LBCD replacement due to loose studs. CARNAGE!!

[GeneralDisorder]

Induction motors - which brushless alternators share much in common with - are REALLY dumb. If you ask more of them then they are rated for they will GIVE everything they have to try to stay at their rated RPM and will die in the attempt if too much load is put on them. The amount of slippage between the rotor RPM and the rotating field causes massive increases to induction and therefore heat (see a description of how an induction cooktop works). If you drag that motor down to hundreds of RPM below it's magnetic field rotation it will quickly overheat and I have seen them glow red, turn the winding varnish black, and burst into flames.

The exact same thing happens in reverse to an induction (brushless) alternator. Ask more than it can deliver and the rotating magnetic field being produced can't travel as fast as the rotor shaft RPM's and you produce a TON of heat and it literally cooks the windings till the varnish burns off and they short out.

 

[Lostchain]

Induction motors - which brushless alternators share much in common with - are REALLY dumb. If you ask more of them then they are rated for they will GIVE everything they have to try to stay at their rated RPM and will die in the attempt if too much load is put on them. The amount of slippage between the rotor RPM and the rotating field causes massive increases to induction and therefore heat (see a description of how an induction cooktop works). If you drag that motor down to hundreds of RPM below it's magnetic field rotation it will quickly overheat and I have seen them glow red, turn the winding varnish black, and burst into flames.

The exact same thing happens in reverse to an induction (brushless) alternator. Ask more than it can deliver and the rotating magnetic field being produced can't travel as fast as the rotor shaft RPM's and you produce a TON of heat and it literally cooks the windings till the varnish burns off and they short out.

I have no doubt your correct, by why does neihoffs documentation specifically say it is self limited? That’s the part I don’t understand, do they not understand the product they produce?

 

[Ronmar]

Sales hype? The cautions in their troubleshooting manuals clearly contradict this…

 

[87cr250r]

The current in the stator creates a magnetic field that opposes the field from the rotor. If you put a fixed voltage into the rotor field, as the stator field increases the field current decreases and the stator output voltage decreases. Capping the output voltage from the regulator to the field caps the alternator output current as the it will stop producing voltage when the stator current gets high. You can't have current without voltage.

 

[GeneralDisorder]

The current in the stator creates a magnetic field that opposes the field from the rotor. If you put a fixed voltage into the rotor field, as the stator field increases the field current decreases and the stator output voltage decreases. Capping the output voltage from the regulator to the field caps the alternator output current as the it will stop producing voltage when the stator current gets high. You can't have current without voltage.

I'm not an expert - I have a dangerous level of understanding from a working mans non-EE (software in my case) engineering experience.

That said I feel like the problem is very tricky for the VR to contain - these alternators have multiple stages - in fact the 12/24 dual voltage alternator has no less than 5 separate stator windings. All being fundamentally controlled by a single PWM field input from the VR that is admittedly slow to respond. I'm sure they have done their best to limit how badly these alternators can "crash and burn" but I can see that problem being very difficult in practice, in an imperfect environment, being operated by the Lowest Common Denominator (PVT Snuffy).

 

[hike]

Deleted a half baked idea once again leaving the purpose of a thread. Thank you for your patience with me—

 

[GeneralDisorder]

The same theory applies to sizing the battery so it wont under any state of discharge, apply too much load to the alt. A class that the folks at S&S must have skipped when they put 240AH of battery onto what amounts to a pair of 50A alts in series…

that IMO is the root cause of all the 100A issues on the LMTV. They are not bad alts they were just asked to do too much.

An interesting aside to this observation - I recently picked up a 1984 M1009 CUCV (Chevy K5 blazer military edition). It runs a similar hybrid 12/24 system to our trucks and has the ability to run two 6TL batteries.....

GM was present in class the day that S&S was playing hooky. These trucks have two 100A 27si Delco isolated ground alternators - each charges and maintains one 6TL (perfectly evenly I might add - which the S&S system does not). That means my little Chevy truck that was designed a decade before the FMTV's was equipped with 400% more alternator in terms of charging to battery ratio than the FMTV's. That's kind of astonishing to consider.

 

[GeneralDisorder]

Maybe a PS Magazine article or something? Please share if you know of one…

I can show that the military is so fed up with the 100A alternator situation and having to constantly replace them to the tune of $2k each that they have gone to the trouble of making 260A upgrade kits for every FMTV even back to the A0 trucks (which a few are still in use by the 82nd as I understand it). All replacement engines including the 3116 come with 260's and there are retrofit kits to convert every generation of the trucks to the 260.

 

[MatthewWBailey]

Induction motors - which brushless alternators share much in common with - are REALLY dumb. If you ask more of them then they are rated for they will GIVE everything they have to try to stay at their rated RPM and will die in the attempt if too much load is put on them. The amount of slippage between the rotor RPM and the rotating field causes massive increases to induction and therefore heat (see a description of how an induction cooktop works). If you drag that motor down to hundreds of RPM below it's magnetic field rotation it will quickly overheat and I have seen them glow red, turn the winding varnish black, and burst into flames.

