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AGM and LiFePO4?

walshjuice

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I have a 1995 M1079 that I’m looking to replace the batteries. I want to keep the 24v side AGM but go with lithium on the 12v side. The 12v system runs the stuff inside the camper and is hooked up to a solar array. I’d still like to charge the 12v with the alternator while driving too. Does anyone see any issues with this or have any suggestions?

Thanks,
Ryan
 

Ronmar

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Are we talking a separate house battery bank or are you talking about mixing lithium and lead in the service battery bank?

If the latter, no, the alt is designed to act as a balancer, assuming you have a 12-24 series battery capable of achieving balance. Different size/capacity or chemistry batteries would make balance impossible...

What do you have for batteries now? Even the original four 6Tbatts in series/parallel are way too much for the alt when discharged. And thats in wet cell, in AGM it is grossely overloading the alt...
 

coachgeo

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Not worth it... add more solar panels and a small generator

and drop to two 12v batts for engine. Maybe upgrade OEM alternator for a hummer 200A or ??? lots of threads in here on alternator woes, upgrading etc.
 

GeneralDisorder

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Don't do that. For a lot of reasons - balance, chemistry, etc.

Reduce the truck batteries to two group 31's (wet cell's, not AGM) if you have the 100A alternator to avoid killing it. Use of AGM's or even the quad 6TL's is really overloading that poor little alternator and asking for problems. Don't use that alternator for more than charging two group 31 wet cell batteries for the truck. Don't use it for house battery charging unless you upgrade it (260A, etc) and then only through something like a Victron Orion DC-DC charger to limit amperage draw.

Charge your house batteries with solar, generator, or from a DC-DC charger but ONLY IF you upgrade the alternator. The 100A is only adequate for the truck load and two group 31's. Don't push it or you will be replacing it sooner or later. Keep it cool and it might last a while. Carry a spare voltage regulator. They weren't the best alternators and 1995 is now 30 years old. The military got fed up with the 100A's failing and now every truck gets a 260A if it needs an engine replacement and 100A alternators are only to be used till stock is depleted. They have kits for all the older trucks to convert them to 260's when needed if they are going to remain in service (most are being phased out to DLA).
 

MatthewWBailey

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I have a 1995 M1079 that I’m looking to replace the batteries. I want to keep the 24v side AGM but go with lithium on the 12v side. The 12v system runs the stuff inside the camper and is hooked up to a solar array. I’d still like to charge the 12v with the alternator while driving too. Does anyone see any issues with this or have any suggestions?

Thanks,
Ryan
Vail ay? If you wanna go camping, come out to the Grand Mesa. There's some nice driving trails too.
 

walshjuice

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Vail, CO
Thank you all for your replies and keeping me from making a huge mistake. I think I‘ll just replace all four with matched agm’s and keep it simple.

Some of you recommended the 260 amp alternator upgrade. Those seem to be going for quite a premium price. 200’s are reasonable and there’s some 570’s from the mraps. Im not sure of fitment issues so any recommendations are appreciated.
 

coachgeo

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Thank you all for your replies and keeping me from making a huge mistake. I think I‘ll just replace all four with matched agm’s and keep it simple.

Some of you recommended the 260 amp alternator upgrade. Those seem to be going for quite a premium price. 200’s are reasonable and there’s some 570’s from the mraps. Im not sure of fitment issues so any recommendations are appreciated.
go to a 120amp? or higher? 24v commercial truck alt and a 24v to 12v converter tagged in to run your 12v systems. There is a couple threads in here on this.

Then you can go back to your previous plan and run a DC to DC lithium charger though you might consider doing your house bank at 24v instead of 12v.. Most RV-ish items these days such as fridges etc are 12v/24v and they run best at 24v anyway. Granted if the 1079 does not see use but a few times a year.... lithium not worth it.
 

hike

—realizing each day
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Good advice above. These units started with a dual 12/24v 100a alternator that as folks have mentioned was overloaded trying to maintain the four batteries in 2 in series-24v banks. Over the years they tried several different configurations. I believe the mid 90's units had a polarity unit between the batteries and alternator. Our mid aughts unit replaced the polarity unit with capacitors (LBCD) and remote disconnect relays to protect the 100a alternator.

