The Hull Truth - Boating and Fishing Forum - View Single Post - Length of battery time on the water?
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Old 10-13-2008, 03:21 AM
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Default Re: Length of battery time on the water?

You can go as big as you want. You are confusing capacity with voltage. I am not aware of any marine battery that is more than 12 volts. People who have 24v systems connect two 12v batteries in series to double voltage.

What kind of engine are you using? My Mercury Optimax calls for a 1000 cca battery. If you are unsure what battery capacity your engine calls for, consult the manual.

If you insist on a single battery configuration, then get the battery with the largest capacity you can - considering how much you want to spend and how big your battery storage area is. Marine "house" batteries can have really large capacities - and a really large size and weight to go along with that. They are not cheap either.

Like I said, so long as whatever battery you get is 12 volts - it will not damage anything.

However, a dual battery setup is better. I have two batteries, one is my 1000 cca starting battery, the other is a deep cycle. When I get somewhere and want to drift (or anchor) with the electronics on, I simply switch to battery 2. That way if I run that thing down I can just switch to 1 and start up. It is a good insurance policy. Some people also carry one of those portable automobile jump starter things.

Batteries last longer if you keep them on an automatic charger when you are not using the boat. Make sure the charger is "100% automatic" before you leave it connected unattended. Many automotive chargers are not automatic and will not drop to a trickle charge once the battery is full. I believe that marine chargers are all automatic. I could be wrong however.

If your battery is only lasting a few hours, then it is possible it is starting to fade. You can take it to an auto parts store and have it load tested. If it fails, or tests good but low - replace it. I would suspect that with only a GPS/sonar and a VHF radio on, the battery is going out on you if it drains after only 2 hours. VHF radios draw almost nothing on standby, and your GPS/Sonar does not draw that much.

A new battery is much cheaper than a tow. Not to mention the hassle of being stuck on the water while waiting for the tow. But you should get the unlimited towing contract from either BoatUS or Sea Tow anyway. The yearly price for the contract is a whole lot cheaper than the cost of one assist.

As for brand names - I do not have a favorite. I like AGM batteries as they are lighter than same capacity wet cell batteries. AGMs are also totally maintenance free, you never have to check the water level in the cells. Some wet cell - but not all - are maintenance free.

Some people have reported problems with Optima AGMs, but by now the problems should have been worked out.

The only battery I would avoid are Auto Zone deep cycle marine batteries. I bought two of them and kept them on an automatic charger when not in use. After a year - one was starting to go out on me. Ill never buy them again.

Sears batteries have a pretty good track record for reliability.