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TempleinCanada's avatar
TempleinCanada
Explorer
Dec 02, 2020

Two Battery Bank Question

I recently installed a 2nd battery bank that is connected through a transfer switch that switches between shore power and Inverter Power. This new addition has a battery charger that is powered through the transfer switch when shore power is connected.
I have left the OEM bank connected to the OEM 12 Volt side with OEM converter which charges the 12 Volt side of my trailer. I have both the OEM Converter and the after market Battery Charger powered through my transfer switch.
I also have 500 watts of solar on the roof with a 30 amp solar controller that can charge 2 battery banks (fully charges the OEM side and then switches to new side when OEM side is fully charged)
This works great as both sides charge with solar when I am not connected to shore power and when I am connected each battery charger charges their respective battery bank.
So both systems are isolated from each other except when the Solar is charging.
Here is my question: If one of my battery banks becomes low in available amp hours could I connect the 2 battery banks together (with a manual switch)to equalize them (I know it is not ideal, but would be for an emergency only)

My main concern is that the solar controller sees the 2 battery banks as separate, what will happen when it sees both of them together????

Here are the specs of my components
170 Watt Carmanah Solar Panel GP-PV-170M
340 Watt BougeRv Solar Panel DSM-170W + DSM-170W
30 Amp Go Power Solar Controller GP-PWM-30-UL
1500 Watt Samlex Inverter PST-1500-12 Pure Sine Inverter
15 Amp Samlex Automatic Charger SEC-1215UL Battery Charger
30 Amp Samlex Transfer Switch STS-30 Transfer Switch
30 Amp Samlex Inverter Remote Control RC-300
  • BFL13's avatar
    BFL13
    Explorer II
    Dec 03, 2020
    I have had split banks something like that. Did it manually though, no transfer switch. I had the same issue with that where the bank for the usual 12v loads got too low but there was still lots of AH in the inverter's bank but couldn't get at it.

    Anyway, the solar controller (IMO no facts) will still only see one bank when they are paralleled. Whichever bank it is on will not be fully charged while it "equalizing" (be careful using that word to not confuse with over-voltage equalizing of a battery to desulphate it) so it will charge it and so also the other.

    I had two different controllers with their own panels, One set for each bank.

    The OEM bank will be neg grounded to the frame. The bank for the inverter does not have to be grounded to the frame at all--just the wires to the inverter. When you parallel the two banks that will neg ground the inverter bank too if that is an issue.
  • valhalla360's avatar
    valhalla360
    Navigator
    Dec 03, 2020
    First question: What is your purpose in splitting the battery banks?

    I don't see what type of RV you have. If it's a MH, putting the starting battery in a separate bank makes sense in case you run down the house bank, you can still start the motor.

    If it's a towable or you are splitting the house bank on a MH, a single large bank with a low voltage cut off has some significant advantages:
    - You can charge at a higher rate (without complex combiner systems)
    - Puerket effect is less of an issue since you are effectively halving the draw as a percent of amp-hr, so you effectively can pull more amp-hr out of the bank.
    - There are fewer parts to fail.

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