Victron DC/DC Charger Problems?

[Shakkles]

So i went ahead and installed my Victron Orion 24/24 DC/DC charger based on the input I got from others on this forum, however although the cabin batteries as indeed charging fine, i'm seeing some bizarre stuff from inside of the actual truck cab.

The voltmeter is constantly thrashing between 24 and up to 30 volts as in the video (apologies about it being short). Also the dash instrumentation is flashing, flickering brightly and randomly the windshield wipers will kick on completely by themselves even with the wiper control switch still in the off position.

I'm a little heartbroken about this because i'd hate to think every vehicle in the world can work with a victron DC/DC charger EXCEPT my M1078 LMTV, but i'm at my wits end unless someone out there with more electro-mechanical expertise can help.

As per advice, i have it wired up in the 24-volt configuration with the positive lead on the positive pole of the left battery and the negative input on the negative pole of the right battery. The Orion states it's putting out 28v; It's only the truck that's freaking out.

 

[Skyhawk13205]

Can you list some details regarding the dc-dc install? Do you have combined grounds? Or are you running an isolated ground? My installation I tried my best to keep the truck chassis ground and the camper battery grounds isolated. I even used a diode block to isolate the positive to prevent combining the camper batteries to the truck batteries.

 

[Shakkles]

I have the isolated version of the 24/24 original because i got a good deal on it, cheaper than the non-isolated version.
Per advice from the other thread, the negative/ground of the input is on the negative/ground of the first of two 12v AGM batteries in series, which connects up to the second to make 24 and i have the positive input lead on the final positive terminal. The unit itself and the habitat system all read everything is working exactly as intended, it's only the truck cab electrical system that's "wigging out".

My understanding is that the trucks alternator is charging the batteries AT 24v and not 12v x 2 or something; So its positive and negative 24v cables are connected to the same exact ports; the bottom negative of the first battery and the top positive of the second battery.

So you mention that you're also Isolating, but you still have your campers ground connecting to the trucks ground don't you? Otherwise the camper would act like a lightning rod as far as i'm aware with no way of reaching the actual earth.

 

[87cr250r]

Your wipers turning on randomly would lead me to think you have a problem unrelated to the charger. Have you disconnected the charger to see if the condition stays or goes away?

24V systems typically use isolated grounds. This means you'll have a cable going directly from alternators, chargers, and loads to the negative battery terminal. Grounded systems turn the engine block into a negative bus bar. There is absolutely zero difference in how they operate. The engine block simply becomes the wire. In practice, isolated ground prevents short circuits if a sensor wire rubs through and touches the block. On electronically controlled engines it gives the ECM a chance to give a low voltage alarm when a fault occurs instead of a blown fuse.

 

[Ronmar]

Ok, how is your alternator connected? The alternator 14V must be connected to the middle of your 24v series pair to regulate properly…

 

[Shakkles]

Your wipers turning on randomly would lead me to think you have a problem unrelated to the charger. Have you disconnected the charger to see if the condition stays or goes away?

24V systems typically use isolated grounds. This means you'll have a cable going directly from alternators, chargers, and loads to the negative battery terminal. Grounded systems turn the engine block into a negative bus bar. There is absolutely zero difference in how they operate. The engine block simply becomes the wire. In practice, isolated ground prevents short circuits if a sensor wire rubs through and touches the block. On electronically controlled engines it gives the ECM a chance to give a low voltage alarm when a fault occurs instead of a blown fuse.

Everything i described is purely with the DC/DC charger installed. There are no electrical problems of any kind with it disconnected.

Ok, how is your alternator connected? The alternator 14V must be connected to the middle of your 24v series pair to regulate properly…

That's a damn good question. So the previous owner had a strange web of wires connected around beginning with a dual 12v marine charger which had its 4 leads plugged into the 3 poles of a bassman battery equalizer. Since i've been charging the truck batteries from the habitat battery/solar i didn't need this and deleted it previously. But tomorrow when the sun is up i'll definitely be raising the cab and checking what you said; Looking to see that the alternators 14v is connected to the middle of the battery series.

 

[hike]

24V systems typically use isolated grounds. This means you'll have a cable going directly from alternators, chargers, and loads to the negative battery terminal. Grounded systems turn the engine block into a negative bus bar.

