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Charging the batteries......

tthomass

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One of my guys thought he would take a look at the truck and must have flipped on the battery switch, which I'm paranoid to cut off every time. It is 100% dead with 3 new batteries. I've never had to charge or jump a 24v system so I don't want to screw anything up. It's a 923a1 with the 250 engine that was all redone in 2010. Just looking for some advice before I hook something up wrong. Thanks.
 

M35A2-AZ

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I would try charging each of the batteries with a 12v charger, Does it not have 4 batteries? It should have 2 or 4 batteries not 3.
 

M543A2

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Charge each disconnected battery individually at 12 volt? I am not familiar with the 900 series so I do not know anything else to tell you. There must be one battery used in another way or some switching magic in these trucks because if they only have three batteries, if all three were in the starting circuit that would be 36 volts. For my M series trucks with two batteries I can jump 12 volts to the battery closest to the starter and get them to go most of the time then let them charge themselves.
But a caution, me being inexperienced with these computer system trucks, one has to be careful to not damage a computer. My gut feel is a 12 volt jump to one battery would not do that but it might not be enough. Here I defer to others with more experience with these trucks.
On a D-6 dozer with two 12 volt batteries that did not want to go I brought up two pickups and jumped each battery with each truck. That worked well.
Regards Martin
 

jamboly

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As others have stated, you should have either 2 or 4 batteries, not three. They should be hooked up so that you have two sets of two batteries in parallel, and then these two sets of two are hooked in series to get you the 24 volts that the truck requires. (Note, there is one wire that connects to the middle of the two sets of parallel batteries that provide 12volts to something in the truck, not sure what it is). Since you say the truck is dead, I would suspect you have some sort of wiring, connection problem. Get a voltmeter or one of the cheap 12v voltage checkers and start at the truck positive battery cable. Check for voltage between the connector on the end of the cable (not the battery terminal) to the negative terminal on the same battery (not chassis ground, that would give you 24v if working right.) You should have 12 volts. If you get 12v, do the same check on the set of two batteries that make up the 12v that are attached to the chassis ground. If you don't get 12v on each of those sets of batteries, check connections and/or charge them as mentioned on previous post. You can charge two batteries on parallel with one charger. As a side note, you don't really need four batteries for this truck unless you needing to start it in extremely cold weather. When the batteries needed replacing in my M936A2, I replaced them with two good sized batteries.
 

Cape Coastie

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I would also charge them individually with a fleet type battery charger. Just disconnect them and start with one and move to the next when it is sufficiently charged. Take a photo of the current set up as you will forget how they were originally wired, don't ask how I know! The 12 volt hook up is for the heater blower motor low speed setting. Good luck. They should come back to life.
 

kblazer87

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This happened with my M923 just after I got it last year. I let one of the neighbor kids sit in it to check it out and he flipped the battery switch on. I didn't realize it until the next day, so 4 completely dead batteries.
I charged them in the truck as well by just disconnecting one battery at a time so I did not have to remember which wire went to which battery. Once all of them fully charged they were still good batteries, didn't lose any of them. After that I disconnected the batteries EVERY time I parked the truck so it would not happen again, either from me leaving the battery switch on or from some one else doing it.
 

Tinstar

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I would recommend that you DO NOT jump start it and then let the alternator try to charge the batteries.

A fried alternator is usually the result.

There are several threads about this already.


The transport company driver left the battery switch on when he loaded my M923A2 on the trailer.
It arrived with 4 dead brand new Hawker batteries.
I just charged them in place separately and they fully recovered. Took almost a week.
 

tthomass

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The truck does have 4 batteries, I was thinking about my International truck. I tried to charge it by connecting where the + and - connect from the external jump start portal but it kept tripping the GFI I was plugged into. Charging individually now at 60amps and hope to crank it up an another hour or so.
 

emr

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You absolutely never ever have to disconnect them, If you only have one good charger, charge each one , one at a time and leave them be, Its just not worth over thinking this, The charger will never put in more than what a new fully charged batt has, Meaning , If its ok for 4 batts to be hooked up fully charged, It is absolutely no different to charge em each one at a time until full, As U do it the other batts will pick up some of the over flow charge, All good, but they will never be fully charged unless you charge each one, And YES that is true with your trucks charger, Its like filling a pool The last batt is always starved a bit, and sulphation develops faster in the last one , and that is always the one that fails first, So to keep this from happening, Always... at least once a year rotate and fully charge each batt, You can do it in the truck or pull them and charge them and rotate, Its up to you , one way is NOT better than the other, :)))))))))) Good luck ... If you have 2 chargers charge 2 of the batts and when the charger cuts off charge the other 2, If you have 3 chargers and 4 batts , Charge 3 of them and when they are done charge the last one, Here is a trick, If you have 6 - 2 amp chargers you can hook them all up to one batt for and fast and fuller charge than a trickle charger can do alone, ( simple math , 6- 2 amp chargers are 12 volts :) ) - as the charger's feel resistance they will shut down one at a time, Oh yes they will :)))))))))))))))))
 
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emr

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Jump starting and letting the truck charge them will take a ridiculously long time of idling or driving, And it will only FULLY charge the first batts in the system , the others will get a charge but will not fully charge and there life will be shortened . and as I stated above, ALL batts should be fully charged individually for them ALL to be charged, people who let only the truck do it have a shorter battery life than those who fully charge and rotate , I have had 10 years from 5 tls, more than once, Its simple technology . You will NOT fry the alt unless there is other trouble somewhere . Frying the alt is almost always human error, short battery life is always human error .
 

