Jump starting 24v with 12v

[crusty]

Wouldn't it be possible to jump start a 24v cucv with 12v? If the lights were left on and killed the battery, it seems to me that only the front battery would be discharged. If that is the case, a 12v jumpered to the front battery should work fine. Am I missing something?

 

[doghead]

That may work, in that case. Boosting one battery at a time can be enough to get them going.

 

[stampy]

Its possible but if both are drained not practical. I would check both batteries individually before trying to jump with only one. I have had success in charging each individually while they were still hooked together using a 12v charger. Just make sure to only connect to one battery's posts at a time.

 

[Croatan_Kid]

Yeah, you're right. Generally, only the front battery will die or get low enough not to crank and a quick 12 volts from another vehicle will fire you right up.

 

[kipman]

Depends on if it cold out, warm day no problem.

 

[hobie237]

I've started my truck in warmish weather using one battery when my starter relay died. I would have used two, but I didn't have enough cable to manually jump both batteries to the starter.

I've also jump started my truck when it was cold (single digits) with a 12v car. Connected to one battery, waited a while, sprayed in starting fluid, connected to other battery, cranked until batteries drained again. This was a 20 minute process or so, but it got the truck started.

 

[BKubu]

Another option is to hook up two 12V sources to the truck...one on each battery. I've done this plenty of times.

 

[underdog]

I was reading the other day.
They claimed it was hard on alternators to use them to charge discharged battery.
I have not thought alot about it but it makes since.
Why not just use a battery charger to get everything back in line.

 

[thedeliverator]

Well, don't do what I did. I left my lights on, killed one battery, and in trying to jump it from a 12V system, managed somehow to get 24V back long enough to kill the other guys alternator.

Though now that I think about, we probably had it hooked up all wrong to start with. Don't mix alcohol and electricity!

 

[papercu]

that only the front battery would be discharged.

The batteries are connected together, and will always try to equalize to the lowest voltage in any one cell. If the front battery is dead, probaby the other is dead too.
From the -10
Wait 3 to 5 minutes after hooking up slave cable to "dead" truck, before
attempting to start it. Damage to tha truck’s electrical system may result if
the truck is started sooner.
If "dead" truck’s engine doas not start within 15 seconds, release ignition key.
Wait 3 to 5 minutes before repeating start procedure to prevent overheating
the starter and damaging the battaries of the "live" truck. If engine does not
start after several attempts, organizational maintenance must perform additional
maintenance.
Any vehicle with a 24 v system is suitable for slave cable starting. DO NOT
attempt to slave start this truck with a 12 v system vehicle.
NOTE
Before slave starting, make sure checks have been made to determine if the
problem is low or dead batteries. If one battery is missing, DO NOT attempt
to slave start.
Good luck, Wayne

 

[hobie237]

Another option is to hook up two 12V sources to the truck...one on each battery. I've done this plenty of times.

Yeah, that would be ideal if possible. Unfortunately, it requires two other vehicles, and two sets of jumper cables, which may or may not be available when necessary.

I was reading the other day.
They claimed it was hard on alternators to use them to charge discharged battery.
I have not thought alot about it but it makes since.
Why not just use a battery charger to get everything back in line.

Yes, the alternator has to work harder than usual. It's usually not going to kill it too quick, though, unless it was already on its way out. Much like the using 2 12v vehicles, while a battery charger is an ideal situation, it may not be available if your truck is dead somewhere away from home, a battery charger, and/or a power source. It may also not be practical if the truck needs to be used NOW, and you don't have time to charge the batteries.

 

[LanceRobson]

I'm not sure of the complete reasoning process but our motor pool gurus recommended disconnecting both positive cables from the batteries and using the 12 cables to charge each battery for a while. Then they put the cables back on and started it normally, without the jumpers attached.

I don't remember ever hearing of of either vehicle getting hurt using this method but know of several problems when 12V sources were tried to start CUCVs and humdingers with direct jumper cable connections.

Lance

 

[hobie237]

If the batteries are tied together, and one of the 12v vehicles (or battery chargers) connected to the 12-24v battery grounds to chassis by accident, bad things could result. by disconnecting the batteries, you remove that chance of something going wrong.

