More 1009 battery problems

[455SD]

For some unknown reason the rear battery on my 1009 is losing juice about once a month. It gets down to around 11 volts and the truck won't start. Overnight on the charger and it is good to go for another several weeks. I am using to regular civi type batteries and the rear is the only one going down. I am swapping out three different batteries with similar results.

Since I know nothing about 24 volt systems, any suggestions on where I should start checking for problems??

Thanks

 

[ida34]

It is not really a 24 volt system. It is two separate 12 volt systems. This makes it easier. The rear battery is just used for the glow plugs and the starter as long as you don't have any military radios hooked up. Does your volt gage work? If so does it read in the marked space in the green area when the vehicle is running? If it is you may just have a week battery. One alternator charges each battery so you could have one alt with a diode out so it does not give full output. The battery for the back battery has an isolated ground. I think the driver's side alt is the one for the back battery. You could take it off and have it bench checked. Remember that the back battery is only used for the glow plugs and starter so it is not used most of the time so any problem with the back battery will take longer to show up. I hope this helps. I would have the battery checked first and they may be able to check the alternator output on the truck. Most auto parts stores will check both for free since they figure you will buy the parts there if they are bad. Remember to tell them that the alternator is an isolated ground. If they do not know what this means than don't let them touch it. I think they can fry the alt if it is hooked up wrong during the load check.

 

[CUCVFAN]

The system is really a "hybrid", not 2 separate 12-volt systems. Both batteries are used to provide power for the glow and starting systems. The passenger (right) alternator is used for charging the 24-volt across both batteries. The driver alternator charges the front battery with 14V and provides 14V to the isolated ground of the right alternator, which then provides 28V to BOTH batteries. Both alternators have isolated grounds, but only the right one really needs it. The volt meter shows what the right alternator is doing. If the right alternator is not putting out 28V, this should show and the rear battery will not get fully re-charged. If the left alternator starts to die, the front battery will not get 14V and as it gets lower and lower, will allow the rear battery to get overcharged and eventually ruined....

 

[ida34]

The alternators are the same for either side. They both put out 14 volts. One charges the front battery and one charges the back. the isolated ground is connected to the negative side of the back battery. It is also connected to the the positive side of the front battery but it is isolated from the ground of the front battery. Neither one of the alternators put out 28 volts. The batteries are isolated by having separate charging systems. If one alt dies only the battery charged by it will die. The other battery would not be effected by an over charge condition like on the deuce. This much I am sure of. I just could not remember which alt charged with batt. The charging systems for all intents an purposes are separate systems.

 

[CUCVFAN]

Alternators are the same. But, unless you have converted your truck to a strictly 12V system, the right alternator is charging the 24V system, not the 12. Trace it's output. It goes straight to the 24V buss bar on the firewall. That, is a 24V source that comes from BOTH batteries wired in series.

Perhaps, this is a case of semantics. Yes, from the alternator's point of view, it is only putting out 14V, but that's because it's ground is a 14V source and it's output is relative to it's ground. The grounds are isolated so that you can run 14V to the negative posts and get 28V output without frying the system.

My comment about overcharging is valid for the M1010 style system. But, theoretically, on a regular CUCV, if you run your front battery low enough by leaving the lights on and then you start the truck, you could still overcharge the rear battery because the amperage will be getting split between the batteries, but the rear battery does not need as much as the front.

I'll test this and check the voltage at the rear battery...

 

[ida34]

I'm sorry but you are wrong on this. I can't talk about the M1010 system but as for the M1009, the alternator for the back battery senses the charge level of the back battery only. It will only charge the back battery if the back battery is low. It does not see the front battery voltage at all. The 24 volt bus bar will only give you 24 volts if you ground to the chassis or ground to the negative side of the front battery. If you ground to the pos side of the front battery or the neg side of the back battery you will find 12 volts. This is why the alt for the back battery has an isolated ground. It does not ground to the chassis. It grounds to the neg side of the back battery and by doing so it only sees the voltage from the back battery and only charges the back battery. If your theory was correct then the back battery is actually a 24 volt battery since it is connected to the 24 volt bus bar. I only argue because I want 455SD to get correct information so that he can get his system working properly. You must correctly understand a system to effectively diagnose a problem with it. I used to be a certified mechanic so I understand charging systems fairly well and have gotten more familiar with the cucv system on the M1009 since I now own a couple. I am not saying I am the end all be all expert but I probably have a much better understanding of the system than a layman.

