RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q's?

vsheetz
vsheetz Registered Users Posts: 18 ✭✭
in Off Grid Solar & Battery Systems #1
Two pairs of Trojan six volt batteries, now existing - 37' class A motorhome:
  • Pair #1, the original pair, located on one side of the coach under the entry steps. All load connections to coach at this pair.
  • Pair #2, added later, located on the other side of the coach in a storage compartment. Inverter co-located in the same storage and wired to this pair of batteries.
  • Pair #1 and #2 connected in parallel by ~15' of heavy cable.

Adding solar components:

Thinking to have battery monitor (Tri-metric, or similar) connected to pair #1 - as this is where the negative lead to the coach loads are for shunt connection. Then have solar controller (Morningstar TS-60) connected to pair #2 - as there is no room under the steps at pair #1.

I am concerned the battery monitor will not properly reflect the status of both battery pairs. Also concerned of the charging effectiveness of not having the pairs no co-located. And how about the battery temp sensor and battery voltage sensing that would be connected to pair #2.

What issues with this setup? Other setup suggestions?

thx!
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    As long as the Charge controllers have their ground wires connected at the shunt /common bus, the battery monitor should be accurate.

    The wiring should be per the Smart Gauge recommendations so that the parallel battery bank remain balanced.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    I would say "as long as all current going in and out of both battery pairs flows through the monitor's shunt" it will work. Usually the shunt is on the negative wiring of the batteries. Beware of any ground wiring that may bypass it.
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  • vsheetz
    vsheetz Registered Users Posts: 18 ✭✭
    #4
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    Yes, that's the problem I think I have - all RV loads will pass through the shunt as they are connected phycally located at battery pair #1, but the charge controller will be connected to battery pair #2. So while the discharge will be shown accuratly, the charge will not. And is this a big problem, as I will have the charge controllers display to see what the charger is doing?

    Attachment not found.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    That's a big problem because it pretty much defeats the purpose of the monitor in respect to one set of batteries. It will only show what is going in/out of the "under steps" batteries. And it will show that inaccurately if it's been programmed for the capacity of both.

    If you want to monitor both you need to break the negative connection to the "storage bin" batteries and run another heavy wire from them to the "under steps" batteries.

    You'll need to up the wire size considerably too. 4 AWG is much too small for a heavy current run between the two battery sets across 15 feet. It may be fine for taking the 60 Amps from the charge controller, but if you connect something like a 2kW inverter to the batteries there will be serious Voltage drop under load.

    If you can, run two lengths of 4/0 between the battery sets. Leave the shunt connection and chassis grounding where it is on the "under steps" set. Take the positive for the RV loads off the (+) of the "storage bin" set.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    simply put, move the - lead from the storage bin batteries to the other side of the shunt. If the connection is difficult then consider using a bus there.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: RV with two pairs of six volt batteries, but the pairs are not co-located - solar Q'

    Like this (unless I goofed something up).
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