LBCD replacement due to loose studs. CARNAGE!!

[GeneralDisorder]

So the question is - did these guys leak or did they blow up? Given I have the 260a alternator.... The truck did already have a newer voltage regulator when I got it. Given the state of the connections though I'm not that surprised.

 

[Ronmar]

Well if this was an A1, I am pretty sure it didn’t come standard with the 260. That may have been the original LBCD though….

So if it had a 100A alt, and had AGMs installed, I could see it disconnecting more frequently due to overload and working those caps harder…

Now if a 260A needs to disconnect, that may be upwards of 4.5KW being absorbed by those caps…

who knows, all the A1s may be in this condition

 

[GeneralDisorder]

This is a 1079 A1R truck that came with the 260a stock. The LBCD is rated at 200a on it's data plate so I would assume it disconnects around/above 200a.... But there's nothing that says if that's the 14v or 28v or combined rating. And the LBCD relies on the VR to send it the load signal which I assume is a some kind of duty cycle or AC frequency that indicates a percentage of full load? What percentage does it trip at? So many questions. 100% or close to it from the 100a alternator is significantly different than 100% from the 260a. Not quite sure how it could be designed to handle both.... It seems rated much too high (200a) for the 100a alt, and possibly too low for the 260 which could hit those caps with quite the force.

The one I got to replace it looked fine from the outside. A bit newer being a 2011 unit. Doesn't mean they aren't starting to leak though.

You bring up a good point - if the batteries are properly maintained the LBCD could pretty much be deleted on the 260a trucks. Especially if amperage gauges were installed for proper output monitoring.

 

[Ronmar]

I forgot yours was an A1R(too many different discussions). Have run across a few with A1 and a 260A.

yep lots of ?

What I have gleaned from other troubleshooting sessions is that the LBCD sends 28V to that F- terminal. If you disconnect that wire you can see it on the wire coming from the LBCD. Connected to F-, the regulator provides a pulsed path to ground for it as well as the field current…

with that wire disconnected i do not think the LBCD can disconnect

a properly sized alt or battery bank teally removes the need for it, and I think the polarity protection function would have been better served by smaller diodes located at any equipment that needs it, instead of in a box mounted out in the weather…

 

[MatthewWBailey]

Well if this was an A1, I am pretty sure it didn’t come standard with the 260. That may have been the original LBCD though….

So if it had a 100A alt, and had AGMs installed, I could see it disconnecting more frequently due to overload and working those caps harder…

Now if a 260A needs to disconnect, that may be upwards of 4.5KW being absorbed by those caps…

who knows, all the A1s may be in this condition

This was a quite entertaining thread for me as an EE, especially since I'm probably an active victim too. You guys are really masterful.

My only contribution is that those Caps would be sized for both the wattage absorbed and the dv/dt that they could see. The overvoltage from dropping the batteries out under full current flow is limited by the alt field itself for the time it sustains, so probably the same/similar dv/dt for both 100a and 260a scenarios But more i for the 260 obviously. The formula for a Cap is I = C*dv/dt. So if there's more current to absorb for the 260 (to suppress) and dv/dt is relatively the same, then the Capacitance size of the caps must be 2.6x larger for the same performance, minus the scale of the voltage drop differential between 100 and 260 if using the same lead size.

My experience with industrial motor caps is that they fail on temp cycles almost exclusively as long as the voltage rating is not exceeded. Otherwise they last forever. Pretty simple if you apply more voltage than the dielectric rating, it'll blow. Heat makes it boil. Exceeding the voltage rating seems hard in this scenario to me, and the dang LBCD sits over top of the trans, oops. Might need coolant lines to that thing.

really great thread

 

[Lostchain]

This is a 1079 A1R truck that came with the 260a stock. The LBCD is rated at 200a on it's data plate so I would assume it disconnects around/above 200a.... But there's nothing that says if that's the 14v or 28v or combined rating. And the LBCD relies on the VR to send it the load signal which I assume is a some kind of duty cycle or AC frequency that indicates a percentage of full load? What percentage does it trip at? So many questions. 100% or close to it from the 100a alternator is significantly different than 100% from the 260a.

