3rd battery
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Freshman User
Joined: Nov 2008
Posts: 25
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3rd battery
I would like to put a 3rd battery in the truck to run the radio and cig lighter. when I'm out fishing i like to turn the radio on and i have a 12volt cooler i would like to mount in the tool box and leave on all the time. how can i set it up so that the alt charges the 3rd battery, but it can not drain the starting batteries?
the only thing better than music, fish, and cold beer is... music, fish, cold beer, and a truck I know will start.
the only thing better than music, fish, and cold beer is... music, fish, cold beer, and a truck I know will start.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Search for a 'BATTERY ISOLATOR"
Very common on camping rigs.
A starter battery saved for starting the engine, second battery for camp power.
That is on a gasser rig though, you need to save two for engine starting.
Very common on camping rigs.
A starter battery saved for starting the engine, second battery for camp power.
That is on a gasser rig though, you need to save two for engine starting.
Freshman User
Joined: Jul 2009
Posts: 26
Likes: 0
From: Puget Sound in WA. State
Any marine store should carry a battery switch. The ones I have had in my boats are made by tempo. It will allow you to turn the extra batter off or on (connected to charging system and other batteries or isolated so it won't drain your starting batteries) I think they are 20-30 bucks and fairly simple to install.
Junior User
Joined: Aug 2007
Posts: 74
Likes: 0
Use the solenoid type, not the diode type, to conserve energy. Diode type looks often like a big brick and I read that about half the energy run through it is wasted. Make sure it's a continuous duty solenoid, I burned up a starter solenoid when I didn't know about that difference.
RV and boating shops will have the right solenoid, $20-30 sounds about right. You run a line to it to turn on or off for charging. Trigger from the ignition line for full time charging while running, or have a manual switch.
I recommend the manual switch, that way if you run the extra battery right down, it can remain disconnected until you're started up and running. Also you can disconnect if it is fully charged.
Or buy one of these smart isolators: http://www.powerstream.com/battery-isolator.htm
The wire to connect it will be expensive, but don't skimp on that part. You could be pushing up to your alternator max output through there and it has to take it.
RV and boating shops will have the right solenoid, $20-30 sounds about right. You run a line to it to turn on or off for charging. Trigger from the ignition line for full time charging while running, or have a manual switch.
I recommend the manual switch, that way if you run the extra battery right down, it can remain disconnected until you're started up and running. Also you can disconnect if it is fully charged.
Or buy one of these smart isolators: http://www.powerstream.com/battery-isolator.htm
The wire to connect it will be expensive, but don't skimp on that part. You could be pushing up to your alternator max output through there and it has to take it.
