LMTV Alternator replacement 24 volt

[Keith Knight]

I'm wanting to have a single place to get all the information for everything involved with changing the 12/24 volt alternator with a readily available 24 volt alternator and 24 to 12 volt equalizer.

I'm Primarily speaking about an A1 truck.

First the Title of this thread. While doing days of research I've come across many threads relating to this but the title never led me there easily. If you have a good suggestion on a better title please share it and i can change it.

Second I want to start with keeping the change as simple as possible but maintain all the functions, such as the charging system indicator light. Later maybe add different more complicated ways of doing it.

Third explaining what each device is, what it does and why. If you must use abbreviations preface it with the full words and include pictures and diagrams or hand drawings. So anyone can understand what you are referring to.


Using this image for primary reference we can identify most of the components we will be discussing.



Load Battery Control/Charge Device "LBCD"
Found the Patent for this with a reasonable description.

I'll start by asking a few general questions that I have so we further understand why we are doing this.

1: Is the original alternator really bad or is the miss use of the vehicle the cause of the alternator failure? Such as letting it sit for long periods of time and depleting the batteries more the reason?

2: Load Battery Control Device "LBCD" why is it there, why should we get rid of it? Because it's a stupid design? Because it Failed? Because???

I have plenty more questions but I want to try keeping it easy to follow.

 

[Ronmar]

1. the alternator is not bad, but it is A. hamstrung by by internal current limitations and only delivers ~1930W worth of power with both the 14 and 28v legs loaded to full capacity. A straight 100A@28V alt delivers 2800W fully loaded(1/3 more power!). and B. Paired with the 4 battery 240AH bank, it can easily be grossly overloaded. this equals premature alt failure and chronic battery under-charge, both ultimately fatal for both parts of this system.

2. I believe the LBCD was a bandaid to help save the alternator from the large battery bank due to situation B above. With a properly sized alternator to battery relationship, it is unnecessary.

The real irony here is that with a straight 100A@24v alt, and a 24-12 converter to provide for the truck 12v loads, that 2800W would be large enough to support a 240AH@24v conventional wet cell battery bank and still be below 100% load worst case...

The fielding of AGM batteries(can draw nearly twice the current of a wet cell when charging) made the LBCD and a larger alt(the proper fix) an absolute necessity... Once the larger alt was in place, it basically became unnecessary...

 

[Keith Knight]

“Paired with the 4 battery 240AH bank, it can easily be grossly overloaded. this equals premature alt failure and chronic battery under-charge, both ultimately fatal for both parts of this system.”
That is typically caused by lake of use. Not design. Correct? Old dead batteries and expecting the alternator to charge them causing alternator failure?

 

[Keith Knight]

Thread title change for the easiest google search???

 

[MatthewWBailey]

that 2800W would be large enough to support a 240AH@24v conventional wet cell battery bank and still be below 100% load worst case...

One thing to interject here is that the 3126b Air Inlet Heater (AIH) on mine draws 88-90Amps for a good 5 minutes while warming up (it's 16F out!) and even with the block heater, that AIH runs a lot, until I get the trans heated up. So IMHO, someone screwed up! Even with my 110A 24v only alt, on a cold day with 4 batteries (I'm only running 2), the alt is Immediately overloaded. With only 2 batts, I'm pulling 115A after immediate startup which is Way more than that dual volt Neihoff could produce. It's not due to lack of use in my case. This is irrelevant over 60F ambient but someone screwed up. Happy to be proven wrong of course.

 

[Ronmar]

“Paired with the 4 battery 240AH bank, it can easily be grossly overloaded. this equals premature alt failure and chronic battery under-charge, both ultimately fatal for both parts of this system.”
That is typically caused by lake of use. Not design. Correct? Old dead batteries and expecting the alternator to charge them causing alternator failure?

Yes and no. any vehicle power system will suffer from neglect. Daily driven the batteries would be less of a load on the alt, but the system needs to be able to cope with worst case, and a depleted 240AH wet cell bank paired with this alt = worst case EVERY TIME. IMO they skipped over some basic design criteria when making the decision on this configuration. It will draw more power than the alt can provide during bulk charge it also takes a LOT longer to charge, and unless it is driven long enough to accomplish a full charge you are headed for trouble.