My understanding is that the LBCD will disconnect if RPM is above 1500 RPM and the system voltage is below 20.5V
Load is not taken into consideration at all, so something as simple as corroded connectors could cause it to trip potentially. RPM comes from the AC pin which is read as Hz X 10 = Shaft RPM

All of the niehoff alternators on our trucks output's are self limited and will not exceed the rated capacity of the alternator, so load is somewhat irrelevant as the alternators are rated for 100% duty cycle.

 

[GeneralDisorder]

My only contribution is that those Caps would be sized for both the wattage absorbed and the dv/dt that they could see. The overvoltage from dropping the batteries out under full current flow is limited by the alt field itself for the time it sustains, so probably the same/similar dv/dt for both 100a and 260a scenarios But more i for the 260 obviously.

Interesting - my discussion with an engineer at Niehoff indicated that these alts - brushless alts in general as I understood it - were slow to respond to voltage changes and also AC ripple of much greater amplitude was considered normal.

Now I would love your EE explanation of how the LBCD could cause the OVCO situation with the flaky ground connection that I encountered on my truck. Because I can't wrap my head around how the LBCD caused the F+ from the voltage regulator to spike up to 28v+ from it's normal PWM signal and drive the alternator to wide open throttle. Please enlighten!

 

[Ronmar]

I forgot yours was an A1R(too many different discussions). Have run across a few with A1 and a 260A.

yep lots of ?

What I have gleaned from other troubleshooting sessions is that the LBCD sends 28V to that F- terminal. If you disconnect that wire you can see it on the wire coming from the LBCD. Connected to F-, the regulator provides a pulsed path to ground for it as well as the field current…

with that wire disconnected i do not think the LBCD can disconnect

a properly sized alt or battery bank teally removes the need for it, and I think the polarity protection function would have been better served by smaller diodes located at any equipment that needs it, instead of in a box mounted out in the weather…

My understanding is that the LBCD will disconnect if RPM is above 1500 RPM and the system voltage is below 20.5V
Load is not taken into consideration at all, so something as simple as corroded connectors could cause it to trip potentially. RPM comes from the AC pin which is read as Hz X 10 = Shaft RPM

All of the niehoff alternators on our trucks output's are self limited and will not exceed the rated capacity of the alternator, so load is somewhat irrelevant as the alternators are rated for 100% duty cycle.

yes and no. Alternators are rated to deliver their rated voltage up to their rated current. At this point they are basically driving the field near or at 100%, so have no more output to give. Any loading beyond this point will cause a decrease in output voltage. This decrease in voltage is what the LBCD is monitoring above 1500RPM to determine if there is a possible issue. Now it appears from the drawing that the LBCD senses this voltage at the disconnect switch along the trickle charge/sense line connected to pin E on the LBCD. Now a discharged battery pulling alt current thru a bad connection between alt and battery could cause a voltage drop at the battery, but a severely discharged or failed battery is the only thing in the normally operating truck that can overload the alt, so they disconnect them and feed them trickle current to protect the alt. This lights the dash lights(batt disconnect and charge system trouble) to alert the operator.

you said it yourself, the reg does not monitor current or load. It only knows voltage output and the 28v regulator drives the field to try and maintain that output. once it maxes field output, output voltage drops off, but at that point you are running the alt at or beyond its max output and making its maximum heat…

 

[GeneralDisorder]

All of the niehoff alternators on our trucks output's are self limited and will not exceed the rated capacity of the alternator, so load is somewhat irrelevant as the alternators are rated for 100% duty cycle.

They claim this in the documentation - I'm a bit skeptical at least as regards the 100A alternators. If that was the case and they limited themselves to their rated output and they were capable of 100% duty cycle then what's with the high failure rate and eventual upgrade to the 260A units? If that was actually the case then they would just plug along at their full output and battery condition/size would be irrelevant. It would just take them longer to charge four 6TAGM's and besides that nothing bad would happen.

But that's not what we see. We see high failure rates of the 100A. And better luck overall with dropping to two batteries to reduce the load on them.

Someone is wrong.

 

[Lostchain]

Any loading beyond this point will cause a decrease in output voltage.

Have you tested and observed this yourself with a load bank on a niehoff? I am working on upgrading the motor on my test stand right now to test this.

