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Chassis Starting Battery Wiring and Chargers
Well my 4 chassis batteries are starting to give me a little trouble. I suspect they are from early 2011 but I do not have records on them. After coach sat for about 8 days and using a few lights on while updating headlights and other bulbs I could get it to spin but just a few turns then starter disenaged.
Marathon jump start feature worked like a charm, fired right up. Just about finished with a 4000 mile trip and bus sat for about 18 hours in 20* temps last week in Texas and again needed a boost from the jump start feature. Otherwise it has been fine, VMSpc reads 13.4 or so going down the road, Prevost gauge shows over 26, charges fine.
Right now in sunny Arizona batteries 12.8 when I put a meter on them. They have been sitting for almost 26 hours.
That seems to be about a full charge or close, maybe just one is bad and dragging others down, not sure, if I will replace one I will replace all of them and be done with it.
My questions are, I can put the meter on any batteries and get 12.8 or so. I can go from one + to one – on different batteries and get 12.8. However if I measure from chassis ground to a pos terminal I get 25.4, that pos terminal goes to the 24V connection on the equalizer. However I noticed not only are the batteris wired in parallel there is a big jumper between pos and neg so also series.
If they are in series why do I not get a 24v reading, only 12v? Ihave a bunch of small 12v wall wart battery tenders laying around. Can I wire one into each battery? Do I need a 24v battery charger? If so why did I measure 12v at all the batteries?
Obvioulsy confused on how Prevost has this stuff wired and how the battery equalizer plays a role.
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21 Replies
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I just went through this over the last three weeks. My four Interstate batteries were new in May 2014. I couldn’t start the bus a few weeks ago. Liberty originally installed a 24volt, 35amp (boat anchor) dumb charger. Flipped the switch for that and after two hours we had nothing. Consulted with Jeff Rowe, we concluded the charger was toast. The batteries were new. I unhooked that charger, removed it from the bus. Obtained a Guest Mariner 2611A and installed that. Ran that for 38 hours, still nothing. Removed the batteries from the bus and took them to the Interstate distributor. They said if they are only six months old, they should be fine … must be your chargers. Interstate charged and load tested them … one battery was bad, it was replaced under warranty, reinstalled the batteries, bus fired right up.
I’m not an expert on this, the other guys should feel free to second guess what I’m going to say.
First thing. If you do this right and don’t do anything wrong, this process is pretty much a non-event. But if you drop a wrench across a positive and negative terminal or hook the batteries up wrong or accidently touch the rachet to the bus frame when working on the positive terminal you are in for quite an exciting and hair raising experience. I’m not going to bore you with stories of batteries exploding and acid being tossed all over. Take your time, take precautions, be careful, have something around who can help if the process goes south on you.
Remove all jewelry first … watch, rings, bracelets, piercing, etc. If you can get by without a belt, remove it (belt buckle could short things out). As Jeff Rowe has told me a number of times, there is MORE than enough amps in those batteries (even with a bad one or two) to weld.
If you’re handy, remove the batteries from the coach. Number the batteries. I took a Brother label machine and marked every wire and cable as to where it went (#1-P, #2N, etc.). Duct tape up your ratchet, 6″ extension, and socket. Have a roll of duct tape, bag of tie wraps and twine/light rope/or heavy string handy. Turn off the two switches next to the batteries (the 12 volt and the 24 volt).
Make a diagram of the batteries and all the wire and cables.
I started with the battery closest to me (my #3). As you remove the wires and cables from each post tie wrap that posts bundle together, duct tape or wrap the bundle with clean shop rags so there is NO bare metal showing, and duct tape the battery post. You might have to tie the bundles up to something above to get them off the battery cluster. Get the positive and negative unhooked for the first battery, pull the battery.
Do the same for the rest. Now you can test the individual batteries, maybe find a bad one. You can also try to charge them with a 12 volt charger, you might be able to find a bad one.
My Interstates came with little labels on the end of the battery (hidden from view when in the coach) with the month/year. Some batteries are marked on the top with a code that you can decipher from the manufacturers web site as to their manufacture date and sometimes first charge date (I found that in Interstate’s website).
I recall you “think” the batteries are three or four years old. If that is the case and you find a bad one, replace them ALL at the same time with the same manufacturer and age. By now you have a NAPA discount card courtesy to the fine folks from PC. Others on PC have spoken highly of NAPA batteries. Either way, get a named battery with nationwide presence. Don’t try to replace just one battery if they are three or four years old. Putting a new battery with three older batteries causes problems in the batteries. Many guys on PC have said that I confirmed that over on the Garage Journal Forum with the truck and bus maintenance guys.
With all the batteries charged up, put them back in.
At some point the batteries need replacing. I’m told five years is about all the life you can expect from a set of batteries. If you think you’re at four or five years, probably time to get a new set.
Anyone else on the PC forum is free and encourage to critique my recommendations.
PS: Final suggestion. If you buy new batteries, hang onto the red and black covers that come with new batteries. They are probably better insulators for safely removing and replacing the batteries than duct tape.
Edit: Suggestion from Tom Chilcotte: “Be sure to unhook the ground wire to the equalizer in case you make a boo boo.“
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Dick, that is all good info, I can swap the batteries no problem, although will probably make my brother the rocket scientist do it….I am a decent wrench, he makes me look like a hack, but he gets paid to do this stuff evrey day.
Anyways, these are interstates in here now, but no one bothered to mark the dots for the date, have not pulled them so maybe some date code stickers elsewhere.
Really mostly curious if I can utilize these battery tenders I have, probably have about 20 of em. They worked good on my Duramax, really just good for keeping a float charge when that thing would sit for a month.