These truck's alternator is grounded to the chassis, battery bank to negative starter terminal then engine block and chassis, PDP is grounded to cab then chassis; no isolated ground wire between any of these. Isn't chassis our main negative bussbar?

 

[hike]

Isn't the point of an isolated dc-dc to have completely isolated circuits? I think a typical isolated dc system would have source hot and ground feeding isolated hot and common to a separate ground. In your case the habitat would have a ground actually running to ground not the chassis (like the natural gas trucks dragging a discharge strap). Not sure this is related to your issue, it is something I don't understand about your system.

A schematic would help greatly—

 

[87cr250r]

The point of isolated power on a metal vehicle is that it will keep operating normally with a wire shorted to ground. No current draw, no blown fuses. This is especially important on electronically controlled engines which many sensors and wires to potentially cause faults.

This of course assumes you don't get simultaneous faults on both your negative and positive circuits.

 

[hike]

—

 

[Ronmar]

Well the only thing on the truck making more than battery voltage is the alternator… So if your gauge is going over 28, then it must be coming from the alt…

What I have observed is that if the alt cannot see the middle of the 24v battery where the 12v is connected, it will derate It’s output.

The 28V part of the alternator works like any other alternator. The regulator monitors the output voltage and modulates the field current to try and maintain it’s 28.2V output.

The 14.1V output is created more like a switching power supply, with the regulator controlling SCR’s tapped off of the middle of the stator windings halfway between ground and the 28V output.

what I think it is also looking for is the relationship between how much field drive it is using to make 28V compared to how much SCR drive it is using to make 14V. I think it has limits as to how far out of whack this relationship can be, and when it is not correct, it throttles back to lower/minimum preset drive signals. At regular intervals it tries to run normal drive and again expects a certain relationship, if it does not see it, it again drops to a low drive output. This keeps a failing battery or wiring from cooking the alt, or cooking a internally shorted battery, while still sending some useable energy to the batteries/powering the truck…

your pulsing indication looks kinda like the alt is cycling in this fashion. A bad connection breaking down under load between battery and alt might also cause something like this…

I don’t see a 12A load from a switching dc-dc converter switching on the 28v battery connections really interfering like this…

 

[Skyhawk13205]

From what I have observed from operation and reading the trouble shooting guides is that the alternator regulator seems to select a voltage from a few factors, battery chemistry, load and temperature.

I noticed with the truck 4 deep cycle flooded lead acid batteries, the voltage will run about 27-28v till the batteries are charged then the voltage will drop to a lower 25-26v. When I run my 24-24 Victron battery chargers, two 400watt chargers in parallel, the voltage will remain at the lower of 25-26v when charging the house batteries. The only time the voltage drives up is when the batteries are discharged.

When the victron battery charger was set up did you set the engine detection voltage low or high? I had to set mine at 25v otherwise it would shutdown when the truck batteries were fully charged. I also had to put a 150amp power relay to disconnect the alternator charger to victron battery charger.

 

[Ronmar]

I have not noted any alt fluctuation away from 14.1/28.2 output with batteries charged(pair of group 31's). My volt meters are measuring the voltage right at the alternator output . The only time I have ever noted a deviation from rated voltage is when I disturbed the 12V connection to the middle of the series wired battery...

 

[hike]

Summary of what has been shared—

Connect Victron 24/24-12 DC to DC Converter input to allow Truck alternator to charge House batteries:
Wipers acting up.
Dash lighting acting up.
Voltage from alternator unstable.
House solar charging Starter/Truck batteries.
Starter/Truck: 1 bank of 2-12v AGM batteries connected in series to converter input.
House: Unknown type (lithium?) and size batteries, assume connected to converter output.
Using a converter instead of a charger.
Using common ground for each side of an isolated unit, truck chassis.
Assume factory settings for converter output voltage, (24.2v at 12a nominal, 15a max, voltage may be adjusted -15% to +25%)
Brushless dual 12v/24v 100a alternator may have electric field delay.
Disconnect DC to DC Converter: all back to normal.

What else @Shakkles?

 

[Shakkles]

Wanted to pop by and leave this message for anyone else who happens to have a similar issue down the lane; The problem is solved now.