 

[Ronmar]

@MatthewWBailey i don’t think that is all that much of an issue witha a straight 24v alt. 115A for a short duration on a straight 100A@24v alt is not terrible, I would call it basiclly a non event on a 110A@24 alt...

The cool thing about lead-acid batteries is that their current draw is entirely dependent upon charge voltage. So while the intake heater is pulling 90A and knocking down the bus voltage, the batteries are just sort of idling along absorbing a little current If it is available Or perhaps even feeding in some to float across any low spots, just like a filter cap on a DC power supply

Thats why batteries and alternators are 2 parts of a system. Alternators self derate, as they reach max field saturation, the voltage starts to fall off, which limits their power output, but the voltage drop also throttles back battery load, because they self limit… The two work together to stabilize the circuit voltage. The truck itself(even the HEUI engines) doesn’t use a horrendous amount of power@24v until you start turning things on, and even then it’s not a lot. all the lights are less than 15A@24v… i did a load study on my A0 but cannot find my notes. I think I posted here on SS about it.

A 240AH wet cell is only going to be looking for 60A worst case, and it can only draw it if the bus voltage is up to 14+ volts to push electrons into the soup
But like you said, that and the 12v loads are way more than the Neihoff can deal with let alone adding an intake heater To that crap show…

 

[Lostchain]

1: Is the original alternator really bad or is the miss use of the vehicle the cause of the alternator failure? Such as letting it sit for long periods of time and depleting the batteries more the reason?

The alternators are extremely robust and counter to forum lore here, they rarely fail. The regulators are perhaps slightly more delicate, but most all assumed “failed” alternators ultimately appear to go back to really poorly maintained wiring, battery problems, and ultimately, poor troubleshooting skills of a (slightly) complex system. No one on this forum has ever demonstrated with any data that the 100a alternators have any elevated failure rates, or that charging drained batteries shortens their life. While it is true that that the output current is split between 12v and 24v, having 12v pegged on an A1 truck is going to be uncommon. 12v is very lightly used and Niehoff’s data (attached) shows that there is ample current available to the 24v side to handle recharging the batteries and running the other 24V loads like the intake air heater.

2: Load Battery Control Device "LBCD" why is it there, why should we get rid of it? Because it's a stupid design? Because it Failed? Because???

This is extremely simple and another subject of lots of forum lore. The LBCD exists to maintain the appropriate voltages to all of the computerized components (think ECM and TCM) even when the batteries are faulted in such a way that the alternator is unable to maintain 20volts in the electrical system. This fault could be a low state of charge, or batteries that became bullet riddled. If the computerized engine stops running due to insufficient voltage, you no longer need to worry about “protecting” the alternator from an overload condition. Perhaps it is helpful to think of the LBCD as a battery “simulator” for use while the main bank is offline. Another anecdote on that point is that the trucks with the 260A alternators still have the LBCD. It exists to make the system more robust, not as a bandaid for an undersized alternator.

 

[Ronmar]

Hmmm then I wonder why the military(or anyone else for that matter) doesn’t use the LBCD in all their vehicles… this is the only system I have ever worked on that employs such a device. A device that does something that is cautioned against(disconnecting battery from alternator while running) in every automotive electric manual I have ever seen…

yep, the Neihoff is incredibly tough, it had to be being placed into this situation, the 100A(60/40) just wasn’t large enough…

I suspect someone is buying them, because if they don’t fail, I wonder why the “suppliers” charge so much for their surplus/new old stock replacements? I am betting they didn’t buy them by the pallet/pound to Not sell them to a market that doesn’t buy them…

just some casual observations of “Forum Lore”…

 

[Keith Knight]

One thing to interject here is that the 3126b Air Inlet Heater (AIH) on mine draws 88-90Amps for a good 5 minutes while warming up (it's 16F out!) and even with the block heater, that AIH runs a lot, until I get the trans heated up. So IMHO, someone screwed up! Even with my 110A 24v only alt, on a cold day with 4 batteries (I'm only running 2), the alt is Immediately overloaded. With only 2 batts, I'm pulling 115A after immediate startup which is Way more than that dual volt Neihoff could produce. It's not due to lack of use in my case. This is irrelevant over 60F ambient but someone screwed up. Happy to be proven wrong of course.

Very valid point.

