battery question

ok guys need a little help with a friends boat, he has a newer 18ft crestliner that came with a bow mounted trolling motor (12volt system) on the newer crestliner boats they have a main power switch near the outdrive control arm that shuts the power off to the starting battery, but not the trolling motor. What would be the best way to recharge the trolling motor battery when on the water? I though about a perko switch, but it already has a turn off switch to the main starting battery, is it possible to just run battery cables to the alternator from the trolling battery? or should I go to the perko? and just one more question, he can only get about 3hrs of trolling off the brand new deepcycle battery, if I were to wire another deep cycle battery positive to positive ect. ect. would this increase trolling time?

Re: battery question

If he has room, a bigger and/or second deep cycle battery (connected in parallel to the other) would be the way to go for more trolling time. Unless he spends a lot of time with the main motor running, he's not going to be recharging that current battery that much if he hooks it up to the alternator. Plus, he'll want to make sure the starting battery remains topped up.

Re: battery question

You need to check the size (capacity) and the "health" of the existing battery. Charge it up and take it to any auto store and have it load tested. Just because the troller has a battery does not mean it will run an unlimited amount of time. How fast you run and how long one operates the motor determines how big the battery needs to be. The smallest battery I would recommend is a group size 27 deep cycle. Next -- trying to keep a trolling motor battery charged while on the water is a lost cause. Why?? Unless the engine has a high capacity alternator 100 amps or so, there is just no way a short run from hole to hole will keep that battery charged. And NO! Solar panels are not a solution. Yes -- two batteries in parallel will roughly double the run time of the motor.