Adding 4 new AGM's is likely not the best idea for your existing system as @GeneralDisorder mentioned. Most folks are dropping to 2 AGM's and that is easy to do with the existing wiring.

With our M1078A1 we also hope to do some off road camping so are in the process of 'upgrading' our cab and chassis wiring before adding the habitat systems. Here is a simple schematic of what we have accomplished so far, a link to the thread here on SS.


concept-electrical-cab-chassis-1.5-progress-20240310.jpg

We are separating the 2-in series 24v banks uses: bank 1 will run the existing cab and chassis plus power windows, door locks, usb charging ports, etcetera; bank 2 will run our 24v cab AC, two way radios, gps, etcetera. Our habitat LiPO4 batteries will be entirely separate, though we may add a special Victron balancer that is designed to manage separate AGM and lithium banks between habitat and chassis.

So far we have replaced the dual 12/24v 100a alternator with a 24v 200a adding a Victron 24/12 70a DC to DC between X1 and X2 at the PDP to provide 12v; and removed our LBCD and disconnect relays.

Welcome to the forum, it is an adventure in learning. @Ronmar and @GeneralDisorder know far more than most here. @MatthewWBailey just replaced his alternator, too, if I recall correctly—
 

Ronmar

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Port angeles wa
Thank you all for your replies and keeping me from making a huge mistake. I think I‘ll just replace all four with matched agm’s and keep it simple.

Some of you recommended the 260 amp alternator upgrade. Those seem to be going for quite a premium price. 200’s are reasonable and there’s some 570’s from the mraps. Im not sure of fitment issues so any recommendations are appreciated.
Replace all 4 with 2. AGMs demand nearly double the current from the alt That wet cells call for. And the original 4 wett cells were already too much for the dual volt alt. It is basically a pair of 50A alts. 4 of the 6T wet cell batts are looking for 60A, 4 of the 6t batts in AGM are looking fir 108A the truck lights pull ~30A all by themselves which really starves the 12v batts which is usually where the problems start as the batts have trouble reaching full charge(biggest killer of batts). This keeps the alt in constant overload and kills it also…

cat specced a pair of group 31 batts for the equip that uses these engines, and it is a great match for the 100A alt. It doesn't need any more than that. The 4 battery bank was the product of the mythical land of Milspec, for a situation you will most likley never encounter, like cold soaking in siberia for 30 days then having to crank up and go to war.

a pair of 31s will charge easily, reach full state faster and last longer, not to mention being easier on that horrendously expensive and unrepairable alternator.

with the batteries not hogging all the alt output, you would actually have a surplus to use a 24-12 converter/charge controller to charge a 12v house battery. With only 2 group 31s in the battery box, you even have room to put the house batteries there, as it can fit up to 8 group 31s in that box. That is what I am planning, have been running a pair of group 31s since I used them to start the truck when I picked it up in the auction yard, still using the same set:)

I would not put any more load on the 12v side of the alt as it really saps overall alt output. In fact I would start thinking about installing LED lights to cut away at that ~30A 12v lighting load… and start making plans for a 24v only alt and a 24-12 converter sometime down the road when that alt fails, because alts do fail…

good luck!
 

GeneralDisorder

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Portland, OR
Thank you all for your replies and keeping me from making a huge mistake. I think I‘ll just replace all four with matched agm’s and keep it simple.

Some of you recommended the 260 amp alternator upgrade. Those seem to be going for quite a premium price. 200’s are reasonable and there’s some 570’s from the mraps. Im not sure of fitment issues so any recommendations are appreciated.
DONT DO THAT! AGM's are capable of pulling a LOT more charging amps. The switch to AGM's was part of the problem the military had with the later 100A trucks. The 100A alternator was really too small for the 6TL wet cell battery bank, and AGM's just make this MUCH worse. The 100A was not designed with this in mind. In fact I'm not sure what was on S&S's mind when they chose that unit other than being cheap and not really understanding the way these vehicles get used in the military (lots of sitting, dead batts, and abused by soldiers that don't have to foot the bill to fix their mistakes). It's a really bad choice for these trucks. As Ronmar likes to say - it's the kind of choice that class action lawsuits are made for in the civilian world. The military just threw more money at the problem by trying to attach useless solar chargers to the trucks and eventually gave up on the 100A in disgust - the 6TAGM's chew these alternators up.