 

[MatthewWBailey]

Interesting - my discussion with an engineer at Niehoff indicated that these alts - brushless alts in general as I understood it - were slow to respond to voltage changes and also AC ripple of much greater amplitude was considered normal.

Now I would love your EE explanation of how the LBCD could cause the OVCO situation with the flaky ground connection that I encountered on my truck. Because I can't wrap my head around how the LBCD caused the F+ from the voltage regulator to spike up to 28v+ from it's normal PWM signal and drive the alternator to wide open throttle. Please enlighten!

Firstly, The niehoff explanation makes total sense to me as brushless dc generators use an induced ac field internally to drive the rotating field current, whereas a brush directly connects voltage to the internal winding, making field current flow instantly. The induced field of the brushless takes more time to build up, or adapt to a change, not a huge time but long in electrical time as compared to a direct connection. Reading neihoffs literature, I liked the style bc it's a maintenance free design, very robust that way.

On your second point, I'd have to sketch it out in a circuit diagram to see the dc equivalent circuit. I see that circuit you posted on the other thread. I'll have to put the discrete element numbers in there and see what it looks like as a raw circuit, not just block schematic. I can dump it into one of those online circuit solvers to see what the resonant frequency is.

My first inclination on the flaky ground wire is to look for AC noise induced on the alt regulator. It's just a low power control circuit that is kinda passive in nature, ie a basic analog feedback circuit. Lost grounds always seem to make unwanted noise references somewhere. That's just a hunch thats always uncovered phantoms before. Bouncing grounds or totally unconnected grounds allow for ac noise to float reference voltages of the assembly, which power circuits don't care much about but control circuits do not like.

I'll see what a dc circuits diagram looks like for that thing based on your previous post.

 

[Lostchain]

We see high failure rates of the 100A.

I hear this a lot, but I myself haven’t come across a post where a failed alternator was definitively diagnosed. People like to claim it, but have they really broken the whole system down, removed all variables and tied it specifically to a failed alternator? Would love to see a forum post like that…. Maybe a PS Magazine article or something? Please share if you know of one…

 

[87cr250r]

I'm late to the thread and don't know if this has been covered but electrolytic capacitors don't tolerate long term storage. When de-energized the insulating oxides inside break down and cause the capacitor to short circuit internally. The general rule of thumb is that electrolytic capacitors must be energized at least once every two years to prevent this.

If they have been in storage for more than two years they must be reformed. Reforming consists of applying a low voltage and then ramping it up slowly to system voltage over a period of an hour or so. If you do not reform the capacitors will short circuit and burn up like this.

If the capacitor sits de-energized for too long it will swell up. If the bare aluminum surface on the capacitor is deformed at all (not flat) remove and replace that capacitor before energizing to prevent short circuits.

If you need your system to be very reliable most manufacturers recommend electrolytic capacitors be replaced every 7 years which means you should probably do it at 14 years.

 

[GeneralDisorder]

I hear this a lot, but I myself haven’t come across a post where a failed alternator was definitively diagnosed. People like to claim it, but have they really broken the whole system down, removed all variables and tied it specifically to a failed alternator? Would love to see a forum post like that…. Maybe a PS Magazine article or something? Please share if you know of one…

Well - it's either the alternator itself or the voltage regulator that's the failing..... the preponderance of evidence though suggests that they were not ultimately capable. The fact that later trucks were upgraded to the 260 despite actually having less load with LED lighting suggests there was not an option that S&S/BAE/Niehoff could persue that allowed the 100A to fulfil this promise of 100% duty and load limiting.

 

[Ronmar]

Have you tested and observed this yourself with a load bank on a niehoff? I am working on upgrading the motor on my test stand right now to test this.

I have only run mine to 100A, Let me see how my schedule shakes out this weekend maybe I can hookup again and collect some other data, as I will be backing the frame into the garage to weld up my hydraulic habitat restraints.. With 100A applied at idle I had .4v drop from 28V and .1V drop at mid throttle/~1500 engine RPM(forget pulley multiplication crank to alt).

