Charge controller needed?

[boznian2]

I have an Optima (yellow top) battery on my trailer which has until now been 'fed' power from the vehicle via what looks to be 12 or 14 gauge wire through cigarette lighter style plugs and many connections. Surprisingly it has always been good to go for whatever we needed. Now however I am going to tax it a little heavier, so I upgraded the trailer wiring to 10g for ground and aux power and the only connection is between the TV (Jeep Grand Cherokee) and trailer via the 7-pin connector. I don't currently use solar but may in the future.
Should I put a charge controller in now?
Suggestions for brand/model?
Is it true that if I leave the trailer plugged into the TV it can actually draw power from the TV battery even if the TV is not running?
Without a controller do I risk over charging the trailer battery?
Is it true that a dead trailer battery can't be brought back to full charge with just the 10g wiring? (Like I said, never had a problem even with the old wiring)
THX!

 

[rayra]

'aux power' in a 7-pin is usually hot with the key off, is it not? I mean that's what that pin is supposed to be there for. So yes it can 'drain' your vehicle battery, but the two batteries are basically equalizing potential. Not a great thing but ok as long as both batteries are healthy and you don't have something in the trailer drawing a lot of juice.
if it was my setup I'd interrupt that aux power feed on the 7 pin with a solenoid so it's only hot while the vehicle is running / things are being charged. Or otherwise interrupt that circuit. All depends if you want to draw down both batteries as one. Or if you deliberately want that trailer battery passively sucking on the vehicle battery. Are your two batteries even matching / similar capacity?

You won't overcharge the trailer battery just having it hooked to the vehicle battery, and when the vehicle is running to load / draw of both batteries just look like one to your vehicle's voltage regulator, so there's no overcharging there either.

 

[boznian2]

I would say 99% of the time the trailer is unhooked if the vehicle is not running, but the 2 batteries are not similar at all. I think a disconnect switch/solenoid is probably a good idea. As long as I remember to do it...

 

[dreadlocks]

Your tow vehicle is only going to feed a few amps through the trailer plug, wont be a great charge source, so no its not worth the cost of a charge controller.. On a Travel Trailer the wiring really only supports absorbing/floating a battery, if it needs a bulk charge your better off providing that via other means (Solar/Generator).. for example last time I left camp with my battery in a low SOC, I drove 6h home.. and when I plugged it in at the house I had only recovered about 25% of the charge.

When your not pulling your trailer, simply unplug it from the tow vehicle.. or rewire the vehicle side of the plug, add a relay that switches on w/ignition.

 

[boznian2]

I guess we must have just been lucky and never really used much out of the aging Optima. Like I said, it has always been up to whatever we needed after a few hours drive. Maybe I'll have to look a little harder at a solar setup - no room for any kind of a generator. Thx

 

[boznian2]

I guess I should also ask is it possible to have a setup where the vehicle AND a solar panel are charging the battery at the same time while under way?

 

[DiploStrat]

I guess I should also ask is it possible to have a setup where the vehicle AND a solar panel are charging the battery at the same time while under way?

Yes. Done it for years.

 

[dreadlocks]

usually works alot better for a camper trailer, as you tend to camp in the shade but when driving its likely to be getting direct sunlight unless its overcast.. If your vehicle is only providing 3-4A, and your solar is providing 8-10A, you should be getting 11-14A while driving and thats suitable for the bulk portion of the charge.. most single battery onboard chargers are in the 10A range.

Solar will also provide correct voltage at the trailer battery, this will let it reach 100% SOC, and faster.. whereas the tow vehicle is going to have quite a bit of voltage drop given the distance and thats not helping anything at all.

 

[luthj]

Take note that solar power will also feed back into the vehicles system, and can reduce charge rates if the alternator voltage is lower than the solar+batteries equilibrium voltage. Essentially the battery will be at the alternator voltage most of the time (minus or plus any voltage drops in the wiring).