I have just installed quite a sound system in my boat and I am wanting to install a on board automatic batterey charger to plug into shore power so when I am listening to my tunes at the dock my batterey dosnt go dead. Can anyone suggest a size type, or brand ? All together my entertainment system can pull up to 400 amps 12v. This is all off of one batterey.

Lincoln makes a nice one, it is usually found around refinery or bridge building sites. It is called the "welder".
I think you have amps and watts confused. Anyway, nobody wants to tolerate that much sound from some one elses stereo.

Are you saying that the boat only has 1 batterie?? If that is the case --a word of advise -- get another batterie and use it for the tunes. Install a batterie isolator so that they both charge when the engine is running.

If your sound system has a 400 amp draw your system will not last very long powered by 1 battery. Also a battery charger will not keep up with that amount of draw. You need a battery isolator and a least 2 batteries to get some play time if not 4 deep cycles. If you choose to not add additional batteries by a battery buddy so you are able to start the boat after you have killed the battery. Good Luck, Forrest

multiple batteries are a must with a high-end stereo, go with the blue top gel cell by Optima, they have 1000 cranking amps and will recharge from zero to full capacity in about an hour.

You need large reserves. You also need to recharge your deep cycles over night as they will not recharge in a short period of time. The yellow tops have 124 minute reserve capacity and the reds have 120 minute reserve capacity. You can get group 31's in a gel cell that have 235 minute reserves. They will last longer than the optima's. Forrest

ohms laws says 400amps x 12volts is 4800 watts thats
a lot of sound not accounting for loses in the amps and wiring
so. I really think you mean 400 watts
cause I use 2x1600rms watts amps for DJing large venus and they need a 15amp 120 volt outlet for each one.
Anyways if your pushing 400watts thats about 35 amps at full volume so u need a second battery a single would be discharged
enough in 2 hours to not start your boat.

also peak audio power and rms power are different
30 watt rms can have 90watt peaks.
and some amp manufactures list peak not rms.

As far as which onboard charger to use, I feel that the Newmar electronic chargers with the external battery temperature sender are among the best you can buy. They will not overcharge your batteries, they will not boil the water out of them. They are also among the most expensive.

Pro Mariner "Flyback" series chargers are also premium chargers, but are more affordable.

Both of the above chargers will also provide juice to power your stereo up to their rated output of they are plugged in. Statpower, and several other chargers will NOT provide juice to power your load, they will wait till the battery is low then recharge it even if lefdt plugged in.

I have heard complaints about the cheaper Guest electronic chargers, but they are the cheapest and if not left on for weeks at a time should do an acceptable job.

Under no circumstance should you buy an "old tech" ferrite core transformer charger. They are hard on the batteries and are very heavy.


There have been some good suggestions in earlier posts: If you keep a single battery, go to a large deep cycle group 31 battery. The optimas and other AGM batteries are expensive and are "better" but if abused will still fail after a couple of years. A cheap big conventional oversized deep cycle is a far better bargain.

A battery buddy will indeed shut down your party when the battery reaches a undercharged level. This will do TWO helpful things: 1) it will preserve enough juice to start your motor and get you home (or allow you to recharge via the alternator). 2) it will keep you from running your battery "too low" which is harmful to it and will shorten its life dramatically.

If you go with two batteries, you can install a switch to allow you to listen off the deepcycle battery, but switch to the other battery when it goes dead to start your motor.

Alternately you can wire the accessory and stereo load to run off one dedicated battery, while leaving the motor and trim system to run off the other. An isolator is required to allow your alternator to charge both banks of batteries in this configuration.

M