charging car battery through solar controller

[SoulRaven]

I apologize in advance, because I'm sure this topic has been discussed ad nauseum.  In any case, while I'm sitting here completing my cargo trailer conversion, I've been using a small solar trickle charger to recharge my truck battery (F150)  ... my buddy mentioned "why don't you hook up the output from your charge controller for your solar to some  jumper cables to your truck battery?".... 

I thought , indeed , why not?  But I trust the experts here to shoot it down if it's a lousy idea!  
and I'll be quite thankful that someone has saved my "solar" batteries from a humiliating death!  

Thanks in advance,

Pat

 

[John61CT]

Consider building in a permanent facility to do so, isolating/combining both circuits, House vs Starter.

Choices between A big wiring vs B DCDC charger.

Do both banks desire different charging voltages?

Doing enough driving you want the Alt to help charging House?

Stationary boondocking enough you want solar to keep Starter topped up? (this scenario, but ongoing).

Could you want Starter to help carry house loads?

 

[B and C]

BlueSky's 3000i is designed for just a scenario, charging the house batteries with a separate output for the starter battery.


http://www.blueskyenergyinc.com/products/details/solar-boost-3000i

 

[SoulRaven]

BlueSky's 3000i is designed for just a scenario, charging the house batteries with a separate output for the starter battery.


http://www.blueskyenergyinc.com/products/details/solar-boost-3000i

Both of you asked really good questions.  The truth is, my solar trickle charger worked really great!  

I'll have to think this all through.  Thanks a lot to both of you. 

Pat

 

[WalkaboutTed]

Yes, we too have the 3000i and the connection is easy.  We're not using that feature, though.

But we also have the CTEK d250s with the Smartpass.  Those units, once the solar battery bank is fully charged, will charge the engine battery-at much more than a trickle- with as many solar watts as you have connected. We have our 100watt portable panel connected to that one. With that, and a jump pack, we'll use the engine battery along with our battery bank with little concern. The van came with an AGM marine battery in the engine compartment, but we'll replace that with a deep cycle when we destroy first one.

The CTEK units are expensive though.  
Ted

 

[SternWake]

As long as the wiring to engine battery from solar controller is not in parallel after sundown all should be well.

My preference, when I had two separate batteries, was to keep the one starting the engine, from ever seeing any loads other than the starter motor itself, and thus never requiring any topping up. I prefer ALL solar current to go into depleted battery, not sharing even even a portion of that wattage with the engine battery.
Once absorption voltage has been reached the amps start tapering and then there is excess poweravailable, and some of the solar controllers will divert this extra and the engine battery is a good place to send it.

 

[DLTooley]

I think the issue is more whether an alternator circuit to charge the house battery will have the unintended consequence of overcharging the starter battery with solar.

 

[John61CT]

I think the issue is more whether an alternator circuit to charge the house battery will have the unintended consequence of overcharging the starter battery with solar.

Not sure what you mean? All significant charge sources should go to all banks, but primarily (wrt max amps, voltage sense, temp compensation etc) to the bigger more expensive more depleted one.

Overcharging is not really a concern, but if it is for you, get a low-end DCDC charger to do it.

Or stick to cheap FLA on the starter and check your levels more often.

 

[DLTooley]

Not sure what you mean? All significant charge sources should go to all banks, but primarily (wrt max amps, voltage sense, temp compensation etc) to the bigger more expensive more depleted one.

Overcharging is not really a concern, but if it is for you, get a low-end DCDC charger to do it.

Or stick to cheap FLA on the starter and check your levels more often.

I haven't had any problem, but I only run a 50 watt solar panel and am planning on an upgrade.  My house battery connects to the battery terminals, as does the solar controller, so all charging happens at that point.  This was an evolution from an alternator only system.  I am concerned that the starter battery will be overcharged while the house battery is being recharged.

 

[John61CT]

My house battery connects to the battery terminals, as does the solar controller, so all charging happens at that point.

Do you mean you have two batteries paralleled all the time?

If so, that is just a larger Starter bank, House means kept separate, perhaps joined only when charging.

And ideally any batteries joined together into a single bank are matched, same model purchased together.

Not that big a deal if not, as long as you're not joining a big new expensive true deep cycle battery (which is suited for House use) with a pseudo-deep-cycle actually a cranking or dual-use battery.

I am concerned that the starter battery will be overcharged while the house battery is being recharged.

Depends on battery type, genearally don't worry, as soon as they're joined they equalize, and then if one is full sooner it will accept very low amps.

Starters are usually cheap and robust anyway, if you need to replace a little more frequwntly NBD.

It's the pricey deep-cycles you want to last 10+ years you should make sure of giving optimal care.

 

[DLTooley]

If so, that is just a larger Starter bank, House means kept separate, perhaps joined only when charging.

Depends on battery type, genearally don't worry, as soon as they're joined they equalize, and then if one is full sooner it will accept very low amps.

It's the pricey deep-cycles you want to last 10+ years you should make sure of giving optimal care.

I do a manual disconnect on the house battery at the battery box.  I forget to do so rarely, and that has not been a problem.

Thanks for the info on the equalizing charging - that was my concern.  It has not been a problem at 50 watts and was concerned it would be at 150 watts.

My Wally World Marine is still holding out, with my modest usage.