 

[Keith Knight]

The alternators are extremely robust and counter to forum lore here, they rarely fail. The regulators are perhaps slightly more delicate, but most all assumed “failed” alternators ultimately appear to go back to really poorly maintained wiring, battery problems, and ultimately, poor troubleshooting skills of a (slightly) complex system. No one on this forum has ever demonstrated with any data that the 100a alternators have any elevated failure rates, or that charging drained batteries shortens their life. While it is true that that the output current is split between 12v and 24v, having 12v pegged on an A1 truck is going to be uncommon. 12v is very lightly used and Niehoff’s data (attached) shows that there is ample current available to the 24v side to handle recharging the batteries and running the other 24V loads like the intake air heater.





This is extremely simple and another subject of lots of forum lore. The LBCD exists to maintain the appropriate voltages to all of the computerized components (think ECM and TCM) even when the batteries are faulted in such a way that the alternator is unable to maintain 20volts in the electrical system. This fault could be a low state of charge, or batteries that became bullet riddled. If the computerized engine stops running due to insufficient voltage, you no longer need to worry about “protecting” the alternator from an overload condition. Perhaps it is helpful to think of the LBCD as a battery “simulator” for use while the main bank is offline. Another anecdote on that point is that the trucks with the 260A alternators still have the LBCD. It exists to make the system more robust, not as a bandaid for an undersized alternator.

That was going to be my next question!

Is the LBCD good or bad?

Seems like it does way more than you think. Read into the patent claims.

 

[GeneralDisorder]

From those in the know, I'm told the upgrade to the 260A alternator was due to increased electrical demands in terms of equipment being added to the trucks once they arrived at the destination unit, rather than the 100A being particularly unreliable. Blue Force Tracker computers, radio and communication equipment, CROWS weapon system integration, etc, etc. As @Lostchain mentioned - 100A failure is rare in my experience. In fact I haven't personally come across a single failed Niehoff alternator of any rating. I have heard of enough voltage regulator failures and witnessed that replacing *just* the regulator "fixed" the problem to believe those do fail although how many of those failures were a result of the charging system being abused or being affected by corroded connections and grounds I do not know. They often get blamed for problems that aren't their fault and I've seen alternators swapped out just because the upper mounting bolt threads were damaged and the Army "technicians" don't have any clue to how to fix that.

The LBCD does perform the task of filtering the dirty voltage from the brushless Niehoff - which tends to have really aggressive AC ripple. Up to +/- 2v is considered "normal" by the Niehoff engineers. There may be modules on our trucks that don't like that.

Personally, for me, it's a matter of the 100A being insufficient for added equipment and lighting and not having the overhead to regularly use it's output for house battery charging while driving. The 260A can easily support four Victron Orion 24/24 17A chargers and not even break a sweat. I wouldn't trust a 100A to push an extra 68A in addition to the chassis requirements as well as all my cab accessories, etc. It would simpy be irresponisble to overload it like that.

I've got half a dozen of the 260A brackets made up and I'll be putting together kits for the 3126 and C7 trucks for anyone wanting to do the 260A upgrade. 3116 mounting isn't something I've had the pleasure of dealing with yet but it appears they don't have the alternator pad mount like the 3126 and C7 have so the mounting situation is entirely different.

 

[Keith Knight]

I’ve read that if you removed the 12v from the 100 amp Niehoff alternator so you only have a 24v alternator that you can get the full rated amperage out of the 24v?

If this is true, would the simplest solution be remove the 12v from the alternator and battery, connect a 24 to 12 equalizer to the 24v load terminal of the LBCD and remove the cable from the 12v load terminal on the LBCD and connect it to the equalizer 12v terminal.

This would keep all the warning lights and everything else functional keeping it simple.


Next question, using a 100 amp 24v to 12v Battery equalizer if you are pulling 50 amps on the 12v side are you only pulling 25 amps from the 24v side?

 

[Keith Knight]

From those in the know, I'm told the upgrade to the 260A alternator was due to increased electrical demands in terms of equipment being added to the trucks once they arrived at the destination unit, rather than the 100A being particularly unreliable. Blue Force Tracker computers, radio and communication equipment, CROWS weapon system integration, etc, etc. As @Lostchain mentioned - 100A failure is rare in my experience. In fact I haven't personally come across a single failed Niehoff alternator of any rating. I have heard of enough voltage regulator failures and witnessed that replacing *just* the regulator "fixed" the problem to believe those do fail although how many of those failures were a result of the charging system being abused or being affected by corroded connections and grounds I do not know. They often get blamed for problems that aren't their fault and I've seen alternators swapped out just because the upper mounting bolt threads were damaged and the Army "technicians" don't have any clue to how to fix that.