The exact same thing happens in reverse to an induction (brushless) alternator. Ask more than it can deliver and the rotating magnetic field being produced can't travel as fast as the rotor shaft RPM's and you produce a TON of heat and it literally cooks the windings till the varnish burns off and they short out.

100%

 

[MatthewWBailey]

I can show that the military is so fed up with the 100A alternator situation and having to constantly replace them to the tune of $2k each that they have gone to the trouble of making 260A upgrade kits for every FMTV even back to the A0 trucks (which a few are still in use by the 82nd as I understand it). All replacement engines including the 3116 come with 260's and there are retrofit kits to convert every generation of the trucks to the 260.

View attachment 915548

Clearly there's a flaw we're not privy too.

 

[MatthewWBailey]

I have no doubt your correct, by why does neihoffs documentation specifically say it is self limited? That’s the part I don’t understand, do they not understand the product they produce?

View attachment 915523

These sales verbiages are always non specific, sounds like rhetoric. Analog control circuits are dated. "Rated capacity" has a time and power spec associated with it like any gen. Unless you have a current limited supply like found in ac inverters or frequency drives, you can't have a "programmed" or hard self limit. Rotating dc/ac machines have a steep Power drop off on a curve above their nameplate due to what @87cr250r and @GeneralDisorder said. The core and copper losses increase exponentially as you go up in both slippage and power out over time. The response of the VR adds to this buts it's not a discrete function like in current limited supplies, hence the 120A+ numbers for short duration. The design of the VR and field electronics may be obsolete/dated in these 100A units even further back than 1994. They're probably attributing the VR as the "self limiting" feature bc it's a sales brochure to the military, good enough for govt work.

 

[Lostchain]

I can show that the military is so fed up with the 100A alternator situation and having to constantly replace them to the tune of $2k each that they have gone to the trouble of making 260A upgrade kits for every FMTV even back to the A0 trucks (which a few are still in use by the 82nd as I understand it). All replacement engines including the 3116 come with 260's and there are retrofit kits to convert every generation of the trucks to the 260.

I didn't see anything that said it was due to high failure rates. I could just as easily speculate that its because any truck in the inventory today needs more current for all the additional radios and computers that go into a truck these days.....

I've seen plenty of things saying the 100A is being obsoleted, I haven't seen any documentation that the reason for that is due to higher failure rates... You know as well as I do the army sends back bad alternators for stripped threads. Every thread on this forum I could flesh out of google where a 100A alternator/regulator was suspected bad, was eventually traced back to some other part of the charging system. In Feb 2018 PS Magazine 783 stated that the 100A alternator will *soon* be obsolete. If the FMTVs went into service in 1996, that's over 2 decades it took to give up on the "high failure rate" 100A alternator. To me, the slowly increasing "digitization" of the fleet is a more likely reason it took so long.

I am not trying to say that 100A is the right size for the truck. I just cannot find any documentation or evidence anywhere that says the 100A alternators have an elevated failure rate... I think that is a claim that is made frequently on this forum, and I have struggled to find any evidence to back that claim up..

 

[Ronmar]

Well if something wasn’t broke, why fix it… it isn’t just alternators that were failing. Low state of charge is the biggest killer of batteries, and it takes long run times to top off 240AH of depleted batts with a 100A dual volt. With more than half their 12V capacity consumed by lighting, that 100A alt is only contributing around 2KW with any real 12v load applied… couple that with a small vampire load on the 12v side and its no wonder the A0 trucks typically have failed 0-12v batts.

this was a terrible matchup. Like the example General gave, pick a vehicle, any vehicle and compare alt spec, elec load and battery AH capacity. You won’t find anywhere this big a mis-match, because it has a high failure rate… as an example, my Toyota tacoma has a group 24 battery with about 70AH capacity. It has about 15A of load when everything is turned on. It has an 80A alternator, so 65A is available to charge. For flooded cells you need about 25% of AH capacity in amps from the alt for the bulk of the charge, so my tacoma alt is still under 50% loaded worst case?

 

[hike]

We are thinking of splitting to a system of two 2-12vAGM's in series (first set to the starter; second set to the PDP @h X1, with a 24/12 70a dc2dc converter between X1 and X2), and replacing the LBCD with a Victron Cyrix-ct 225a 12/24v battery combiner. At the same time it looks like we can drop the polarity protection, too?

If I am thinking about this right the starter batteries would be charged 'first' and maintained. The PDP set would only need be maintained as needed, and charged after running accessories that we may run while parked without the engine running. The Cyrix also allows the PDP set to back up the starter set if needed.

This will also work when we replace the dual Niehoff with a straight 24v 150a+ alternator when that time comes.

