charging a deep cycle battery on board

R

randy becraft

Seaman Apprentice
Joined
Jun 25, 2005
Messages
36
Hi ,Just bought a deep cycle battery as a sorce for my sonar and radio/light's.Trying to save starting battery for starting... Also can use this with trolling motor on john boat...My question is, is their anyway I can charge this battery underway with out over amping it and frying it?Was thinking about an inverter to run my trickle charger on,but it would zap main battery once engine is shut down unless I disconnected it wouldn't it? Thanks
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: charging a deep cycle battery on board

All you need is an ACR or dual battery switch and let the engine charge the battery just like it does for the starting battery. Using one battery to run and inverter to run a trickle charger to charge another battery is about the most expensive, inefficient and ineffective way to accomplish this task. A dual battery switch is about 30 bucks, bullet proof, and versatile. Use the SEARCH feature on this forum and the keywords DUAL BATTERY SWITCH and you will have enough reading to make your eyes bleed. What you are suggesting shows you were thinking but it is outragiously ineffective and the two alternatives are simply far more effective. Keep in mind that trolling motor batteries that run trolling motors tend to be deeply discharged and must be "fully" charged immediately after use to get any life out of them. Trickle chargers take way too long to do that so you need a much higher charge rate. Even the engine charging system would have a tough time fully charging a deep cycle battery unless it had an output rating of 30 amps or more. Even then you would need to run wide open for a couple hours to fully charge a deeply discharged deepcycle. Most folks install an on-board charger that you plug in at the dock at the end of the day. A 6 amp - 10 amp charger will top the battery off over night and costs 40 - 80 bucks depending on where and what you buy.
 
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