The LBCD does perform the task of filtering the dirty voltage from the brushless Niehoff - which tends to have really aggressive AC ripple. Up to +/- 2v is considered "normal" by the Niehoff engineers. There may be modules on our trucks that don't like that.

Personally, for me, it's a matter of the 100A being insufficient for added equipment and lighting and not having the overhead to regularly use it's output for house battery charging while driving. The 260A can easily support four Victron Orion 24/24 17A chargers and not even break a sweat. I wouldn't trust a 100A to push an extra 68A in addition to the chassis requirements as well as all my cab accessories, etc. It would simpy be irresponisble to overload it like that.

I've got half a dozen of the 260A brackets made up and I'll be putting together kits for the 3126 and C7 trucks for anyone wanting to do the 260A upgrade. 3116 mounting isn't something I've had the pleasure of dealing with yet but it appears they don't have the alternator pad mount like the 3126 and C7 have so the mounting situation is entirely different.

View attachment 935929

What’s the differences between the 100amp and the 260amp alternators?
Why a new bracket?

 

[Ronmar]

I’ve read that if you removed the 12v from the 100 amp Niehoff alternator so you only have a 24v alternator that you can get the full rated amperage out of the 24v?

If this is true, would the simplest solution be remove the 12v from the alternator and battery, connect a 24 to 12 equalizer to the 24v load terminal of the LBCD and remove the cable from the 12v load terminal on the LBCD and connect it to the equalizer 12v terminal.

This would keep all the warning lights and everything else functional keeping it simple.
View attachment 935930

Next question, using a 100 amp 24v to 12v Battery equalizer if you are pulling 50 amps on the 12v side are you only pulling 25 amps from the 24v side?

You need to keep the 12v connection between battery and alternator as the regulator is looking for that input/relationship to regulate the 14v output to exactly 1/2 of the 28v output. I think if it is seeing a certain amount of field drive to reach 28V it is expecting to see a certain amount of drive to fire the SCRs to 14V and with nothing attached it would see a mismatch trying to maintain its output voltages. I think it monitors this relationship to indicate a wiring or battery issue. Mine did not respond properly when it had no 12v connection to battery. I have encountered this in troubleshooting with others also due to bad connections, it dropped the 28V output down around 26V on mine when I experimented with it if i recall.

That is how I am currently running mine, alt 12 and 24v lines connected to the battery but no draw on that 12v leg whatsoever, beyond what the middle of the series battery would see when 24v is loaded... in fact there is only a 24V line running to the cab where I connect it to the 24-12 converter/equalizer(100A Vanner). The 12v equalizer output connects to the power panel 12v. The alt maintains an acceptable voltage(27.9V on mine) with 100A load applied across the alt output... I expect the Neihoff will last a good long time like this but if it hiccups, it will get a straight 24V Delco alt... Or if the reg craps I will look at fitting a different reg and convert it to a straight 24v alt...

What you describes sounds viable, at least on an A1. The A0 used 12v power to control the 24V ignition power relay. If you brown out the 24v circuit enough say during a long cold start, and the equalizer drops the 12v output, it will open the 24V ignition relay K2 and halt the start. They did away with this "feature" on the A1 and use 24v for ignition control power on both the 12 and 24v ignition relays... This is an easy thing to fix on the A0 as well(power k2 ignition relay with 24V vis 12) which I have done on mine as well...

You are correct 50A@12V is 25A@24v plus a little bit for converter efficiency/loss. With all the LED's I have converted to now, I think my truck 12v load is less than 10A@24v(measured it, can't find my notes)...

 

[Keith Knight]

Great information, so that makes it even simpler. I corrected my diagram.
I’m liking this. Also if the 24v to 12v battery equalizer stops working it a quick reconnect and you’re back working again.

 

[Keith Knight]

Here’s the question that I find difficult to answer.
Why charge the same batteries with 24v and 12v?

With the 4 batteries in series parallel I’ve actually charged all four batteries with a 12v charger and with a 24v charger at separate times. Both methods have worked in a pinch.