 

[CUCVFAN]

Re: RE: More 1009 battery problems

I'm with you. Everyone needs the right information. This must be a semantic problem, because you obviously haven't blown up either of your systems yet. This charging system has been discussed many times on this board.

There is no 24V battery, so I'm not sure where you get that from. The series wiring provides the 24V. The right alternator puts out 14.4V above the output of the left alternator (hooked to it's ground), which should be maintianing 14.4V as well. The output goes straight to the 24V bus, which comes from BOTH batteries. It "thinks" it is charging a 12V system, but in the context of the entire system, it is actually charging 24V across both batteries, which is why the grounds are isolated. Essentially, the alternators are run in series, just like the batteries.

The 12V for the lights on the truck comes from the positive of the front battery, which happens to be hooked to the negative of the rear battery. I think you should research dual voltage systems a little further as they can be confusing.

I don't discount your knowledge and experience, but you are mistaken here. If you don't believe me, check the wiring diagram in the -34 an -20 manuals. Follow the wires and you will see. It even spells it out like this: "Generator 2 (right) - BOTH BATTERIES CHARGING" and "Generator 1 (left) - FRONT BATTERY CHARGING". It's not a misprint.

 

[ida34]

RE: Re: RE: More 1009 battery problems

I am not mistaken. The front 12 volt battery is only connected to the rear battery alt by the positive side. The negative side of the front battery does not make a connection to the negative of the alt. You can't have a complete circuit with out the connection to the negative side of the front battery. This is the whole reason for the isolated ground. If you leave the lights on in the cucv it will discharge the front battery but will not effect the rear battery. This is because the 12 volt side of the system does not make a connection to the pos side of the front battery. To make room for an A/C compressor some of the cucv series have a 24 volt alt or gen instead of the two 12 volt ones. In this case what you say would be true since the regulator only senses total out put from two 12 volt batteries. If one was down the other gets over charges and an imbalance occurs. This can't happen in the cucv's with 2 volt alts.

I really don't see how you think a 12 volt internal regulator running a 12 volt alt can somehow charge 24 volts. The alternators are not run in series they are "isolated". If they were run in series they would not need an isolated ground. The system was set up purposely because the front battery has more of a load than the rear battery and this would create the imbalance an overcharging of the rear battery that you speak of. I am not sure how the 28 volt gen cucv's overcome this but I thought they had a huge 24 volt to 12 volt converter. I am note sure about the 28 volt gen systems because I don't have one and don't need to know how to work on it at this time. Are you sure you are looking at a M1009 or M1008 schematic and not the schematic for a 28 volt gen cucv?

If that is what the manual says it is misleading and wrong. I have found more than one wrong item on the military schematics. The Gen 2 could not charge the front battery without a connection to the rear battery negative side and this can only be done if the batteries are in parallel like in the civy diesels. If what you say the manual said is true then why do we need the gen 1 alt? If the gen2 alt charges both batteries then why do we need the other alt?

It seems like you are blindly relying on the manual without understanding exactly how the electrical system works. If you give me the figure number or schematic number you are looking at I will look at it to see where the breakdown in communication is.

 

[CUCVFAN]

RE: Re: RE: More 1009 battery problems

Well, you are absolutely correct. Once I drew out the circuit for myself, I realized that the M1010 with it's 24V system was clouding my brain. The isolated grounds make each alternator charge each battery separately as it's own 12V system, as you indicated. Sorry or the confusion.

And, the TM is abviously wrong with that statement. The diagram shows this to be true.

Thanks for making me think about it and learn something. That's why this forum is great!

