Using a dual battery solar charger properly
 

I just received a duo battery charger from China.. Unfortunately the instructions are not very clear at beat and don't address the situation I bought it for. I'm hoping that someone here can answer some questions for me before I wreck something.

I have a 70 watt Coleman solar panel. I currently use it to charge/maintain the battery of my plow truck during the winter... the truck sometimes sits for a month or more at -30 or colder and when I need it to start I just can't afford a dead battery. I have been using the single battery charge controller it came with.

So far so good... This year i plan on onsimultaneously charging and maintaining my garden tractors battery... It has a front mounted snowblower and is a bear to start if the battery is low..

Consequently I bought the duo charger...

My concern is regarding its charging logic.. Can I unplug either the truck or tractor independantly without damaging the charge controller or solar panel.. Truck is battery 1 tractor battery 2.

Should I add a switch in the solar panel feed to the controller to turn off all power to the controller when unhooking a vehicle?

Thanks... I looking forward to learning more

Since you're only looking to do a trickle charge, just connect the batteries in parallel (assuming they're the same voltage) with a PTC or similar (a car light bulb is another option) to limit the maximum current.

I wondered about that... the truck battery is a 1000 amp hour and the tractor 500!!

also can you provide translation... PTC?

Thanks

PTC is a self resetting fuse. Since it might be difficult to find one locally, a good alternative for this application is a car light bulb.

I googled it and now understand what it is and how it works but am mystified how it might work in my dual battery situation.

I wonder if my idea of adding a simple switch in the solar panel line to the CC would work adequately to isolate the panel from the CC when disconnecting one of more of the batteries.

If the PTC or light bulb are better if charging both in parallel on one of the outputs from the duo charger then that would free up the second output for a third battery or bank!

Is there a diagram of the PTC and bulb circuit I could see?

It's just a simple matter of connecting the batteries in parallel with a PTC as a current limiter. The PTC only comes into play if there's a big difference in charge level that would otherwise cause too much current flow.

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Get 2 of these somewhere and install one in the positive lead between the controller and each battery. It will work fine if the battery being connected isn't discharged too deeply.