By the way thanks for everyone’s input. As I was hoping that we could look at this open minds and address some speculation versus reality.

 

[MatthewWBailey]

I wouldn't trust a 100A to push an extra 68A in addition to the chassis requirements as well as all my cab accessories, etc. It would simpy be irresponisble to overload it like that.

So with all the accolades we're giving Neihoff at this point, perhaps there's a better question: Is it (100A) overloaded in a stock A1? Seems like the adjectives of "robust" and "rarely fail" and "no data" are ignored when it's considered overloaded. So is it overloaded? Yes or no? (Don't forget that hard pulsing 90A AIH draw)

For the record, I DO have a failed 100a Neihoff alternator at the local rebuild shop. Already dropped $800 on a failed regulator 2k miles ago with only 9k on the truck at the time. He tested it on his bench setup and it's putting out 50A max on his tester. So he's tearing into it. I'll know more once he's done. So apparently I'm the only person in the known universe that's ever had a bad Neihoff alt?, I should be shamed drawn and quartered. lol. Tyler screwed me again? I'm betting that's it.

On the LBCD, I see 2 big capacitors and 2 diodes. The diodes can go in the PDP. The patent app discuses "ripple reduction during battery-less operation". If you eliminate "battery less operation" you don't need this mystical black box which imho as an EE does nothing but bust my balls. I gave mine away, with cash and bitcoin to a needy family along with the power relay. I shorted my manual disco terminals with bus bars for security but they're easily removable for maintenance. I'll post that another place. So I'm never in battery less mode

Further food for thought, convince me that at $800+ per regulator and god knows what for the alt itself ($1200), why isn't this thing able to produce 200% and never fail regardless of load duty? If I gave you $2000, could you buy a better more capable unit in the commercial market? With ALL the 12v load removed on mine with 2batts I'm pulling 115A during initial startup for several minutes. Is that an overload on a N1511?

my professional opinion (FWIW) is that this pulsing 90A AIH is an ALT wrecker or at least a Regulator wrecker. I'd have to test 2 units side by side to prove it thou.

 

[MatthewWBailey]

Great information, so that makes it even simpler. I corrected my diagram. View attachment 935939
I’m liking this. Also if the 24v to 12v battery equalizer stops working it a quick reconnect and you’re back working again.

I basically do the same thing with the 24v only alt, except I left a single 12v battery on x2. So I have lights even when ignition is off just like stock and I can leave the lights on and not kill my starter batteries. (Never happened)

 

[Keith Knight]

So with all the accolades we're giving Neihoff at this point, perhaps there's a better question: Is it (100A) overloaded in a stock A1? Seems like the adjectives of "robust" and "rarely fail" and "no data" are ignored when it's considered overloaded. So is it overloaded? Yes or no? (Don't forget that hard pulsing 90A AIH draw)

For the record, I DO have a failed 100a Neihoff alternator at the local rebuild shop. Already dropped $800 on a failed regulator 2k miles ago with only 9k on the truck at the time. He tested it on his bench setup and it's putting out 50A max on his tester. So he's tearing into it. I'll know more once he's done. So apparently I'm the only person in the known universe that's ever had a bad Neihoff alt?, I should be shamed drawn and quartered. lol. Tyler screwed me again? I'm betting that's it.

On the LBCD, I see 2 big capacitors and 2 diodes. The diodes can go in the PDP. The patent app discuses "ripple reduction during battery-less operation". If you eliminate "battery less operation" you don't need this mystical black box which imho as an EE does nothing but bust my balls. I gave mine away, with cash and bitcoin to a needy family along with the power relay. I shorted my manual disco terminals with bus bars for security but they're easily removable for maintenance. I'll post that another place. So I'm never in battery less mode

Further food for thought, convince me that at $800+ per regulator and god knows what for the alt itself ($1200), why isn't this thing able to produce 200% and never fail regardless of load duty? If I gave you $2000, could you buy a better more capable unit in the commercial market? With ALL the 12v load removed on mine with 2batts I'm pulling 115A during initial startup for several minutes. Is that an overload on a N1511?

my professional opinion (FWIW) is that this pulsing 90A AIH is an ALT wrecker or at least a Regulator wrecker. I'd have to test 2 units side by side to prove it thou.

You’re killing me with abbreviations without stating what they are! LOL!!!