Charge Dinghy Battery

[Knot In Court]

I have a 2014 R 27 delivered in October 2013. I have decided to use an electric Motorguide trolling motor to power my Portland Pudgy Dinghy. The Battery is a 24 series deep cycle, which will be kept in a battery box to the rear of the water heater when not on the dinghy. I would like the ability to hook the battery up to the boat's charging system when the battery is low. I will just unhook it once it is charged. It may also be possible to include this battery with the house or engine battery banks if needed, which is probably unlikely. In any event where is the best place to hook the battery up to accomplish this and what size wire should I use?
Thanks,
Bob Mudge

 

[RProffer]

The battery charger on the R21-EC is capable of charging 3 battery banks. That may be an option. You could also charge it off the generator, if you have one. Or possibly charge it off your alternator. Lots of options depending upon how your boat is configured. It should be easy and inexpensive.

 

[Newtugnut]

One simple solution is too hook up the battery temporarily with cables to the house set.

Take care hooking these up and consider say a 30a slo blo fuse in the positive lead of your hookup

The only issue may be current sharing on the house set vs the dinghy battery

If you can, measure the charging current into the dinghy battery with a clip on dc ammeter
(Sears has one for <100$)

Charging current should not be more than 25% of the a-hr capacity of the battery

Eg for a 100 a-hr battery do not charge more than 25a for the bulk charge phase

 

[sdubnoff]

It is generally a bad idea to directly hook one battery (not in the same logical bank) directly to another. If you were, for instance, to wire the dinghy battery directly to the house, however temporarily, you might find the currently running in the from the dinghy battery to house battery, rather than vice-versa. You should install a charging relay of some sort between your dinghy battery and whichever other one you choose. This is precisely how the charging between the house, engine and thruster batteries is controlled in the stock configuration.

The battery combiners simply sense voltage and, when the voltage is high enough to indicate that a charge source is attached, connect the two batteries together.

An inexpensive, but well proven, battery combiner can be found here:
http://yandina.com/c100InfoR3.htm

Steve