12v from 24v Battery Bank ?

BFL13 wrote:
This would not be a normal procedure, but a way to get by for a while. It would require hands on management.

Obviously not balanced but being in parallel for the night should get them evened up some. I know the high one only charges the low one slowly, but it would depend how far apart they are in AH if they have time to even up.

2 amps recharge evening up for 10 hours would do 20AH so they could be 40AH apart at first for instance?

Sure they could, depending on how much power you drew. Every AH you use from the split battery is an AH of charge that it's not getting. (It's not quite that straightforward in practice because charging the battery isn't perfectly efficient, so the unbalance won't be quite as bad as simply deducting your usage, but the concept is still there.)

If you have the space and so forth, you could have two pairs of batteries, one in series recharging and one in parallel discharging, swapping roles as needed.

Edit: misread/misunderstood the question at first. The rebalancing would not be a linear function; the current varies with the voltage difference, so it will taper off as they get closer to being even.

This would not be a normal procedure, but a way to get by for a while. It would require hands on management.

Obviously not balanced but being in parallel for the night should get them evened up some. I know the high one only charges the low one slowly, but it would depend how far apart they are in AH if they have time to even up.

2 amps recharge evening up for 10 hours would do 20AH so they could be 40AH apart at first for instance?

Talk about unbalanced :E Use the dc/dc converter.

..

I would not to it you would always have to keep the draw equal on both batteries because they will never become equal when charging. On the 24v charge they will both get the same amps no mater which one is lower.

It might work if you charged during the day but had no draw them at all during the day. At night if you had the same draw on both.

I use a Victron dc/dc converter to get my 12.5v from a 24V bank. I found it's not a great idea to tap one.

I think it was pianotuna who first warned about that.

So if I charged all day with solar at 24 and the batts in series at 24, but had the rig on one of the batts at 12, then I would need to put the batts in parallel (say after supper till after breakfast--solar disconnected) so they would even up?

I could also swap which batt is being drawn upon at some half way point during the day.

( I am dreaming up an emergency scenario where I have to use my 230w 24v panel with my 12/24 PWM solar controller. That would need the batts at 24v to do a recharge, but I still want some 12v for the rig during the day. )

If you charge at 24V and you only draw down one battery you will eventualy have one battery at say 10v and the other at 14v and it will continue to get worse.

Ok, but what about the recharge in progress? Will the battery being drawn upon still get any charge (reducing its draw down amount)? What about after the draw on the one is removed, will the two in series ever even out?

What if I had a 12v draw on each 12 and charged both in series at 24? Would that keep them even if their draws were the same amps?

I suppose the two 12v draws would have to be separated so they were not in parallel. One from an inverter and the other from the rig's 12v regular draws?

Yes, you could draw 12V if you only use one of the batteries while it's charging.
As you surmise there's no way to use both while charging at 24V.