Batteries, alternator, and battery isolator/combiner all off the shelf, reasonably available overnight for a reasonable cost without reconfiguring the whole system: Cyrix replaces LBCD, polarity disconnect comes out (or not), 24/12v 70a added at the PDP—

 

[Lostchain]

this was a terrible matchup. Like the example General gave, pick a vehicle, any vehicle and compare alt spec, elec load and battery AH capacity.

100% agree, but fixing that by deleting batteries is problematic as @aw113sgte unfortunately found out in the dead of winter. For folks that don't want to deal with the suspension upgrade hassle necessary to upgrade a 100A truck to a bigger alternator, really should pursue your advice further up the thread:

"Now if you want self limiting output, you follow the scheme used for charging lithium. You put a intermediary switching power supply between alt and batts/load that CAN limit its output current, and which will only be capable of loading the alt to a point within its limit."

This seems the correct and most direct solution.....

 

[aw113sgte]

100% agree, but fixing that by deleting batteries is problematic as @aw113sgte unfortunately found out in the dead of winter. For folks that don't want to deal with the suspension upgrade hassle necessary to upgrade a 100A truck to a bigger alternator, really should pursue your advice further up the thread:

"Now if you want self limiting output, you follow the scheme used for charging lithium. You put a intermediary switching power supply between alt and batts/load that CAN limit its output current, and which will only be capable of loading the alt to a point within its limit."

This seems the correct and most direct solution.....

Yep, unable to start in -12 F (or maybe it was -14). Today it was 34 and truck started totally normally. On the alternator route, my 100amp temporarily disconnects (although I don't get a dash light) when the grid heater is running. Have dual blinking orange lights on the regulator (this is at idle).

 

[Lostchain]

Yep, unable to start in -12 F (or maybe it was -14). Today it was 34 and truck started totally normally. On the alternator route, my 100amp temporarily disconnects (although I don't get a dash light) when the grid heater is running. Have dual blinking orange lights on the regulator (this is at idle).

My stock 2003A1 with original alternator goes dual orange when grid heater is on HOWEVER it does not disconnect the battery. First thing I would do is check the voltage at the 28V terminal on the alternator while the grid heater is on and engine running. What is the voltage? On my truck it was about 25v at the time. If it is above 20.5 V than I would say that the LBCD isn't sensing the correct voltages due to flakey wiring (or bad unit) and disconnecting improperly. If the alternator is truly being drug down to below 20.5V I would be investigating the grid heater for some sort of failure...

Testing procedures on the LBCD:

https://www.ceniehoff.com/Documents/Ctrl_Hyperlink/TG53B_uid1252012258102.pdf

 

[aw113sgte]

My stock 2003A1 with original alternator goes dual orange when grid heater is on HOWEVER it does not disconnect the battery. First thing I would do is check the voltage at the 28V terminal on the alternator while the grid heater is on and engine running. What is the voltage? On my truck it was about 25v at the time. If it is above 20.5 V than I would say that the LBCD isn't sensing the correct voltages due to flakey wiring (or bad unit) and disconnecting improperly. If the alternator is truly being drug down to below 20.5V I would be investigating the grid heater for some sort of failure...

Testing procedures on the LBCD:

https://www.ceniehoff.com/Documents/Ctrl_Hyperlink/TG53B_uid1252012258102.pdf

I think it's a wording thing and I wasn't clear. My batteries do not disconnect, I see a decent amount of voltage sag when the grid heater is on, that's also when the alternator is flashing orange. I meant the alternator "disconnected" not the batteries. I looked it up at One point but I forget what the flashing amber / orange means. Maybe the alternator isn't disconnecting it's just a detecting low voltage or something

 

[Lostchain]

I think it's a wording thing and I wasn't clear. My batteries do not disconnect, I see a decent amount of voltage sag when the grid heater is on, that's also when the alternator is flashing orange. I meant the alternator "disconnected" not the batteries. I looked it up at One point but I forget what the flashing amber / orange means. Maybe the alternator isn't disconnecting it's just a detecting low voltage or something

Amber simply means it is below the setpoint, the alternator doesn't "disconnect" in low voltage, only over voltage.

Sounds like your system is behaving normally.





As has been discussed at length on this post and many others, the 100A alternator is undersized for the job, For some reason a number of 70A for the grid heater sticks in my mind, so that one load alone will overload the alternator at idle.... Whether this overload requires any action at all is subject to huge amounts of debate. I wouldn't think twice about it in my opinion....

 

[aw113sgte]

Amber simply means it is below the setpoint, the alternator doesn't "disconnect" in low voltage, only over voltage.

Sounds like your system is behaving normally.

View attachment 915559



As has been discussed at length on this post and many others, the 100A alternator is undersized for the job, For some reason a number of 70A for the grid heater sticks in my mind, so that one load alone will overload the alternator at idle.... Whether this overload requires any action at all is subject to huge amounts of debate. I wouldn't think twice about it in my opinion....

View attachment 915560

What the

Thanks for the refresher!