Car Stereos: installing a radio powered by batteries?, trolling motor battery, deep cycle battery

Question
alright its not on a car but a car expert will know if there is any way to do this. im going on a 3 day canoe trip and want to install a head unit on my canoe i have the space for it and can enclose and waterproof, but its going to need power to play for a few days without a motor. the only way i can think to do this is with batteries (a few lol). is this possible and what size and how many will i need. also what would be a good ground and is there any other way other than buying a portable radio or something? also if you have any ideas on what type marine deck and speakers that would also help. thx

Answer
Hi Andy,

This isn't something I've tried, so I can just give you some ideas on what I think would work.  

If you're set on using a marine audio system, then really the only effective power source would be a deep-cycle battery.  Something designed for a trolling motor would probably work out pretty well.  The average current draw of a marine CD player with a couple speakers would probably be less than 5 amps; however, that's a bit much for stacking up a bunch of D-cells.

A trolling motor battery should be able to handle the current draw, but eventually it will run out.  You might try using a solar-powered trickle charger to keep it charged.  There are a few inexpensive models that run around $30-$40.  These are fairly low-power and wouldn't be able to keep the battery charged while it was in use, but if you have a lot of dead time it might be able to keep the battery topped off.  Of course, the down side to a solar charger is that you wouldn't be able to just connect it overnight; you'd need to have some daylight hours available when you wouldn't be using the audio system.

I would caution against using a 12-volt motorcycle or lawn tractor battery.  This type of battery isn't meant to be discharged all the way; doing so will quickly ruin the battery.  A deep-cycle battery is made to be fully discharged.  

I'm honestly not sure what kind of results you'll get using a trolling motor battery with a small audio system; it's just not something I've ever tried before.  Hopefully you won't end up with a few hours of audio then two days with a dead battery.  

Note that marine head units don't come with a built-in antenna; if you want to pick up AM/FM radio broadcasts, you'll need to purchase an antenna in addition to the head unit, speakers, and power source.

In the end, you might find it more practical to pick up a water-resistant portable boombox, like Sony's "Sport" series.

Hope this helps!

Brian