24 volt dual batt Q's.

[sixbennetts]

Truck is an ex Swedish army Volvo Tgb111C with a 24 volt system. It has 2 12 volt, 100 amp batteries. Can I just install a cut-off between the two batteries for the night, using one for house to run fridge, lights, etc., then reconnect them, start the truck, and recharge the house one while driving?

Probably wouldn't be enough juice in the one good battery and one run down battery to start, huh?

 

[charlieaarons]

Don't do it that way. Running off 1 12V battery in a 24V system will rapidly cause battery failure - undercharge one, overcharge the other.
Instead get a 24V-12V converter. They aren't very expensive. Be sure it is adequately sized (at least twice your estimated current draw, or mmore, since there are surges when starting refrigerators).
Better yet, inorder to save your starting batteries, hook up the converter (sized to your alternator output) to a 3rd 12V battery, to be used exclusively for running accessories, with a ignition controlled solenoid to cut it off from the 2 big batteries and alternator when the ignition is off.
The BEST solution:
http://www.sterlingpowerproductsbam.co.uk/products-battbatt.htm
along with the 3rd battery.

Charlie

 

[sixbennetts]

Thanks, Charlie. I'll look into them.

 

[chet]

be careful with the converters they draw power even when nothing is being used. if they are on they draw power. Also most will convert 23-28v to 12v but to truely charge a 12v battery they need 13.8 so a normal converter will not totally charge a battery.

Like Charlie said though never draw from on battery in a 24v system

 

[sixbennetts]

K, thanks guys. How about if I want to jump start somebody this winter. Can their 12 volt system take a monetary touch of 24 volt to get started, or do I have to disconnect one of my batts to jump them?

 

[762X39]

Since you probably have an ex military vehicle, it is likely that you have a battery disconnect to, well disconnect the batteries when shut down so you won't have to worry about the 24 to 12 volt converter drawing down your batteries. I use a 24 to to 12 volt converter that can supply 10 amps of current to my cell phone charger, CB radio and 12 volt socket for whatever. I carry a 12 volt jump start box to help those in need, if you connect 24 volts to a 12 volt vehicle to jump start it you will likely blow up most of the electronics on board (like the cpu that runs the vehicle).

 

[MakersTeleMark]

Just use the posts on the front battery to jump. Never the 24v. I run the same setup you have, but have a 3rd battery in the camper that is connected to an automatic relay to the truck batteries. I also power the camper battery with solar. Definitely the way to go.

 

[rezdiver]

here is my setup for my mil truck.
I added a second booster plug and connected it to the center post 12v side. now i can boost from 24v or 12v and run winches and accessories from those plugs.

I also added a 40amp Surepower battery equalizer. this can be run either as a battery equalizer or a converter to feed 12v for your accessories and charge a third isolated battery to run your accessories.
I am very impressed with this battery equalizer. I had a short circuit between 24v and 12V that caused a fire melting 4 guage wires, the equalizer survived with a lack of fuses or breakers with no damage. put in some breakers or fuses if you are going to use one.

 

[sixbennetts]

Thanks, guys. I'll use this for reference when I get out of the hospital.

 

[charlieaarons]

be careful with the converters they draw power even when nothing is being used. if they are on they draw power. Also most will convert 23-28v to 12v but to truely charge a 12v battery they need 13.8 so a normal converter will not totally charge a battery.

Like Charlie said though never draw from on battery in a 24v system

A normal 24-12V converter does draw power and should be on an ignition controlled relay. But the Sterling chargers draw no power when engine is off since it turns off when V<26.0V. V is only > 26.0V when the alternator is running.

Charlie