So turns out it wasn't the victron, the alternator, nothing to do with the truck at all. What was happening was something to do with how the alternator/battery power was normally "modulating" was actually causing the electronic battery cutoff my truck has to kill the power entirely and the reason the voltmeter and the lights on the dash were "wigging out" was because "this is what happens when one of our trucks is running and the batteries are suddenly disconnected from the truck". That's it. When that happens, all the lighting and etc is getting it's power only from the alternator, so it's "wonky".

NOW... For anyone else who's also looking to slay the "my damn transmission is draining the batteries" boo-hoo that we all have, i still recommend using an electronic cutoff. BUT... The correct placement is in the very, very beginning of the electrical chain, meaning "install it between the negative/ground cable and the negative terminal of four first 12v battery BEFORE it feeds the next battery to make 24v. In this configuration when the cutoff breaks the connection it's breaking the ENTIRE connection before even the first battery is connected. You do this and you'll be fine.

 

[Ronmar]

SO when you get a moment, can you tell us more about this electronic cutout? where it is connected, what is supposed to control it?

In general disconnecting a alternator from it's load(battery) is really bad medicine, especially if it is trying to fill dead batteries. This is something listed as a big fat caution in every automotive electrical manual or the electrical section of every maintenance manual i have ever seen. DO NOT DISCONNECT BATTERY FROM RUNNING ALTERNATOR!

The reason is that the regulator is reactionary and the magnetic field in an alternator does not collapse instantly, so if the alt is running a high field current tryin to maintain it's rated output voltage charging thirsty batteries, and you suddenly disconnect the batteries, that field can drive the voltage of the now only lightly loaded alt(only truck loads), to terribly high levels before it collapses. These voltages can easily reach over a hundred volts! Brushless alts have two fields that must collapse, which makes them even less responsive.

The A1 trucks actually do this on purpose, with the LBCD having automatic control over the battery disconnect relay to remove failed batts from an overloaded alternator. But built into the LBCD are a bank of capacitors designed to take the edge off of the voltage spike this inevitably creates, to save the rest of the truck electronics. was absolutely floored when I learned how the LBCD worked, and have never seen anything like this in practice anywhere else.

The proper way to disconnect would be to drop the field current first, early enough to allow the alternator field to collapse, then disconnect the batteries...

 

[Shakkles]

Sure thing.
So this is the unit I have:

https://www.amazon.com/dp/B0DNFDQMV5?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_8&th=1

Maybe i wasn't clear before, i absolutely would never intentionally disconnect the batteries while the truck is running lol The reason this was happening (and causing the wonkiness) was because the isolator has a set max voltage and minimum voltage specifically for safety reasons. When it senses the battery is above 25v it assumes "the vehicle is running and charging above the 24v minimum" and thus it actually disables the dongle; Ergo your ability to intentionally disconnect the batteries "while you're driving down the road".
But. It also has a minimum voltage of, I think 23v or something where it assumes "your battery voltage is too low, I'll just disconnect your battery to keep it from draining any lower and you can't start your Kenworth Semi-Truck!" This is good practice but you have to understand one thing that i did NOT know when i bought the unit;

This item specifically believes "your 24v battery" is indeed "one single 24v battery" and not "two 12v batteries in series to make 24v".

And since i originally had the isolator/cutoff installed between the two batteries, it was sensing what it thought to be one 24v battery AT 12v and saying, "HOLY SHIT, your battery is WAY, WAY TOO LOW, I MUST DISCONNECT!" and poof, disconnecting while the truck is running, because it was measuring just one of the two batteries.

That's why, after installing it at the very, very beginning and LEAVING the two batteries permanently in series, the problem fixed itself.

With the system now installed (what I believe to be) ideally, I highly recommend this product and this system to my fellow LMTV owners (obviously only A0s without the super cool manual battery cutoff you spiffy A1 owners have) for a couple reasons. Among those;

1) It's automatic in most cases. If your (combined) battery(s) drop below the voltage necessary to crank the truck, it disconnects until you "turn it back on".
2) If you're parking the truck to get coffee and sign autographed tits to the crowd of cheering 20 year old blondes as i frequently do, you can just "click" the dongle and voila, your LMTV is completely disabled and unable to be stolen by the general public.
3) Even if you forgot and left the system "armed" for say, the 4-ish days it takes our parasitic transmission to kill the batteries, after a day or so the system will automatically kill the battery connection anyway until the next time you're in the truck, remember you need to enable the batteries and "re-arm" the system.
4) Even if the person attempting to steal your LMTV either "has youtube and can search for how to start big sexy army truck" or "is former military themselves" and thus "knows how to start an LMTV", they won't know about your sneaky electrical cutoff. Nothing is 100% fool proof and in every vehicle i own i actually advocate for a fuel cutoff as well, but it'll buy you time at least and in this day and age, maybe that's the best we all can hope for.