I just want to clarify if you can apply a 12 v charge to these since that is what I read off them except for the one POS terminal that connects to the Equalizer. BTW I have a Sure Power one….got a new one ordered today under recall, will show up in 6-8 weeks…..
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My coach is older but I imagine the start batteries are wired up the same. My manual specifically says charge the batteries with 24 volts or disconnect and charge each battery individually with 12 volts.
Davy
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G-man,
Load test each battery while disconnected, making sure they were fully charged when you test them. Once you know you have good batteries, be sure to check that someone hasn’t used the chassis batteries 12 or 24 for a power source for some other device. Usually only DDEC wires are present.
As you stated, your chassis is wired series/parallel, so you have 12 and 24. I have installed Quest chargers that have two power leads, you can charge 2 of the 12v or combine to charge 1 24v, either will work. I now use a 24v Battery Tender wired to the 24v jump lug, so if I’m using juice working on things with the key on, the tender will bring the 24v back to float.
All the buses I’ve owned will set for a month or two with no start problem. So you probably will have a bad battery or some phantom load taking your batteries down.
By the way, you should have a sticker or label on the door with the wiring diagram so you can pick out the 12 and 24v leads at the batteries.
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Dick,
Good post. I only have one minor detail to add. As a safety precaution remove ALL jewelry from your fingers and wrists. That would be wedding rings, class rings, watches, anything metal. If you wear a gold (silver/copper) necklace remove that also. Its easy to get a second degree burn from a 12 volt battery, my Uncle did that once. I can only guess how bad the burn would be from 24 volts.
On labeling the cables, tie wraps are available with a flat tag molded onto the tie wrap. When I changed my Lifelines, thanks Tom, the first thing I did AFTER removing my rings and watch was to tie wrap the cable bundles or singles with that type tie wrap and using a permanent marker, such as a Sharpie, was to lable which battery and post the cable bundle or single came from. That made reassembly much easier. Now if I can just find help lifting those 162 pound beauties in five or so years I’ll be a happy camper. I’m thinking my engine hoist fro may gasoline burning engine building days might just be the ticket to do the heavy lifting next time.
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I always take a picture of the battery cables before starting to remove them. If it won’t start, and batteries are showing charged, 9 times out of 10, like Tom said, you will have a shorted out battery once you put a load tester on them. they will show charged until a load is put on them.
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For anyone contemplating changing their chassis or house batteries be aware that the two most critical things associated with that are insulating the terminals once they are removed, and making certain the cables go back together exactly as they were when removed.
But there are other things to consider. Clean the terminals if they have any corrosion. Take the stack of terminals off the chassis ground and clean all terminals as well. Protect the terminals and battery posts after everything is put back together with the spray protectant you can get at any parts store.
Of all the phone calls I get from folks with problems the number one is that an owner has a problem after replacing batteries and in every instance it was either miswired batteries or a DDEC wire not connected. In almost every instance the owner was certain it was put back togeher exactly as it was, but in fact it was not. That means all of the tips above about keeping track of the cables and their locations are correct and vital.
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When I have replaced the batteries I draw a picture and include the number of wires that are on each battery post,I usually have to find a wire somewhere as they seem to disappear under something,but knowing how many are on each post really helps.I also use electrical numbers on each wire.
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Hi all, just wondering what chassis battery tender to buy. I just replaced my chassis batterys and I’m wanting to add a tender just to keep them topped off. Our bus can sit for six months without being used 🙁 so I just thought it might be a good idea to install a tender.
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Dale,
I would not use a constant “on” device. You have a pre-DDEC coach so if you shut the master off I don’t believe you have any loads no matter how small. If your posts and battery tops are clean so you don’t have even a small current path it is likely your batteries will go for several months before they get down to 12.2 or 12.4 volts. Then at that level put a small charger on for a few hours and you are good for another three months or so.
For a charger I would install one of the Guest 3 stage chargers. A number of us are now using them with good results. You can set them up for 12 or 24 volt if you get the right one.
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3 weeks ago went to start the bus and for the first time would not start. Managed to charge through one battery with a large charger and got going again. It was time to replace. Best place I found was NAPA and with our discount program all four were less then $500. including tax. They also carried the best warrenty I could find. Note: the faulty ones were 5 years old! When in storage cut the chassie system with the disconnects. They will hold for weeks without notable discharge.
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Thanks for the replies!
I usually take my 12 volt charger out there and top them off 1 12v bank and then the other but it is a hassel. Just thought about a small permenant charger. I was looking at the Battery Tender brand so I will look at a three stage Guest also.
Having the four batteries wired the way they are, is there a 3 stage charger that would connect to the ground post (to the bus frame) and and the 24v post (going to the disconnect)? I have been reading and it looks like they are made for a 2 bank system. I’m assuming I have a 2 bank system with 2-12v (1 bank) and 2-12v (1 bank) = 2 banks.
Here is what was taken from the web, ” Guest 6 amp 3-stage fully automatic electronic dual output charger is designed to recharge 2 batteries, either 24 volt series or 2 separate 12 volt batteries. Each battery receives a dedicated maximum 3 amps of charge current. Output leads may be paired to one 12 volt battery for a total of 6 amps of charge current. Will not work on single 24 volt battery such as aircraft design batteries. ” end.
Jan and I really need to start traveling more then we wouldn’t have a battery issue.
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Dale, You can make all connections at the equalizer on the 24V side.
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That is a great place to connect it, thanks Jon!
Here is one I’m looking at…. http://www.geniuschargers.com/G7200
On this site while chatting she said maybe go with the GEN4 and connect it to eack battery. I ask her why not just go with a G7200 and she said that it’s better to charge each battery seperatly. Any thoughts?
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I’ve got the smaller version of that to try to keep up with the batteries on all the cars. I like it.
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