Battery Question

[GallenH]

For those of us who might want to add battery capability: I've read that with AGM and flooded LA batteries, you don't want to just add a battery; but replace the existing battery(ies) at the same time. Can't remember the reason but it seems like a rule of thumb, correct? Can someone explain why. Also, if your batteries were Lithium, would the same rule apply?

thx! glenn

[rowiebowie]

Originally Posted by GallenH

For those of us who might want to add battery capability: I've read that with AGM and flooded LA batteries, you don't want to just add a battery; but replace the existing battery(ies) at the same time. Can't remember the reason but it seems like a rule of thumb, correct? Can someone explain why. Also, if your batteries were Lithium, would the same rule apply?

thx! glenn

I've also heard that it's best for all your batteries to the same size, make, and age. Probably for proper balance in the charging.

As to the lithium part of your question; most have internal Battery Management Systems (BMS). But I wonder if the BMS would compensate for mixing new batteries with used ones with a few hundred recharge cycles on them. I have no clue on that one.

Good question. I always thought I could later add more lithiums of the same kind to the two in my recent conversion. Now I'm not so sure.

[booster]

As rowiebowie said for the lead acid batteries best to have same brand/model/age/even production run if possible for best use balance for both charging and discharging so the stay even in SOC at all times.


Good question on the lithium, as I don't think this has ever been answered that I have seen.

[ikanode]

I asked Trojan about this issue a few months ago.

Question
With your BMS in the Trillium LiFePO4s, in case one battery failed for some reason is it feasible to drop a new Trillium into the string? Versus, when a lead acid battery fails in an aging string, the recommendation is to replace the whole string.

Below is Trojan Battery's response:

If for some reason one of your Trillium batteries was to fail, yes you can replace it. Just make sure you have charged the new battery up to a solid green indicator to ensure the battery is balanced before putting it into the battery pack.

[RossWilliams]

It is optimal for all the batteries to be the same, but it isn't essential. You can just add a new battery in parallel with no real ill-effects if the existing battery is still good. Here is a link to one explanation.