 

[ida34]

RE: Re: RE: More 1009 battery problems

Well I must also say I am sorry because what you say may be correct also. I looked over the schematic for the charging circuit. The isolated ground is connected to the pos side of the front battery by the post on the firewall. The small one near the glow plug relay not the 24 volt bus. The #1 terminal on gen 2 is the one that is energized to excite the field and start the charging. The #2 terminal goes to the 24 volt bus effectively connecting it to the pos term of the back battery. The outside case still grounds to chassis ground. Now, it may be the case that the isolated ground provides 14.4 volts when a connection is made to chassis ground. If this is the case then it would charge both batteries but only take it's order to charge from the back battery ignoring any load between the isolated ground terminal and chassis ground. If this is the case you should be able to get 14.4 volts with a meter on a connection between the isolated ground and the chassis ground. This would make your argument correct and the manual correct. I plan on checking this when I get a chance. The front battery takes on more of a load over time and the gen 1 should be working more than the gen 2 over time. Gen 2 should shut down fairly quickly because it only has to charge up what it took to use the glow plugs and start the engine. This would make it nearly impossible for the front battery to be over charged unless the back battery fails and the #2 gen starts over charging to compensate. The regulator in gen 2 would only see the low condition of the back battery.

I have not confirmed this yet but this would make your statements possibly true.

This came to me while sitting at work thinking it though then looking at the schematic confirmed that it was possible. I will post what I find out.

 

[ida34]

RE: Re: RE: More 1009 battery problems

455SD,
Looking at the schematic reminded me that you need to check to make sure the 28 volt fuse in the fuse panel is not blow and the #2 gen relay under the dash is working. It is what tells the #2 gen to working and it will not work if the 28 volt fuse is blow.

 

[BKinzey]

ARE YOU READY TO RRRUUUUMMMMMMMBBBBBBLLLE!!!



Ok, it's not that bad, it's interesting.

 

[Ambulancechser]

yup...

interesting indeed...also confirms my personnal opinion that vehicles should only have one alternator...

 

[ida34]

RE: yup...

If I fight I don't talk about it first. I just get busy.

 

[CUCVFAN]

RE: yup...

No rumbling here. My confusion was cleared up. I think ida34 is very correct with his initial assesment. Although I am glad to hear he can see how the system can be mis-leading...

I just could not see the circuit until I drew it out. I blame that on my familiarity with the 200-amp system. I am way more familiar with the M1010 system than most would care to be. It uses 24V alternators and has it's own problems and was clouding my brain...

On this system, I know if you check voltage from the output of the right alternator to chassis ground, you will see 28V, but that is mis-leading, because, as you pointed out, the right alternator does not see chassis ground because it's ground is isolated and hooked to the negative of the rear battery, while it's positive is hooked the positive of the rear battery. That is it's circuit. Technically, it is charging 14.4 volts to the rear battery as you point out, because the negative of the 24V system does not exist in it's circuit. The negative of the right alternator being tied to the 12V junction is mis-leading because that's where the positive 12V is pulled from to power the other stuff. But, it's also the negative of the rear battery. And, it also happens to be where the left alternator charges the front battery. But, that ground isolation is really the key. The right alternator only knows about the rear batteries positive and negative, not the front batteries negatve, so it really is only charging 14.4 to that circuit. The left alternator knows about the positive of the front battery and chassis ground, which is the negative of the front battrery. That is it's circuit.

I don't think you will find anything different, but please post here if you do. As of now I can't see it any other way but as 2 separate systems, so if you find something different about the grounding, you'll have to convince me back over to the other side in another thread...

 

[ARMYMAN30YearsPlus]

RE: yup...

Stupid Question I guess but if I hook up my slave cable from the deuce the the M1009 how does that 24 Volt go through all these isolated grounds and stuff and is it going to both batteries or what I am a little fuzzy here

 

[ida34]

RE: yup...

There is a 28 volt bus bar. The slave connector connects to this. It does charge both batteries because I charged one M1009 with the other one before attempting the start. All the starter is 24 volts so this is not problem. The big resister on the firewall drops the 24 volts down to 12 volts for the glow plug system to operate. This all was done to allow slave cable starts. After thinking about it, I would guess that the load from the slave vehilce would read equally across both of batteries on the M1009 and trigger both alts to produce an output. I am kind of fuzzy as to how this would happen but my good m1009 did charge the batteries on the bad m1009 enough to attempt a start so they do charge the vehicle at the other end of the slave cable. With totally dead batteries the bad one would not start just by the connection of the slave cable. I had to charge the bad batteries for about a half an hour before it would try to start. If the batteries were not totally dead then a jump would have worked fine.

 

[ARMYMAN30YearsPlus]

RE: yup...

Thanks cause i have brand new batteries in the duece and the winter is coming so I may need to slave the cucv some days