Maintaining a 24V+ Battery Bank with a Victron 12V Battery Balancer

Once you connect more than one 12V LiFePO4 battery in series, how can you be sure the two 12V batteries remain at the same state of charge? All batteries will have a different self-discharge rate no matter how closely matched they are. This can become more apparent as your battery bank ages over many years. The Victron 12V battery balancer can help with that!

*WARNING:* Lithium batteries are dangerous and can result in fire! This video is NOT intended to be instructional or a "how-to" lesson. I am not a professional. Do not attempt anything you see here without first contacting a certified and/or licensed professional.

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*Chapters:*
00:00 Introduction
00:28 Matching State of Charge
01:51 Victron Battery Balancer
02:37 Battery Connections
05:07 Power-On and Testing
06:34 Do You Need One?

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*Disclaimers and Statements:*
► I receive a small commission on purchases made using my affiliated links shared the video description and comments section. The views and opinions expressed here are my own, unbiased, and not influenced by this commission in any way.
► My videos are in no way intended to be instructional "how-to" lessons. I am simply documenting my project for informational purposes. Property damage, personal injury, or death may result, even when following manufacturer's instructions. I cannot be held liable for such damage or injury. It is YOUR OBLIGATION to ensure that you are complying with any local and federal laws as well as code and permit requirements.

[aurumargentum]

I just bought one of these Victron battery balancers for my two x 12 volt 150 Ah = 24 volt 300 Ah system. I love this clear and concise video explaining the issues involved. Really excellent!

[Michael_Mears]

8:13 this is how I prefer to do it. Leave something on the table with respect to upper and lower limits. Over the full range it still provides a usable 90% or 80%. I stay well away from upper and lower BMS voltage thresholds to keep things simple. Also, your advice about not using multiple 12V batteries and use systems voltage batteries instead (24V, 48V) in parallel is how I would approach it, or the advice I would offer others. Most of my systems are or have been 48V, so over the last 20 years they were systems made of 2V, 6V or 12V various lead-acid or AGMs to achieve 48V. Another benefit of LiFePO4, with 48V units available off the shelf, certainly makes paralleling them easy. Another good video. Cheer, from Australia.

[NSaw]

Hey I just installed 3 of these on our 48v bank of 12v batteries!
Been using cheap Amazon balancers since we started having issues with ballance and have gone through 3 of them. Finally decided to just spend the extra money on Victron so we stop having to replace things.
We had used our 4 lifepo4 Enjoybot batteries for a while before we used them in a series config. But once we got the inverters and switched over to 48v even though I had top ballanced all of them (had them all in parallel and connected our victron blue smart charger)
After about 4 months of light use at first, we basically had no capacity because one of the batteries had already gotten very low compared to the other 3.
Once we got the first Amazon special ballancer it gained majority of the 5kw capacity back. Although it still didn't come to full capacity. (I assume because the ballancer's where on all the time instead of just when at a high soc)
But yeah, hopefully these will do a lot better! Definitely excited to have them finally.

[WillProwse]

I have not used one of these, but going by your test, the battery balancer seems to only come on at high SOC, correct? Because at the majority of the SOC curve, the voltage differential between the packs will be either non-existent or very small. Your argument at the end for needing a balancer for solar batteries that are not charged to 100% makes good sense for other lithium-ion chemistries, but I do not think it applies to lifepo4.

And the cell drift in the individual packs from cycling every day is minimal, even when doing shallow cycles. The cell drift is typically only a few percent every couple of months. The built-in BMS passive dissipative balancing circuit is more than enough to keep the packs balanced.

My friend who does EV conversions with lifepo4 cells showed me that when using an Orion BMS with a pretty limited dissipative balance current, was more than ideal for 60-100kWh battery packs with shallow cycles and high surges. Less demanding than solar, but still kept up with cell drift over time. The battery engineers understand this and have tested it for a long time.

What you can do instead is use a 12V battery charger to charge each pack to 100% before connecting in series. Then the two packs will cycle together without issue. Try it out, and over 6 months, check the state of charge to see if one is drifting more than the other. Balancing does not take that long, and hitting 100% SOC is the only time you can balance them anyways, whether you use the victron balancer or the BMS balance circuit.

