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24 volt jumpstart

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j hook 74	24 volt jumpstart		Lead	[-]
Posts: 884 02/25/2008 4:53 PM Rotator Southern California	Tags : None This weekend we got a call to jump start a bus. The coach was what looked like a old mci bus. After about 30 minutes of stanby with the cables on the coach the unit still would not start. We finally figuered out that it was a 24 volt system. Can we cause any damage trying to jump start it with a 12 volt system. I dont think there are many 24 volt trucks out there. And is there any procedure if any to joump start these vehicles. Any input appriciated.
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Rolngthun		#1	[url]	[-]
Posts: 508 02/25/2008 5:00 PM Michigan	What are using to jump start with? If there were to be a harm done it would have been to the jump start unit. Otherwise just charge each battery separate. I use a Goodall Jumpstart unit. I will put the cables on one battery and charge for about 15 minutes, then the other for about the same and then start bus. You don't have to disconnect any cables. Just pos to pos, neg to neg as marked on the battery. I do flip the disconnect switch on the bus until ready to start.
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j hook 74		#2	[url]	[-]
Posts: 884 02/25/2008 7:23 PM Rotator Southern California	We were using a 05 International flatbed truck with a 12 volt system. We also called in for a second truck with no luck.
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auto rescue		#3	[url]	[-]
Posts: 23374 02/25/2008 8:44 PM Featured Member November 2004 March 2010 Since 2007 Moderator Michigan	Trying to start a 24 volt system with a 12 volt jump will not hurt the 24 volt system is there any procedure if any to jump start these vehicles. As already posted "a Goodall jump start unit" . John R.___" WATCH YOUR BACK"____www.formulaonetowing.com
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Spitz		#4	[url]	[-]
Posts: 525 02/25/2008 10:04 PM	Like said it wont hurt it but it also wont be affective really... Think voltage as if its water pressure. Your taking 12v (psi) and trying to fill a tank thats 24v (psi), it doesnt work like that, there wont be any flow going into that tank, the highest voltage it will ever get to is 12v or whatever the charger tops out at.. As you can see it doesnt do any good at all..
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ASAPautomotive		#5	[url]	[-]
Posts: 2293 02/25/2008 10:18 PM WreckMaster #110886 TRAA MT#14057 Level II Louisiana	As was stated earlier, if you are going to use a 12 V system to jump, then you must isolate the batteries that are linked to create the 24 volt system and charge them seperately. But remember, once you switch the isolater switch in the bus back to 24 V (or combining the 2 batteries back together) if 1 of the 2 batteries has a bad or shorted cell, it is immediately going to have a negative effect on the 1 good remaining battery. So if the 1 good battery has achieved a minimal charge from the jump start attempt, it is going to be drained pretty quick. Before trying to do these jump starts, I would suggest going to NAPA and spending a few bucks on a semi decent battery / alternator tester. Charge each battery for 15 minutes or so as described previously, and before switching the isolator to join them back together, test them individually with the battery tester. This can help eliminate a lot of head scratching if the bus still doesn't start. Slidell, Louisiana "Yesterday is History, Tomorrow is a Mystery, Today is a Gift, That is why they call it the Present"...unk
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Rolngthun		#6	[url]	[-]
Posts: 508 02/26/2008 7:03 AM Michigan	I would be more worried about damage to the 12 volt system. Notice John's Startall has two sides, two switches and two gauges. So he could charge both batteries at the same time. The only way to get the 24 volts is to go from neg of the one battery and pos of the second. If you go pos and neg of one battery you get 12 volts. That is true of each battery. So you do not need to isolate them. But like I said I do flip the disconnect switch. But that is not needed either.
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j hook 74		#7	[url]	[-]
Posts: 884 02/26/2008 11:37 AM Rotator Southern California	I think I understand that if you separate the batterries that are bridged and charge them seperately then you can apply a charge to each individual battery. Does this mean that the batterries are 12 volts but when bridged become 24 volt.
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Freelance66		#8	[url]	[-]
Posts: 24792 02/26/2008 2:07 PM Featured Member December 2002 I.T.R.H.F.M. Regular Member WreckMaster #050354 20,000 +	Yes. BTW if they are really cold it has been proven more effective to just remove the batteries (much better with the carrier). Haul em back to the shop and charge for an hour inside. Batteries have a water/sulfuric acid mix that creates the power. When the battery discharges the mix turnes back into mostly water. This freezes and in order to get the mix back to a more sulfuric acid state the ice needs to be warmed up. Charging will do it - eventually. Many older coaches will have old batteries that can't even hold much of a charge even when topped off...... It has been told that an expert is someone that has made all the mistakes possible in a narrow field.......
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Rolngthun		#9	[url]	[-]
Posts: 508 02/26/2008 4:21 PM Michigan	You don't have to disconnect them. Treat each one as a 12 volt battery. And they are each a 12 volt battery. Freelance makes a good point for any battery. If you put a Goodall unit to a frozen battery, there is a very good chance it will blow up on you.
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TRUCKNTOW		#10	[url]	[-]
Posts: 319 02/27/2008 6:50 PM Supplier Member Michigan	IF it's that cold out there, BEFORE you attach the jumper, open up the vent caps and peek inside (or use your dental mirror and a flashlight) DON'T USE A MATCH OR LIGHTER!!! Be sure there is no ice inside the individual cells. A FROZEN BATTERY HAS A MUCH GREATER CHANCE OF BLOWING UP ON YOU!!. (did that once. I learned, NEVER gonna do that again) If the electolyte is frozen solid, take the batteries out of the vehicle, take them inside a nice warm garage to thaw slowly. Charge the batteries only after it's all liquid again. If the batteries freeze solid, they're probably junk (or at least on their way out.) The plates warp, and don't work with the rest of the cell any more. Don't blowup the batteries in your face, the Sulphuric acid mix tastes like SH-T!!!!! (Sulphur dioxide is another name for the smell of ROTTEN EGGS yuck!!) Jeff TRUCKNTOW.COM WWW.TRUCKNTOW.COM JEFF@TRUCKNTOW.COM 888-918-8150 X230
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Towguy1763		#11	[url]	[-]
Posts: 286 02/28/2008 9:14 PM	Or if you have two trucks handy you can use the two trucks and two pair of jumper cables. You only get the 24 volts when measuring between the hot of the first battery and the ground of the second battery (or vice versa), with the batteries wired in series. As long as you only connect 12 volts to each 12 volt section you are fine.
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j hook 74		#12	[url]	[-]
Posts: 884 02/29/2008 11:58 AM Rotator Southern California	I want to thank everybody for thier input. I learned something again from this site. As far as frozen batteries I dont think we have to worry about that over in sunny California. Although it has been pretty cold lately somewhere in the high 50 frt. My hats off to operators working in those extreme condition. Stay safe and again THANKS!!
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