question

amidships avatar image

Is there any Victron device that allows me to mix LiFeP04 battery sizes?

Hello,


I am dealing with a van upgrade that has a single existing 110 Ah LiFeP04 battery. The system will be upgraded with multiplus, smartsolar mppt, orion, cerbo

The target is to have a 200 Ah battery system and we are currently considering several options.

- Adding one 110 Ah battery. (The state of the current battery os unknown)

- Replacing the system with 2 x 100 Ah batteries (Space is limited and we would like to avoid this solution)

- Replacing the system with 1 x 200 Ah. (Preferred solution so far)


If we go we option 2 or 3, I was wondering if there is any way to re-use the old battery even if amp and size are not the same? Could it somehow be hooked up to the system without reducing the performance of the new battery(ies)?

Thanks

MPPT - Solar Charge ControllerLithium Batterybattery chargingBMSsmart shunt
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2 Answers
Alexandra avatar image
Alexandra answered ·

@amidships

In theory it should be ok to add the battery if it is a 12v system it should balance out. Just make sure before adding it that they are both fully charged. Dont add a half charged one to a full one.

Different brands are not good to mix as they often have different bulk charge, float voltages and c ratings. But same brand different capacity should be ok in 12v, not recommended though generally (maybe an idea that is a carryover from lead based systems where adding old to new and different capacity was considered a bad idea)

How the original was being charged may be a concern,. With a bit of therapy from a victron charger could possibly sort it out. you could always wait for your system to run a bit and then see. The one brand we had worked with specified at max a 12 month max span when adding more to the bank. It may be due to the fact that were pouch cells not prismatic.

At the end of the day though if in doubt swap it out and as you were saying if you need 200ah and space is an issue then go for the final and preferred solution from the beginning if it is not too much of a financial issue.

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Thank you @Alexandra.

We have decided to go for a new 200 aH

Yes I agree with Alexandra

cpt-pat avatar image
cpt-pat answered ·

If the batteries are the same chemistry and connected in parallel, it should not be an issue. Matching battery sizes and SOC is only a concern with series-connected batteries.

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