battery 1 will discharge slightly more than battery 2. It would be working harder to supply the load. It would essentially lose more energy and its voltage would be slightly lower than battery 2. When this high discharge current is removed, Battery 2s voltage would be slightly higher and it will charge battery 1 until they are balanced. This process happening over and over is what method B prevents. Method B just simply prevents this by the physical nature on the wiring. Each battery the same wire length as all the others. Therefore each has the same resistance in the circuit. This is because they are all in a loop, as opposed to a string with one on the end like method A. So, method A is not going to ruin your batteries but method B is better for them. If you have new lithium batteries I would recommend changing the wiring to method B as earlier a possible. They last a long time and method B will help make them last. If you are running lead acid, leave them alone. They don't last that long anyway. If you are only, ever, running very low currents, it is probably not worth changing to method B either unless it is a simple task. If you are running an inverter from your batteries, I would make the change as soon as possible. Also if you are running more than 2 of any type of batteries I would change it. I know I did not exactly answer your question but I hope I least gave you a better understanding of how battery 1 gets "exercised" more then battery 2. Oh, part 2 to your question, I kind of answered but, this is only happening during "running time" and mostly during high current loads. During "idle time" the batteries balance each other to equal loads. JT

[@Bilskirnir030]

Cheers. I think the “buzz” word is current. Less pressure on the battery and adding a fuse. @@TravelingLightReflections

[@brycemcleod1]

Can the two lithium batteries be separated by distance... One under the bonnet of a car and the second in the boot of the car? I currently have a itech lithium battery under the bonnet that i run my camping fridge off and want to add a second to double the capacity

[@TravelingLightReflections]

You can do this under two conditions. One, do not use the chassis as a ground. Run equal length wire Red positive as Black Negative. Because you are running parallel batteries you can should wire larger than your expected load and fuse the positive wire. Being as your system currently has a battery that already handles your load, your single battery under the bonnet, will still get a large percentage of your load, unless you run third wire as I showed in the diagram. In other words. The positive load wire from the positive of battery 1 and the negative load wire from the negative of battery 2. My concerns are, the cost of the wires, the voltage drop, any heat and protecting the wire from a short. Hence the fuse between the batteries. Is it possible to by a double size battery that with will fit in the bonnet? The cost may be more for the battery but it will save a lot on wiring, components and work. It will also be safer. So, yes this is possible but use GOOD wire, fuses and do not use the negative as ground. Determine your max current before you buy wires. This is one source to look at a good variety of batteries. www.litime.com/?ref=q12mEP4EB0Q2EJ

[@notconnected3815]

I think that the point here is, that all batteries should have the same overall cable length (positive and negative added together). Because i guess modern batteries have such a low internal resistance, that it forms a voltage divider with the (also very low) resistance of the cable. The effect could alternatively be minimized by using thicker cables, that have significantly lower resistance compared to the battery's internal resistance.

[@TravelingLightReflections]

Yes , I would agree. That is great, short and complete summary of the idea.

[@djperfecto1]

Dear friend thanks for your video...what is the proper connection of the power inverter?direct positive and negative one battery 1 or 2? Or positive on battery 1 and negative one battery 2? Thanks!!!

[@TravelingLightReflections]

If you have a 2 battery setup with the batteries in parallel, then the inverter should be connected the same as any charger. Use method B. Regardless of whether the battery is being charged or discharged the connections should be the same. Throughout the batteries' life it will get an equal amount of charge as it get discharge. I hope I answered your question.

[@djperfecto1]

I have connected as the B...I was not sure but finally is the best way.also the chargers cables are connected as the B. Thanks a lot!!!!also I don't know if you can help batteries during day are full charge 13.8v as the panels produce power.with no loads and the 12v power inverter off at next morning controler shows 12.7v.batteries are 2x 12v gell deep cycle 150ah each connected parallel.any ideas?connections are ok charger is an mppt powmr 60a maximum

[@TravelingLightReflections]

@@djperfecto1 Your batteries look like they are okay. The float voltage is also higher than the resting voltage. Your solar controller is correctly bringing the batteries up to 13.8 volts. When it shuts down the battery voltage settles down to it's resting voltage. For AGM the fully charged resting voltage can be between 12.7 and 12.85. It depends on the manufacturer and also on the whether there is any voltage drop in the device you are reading the voltage from. Regardless, from all that you have told me, your system is working fine.

[@user-zy2kh2rp4m]

My electric scooter has a 48v 30ah LFP battery. And I want to add another 48v 18ah battery to it. Can I connect both positive and negative in parallel at the charging point?

[@TravelingLightReflections]

Theoretically you can connect these 2 different batteries in parallel. However, I would not recommend it. Others may say it is okay, but I personally would not recommend it.

[@user-zy2kh2rp4m]

@@TravelingLightReflections ok sir but I can use it through change over switch. This way I can use both the batteries one by one.