200's are possible. You'll never get a 570 to fit (way too long, hits the turbo, no other possible mounting positions due to cab clearance). The 3116 needs special/custom mounts for the 260.... or really anything other than the 100A. The "cheap" solution seems to be a Delco or Prestolite 24v commercial alternator along with a 24v to 12v DC-DC charger (Victron Orion would be my choice) to feed the 12v side of the truck. Lots of threads on how to modify the lower bracket and make a new upper bracket to hold one. The only real downside is the introduction of a second electronic unit, and losing the brushless/totally enclosed nature of the Niehoff - and the factory appearance. That is the way most guys with 3116's and 3126's go. Another advantage to getting into a C7 truck from the start. Many already have the 260 and the brackets to mount them if you have a C7 100A truck aren't unobtainable.
 

MatthewWBailey

Father, Husband and Barn Hermit
Steel Soldiers Supporter
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Mesa, Colorado
Good advice above. These units started with a dual 12/24v 100a alternator that as folks have mentioned was overloaded trying to maintain the four batteries in 2 in series-24v banks. Over the years they tried several different configurations. I believe the mid 90's units had a polarity unit between the batteries and alternator. Our mid aughts unit replaced the polarity unit with capacitors (LBCD) and remote disconnect relays to protect the 100a alternator.

Adding 4 new AGM's is likely not the best idea for your existing system as @GeneralDisorder mentioned. Most folks are dropping to 2 AGM's and that is easy to do with the existing wiring.

With our M1078A1 we also hope to do some off road camping so are in the process of 'upgrading' our cab and chassis wiring before adding the habitat systems. Here is a simple schematic of what we have accomplished so far, a link to the thread here on SS.


View attachment 920420

We are separating the 2-in series 24v banks uses: bank 1 will run the existing cab and chassis plus power windows, door locks, usb charging ports, etcetera; bank 2 will run our 24v cab AC, two way radios, gps, etcetera. Our habitat LiPO4 batteries will be entirely separate, though we may add a special Victron balancer that is designed to manage separate AGM and lithium banks between habitat and chassis.

So far we have replaced the dual 12/24v 100a alternator with a 24v 200a adding a Victron 24/12 70a DC to DC between X1 and X2 at the PDP to provide 12v; and removed our LBCD and disconnect relays.

Welcome to the forum, it is an adventure in learning. @Ronmar and @GeneralDisorder know far more than most here. @MatthewWBailey just replaced his alternator, too, if I recall correctly—
Yes💪. I was kinda obsessed with the pad mount config alternative lol. It's appeals to my sense of symmetry. Mine is now a 24v only 110a high output alt from delco, COTs and cheap. We'll see how it holds up. (Denso makes one too but I'm still trying to find the part number that matches the bolt configuration.). I only have 2 batts for the 24v and the victrons Power the 12v side from 24v ignition after a delay. There is no center 12v tap from the series batteries. I keep the plug charged overnight too. I kept a 3rd battery to backup the 12vbatt bus. I have no LBCD or disconnect relay. Been working great. The poor chassis ground cables were a huge problem obviously. I'm about to install a dc chopper drive on the AIH to drop its power draw to <70amps to ease the load at startup. I'll update that on the other thread. Pretty cool. This truck, as stock, has waaayyy too much load at cold startup for a 100a alt. So I tried to unload the alt as much as possible. The 220a leece alt is the biggest non-neihoff I've seen around but really expensive. I could always go back to the neihoff but they are expensive as are the regulators.
96B9F3D1-DBE9-4983-A657-E1EC64742D64.jpeg4A9B24F9-99AB-4E58-A1AB-F584DB488E58.jpeg1F40AE1B-CDF8-4BC1-861E-1B712BF80D79.jpeg
 

MatthewWBailey

Father, Husband and Barn Hermit
Steel Soldiers Supporter
312
767
93
Location
Mesa, Colorado
I was once accused of being a cheap SOB(very politely) on this forum for advocating a switch from the "military proven" 4 batteries, to only two "undersized" group 31s...:)

This is one of those rare occasions that come along in life, where doing the right thing actually costs less money...
That's pretty good. At least It's better than being labeled a "cheap bastard".
 
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