Where I keep my boat there's no electricity. I am happy to pull out my trolling batteries to take them home to charge them, but was wondering whether it would be a good idea to get a solar panel to trickle charge the starter battery? It shouldn't be too depleted as the motor will add some charge, but could probably benefit from a top up. Can solar panels damage the battery by over charging it if it's left plugged in for a few weeks?

My friend and his family own a remote lake with a small cabin. we use the cabin when a storm blows in, to eat lunch or get out of the conditions and to store some gear and accessories. He keeps 5 or 6 deep cycle marine batteries hooked up in there wired to 2 small solar panels on the top of the cabin. The batteries seem to be holding up fine and they stay plugged in for 7-10 in a row. Sometimes more.  It does take a long time for them to charge but that is ok since they are plugged in for a long time between uses

Also i believe his panels are pretty low end and aren't real powerful so I can only see added benefits to buying nicer panels and having them do a better job and lasting for years and years

I have a friend who has panels on the top of his boathouse (no power to it) and used enough and the proper size panels to run his on-board charger.  Per him it works great and there's no chance of overcharging because his on-board will switch into trickle mode when the batteries are charged.  

There are several solar powered 12v battery chargers available. Most appear to be 20 watt units or about 1.9 amps and 100 watt units about 8.4 amps. The 100 watt unit would definately charge a 12V marine battery, the issue may be automatic shut off. The trickle charging 1.9 amps can be a problem if the battery isn't fully charged to start with  and could create a surface charge only, not sufficient to start your engine. 

Good luck with your search.

Maybe someone has experience and can point you in the right direction.

Tom

Old thread, but here's something I didn't see considered yet.  

 

The biggest issue is probably going to be temperature.  Most batteries don't like to be charged near or below freezing, as this can damage them.  Some batteries (usually some, but not all, lithium batteries), have low and high temperature cut offs to prevent damage from doing this.  I would imagine that some solar chargers (and regular battery chargers) might have this function as well.  And high temperatures, like in the heat of summer, especially if it's uncovered, can create issues as well.  So this will be something you'll want to look into if you plan to use it all year long.  Though I imagine it would be fine for most of the fishing year.  

 

Also, as noted, don't go with the old trickle charger, as they can cause damage and even fires by overcharging the battery.  But most, newer smart charges shouldn't have that issue.  But it is something you'll want to verify.  

 

I used a solar panel on the roof of my boat dock to charge a lawn mower battery for my boat lift.  I'd monitor the battery every few days with a volt meter.