Tinstar

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There are tons of threads about human error then.... AKA Frying alternators
I personally have never done it, was just relaying what I have read others doing.
It has been covered many times already.

If the OP had searched the site, all the questions have been answered before.
 

74M35A2

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Jump starting and letting the truck charge them will take a ridiculously long time of idling or driving, And it will only FULLY charge the first batts in the system , the others will get a charge but will not fully charge and there life will be shortened . and as I stated above, ALL batts should be fully charged individually for them ALL to be charged, people who let only the truck do it have a shorter battery life than those who fully charge and rotate , I have had 10 years from 5 tls, more than once, Its simple technology . You will NOT fry the alt unless there is other trouble somewhere . Frying the alt is almost always human error, short battery life is always human error .
Disagree. How does human error produce a dead alternator? Poor system architecture, low temp rated electronics, and inadequate cooling typically wipes out the stock MV alternators, pages of them here of which committed suicide while trying to recharge low SOC (state of charge) batteries after a jump, which is the alternators primary function. In the end, everything can be labeled as human error, but, you have 10 years from your batteries because it simply does not require 4 batteries to start these engines in modest temperatures, regularly. Typical battery will last about 5 years until its performance rating drops below the advertised capacity (CCA, CA, AH, RC, etc...). Sure, it will still work, but is acting like a smaller and smaller battery as it ages. I highly doubt your batteries will test to their advertised specifications at 10 years old. You can charge them one by one with a conventional 12v battery charger, without disconnecting or removing anything. If you can get the truck started via a jump, the 60 amp alternator will charge them faster than a plug in battery charger due to the 60 amp output, unless your plug in charger is 60 amp capable or higher. But there is risk here as doing so at idle will overheat the alternator due to low alternator cooling fan speed, which is what typically happens in the pages of alternator failure here, amongst broken alternator shafts, spun pulleys, etc... Yes, a battery charger can over-charge a battery, unless it is a manual charger with a timer, or an automatic charger.
 
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PsycoBob

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Alternators designed to charge off-grid batteries include all sorts of limit systems, as well as overbuilt cooling. Rotor temp sensing, stator temp, erectifier & regulator temp, battery temp, compensation for voltage drop in battery cables, etc.

Charging a dead 4-battery system is a lot to ask of a 28v 60a alternator.
 
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Dallas tx
I would recommend that you DO NOT jump start it and then let the alternator try to charge the batteries.

A fried alternator is usually the result.

There are several threads about this already.


The transport company driver left the battery switch on when he loaded my M923A2 on the trailer.
It arrived with 4 dead brand new Hawker batteries.
I just charged them in place separately and they fully recovered. Took almost a week.
I was actually going to do this guess I won't.
 

74M35A2

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Alternators designed to charge off-grid batteries include all sorts of limit systems, as well as overbuilt cooling. Rotor temp sensing, stator temp, erectifier & regulator temp, battery temp, compensation for voltage drop in battery cables, etc.Charging a dead 4-battery system is a lot to ask of a 28v 60a alternator.
I disagree, but each their own. When we design and sell alternators to our customers, we don't label them as not being able to recharge the vehicle batteries if low. If we did, our sales would drop to zero. The problem is low quality alternators sourced from the lowest bidder without considering conditions outside of new/normal. These alternators met specifications at the time, so they were awarded the contract to supply them. If the batteries are healthy and just low on charge, they should recharge quickly. You could lessen the stress on the alternator when doing so by increasing the idle speed to improve cooling airflow, opening the hood to allow cooler air to circulate, and leaving the slave vehicle connected and running while doing so also, as it will cut the total load required (power and time considered) of each alternator in half. These units are not only low cost/quality, but they also now have 25 years of heat and vibration cycling on those low cost/quality components. Plus, this is not an off-grid power system, it is a vehicle, and it will experience dead batteries.
 
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CARMAN

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So, bringing this thread to life...Truck has been sitting and last night...no start. Mine has the 4 huge assume 6 volt batteries under the seat. So I can charge 2 at a time in series with a 12V charger? Forgot to take a picture, but the 4 batteries are hooked up in series. So assume 6V each?
 
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