What I think i'll do is, when i have time, probably start a new thread with "Here's how i installed an Amazon remote battery cutoff and evolved to an LMTV Chad" for folks to read up on when they run into a similar situation. Also, I should probably make a new thread about the proper (again, just the "proper way" that I've found to be successful in)" installing/integrating a victron DC/DC charger with an LMTV.

 

[Ronmar]

OK, that makes sense. Your smart switch was creating that "bad connection" between battery and alt I mentioned above...

On my A0, the transmission vampire load was on 12V as they fed the trans 12V battery and 24V ignition power. When I did my conversion to straight 24V ignition and trans power(like the A1 trucks), it went away, or at 24V the trans pulls an insignificant amount of energy as I have noted no perceptible drain with batteries continuously connected...

Thanks for the details.

 

[Big Rover]

Sure thing.
So this is the unit I have:

https://www.amazon.com/dp/B0DNFDQMV5?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_8&th=1

Maybe i wasn't clear before, i absolutely would never intentionally disconnect the batteries while the truck is running lol The reason this was happening (and causing the wonkiness) was because the isolator has a set max voltage and minimum voltage specifically for safety reasons. When it senses the battery is above 25v it assumes "the vehicle is running and charging above the 24v minimum" and thus it actually disables the dongle; Ergo your ability to intentionally disconnect the batteries "while you're driving down the road".
But. It also has a minimum voltage of, I think 23v or something where it assumes "your battery voltage is too low, I'll just disconnect your battery to keep it from draining any lower and you can't start your Kenworth Semi-Truck!" This is good practice but you have to understand one thing that i did NOT know when i bought the unit;

This item specifically believes "your 24v battery" is indeed "one single 24v battery" and not "two 12v batteries in series to make 24v".

And since i originally had the isolator/cutoff installed between the two batteries, it was sensing what it thought to be one 24v battery AT 12v and saying, "HOLY SHIT, your battery is WAY, WAY TOO LOW, I MUST DISCONNECT!" and poof, disconnecting while the truck is running, because it was measuring just one of the two batteries.

That's why, after installing it at the very, very beginning and LEAVING the two batteries permanently in series, the problem fixed itself.

With the system now installed (what I believe to be) ideally, I highly recommend this product and this system to my fellow LMTV owners (obviously only A0s without the super cool manual battery cutoff you spiffy A1 owners have) for a couple reasons. Among those;

1) It's automatic in most cases. If your (combined) battery(s) drop below the voltage necessary to crank the truck, it disconnects until you "turn it back on".
2) If you're parking the truck to get coffee and sign autographed tits to the crowd of cheering 20 year old blondes as i frequently do, you can just "click" the dongle and voila, your LMTV is completely disabled and unable to be stolen by the general public.
3) Even if you forgot and left the system "armed" for say, the 4-ish days it takes our parasitic transmission to kill the batteries, after a day or so the system will automatically kill the battery connection anyway until the next time you're in the truck, remember you need to enable the batteries and "re-arm" the system.
4) Even if the person attempting to steal your LMTV either "has youtube and can search for how to start big sexy army truck" or "is former military themselves" and thus "knows how to start an LMTV", they won't know about your sneaky electrical cutoff. Nothing is 100% fool proof and in every vehicle i own i actually advocate for a fuel cutoff as well, but it'll buy you time at least and in this day and age, maybe that's the best we all can hope for.

What I think i'll do is, when i have time, probably start a new thread with "Here's how i installed an Amazon remote battery cutoff and evolved to an LMTV Chad" for folks to read up on when they run into a similar situation. Also, I should probably make a new thread about the proper (again, just the "proper way" that I've found to be successful in)" installing/integrating a victron DC/DC charger with an LMTV.

Great write-up. Looking FWD to reading the two other threads when you publish them.