Again, reg has no way to know what its load is. And the only way it could derate its output would be to reduce its output voltage… alternators are completely reactionary to the load applied to them, always have been. nothing in this configuration leads me to believe this will behave any differently than any other alt, except that it is perhaps a little underrated. alts are typically rated +/- 0.5v of their specified voltage. I have always interpreted this to include at full load.

these use PWM to regulate field current, but even at 100% duty cycle, the field can only flow X amount of current and build X amount of field Due to wire resistance. 100A@28V = 2800W Max rated output. If loaded down to produce a .5v drop, it doesn’t take much additional current to reach that same 2800W max rated output. 2800/27.5V = 101.8A… anything over 2800W = overload. In the end the internal heat and cooling capability ultimately determine its 100% rating/duty cycle. The alt will overload if it can because it doesn't know any better Neihoff even alludes to damage from overloads in their troubleshooting guides, which is right in line with operation of any other alternator.

From the 1509/1511 and N2003 LBCD troubleshooting guide: 240AH of AGM is looking for ~108A, lithiums need a buffer/intermediary power converter to limit current load placed on an alt…

 

[Ronmar]

I got a chance to play with the alt this afternoon, and voltage dropped off steeply once it hit full field Drive, same as any other alt. Using the rated +/- 0.5 criteria, I hit 27.5V ~120A(3300W). It fell past 25V just above that. I have an aging 1000A pile, so precise adjustments in the low hundreds range are not its specialty

That was at mid throttle(don’t have a tach) but advanced to the point of full fuel pressure, which should be by peak torque/1500RPM… crank pulley ~9”, alt pulley 4”, so 2.25:1~3375 alt RPM…

 

[Lostchain]

Well - it's either the alternator itself or the voltage regulator that's the failing.....

people claim that for sure…

I called neihoff about my 100a alternator that I suspected had a bad regulator (mainly due to comments I’ve read on this forum) and they steadfastly refused to consider that my regulator was bad, the technician repeatedly tried to steer me back towards some problem with my wiring or batteries or some other segment of the system other than the regulator or alternator. If it was a foregone conclusion that the 100a system had higher failure rates, he certainly wasn’t willing to entertain that possibility with me on the phone…

I got a chance to play with the alt this afternoon, and voltage dropped off steeply once it hit full field Drive, same as any other alt. Using the rated +/- 0.5 criteria, I hit 27.5V ~120A(3300W). It fell past 25V just above that. I have an aging 1000A pile, so precise adjustments in the low hundreds range are not its specialty

That was at mid throttle(don’t have a tach) but advanced to the point of full fuel pressure, which should be by peak torque/1500RPM… crank pulley ~9”, alt pulley 4”, so 2.25:1~3375 alt RPM…

Interesting, thanks for running that test!

Where did you measure the current at? The load bank, or at the alternator? If load bank, where was it connected?

 

[Ronmar]

The shunt is in the loadbank connected at alternator...

 

[Lostchain]

The shunt is in the loadbank connected at alternator...

So as you passed beyond 120a and the voltage started to drop, isn’t that showing that the alternator is limiting its current, thus protecting itself? Said another way, if you had had the load bank at the batteries, and an inductive clamp at the alternator, even if you put 500a at the batteries, wouldn’t the inductive clamp only shown the 120a the alternator was limiting itself at?

 

[Ronmar]

it isn’t limiting its current it limits its voltage, simply because it cannot make any more under increasing load Despite full field being applied… I can increase the load on it, and the voltage drops. but if you look at it in terms of watts, you will find the alt is still putting out a significant percentage over its rating. Todays test was still delivering 3300W(117%) when the voltage dropped out of spec Still overloaded, still going to heat up, shorten its life or cook if it persists… just like every other alt I have ever worked with and every Neihoff troubleshooting docs says it will… But feel free to put a couple hundred A on your alt and hold it there

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. Victron has some interesting videos on how to charge lithium without cooking your alt… 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. That is where the LBCD came from, a device that disconnects the load from a fully excited alt to save the alt from bad/dead batts. something I have never seen used anywhere in my 40 years working with power systems, doing something that most every automotive electric service manual says is a no-no(disconnecting batt from running/loaded alt)… Then along came AGM batts, needing nearly double the charge current. The LBCD couldnt fix that so they finally brought on a alt appropriately sized for 240AH of AGM…

if the 100A alt could limit its output to protect itself, the LBCD would never have been necessary…