[@TravelingLightReflections]

@@user-zy2kh2rp4m It is most important that you keep the voltages of all of the batteries in a parallel system equal. If by using a change over switch, you will be connecting and disconnecting the second battery, You will cause a rush of high current between any battery of unequal voltage. If you intend to always keep them isolated from each other and charge the 30Ah and 18Ah separate, you can use a change over switch. Just never connect them together when they have even slightly different voltages. With Lithium there could be a bit SOC difference with a slight voltage difference. This can cause a very high current enough to melt small cables.

[@user-zy2kh2rp4m]

@@TravelingLightReflections sir ji I will use both batteries separately. When I will switch the change over switch on mode A, scooty mains positive and negative will connect on battery 1(30ah). Then scooter will use battery 1 and charging also. When I will switch the change over switch on mode B, scooty mains positive and negative will connect on battery 2(18ah). Scooter will use and charge only 2nd battery. At that time 1st battery will be fully disconnected. What do you think sir about it?

[@TravelingLightReflections]

@@user-zy2kh2rp4m Sounds good!

[@TheCSRTech]

In what way is hook-up B SAFER than hookup A?

[@TravelingLightReflections]

It can keep you from overloading one of the batteries.

[@TheCSRTech]

@@TravelingLightReflections Nope, incorrect, try again.

[@princesunnyboy]

How to connect with 3 batteries or more?

[@TravelingLightReflections]

Many people suggest using a bus bar. If you can make every cable the same length and insure every connector is crimped perfectly then a bus bar is a good choice. To contradict this though, using a bus bar means 2 times as many connector to crimp and more chance of a failure. Also with today lithium batteries the BMS's also regulate charge so it become near impossible to get all cells and all batteries perfect. So, for beginners doing the work themselves and making your own crimps, I would put the 3 batteries in parallel and not use bus bars. If you are a pro you probably not interested in my input but if you can get excellent crimps then go with bus bars. Of course bad crimps are dangerous in all cases. I am just suggesting using as few as possible. Also, I always put the system under a high current load and use an infrared thermometer to look for hot spots that need to be repaired.

[@brianrhodebeck6465]

You didn't mention, Lithium batteries. Having B u s s bars with charging on each Battery is equally Charged

[@TravelingLightReflections]

It is not actually equal but closer with a bus bar and only if the crimps are done perfectly. Plus with the bus bar you have 2X as many crimps. I removed that section of the video because I made the video to stop DIY people from doing Method A.

[@rithlim6016]

Great video! I could be wrong but I think in "Method B more extreme example", if you connect the positive load cable to Battery 3 (versus Battery 4) and connect the negative load cable to Battery 2 (versus Battery 1), you'd get a more even distribution of power while charging and under load. This will better help the lifespan of all the batteries.

[@TravelingLightReflections]

You may be right.

[@Jarda_B]

The resistance of the cable it not as big as you think, if you are not cheepo. if you use 16mm2 cable to cenect them and have proper conection it will not go over 1 ohm in total. 1m of cable like this have 0,00013ohms, if it will not go over 0,5 ohm there is not going to be a noticible difference.

[@TravelingLightReflections]

I knew there was a difference under load that would balance out as the batteries recharge. I have had a lot of people's comments telling me I am wrong. I went looking for other videos and found this. I was shocked at the difference. I created this video based on theory. This video shows actual tests in action. Even though the resistance is low, it still follows that if the cable length is doubled, so is the resistance. I learned from the links video too. I am curious how the quality of a crimp affects the performance. I originally made my video to help people see that they could easily use method B. Here is the other link. kzbin.info/www/bejne/laG0YYqgpbh4l5I

[@starcruiser9325]

When you’re talking hundredths of a volt between 90% and 100% charged, every micro ohm matters and the way you’ve shown it is the correct way to easily equalise between battery 1 and 2 when wiring direct and not from a busbar.

[@nickj7335]

Thanks

[@TravelingLightReflections]

Your welcome. It is an easily overlooked installation error but so easily fixed.

[@twofingers2233]

To the source? Shouldn’t you be saying the load?

[@TravelingLightReflections]

I may have used the term source when I meant load. If so thank you for pointing this out. Being as we are talking about batteries where the current can flow both ways depending on whether it is being charged or being discharged. I wish I had put more emphasis on this.

[@geoffculp2019]

Seems like there could be a diod on the discharge if 1dosent charge or disharge as much it wont be drawing away from others of more capacity n maybe have sepret wires between each for balance charging and monitoring each and not having to unhook them not shure what size diod can carry what ampraje though ones in a car alternator seem big to me guess there called a bridge rectifer in an alternater to though.

[@TravelingLightReflections]

The BMS takes care of the balancing among the cells that make up each battery.

[@EarlBalentine]

Mine batteries look like the Method B.

[@ntal5859]

MY.. not MINE. or are you making LANDMINES.

[@TravelingLightReflections]

Mine do to!

[@bubbafrump74]

If that makes ANY difference at all, it would be sooo negligible as to be completely pointless. Especially with just 2 batteries.

[@TravelingLightReflections]

Do you have a clamp type amp meter? If you do, test it for yourself.

