help with batteries

[claytonr]

I have hooked up some lights on the front of my boat (two-55watt) for finding my way around at night. I will also be running a spotlight and a trolling motor. I planned on getting two batteries, one for the trolling motor and one for the lights. My question is what do you think is sufficient. Could I use a normal 12v car battery for running the lights and use a deep cycle for the trolling motor? I know nothing about batteries, and don't really understand on how the numbers (cold cranking amps, etc.) would relate to this specific situation.

 

[miloman]

Re: help with batteries

claden I suggest that you use a deep cycle marine battery for all your needs. Another suggestion I have moved all my accessories to deep cycle battires used for golf carts I find them to perform better and last longer between charges

 

[ebbtide176]

Re: help with batteries

a regular car battery needs to be kept fully charged, as in cranking the motor, then being charged by the engine's charging system. for lights, trolling, and using power without running engine/recharging, you would be better served with a deep cycle battery.<br /><br />if you're only going to be running the lights when running engine, and if the deepcycle you use for the trolling motor is also charged by engine, you should be fine with the same battery. but you do have a separate battery for engine?

 

[Jack Shellac]

Re: help with batteries

Just be sure you get marine batteries. They are built for heavier service than autos, due to boat bouncing and pounding. A starter battery and a deep cycle for accessories and trolling motor is a good setup.

 

[Paul Moir]

Re: help with batteries

Cold cranking amps is for starting batteries and that tells you how many amps your battery will supply at 0degF for 30s and not drop below 7.2v. MCA or CA (Marine Cranking Amps) is the same thing but at 32deg F. <br />You're more interested in the Amp-Hour (Ah) rating of a deep cycle battery. It tells your how long your battery will last before needing a recharge. That, of course, depends on your load, so you have to calculate it. For example, your lights are 55W. W = V x A, and say your battery is a 12v one, then A = 55W / 12V = 4.6A. Ah = A x h(ours) so a 100Ah rated deep cycle battery will last for 100Ah / 4.6A = 21.7h(ours). <br />Running the trolling motor will consume a lot more juice. Say your manual says it consumes 43A max. Your 100Ah battery will then last 100Ah / 43A = 2.3h when operated at full throttle. The trolling motor will consume just slightly above half that at 1/2 throttle.<br />If you insist on using an starting battery, which is a very bad idea as the above posters indicated, you should observe the RC (Reserve Capacity) rating of the battery. RC is the number of minutes a battery can supply 25A at 80degF and not drop below 10.5v, where battery damage gets much worse. So the equivalant of Ah for RC rated batteries is Ah = RC / 2.4.<br />Keep em cool and keep em fully charged and you'll get a lot more life out of you batteries. No battery likes to be fully discharged.

 

[claytonr]

Re: help with batteries

Thank you all for your wonderful responses. Paul, your information is exactly what I needed to help me select the right battery. Does anyone know if you have to go somewhere special to get a golf cart battery.