Hello All,

While reading the 'isolator' post, the question (from Joel) came up: Do you leave your chargers on or off when away from boat?

There's some good reading about the 'what fors' and 'why nots' in the primer chapter at Ample Power.com where you can learn the basics of battery management and system design.


A sample of what you will find at Ample Power:

There are many ways to kill your batteries ...even very expensive batteries. Below are a few ways to NOT to treat batteries...
*Overcharge the battery by applying a voltage above 13.8 Volts for extended period
*Undercharge the battery by never charging it beyond 13.8 Volts.
*Discharge the battery and leave it that way for a few days or weeks.
*Let the battery sit unattended without charging for 3 weeks or longer.
*Repeatedly discharge the battery beyond the optimum 50%.
*Slosh the battery around when it is deeply discharged.
*Boil enough electrolyte from the battery that the plates are exposed to air.
*Periodically add more acid, or unpure water.
*Use a ferroresonant charger in a liveaboard situation.
*Sock the battery with a high output alternator that produces more than 40% of the Ah capacity of the battery.
*Mount the battery where it regularly gets above 90*F.
*Charge it hot until you can't even touch the case anymore.
*Use a big inverter on a small battery and run the inverter until it cuts out from low voltage.
*Freeze the battery in a discharged state.
*Use a starter battery in a deep cycle application.

The battery you choose should match the way you use it. The very thick plate liquid batteries can provide years of trouble free service if they are used mostly for weekend trips where most of the recharge is done at dockside using a small charger. That is, low rate discharges and long slow charges. If you stay out for longer periods and use a high output alternator or battery charger on a daily basis to recharge, then golf cart or heavy duty 8D batteries are appropriate. They'll take a daily discharge and accept a fairly high rate of charge so that you won't need to run a genset forever. Expect to replace the units frequently if used extensively.

I leave my Guest 15A charger on nearly the entire summer but I live on the boat so the batteries are always in use.

I have noticed the starboard battery looses electrolyte during approx 1 months time. It can and has gone below the plates. The port battery never looses electrolyte. My guess is the starboard battery does all the house work and the port is designed for reserve/engine cranking.

The battery charger should assume the house loads and keep the batteries charged.
If you leave it on all the time I would keep a jug of distilled water, turkey baster and a hydrometer on hand and check the battery fluid every couple of weeks.

I also swap batteries from port to starboard each year to give them an equal use.

-Karl

Try installing hot water heater timer on charger to let come on an hour or so a day. I mentioned this in above discussion. Sorrydog