Re: Onboard Battery Charger
An on board battery charger is not a battery charging another battery, however a 'jump-box' basically is.
A permanently installed on-board charger is a 110v powered device that, when plugged in or run by generator, supplies a constant trickle charge to your battery(s) to maintain them at optimum level. A quality trickle (smart) charger will shut itself off when the battery reaches it's charge capacity and will monitor the battery, activating again once the charge drops. However, this has to be plugged into a 110v outlet for operation.
If you are depleting the battery's life while powering devices and are worried about the ability to start the engine, you have a few options available:
1) Put in a second dedicated 'house' battery on a selector switch. This allows you to be away from the dock, run all electrical devices, and reserve an isolated battery for starting the engine when ready. However, this would entail you remembering to set the selector switch to battery "2" when out or you run the risk of killing both batterys if left on the "both" setting. If you continue to deplete the house battery running stereos & what not, your battery life will be drastically reduced.
2) Get a jump box. This is basically a portable, encased motorcycle battery that is kept in a fully charged state (by you) when not on the boat for emergency jump starting in the event you kill the starting battery. This is NOT a recommended way to spend the weekends, but it is a good idea to have one aboard when out for extended periods of time. You can find them relatively cheap now ($50-$75), but you have to assure that it is fully charged. Also, it's nice to have when you come across another boater that has a dead battery.
3) Invest in a small portable generator. These little 450-1100 watt units are anywhere from $450-$1200, but they can be used to supply 110v power for on board 110v devices and if you have a trickle charger, you can plug it into the genset set while out and have it constantly charging the batteries while you're using the 12v power for other things. Most larger boats have the set up, although it's permanently installed (genset runs the battery charger while lights/fridge/stereo burn battery power).
All in all, I would recommend a second battery installed on a selector switch. Have this done by a professional. This will assure that you have a dedicated starting battery and all other items are isolated to the largest spare battery. make sure you are fully aware how the switch is set up and use it correctly.
