My goal is to build a semi-portable system to transfer between my house and my trailer. I have twelve 285W Silevo solar panels four of which I will be mounting on the trailer and eight for the house. I will be using a Midnite Solar Classic 150 charge controller, four 6V Fullriver DC250 AGM Batteries and I have one Xantrex Prowatt SW2000 12V Inverter.What I am hoping to do is to configure the four batteries in series for 24V to be able to maximize the power harvest of the eight solar panels at my house (the Midnite string sizing tool will allow this 24V battery configuration with four parallel strings of two panels). If I drop the battery bank down to 12V I can only use four panels at a time. My question is can I configure the 12 volt inverter to be used with a Blue Sea 9001e dual bank battery switch to pull power from each 12V set of two batteries (so to speak a sub-bank 1 and sub-bank 2) while keeping all four wired in series? The Blue Sea switch has a setting for bank 1, bank 2 or banks 1+2.Thanks for your input!

You really want a 24v inverter. Very common.That switch is not designed to change voltage configuration.And no you cannot draw 12v from all four at the same time as they are in series.

howardq99 wrote:can I configure the 12 volt inverter to be used with a Blue Sea 9001e dual bank battery switch to pull power from each 12V set of two batteries (so to speak a sub-bank 1 and sub-bank 2) while keeping all four wired in series? In theory it can work, but it will be a real challenge to keep each set of two in balance to be properly charged at 24v.I've done something similar..drawing off 1 12v battery in a series string of 36v. Things get out of balance very quickly, and series charging is not very forgiving.

Brain trouble here. :( I know that the controller allows twice the wattage of panels when batts are 24 vs 12.I know that half the amps charge 24v batts the same as twice the amps do 12s. So if you do 24-24 at 8 amps DC output that is as good as doing 16 amps output with 24-12.But where does it say you can have twice the wattage on the same set of batts by going 24 instead of 12, so you get the same amps---which is worth twice as much for recharging?Please explain. I know I am having a problem here! :)

You are really making things complicated for yourself. I'd just use a 24v inverter in the RV. Trying to pull 12v out of a 24v bank is asking for trouble. The bank will get out of balance very quickly, shortening it's life. I take it you're going to move the charge controller, batteries, and inverter back and forth between the RV and house? I hope not often. That's a lot of work to do it once. I can't imagine doing it several times. Why not leave it all in the RV and fix up a plug to connect the additional 8 panels on the house when the RV is parked there. You can then plug in whatever home load you were going to power to the RV system as it sits there.

BTW that is a lot of solar on just 4 batteries.

Battery Bank/ Inverter Question | Good Sam Community

15 Replies

time2roll
Nomad
Oct 23, 2016
BTW that is a lot of solar on just 4 batteries.
KD4UPL
Explorer II
Oct 23, 2016
You are really making things complicated for yourself. I'd just use a 24v inverter in the RV. Trying to pull 12v out of a 24v bank is asking for trouble. The bank will get out of balance very quickly, shortening it's life.
I take it you're going to move the charge controller, batteries, and inverter back and forth between the RV and house? I hope not often. That's a lot of work to do it once. I can't imagine doing it several times. Why not leave it all in the RV and fix up a plug to connect the additional 8 panels on the house when the RV is parked there. You can then plug in whatever home load you were going to power to the RV system as it sits there.
BFL13
Explorer II
Oct 23, 2016
Brain trouble here. :( I know that the controller allows twice the wattage of panels when batts are 24 vs 12.

I know that half the amps charge 24v batts the same as twice the amps do 12s. So if you do 24-24 at 8 amps DC output that is as good as doing 16 amps output with 24-12.

But where does it say you can have twice the wattage on the same set of batts by going 24 instead of 12, so you get the same amps---which is worth twice as much for recharging?

Please explain. I know I am having a problem here! :)
2oldman
Explorer II
Oct 22, 2016
howardq99 wrote:
can I configure the 12 volt inverter to be used with a Blue Sea 9001e dual bank battery switch to pull power from each 12V set of two batteries (so to speak a sub-bank 1 and sub-bank 2) while keeping all four wired in series?
In theory it can work, but it will be a real challenge to keep each set of two in balance to be properly charged at 24v.

I've done something similar..drawing off 1 12v battery in a series string of 36v. Things get out of balance very quickly, and series charging is not very forgiving.
time2roll
Nomad
Oct 22, 2016
You really want a 24v inverter. Very common.
That switch is not designed to change voltage configuration.
And no you cannot draw 12v from all four at the same time as they are in series.

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Battery Bank/ Inverter Question

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