marine battery charging question

[aceman387]

i had a question on charging my marine battery i use for my trolling motor. on my days off i will go fishing in the morning say 6am to 9 am then come in do some work around the house throw the battery on charge for3-4 hrs and go back out fishing  till evening and then charge it again when i come in at   night is there such a thing as charging to much or would i be better off with just letting it sit in the afternoon and charge it just at night.  my boat is just a 10 ft pond prowler and most of the time  i just use the slow speed so the battery never really gets real drained i guess  was wondering if i was shortening the life of my battery charging it too much some days

[ohioriverrat]

The very best way to know if a battery NEEDS to charge is by using a digital volt meter. Your 12 volt battery should have about 12.7 volts when fully charged. A battery is normally considered completely discharged at anything below 11.6 volts. All measurements should be taken with the battery at rest, like an hour or so after last use, or just before first use.

I think you will find that if you have a good quality deep cycle battery, you probably have plenty of power to run both sessions. But your charger plays an important roll too. A cheap charger can boil the water right out of a battery. I like to charge batteries around 3-6 amps, and use a charger that is equipped with a "float" option. In other words, once the battery is fully charged, the charger will drop the amperage to a very low level, just enough to maintain the full charge. RVs use this type of charger, and most marine grade chargers will do the same thing.

So, if you have a good battery, and a good charger, it will not hurt to do exactly what you do. But if you wat to measure what you do and then make adjustments to your routine, even better! Might save YOU some energy.

This link is a table of battery discharge state. You may find it useful if you want to really know what your battery is doing.

http://www.xantrex.com/web/id/329/DocServe.aspx

Cheers,

Mark