Now these balancers are fantastic for NMC, LTO and lead acid. Absolutely. More linear SOC curve and large installations need it. But for lifepo4? I just do not see the point of it. The BMS balancers are more than enough to correct cell drift over time.

[RolandOfGileadOnYT]

Got a JK 8S with 2A balancing current, didn't even need to top balance the cells, works like a treat!

[jasonbroom]

I am having a problem with the exact type of setup you tested in this video. After just a few months, I was getting low voltage alarms from my 2024 inverter. I checked and one of the 12v batteries I had connected in series was at nearly zero state of charge, while the other was around 40% SOC. I was really stunned by this, thought it was a fluke, charged up both batteries to 100%, connected them in series and then connected them back to the bus bars for my system. Within just weeks, they were grossly out of balance again!

My question is about how this unit balances. You said it creates a "dissipative" load. Does that mean it just bleeds off current from the battery showing higher voltage until they are close enough, then stops doing anything? It doesn't take current from that battery and trickle charge the other battery until the voltages are basically the same? I want the two batteries to be in balance, but I'd rather not just dissipate (via heat?) current to achieve that. I mean, if that's the only way to do it, I guess that is what it takes, but not exactly ideal.

[sspence]

My understanding is that if using the victron smart lithium batteries, the BMS balances the series batteries?

[JohnMarkMaina]

This is a handy little gadget.. Just follow the wiring instructions and all will be well.. I had done the wiring ad-hoc and it didnt work but after reviewing the argumentation.. All is well now.

[joshg]

This item is exactly what I was looking for, thanks for sharing!

[lazguevara]

I’m running 4 batteries in 12v parallel and they don’t stay in balance with each other will this help?

[Fincabaracoa]

Good video sir.... Q, can I have the balancer connected to the 2 bank battery at the same time having one mini voltage monitor in each battery?

[alexbik]

Even if you use 12V batteries in an UPS application, I would recommend using a balancer. It's true that the internal BMS of the battery will balance the cells (even with a higher current than stated in this video), but the individual BMSes do not communicate with each other. They will balance two groups of four cells but those BMSes will NOT balance those two cell groups. No matter how much time you give them. It would be even better to use a BMS designed for 8S operation, but that's not an option if you buy 12V lithium batteries. Unless you are willing to take them apart, but then you might as well buy the parts seperately and build your own battery.

[patrickbrideauful]

Hi
I am wondering how to wire the balencer on 4 battery 12 volt for 24 olt system

[bowen]

The part at the end seems to confuse cell balancing with battery balancing. As I understand it, only the BMS can balance individual cells, and a balancer such as the Victron can only balance batteries. I think it helps also to remember, the word battery means a grouping of smaller units, and a cell is an individual unit. That is where "artillery battery" reminds us of that general meaning, just as living cells remind us that a cell is the individual unit..

[hamiltonharper]

I have 2 parallel strings in series. I imagine I would have to buy two of these?

[aghbary]

What if I have 24v system but 3 pairs of batteries (6 Batteries). How to install the balancer please. Thank you for this helpful video.

[Zen-mmto]

Hello, thanks for this video !
In a parallel + series scenario(4 batteries), do you recommend 1 or 2 balancers ?
I feel a bit nervous to connect the 2 mid-point 😮

[SuperJVx]

do you know what the 'shelf life' is of those SOK batteries? I have 2 of the ones on the right (viewer's right). By shelf life, I mean the battery sitting on a shelf and not powering anything. Does this shorten the life? thanks

[urbanturbine]

i have a truck with 24V system, 2 series batteries. Does this device drain battery if it is left connected to the batteries?
The system will only go over 24 volts when the engine is running and alternator is charging . It will show about 28volts when engine is running..
So, i assume it would remain idle when the engine is off. Does it use any power when it is idle?

[donavanlawrence]

Hi there
Really enjoyed your explanation
How would i go about using the battery ballancer if i have 2 x 12v in series (24v) just as your video, but have two extra 12v in parallel to increase a/h