 

[dunedigger]

The batteries are connected together, and will always try to equalize to the lowest voltage in any one cell. If the front battery is dead, probaby the other is dead too.
From the -10
Wait 3 to 5 minutes after hooking up slave cable to "dead" truck, before
attempting to start it. Damage to tha truck’s electrical system may result if
the truck is started sooner.
If "dead" truck’s engine doas not start within 15 seconds, release ignition key.
Wait 3 to 5 minutes before repeating start procedure to prevent overheating
the starter and damaging the battaries of the "live" truck. If engine does not
start after several attempts, organizational maintenance must perform additional
maintenance.
Any vehicle with a 24 v system is suitable for slave cable starting. DO NOT
attempt to slave start this truck with a 12 v system vehicle.
NOTE
Before slave starting, make sure checks have been made to determine if the
problem is low or dead batteries. If one battery is missing, DO NOT attempt
to slave start.
Good luck, Wayne

I believe this is only in a parallel hookup, the cucv in series shouldn't equalize. atleast mine do not. When one is dead has no affect on the other. I even jumped my front battery with a portable jump set to get me going.

 

[allrevup]

Would the CUCV recomended sequence for their series battery's installation/removal shead any light on negative effects on the batterys and/or charge system? Sorry but I can't recall it other then "DO NOT jump start" and that if the sequence was not followed damage may occuere. Or is that as hobie237 aluded too; becouse of posible crossing or grounding problems, as any other vehicle?

 

[hobie237]

Not really. The recommended order has more to do with containing arcs that may be generated when you are hooking them up. So long as the jumpers are insulated so they are only connected to one battery, and the "system" remains 12v, all is good, it's just a problem if you allow the 24v of the second battery to make itself known to a 12v vehicle.

 

[Orionspath]

Another option is to hook up two 12V sources to the truck...one on each battery. I've done this plenty of times.

Thanks again Bruce for the help via cell phone last July. I can honestly say that this advice worked for me while enroute to the shore to participate in a parade.

 

[goatowner]

I have been able to use a 12v jump box hooked up in the reverse fasion (pos to neg and neg to pos) to jump my deuce. It usually works as long as the jump box is up to par. I connect to the outter most post and then to the center cable between the two batteries.

 

[Sarge]

jumping 24V with 12V

Okay, it's story time with Sarge.........
Three years ago the Three Musketeers drove from Texas to Virginia to pick up an awesome Deuce. We took a Suburban loaded with regular tools, tire changing equipment and lots of weapons.
When I say an awesome deuce, I mean it. In the military I drove literally hundreds of deuces, this one was the most powerful one ever! It went up and down the mountains in West Virginia in 5th gear, never once slowing down.
I just knew that it was going to blow up soon. Well, it's 3 years later and it's still the most powerful deuce ever!
I'm sort of blathering here, so I'll try to get back on topic.
We noticed in West Virginia that the lights were getting dimmer and dimmer.
Driving another 1300 miles without lights or without shutting the deuce off was out of the question. I put a meter across each battery and they were low, very low.
You make do with what you've got, right?
We hooked up the Suburban 12v jumper cables to one battery and disconnected the Suburban with it still running. Ran the Suburban up to 1800 rpm. Now all of the Sububan alternator power is being used to charge the deuce battery. After the deuce battery showed 13v,(disconnected) we shut down and repeated the whole process with the second deuce battery.
Then we drove without lights until it got dark. Lights on, another couple of hundred miles. Well, we repeated this process three times until we got to Memphis. Sure we burned a bit of the gas in the Suburban but it's a heck of a lot cheaper than hiring a tow truck.
In Memphis the deuce owner was poking around under the hood and remarked "hey, what does this disconnected wire go to?"
hee-hee-hee!
The rest of the trip was uneventful.
Translation - 'nobody got shot.'
A lot of extremely funny things did happen on the way back, but that's another story.......

 

[Crash_AF]

I have started my 816 with my Land Cruiser a couple of times... it just needed a little extra help because it was cold... Connect to only one battery at a time, let it charge for a little while, then move to another if they are all really low.

On a CUCV, the system is different because there is an alternator for each battery. The front battery (the one that feeds all the 12V) will be the one dead if you leave the lights on. Connect your jumper cables to the appropriate posts on the front battery (NOT TO THE CHASSIS GROUND) like a normal 12V jump and you will be fine as long as the back battery still has a good charge. Have done this MANY times with absolutely no problems.

If both batteries are dead, hook the cables to the rear battery for a few minutes, then switch them to the front or use two vehicles as was suggested earlier.

Later,
Joe