question

kuban-invertor avatar image

Battery balancer for Gel Batteries.

Hi experts! I need your advice. I have lead-acid batteries. Type GEL.

Amount - 72pcs. And three Quattro inverters (10kW).

How much do I need a Battary Balancer to equalize the charge?

According to which scheme is it optimal to connect?

It will be an ESS system with Fronius Symo. Thanks!

Battery Balancer
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forgot to add - 48 volt system

3 Answers
porcini avatar image
porcini answered ·

Due to tolerances every battery has its own values, so litte deviations are quite normal (apart from cell drifts). When you force a battery to a voltage level which is different from its natural one it is harmful in the long run. That is why I avoid using many batterys in parallel and don't recommend using balancers in a lead battery system. I also don't recommend 12V blocks for a 48V system. 2V cells are the way to go. They are more similar (less tolerances) and balancing is done by a careful overcharge. Cell drifts are more rare. That is why I recommend for the 3rd time to go for 2V cells as long as you won't want to buy new batteries after 5 years. But as I see you want to have your own experience ...

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thanks for the info. 5 years is a sufficient period for the system. What do you think about the fuses for each string. Photo as an attachment. Connect a battery balancer with midpoints. How will it work?
eti.png (237.1 KiB)
kuban-invertor avatar image
kuban-invertor answered ·


Thanks for the help! very useful information! What is the best way to connect the midpoints of all batteries?

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You can't. Each series has its own midpoint.

I would really recommend you to sell all these batteries and go for 2V cells instead .. otherwise you won't get happy.

Why do you think that you do not need to combine the midpoints of all batteries? This is not logical (in my opinion). After all, then you get something like islands. And each island will have its own tension. I think it can be balanced. Need more info.
porcini avatar image
porcini answered ·

Holy cow! ... 72 Pcs of single 12V(?) gel batteries in a 48V system? I promise that won't last that long, no matter if balancers are used or not.

Looks like a very big system to me with 3 10kVA Quattros in it. Who told you to use that many small batteries? You better should use 2V cells for a system that big.

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Initially, the project was supposed to be 20 batteries. But in the end it turned oгt that way. Now my task is to make the system as balanced as possible. Do you think this is impossible?)

Take a look at the datasheet.

https://www.victronenergy.com/upload/documents/Datasheet-Battery-Balancer-EN.pdf

For a 48V system you need at least 3 balancer. But with such a big system you will need a "few" more.

kuban-invertor avatar image kuban-invertor Matthias Lange - DE ♦ ·

Thanks for the answer! I tried to draw the placement of inverters and batteries.

It is believed that the wires from the batteries to the bus

bar should be all the same length.

Without exception, and despite the fact that the bus bar is close.

I understand that this is a big expense of wire.

But if this is a solution to the problem, then does it make sense?

What do you think - how many battery balancers do I need?

What is the cross section of the wire connecting the midpoints?

Also 50 mm²? Not a simple object I have to do.

I hope it will be easier with your help. thanks

ess-victron.png (29.2 KiB)

IDK such a huge system is very uncommon and as @Porcini said normally this would be build with 2V cells.

Maybe 3 Sets of 4 12V together!? So you will end up with 18 balancers.

Datasheet says:
In case of series-parallel connection, the midpoint interconnecting cables must be sized to at least carry the current that arises when one battery becomes open-circuited.
- In case of 2 parallel strings: cross section 50% of the series interconnecting cables.
- In case of 3 parallel strings: cross section 33% of the series interconnecting cables, etc.

-> 50mm²/3 = 16,666666mm²

kuban-invertor avatar image kuban-invertor Matthias Lange - DE ♦ ·
Your help is important to me! Should the wires from the battery bundles to the busbar all be the same length? What do you think about the battery connection scheme (in the attachment)
kuban-invertor avatar image kuban-invertor Matthias Lange - DE ♦ ·


Here is a diagram. I was advised by one person

ess-victron2.png (10.7 KiB)

Your diagram is totally wrong.
Only the first batteries(on the right side) are (over-)charged and discharged, the other batteries not.

It should be like this (not 100% sure):

I think you should take a look at the "Wiring Unlimited Book" (chapter 3.3 - and everything else)
https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf
(also available in other languages https://www.victronenergy.com/support-and-downloads/technical-information - change this site into you language at the top right)

kuban-invertor avatar image kuban-invertor Matthias Lange - DE ♦ ·


Hello! What do you think about the fuses on each string?

eti.png (237.1 KiB)

Dear Matthias , Help!

kuban-invertor avatar image kuban-invertor Matthias Lange - DE ♦ ·

Dc fuses on all strings of batteries?