connect coach and house batteries?

[altblank]

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!

[MNtundraRet]

I would not recommend having the chassis battery(s) connected "full time" to the house batteries. The Chassis (starting batteries) are not deep cycle. They will draw down first before the deep cycle batteries if any 12v device is in use.

The temporary hold button is meant to use when needing help starting the engine.

[wa8yxm]

If you connect the two HARD. then if you do something stupid (And you will, we all do) like leave the headlights on.. You are... In trouble.

So there is a device called a "Trick-L-Start" 3 wire hookup at the battery isolator solenoid.. one lead to HOUSE. one to MAIN. and ground.

IF the house batteries are charging/charged. it will "Connect" the chassis to keep it charged as well.. IF NOT or if the voltage drops below some point.. it Isolates.. So you still have power in one of the batteries you can use to crank up Mr. Onan's contribution to your RV (or whatever generator you have).

[altblank]

hey all. thank you for your very valuable replies. there are a bunch of great suggestions, which i will take up over the next few days:
- find out parasitic draw
- fix the root cause of the chassis battery's discharging

in addition, i'll pick up a 100w solar panel and plug it in to the chassis battery, just to be sure it will never die on me. will also replace the battery; i'm sure a few months of sitting at 0 is likely not very good for its longevity 😉

i already have a bunch of cables and a spare charge controller (picked up 2 full sets earlier and connected both panels to a single controller that maintains the house battery), and have the remaining pieces still lying around.

i'll respond in detail once i've had a chance to test the parasitic draw off of the battery, and will check individual fuses to figure out what exactly may be going on. thanks!

[MrWizard]

Just a tip, extend the steps turn off the step switch, some have a light. That will be on, many steps are wired.to chassis battery , double.check your storage compartments lights are off , also entry/porch and security/docking lights
I have seen lots of weird mods done to RV wiring

[Gjac]

I would just disconnect the neg cable on your chassis battery set your HF multimeter to 10 amps and put the leads between the neg post and neg terminal and see what your parasitic draw is. Post that number here and we can tell you what to do next. To see if your chassis battery would charge when connected to the house batteries just turn your key to the ACC position don’t start the eng and take a reading on both batteries they should read 13 + volts .

[pianotuna]

KD4UPL wrote:
What you need is called Trik-L-Start.

I love my Trik-L-Start

There are also voltage sensitive relays. I use one on my generator battery and I'm well please by it.

Do make the effort to find the parasitic load.

[Ed_Gee]

KD4UPL wrote:
What you need is called Trik-L-Start.

What KD4UPL said. Works great on our coach too, letting our solar or shore power harge both house batteries and coach battery..

[theoldwizard1]

Lwiddis wrote:
Matt's right. Get it fixed right. It will never fix itself and makes your vehicle undependable.

AGREE !!

Start by buying an amp clamp meter. Under $75. Make sure it does DC amps. Simply clamp it on either the positive or negative battery cable in the engine compartment. You might get a reading for a couple of minutes after turn off the engine before it goes to very near zero.

It you me getting a reading, you will need to do more investigation. This can be a bit daunting for a novice but there are a lot of videos on YouTube.

[KD4UPL]

What you need is called Trik-L-Start.

[CA_Traveler]

altblank wrote:
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
This will initially cause the higher voltage battery to discharge to the lower voltage battery and then solar will charge both during the day and both will discharge at night due to whatever is causing the excessive drain.
- 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 This will add the additional drain of the solenoid to the above.

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? Yes the battery boost solenoid.
thank you!

I also have full battery disconnect switches on both battery bank posts. That does leave battery self discharge which is low.

[Lwiddis]

Matt's right. Get it fixed right. It will never fix itself and makes your vehicle undependable.

[Matt_Colie]

Hey Alt,

You really should just bite that bullet and fix it right the first time. It's an 18yo coach and someone has connected something to the chassis battery that should not be there. So, pop the hood and look for what got added first. If you don't find it, attach two wires with alligator clips to a small (like interior light size) light bulb.

Put that in series with the main engine (aka chassis) battery and start pulling fuses and disconnecting things. Neither the keep-alive power for the ECU or the radio should light a small light bulb, but if something does, find out what it is.

When you have that found and removed, the find a Trik-L-Start or similar to keep the chassis battery at full charge.

Matt

[way2roll]

altblank wrote:

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!

You're not wasting solar, you just aren't leveraging it for charging your chassis battery (coach and house batteries are the same thing). And you shouldn't have to. And a shut off would stop the drain. You wouldn't continually run water to fill your FW tank because it had a hole in it would you? You would find the leak. Your Chassis battery (like any car or truck) gets charged by the alternator when running and if things are working as they should, should not need recharging for a reasonable amount of time. A week is unreasonable. House/coach batteries however get used while camping and thus the reason for the solar charger to keep them topped off.

You are attempting to put a band aid on the problem. You need to find the reason for the chassis battery drain. Or at a minimum, install a shutoff to stop the drain.

On edit - something to consider with your proposed solution of linking the House and chassis batteries together to benefit from the house battery solar charging. Whatever the draw is on your chassis battery could be strong enough to now also drain the house batteries in spite of adding them to the solar chain. The point is that you don't know what this draw is causing the chassis battery to be drained in a week. And if you don't know that, you don't know that the solar which would now be required to charge yet another battery, is enough to offset that drain. You could potentially exacerbate your problem by spreading the drain to the house batteries.

[BFL13]

altblank wrote:

BFL13 wrote:
Run that from inverter on house

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

I was able to fashion a socket to socket cable using 12v plugs that goes from the house powered TV panel socket down to the engine batt powered dash socket. Tricky getting polarities right reversing end to end.

Another way is portable solar just on the engine batt.

Hard to parallel the batteries from inside instead of external jumper. The Ford isolator is ignition controlled. I suppose you can go through the emerg start somehow--Class C in sig doesn't have that so don't know how.

Easier with a Chev via 7-pin where 12v is always on with engine off.