solar advice needed

Guys, I have a 100 watt panel w/ controller hooked up already. it works fine, keeping a dedicated 12 volt battery topped off. So far, in the last year, I haven't needed anything more. I only use it for stereo, vhf, depth sounder and occasional nav lights.

i have an electric trolling motor and I am thinking about using it occasionally in the dingy, along with another smaller 12 volt battery. The simplest thing for me to do would be to rig some jumpers and store the battery next to the existing house battery, in parallel, removing it to the dingy when I want to use it. If the battery was drained flat during dingy use, would it be too much strain on things to hook it back up with jumpers and re charge?

 

I see no reasons why that wouldn't work. Without solar input some charge will flow from the large battery to the small one, with solar input the small one gets most of the charge current until both batteries reach the same charge level.

Draining a battery flat is not a good idea!

 

Thanks CDK. Maybe then I will just use the trolling motor till it gets "tired" and row back. ;-)

Also, I just ordered one of those small lithium ion jumper batteries from amazon. Anyone have experience with those? I assume there is a limit to how much stuff you can load up onto just one 100 watt solar panel.

 

We always measure a solar panel with their open voltage and SHORT CIRCUIT current. All what happens if you load your solar panel too much, is that the voltage will drop, but you can't damage the panel. You should check with those ion jumper batteries, that it does not charge your flat batteries more than the given maximum charge current of those flat batteries.

 

I just repaired a small MPPT unit. My advice to you is, to have one of those units between your battery and solar panel. What it does is to give you up to 30% more power from your solar panel due to the "M (maximum) P (power) P (point) T (tracking) . Have a look at this website a 20 Ampere unit should be fine. They are automatically switching between 12 and 24 Volt. It senses what kind of solar panel you are using 12 Volt or 24 Volt.

 

I have a gizmo that disconnects the battery from the load if the voltage drops below a certain level to prevent the battery from draining too low. The solar panel can then raises the voltages.

 

That is very useful. Most of the sailors have their solar panel horizontal mounted and then a MPPT unit will help to get more out of your panel. If the sunrays with their radiation shines at a lousy angle, the voltage will be too low to charge any energy into your battery. The MPPT unit boost it up and then pump current bursts into your battery, which would give you the additional energy. Very energy effective.
Bert