Dual Batteries

[95yj]

This is probably a no brainer, but I wanted to make sure I wasn't missing anything before purchasing a second battery, dual battery switch, cables, etc.

I have always done my boating on Lake Erie and haven't really used the batteries much when out on the water. Now I live on in the Caribbean and have a 23' express cruiser. I plan on spending a lot of time on the boat overnight, etc. moored just offshore and will be using lights, radio, other various electronics and even a laptop plugged into a small inverter. The last thing I want to have happen is to drain the battery so the boat won't start.

I'm aware of voltage limiters that will cut power when battery voltage drops down, but I was wondering if the safest way would be to install dual batteries and switch over to a single battery to power stuff while the boat is sitting. To start the boat, switch over to the other battery and once under way, switch to both batteries.

Is this the accepted way to safely use electrical while no charging power is available without endagering starting voltage?

 

[Silvertip]

Re: Dual Batteries

Yes -- as long as the battery switch has "make-before-break" contacts. That means the new connection is made before the last connection is broken. Older switches did not have that functionality which resulted in a momentary total disconnection of the charging system when changing switch settings. Charging systems (particularly the rectifier/regulator) don't like that and the unit can be damaged in a heartbeat. Since you are offshore with no access to power, I would suggest the purchase of a small 500 or 750 Honda generator. They are hardly bigger than a couple of brief cases. You may not need it often but in an emergency it could be a lifesaver. It provides clean 120 VAC as well as 12VDC for battery charging.

 

[95yj]

Re: Dual Batteries

Kewl. Thanks for the response. I figured that was the best way logically and by reading up on some of the other threads. I'll check into the small generators also.

 

[ricksrster]

Re: Dual Batteries

here is a wiring diagram for two batteries with isolator to caharge both. in this configuration you do not have to worry about make before break:

 

[bruceb58]

Re: Dual Batteries

Or better yet, use a battery combiner. Doesn't have the voltage drop problems that an isolator has.

http://bluesea.com/category/2/productline/236