Jump starting M923A2

[Scott88M]

Either I left the battery switch on this whole 3 day weekend or my daughter bumped it either way the trucks dead. I had to use my wife's vehicle this morning since my 5 ton is also my daily driver.

I searched and searched all day while at work but I'm having some trouble hunting down exactly where to hook up my jumper cables. I don't have access to a second MV so I have to use my pickup and my set of huge homemade cables. I remember reading here that I can do it without unhooking all the cables, can anyone post a link or explain how to do it please? The batteries were great up until now so I'm thinking it shouldn't take much to get the truck to turn over.

 

[Scar59]

Your pickup is 12 volts, correct. It will not jump a 24 volt system. Separate the 923's batteries and charge independently.

 

[Scott88M]

Yes it is 12 volts. I just thought I remembered someone mentioning that you could do it without unhooking most of the battery cables in the truck that's all maybe I'm remembering it wrong or out of context.

 

[gimpyrobb]

Yup, what he said.

 

[Scott88M]

Thanks I figured I'd have to do that but was crossing my fingers. Oh well that'll teach me to pay better attention.

 

[Scott88M]

It might have been that I read someone say they charged them in the truck and didn't take them out just unhooked them.

 

[gimpyrobb]

Yes, you can charge each battery, individually, with them in the truck. That seems like it would be a pita though.

 

[Motiracer38]

I tied every combination I could think of to jump with either one or two other 12v cars and just ended up with lots of sparks and no success. Eventually I had to grab two 12v battery chargers and hook them to two batteries at a time for at least an hour apiece to get it to crank. You can hook the chargers straight onto the batteries without unhooking anything. It may be prudent to unhook them all and charge individually up to the same level just to be nice to them if you have the time, but lead acid batteries are pretty tolerant of volatge mismatch and always seem to leel themselves off anyways.

 

[wreckerman893]

Just jump starting the truck won't necessarily solve your problem. The alternator is made to maintain a charge, not to charge a very dead battery(s). You can set a battery charger up in the cab and charge one at a time. To do a slow charge on all four batteries will take a couple of days. I've done it on two of the 900 series trucks I have in the yard. Just remove the terminals one battery at a time to make sure you don't get anything crossed up.

 

[Scar59]

I tied every combination I could think of to jump with either one or two other 12v cars and just ended up with lots of sparks and no success. Eventually I had to grab two 12v battery chargers and hook them to two batteries at a time for at least an hour apiece to get it to crank. You can hook the chargers straight onto the batteries without unhooking anything. It may be prudent to unhook them all and charge individually up to the same level just to be nice to them if you have the time, but lead acid batteries are pretty tolerant of volatge mismatch and always seem to leel themselves off anyways.

Yes, "it may be prudent to unhook them all and charge individually up to the same level", or be prepared to buy a new alternator. It may also be prudent to keep the local fire departments number handy because you might just succeed burning your truck to the ground. "Short" cuts will get you in trouble.
Be safe.

 

[Gunzy]

I have jumped my M923 from 2 trucks that were 12v. Hook one to one 12v pair and the other to the other 12v pair. This does require 2 sets of cables. Run both vehicles at about 13-1500 rpm for 5-10 minutes the try to start the truck. This did work for me and the batteries charged back up driving the truck around.

 

[Scott88M]

When hooking to each 12v pair what did you attach everything to on the m923 side?

 

[74M35A2]

Since it is an 8.3 and 24V, it won't require that much current to start. Use one running 12V vehicle, and a second stand alone fully charged battery in series with the jumper cables to get 24V. This will require 2 sets of jumper cables to do.

You could also disconnect the jumper battery cable which bridges each set of batteries into 24V, and charge each set of 2 batteries while in the truck at 12V. Do it off a running car for 15 minutes per set, remove jump cables, reconnect the batteries, and away you go.

 

[Scott88M]

I just checked with my multimeter they were about:
1. 11.9
2. 8.7
3. 7.7
4. 3.8

I'm thinking I might just have to buy at least one for now and switch to a 2 battery system. I don't own a charger right now I was just going to try and jump it but they're pretty far gone for that I think. Once the weekend hits I can sort everything out easier.

 

[MuleMac01]

Volts don't mean anything a dead battery can read 12 volts it's the load on em that's the issue. Get a 12 volt battery charger set it on lowest like 2 amps and charge each one for 2 or 3 days no more then 8 hours at a time I had the same issue as you a 3 weeks ago charged mine and took them to a battery shop to load test them and they passed 2 at 100% and the other 2 at 90% I was happy wasn't in the mood to spend 300 bucks on 6TMF's that I have. Hope it helps.

 

[Scott88M]

Thanks I will definitely look into doing that, I'm hoping I can save at least a couple of them. I'm gonna have to bite the bullet and grab a charger and probably a battery or 2 to get me back on the road immediately.

 

[Gunzy]

When hooking to each 12v pair what did you attach everything to on the m923 side?

Just pos to pos and neg to neg on the 12v pair. You can connect to one battery. Then the same to the other pair.

 

[juanprado]

trying to charge a bad battery(s) with the Alternator is a quick recipe for blowing the voltage regulator and / or Alt and letting the magic smoke escape. Ask me how I know?

Batteries should be charged and load tested. Slaving or jumping to bring them back is a short term fix that will lead to expensive problems and more headaches.

Sparking all those cables is screaming you want to buy a pcb box also

 

[helomech]

I have jumped many vehicles in my life and never seen a weak battery cause failure to a alternator, or generator. Jump it and go. If the battery is truly bad, then it will not accept more charge, and therefore will cause no increase in work for the alternator. Charging does not ham an alternator.

 

[98G]

I have jumped many vehicles in my life and never seen a weak battery cause failure to a alternator, or generator. Jump it and go. If the battery is truly bad, then it will not accept more charge, and therefore will cause no increase in work for the alternator. Charging does not ham an alternator.

On the electrical system on the 939 series trucks trying to charge bad batteries will most certainly cause generator failure.....