Battery Charging Question

Millhouse2020 · May 22, 2012

Hello everyone,

I have a question regarding charging batteries. I have a spare battery on board my boat which is dedicated to the trolling motor. I am wondering how long it should take, approximately, to recharge the battery while running the main engine. I know after several hours of trolling this weekend for example, the battery did not regain a significant amount of charge judging by the battery meter on the trolling motor itself. I would like to know what I can expect in terms of recharging ability when Im on the water and not able to use a plug-in type charger and have to rely on the main engine to charge the spare. I also have a 1-2 watt solar panel as well but Im sure that would take several days to fully charge a battery, if not longer. My main engine is a 60HP E-Tec if that impacts the process. Your feedback is appreciated, thanks to all.

Millhouse2020

Roy · May 22, 2012

Don't expect to recharge your trolling motor battery with you main outboard. You'll need a dedicated charger for that.

misfish · May 22, 2012

You need to dedicate an onboard charger, to that battery.If you have room,set up 2 deep cells.Longer day for you.

Fisherman · May 22, 2012

As the others have said, the O/B motors generally only put out at higher rpm's. Some 4 strokes have better alternators and give a reasonable charge at lower speed. Recharging deep cycle batteries is usually limited to C20, or 20% of the batteries capacity so you don't damage the plates. I'm estimating it would take your O/B a number of hourS to recharge the battery running at pretty close to full tilt.

As for your solar panels, here is reality: The average 12 volt, 15 watt solar panel will put out one amp (1A) per hour in direct sunlight. Direct sunlight is what you get from about 9:30am to 4:30pm and that;s with rotating the panel to face the sun directly(not on an angle). You do the math, 7 hours per day, you'll get about 7 amps. Take into account that batteries self discharge as part of the chemical process and you're blowing steam up a mouses butt. Some will say that their little 5 watt panel fully charges their battery in short time, it's physically impossible...but not mentally. Get the hint..