[@thanhha2686]

Cannot believe there were folks making video bc they think they know better. Not necessarily smarter.

[@TravelingLightReflections]

I can not believe you wrote that comment. Do you think this is wrong? If so, do whatever you want. Or, do some research.

[@ntal5859]

In method 1, ALL the current passes via the negative and positive post(terminal) of battery(1) so in effect that will have twice the power loss of terminals COMPARED TO battery(2), assume both batteries supply 50% of the current... So in long term applications you will see a drift in both charge and discharge of both batteries. For the dummies out there, imagine two garden hoses and you trying to force both into one. at the point where they join it will have losses.

[@TravelingLightReflections]

It is much greater too, at high currents.

[@bcrew63]

Better yet, follow mfg recommendations

[@sleddy01]

I love videos that open with music i hate

[@TravelingLightReflections]

Thanks, Not sure what to say but....

[@dany67230]

Method B Not the best method also

[@TravelingLightReflections]

Care to elaborate?

[@DirectCurrent4u]

This is correct!💯

[@davidbalgosky4107]

To expand on that you are correct with load using method B but add to it the charge circuit should also use method B bur reverse the + and the -

[@LarryWebb-g5d]

​@@davidbalgosky4107 So your saying use method 2 but then add the battery charger with its positive going to battery 1 and the chargers negative going to battery 2 ?. What if your going to add 2 battery chargers ? I assume the one battery charger would be applied to battery 1 and the other battery charger applied to battery 2 ?

[@fitzwilly7132]

What a load of bs!!! How do the batteries know who is 1 and who is 2???? What a load of crap!!!!!

[@TravelingLightReflections]

@@fitzwilly7132 The longer wire has more resistance. In fact if one wire is twice as long as another identical wire it will have twice the resistance. But really don’t take my word. You do what you want.

[@ChrisBrocksmith]

NO

[@TravelingLightReflections]

.

[@MrSummitville]

Method B More Extreme also wrong.

[@TravelingLightReflections]

See my other responses.

[@falcorthewonderdog2758]

Yeah that's not going to make any difference.

[@TravelingLightReflections]

It does. It actually makes a big difference. That is why I made the video.

[@mattxr6t]

As an auto elec, yes, it does make a difference.

[@slowbrezze]

wow Ai is doing it's job living loud with Andy

[@GetOnEmTV]

Dudes actually right I'm about to drop a video on this right now I actually killed one of my lifepo4 batteries because of this. Let them sit in the garage for a whole year connected the same way as in the original diagram not the second diagram(the way hes showing you to do it) and the one works great and the other one won't take a charge but I saw a video where you can jump start the one that doesn't take a charge with the one that is fully charged and it'll actually charge back up normally

[@Brian-jz1pi]

I would love to know the reasoning behind it it wouldn't make any difference it makes total sense open up a lithium ion and I believe they're in seres.

[@kschildt1]

What a load of BS! As long as the cable is the proper size for the amperage required and the battereis have the same characteristics...

[@TravelingLightReflections]

You should do some scientific test before you call this BS. There is an incredible difference between the load on battery 1 and 2 in method A when you piggy back and pull off the same battery.

[@kschildt1]

@@TravelingLightReflections No there is not. And your electrical engineering masters degree is from?

[@nixxonnor]

@@TravelingLightReflections If the cable cross section is correctly dimensioned for the current going through the cables it does not matter how you connect the wires to the load/charger. When charging the batteries, they will all get up to the same voltage as the charger is topping off / trickle charging

[@TravelingLightReflections]

@@nixxonnor What you are saying is true only if a low current is being trickled into or out of the battery. As the current gets higher, is when this becomes more extreme. Electricity always takes the path of least resistance. In Method A you can have a huge difference in the current coming out of battery 1 compared to battery 2. Some other critics here are correct that for more than three batteries a bus bar is better. With the bus bar the currents in and out of each battery is closer than my Method B. However, This way doubles the # of connections. A failed terminal/lug crimp is the most common failure. Making good high amp connections takes practice. This video was made for DIYer, not professionals with lots of experience. I made it because I see too many people parallel batteries like Method A. I also made it short so people would watch it. If I was to remake this video I would add the bus bar method too. Even with the bus bar, under heavy loads, there is still a current difference within the batteries. The difference is slightly better and ONLY if the crimps are perfect and the wire lengths are exactly the same.

[@NackDSP]

@@kschildt1 You apparently forgot your first year high school electronics. Draw the equivalent circuit with the resistance of each cable segment and battery ESR. Maybe capture the schematic in LTSpice and run the simulation with a 200 amp load. Look at the difference in current from each battery. Some engineers graduate with a 2.0 grade average and others with a 4.0 average. So you barely got an engineering degree ten years ago, that isn't the same as being correct. You apparently didn't study logic.

[@lormicidemoise9509]

Not good

[@TravelingLightReflections]

Okay

[@paulna5526]

wrong

[@TravelingLightReflections]

Thank you for your well thought out and detailed expert response about this.

[@zigmass4899]

[@TravelingLightReflections]

Peace