connect coach and house batteries?

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hey all. we have a 2004 coachmen freelander 3100so with the ford e-450 super duty engine.

i recently replaced both coach and house batteries (we bought the rig 1.5yrs ago and these were simply old and wouldn't hold much charge), with new interstate 12v agms. house got a group 27 and coach got (if i remember correctly) a group 24.

now the house battery is part of a solar charging system. 2 100w panels through a 30amp pwm charge controller maintain the house battery, and this has been working like a champ for the 10 or so months this has been in place.

however, the coach battery is a different story altogether. even though nothing is running, it runs down entirely within a week or so of sitting. i suspect that the alternator is bad, but don't want to dig in and see what's going on just yet (don't have the skills *yet*).

i'd like the solar panels to charge both house and coach batteries if possible, and am considering two options:
- one, add a positive wire between both batteries (assuming they're grounded to the same setup) so any overage from the house battery trickles down to the coach battery
- two, change the momentary battery boost button to an actual toggle (and leave it on), assuming that this won't screw up the larger converter or other systems

any advise is appreciated... if i'm clear to go option one (which i prefer), is there a shorter path to connect both batteries together instead of routing an 8gauge wire between house steps and engine bay?

thank you!

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hornet28 wrote:
You have a drain someplace. Use a battery shutoff on the coach battery

agreed totally, there's a definite drain somewhere. but a shutoff means i'm wasting the excess solar power that's generated for free, and i'll just be that bit closer to having the engine battery work better... but not quite.

thanks!

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BFL13 wrote:
Run that from inverter on house

thanks, but I don't have an inverter on the house battery; only a converter / charger.

[hornet28]

You have a drain someplace. Use a battery shutoff on the coach battery. Here's an example

[BFL13]

Plug a 2a maintenance charger that has a 12v plug into the dash cig lighter socket

Run that from inverter on house Not efficient but who cares with solar

[way2roll]

It sounds like you may want to find out what is drawing on your chassis battery that's causing it to drain like that before going through any mods. A chassis battery should not discharge completely in a week. Something is drawing it down - a light left on, the radio etc. You could (or should) install a disconnect on the chassis battery and shut it down prior to putting the RV away for any length of time. Granted an alternator could be part of the problem but it sounds like it's going dead in a week of sitting and not running in which case neither is the alternator.

You did mention you just replaced the batteries. Did this problem occur before you replaced them?

If you wanted to try to see if a solar charger would help, try a stand alone model for little cost before running any wires.

Car solar charger