I have twin engines, and a 20amp battery charger that supports two banks. I
want to add a stereo and an amp to the boat. I want to add a third deep
cycle battery just for the stereo, but I would like it to charge while at
the dock and charge while the engine is running. How can this be done?

Also, should I keep my batteries on All while plugged in to shore power? Or
should they be in the off position.

Glenn

"Glenn Deneweth" wrote in message
...

I have twin engines, and a 20amp battery charger that supports two banks.
I
want to add a stereo and an amp to the boat. I want to add a third deep
cycle battery just for the stereo, but I would like it to charge while at
the dock and charge while the engine is running. How can this be done?

The easiest thing to do (and best in my opinion) is to use a pair of
"battery combiners" to connect the stereo battery to the other two
batteries. The combiner monitors the voltage on the batteries, and if it
sees a voltage high enough to indicate that charging is taking place (~13.5
volts) then it connects the two batteries together so they both charge. It
doesn't matter if the source of the charge is the alternator or battery
charger. Its simple, automatic, easy to install and foolproof.


Also, should I keep my batteries on All while plugged in to shore power?
Or
should they be in the off position.

If your battery charger has two bank outputs then it should be connected to
each battery, thus there is no need to switch to BOTH for charging reasons.

How are your batteries and switch wired? Ideally, you would have one
battery, through a switch, to one engine. You may have a third switch to
connect the two batteries together, or one (or both) of the main switches
could be a 1-both-2 style.

My recommendations are that you leave the battery switches configured so
that each battery is connected only to its associated engine. If you have a
problem, such as a battery goes bad or an alternator stops charging, you
will discover it in a timely manner and can then switch to the opposite
battery to start the disabled engine. If you always have the switch in the
BOTH position, you won't know of a problem until both batteries are dead,
and then you don't have many options left.

Rod

"Rod McInnis"
The easiest thing to do (and best in my opinion) is to use a pair of
"battery combiners" to connect the stereo battery to the other two
batteries. The combiner monitors the voltage on the batteries, and if it
sees a voltage high enough to indicate that charging is taking place
(~13.5
volts) then it connects the two batteries together so they both charge.
It
doesn't matter if the source of the charge is the alternator or battery
charger. Its simple, automatic, easy to install and foolproof.


Sounds like a plan!

Thanks!

Glenn