M1078 remove 2 batteries

[Plasa]

Hello.
I'm a completely newbe in this forum, so please apologize for any mistake... I'm from Italy and going to buy a M1078 LMTV for motorhome transformation.

Looking at the batteries wiring and trying to find a nice storage for the shelter batteries I ask if it's possibile to modify the starter batteries from 4 batteries to only 2, using the space for the shelter batteries. The wiring should be the same as for 4 batteries, as they are connected in parallel.

It should be possible, but I'm not sure, I don't know the 12/24 alternator of the LMTV.

Thanks a lot and sorry for my poor english and questions...

Christian

 

[Rebuilder]

Hello.
I'm a completely newbe in this forum, so please apologize for any mistake... I'm from Italy and going to buy a M1078 LMTV for motorhome transformation.
Looking at the batteries wiring and trying to find a nice storage for the shelter batteries I ask if it's possibile to modify the starter batteries from 4 batteries to only 2, using the space for the shelter batteries. The wiring should be the same as for 4 batteries, as they are connected in parallel.

It should be possible, but I'm not sure, I don't know the 12/24 alternator of the LMTV.

Thanks a lot and sorry for my poor english and questions...

Christian

Welcome... You can run 2 batteries at 24 volts with the stock setup. No modification necessary. The wiring diagram is on the inside of the battery cover.

 

[Plasa]

Welcome... You can run 2 batteries at 24 volts with the stock setup. No modification necessary. The wiring diagram is on the inside of the battery cover.

Hello Rebuilder.
Thank you for the fast answer. So should be like this:

It should be enough to eleminate the 2 batteries that are in parallel, from the wiring diagram of the M1078 the 2 in front or in back...

Thanks again!

Christian

 

[Plasa]

Thank you! I think I found the right solution!

Christian

 

[TNriverjet]

Yes, I ran my truck that way for a few weeks while I was looking for a couple replacements. It worked fine. I can't speak to long term effects, but if you have healthy batteries and a good working alternator, it should work fine.

 

[tennmogger]

Christian, I like your idea. I have also run my LMTV on two batteries, and those were not new. A good running truck will start on two batteries easily, in warm weather at least.

Your idea to separate the two "sets" of 24 volt pairs is a good one. The whole point of having separate "house" batteries is to avoid running down the chassis batteries when camping. There is no reason not to have a switch to again parallel the two sets if desired. When the camping is over, one could simply reconnect the battery sets, run the truck and recharge the batteries. There is no problem charging two sets of batteries in parallel.

In this scenario I would suggest you run your camper off the 24v set but use a 24 to 12 converter. That will avoid unbalancing the two house batteries in series.

I like your idea so much I may just convert my camper to run like you suggest. I have a 10 ft Alaskan hydraulic hardside popup on my LMTV and use it a lot. Present battery setup is a single 125 AH AGM battery maintained by 180 Watts of solar panels on the roof. We run everything in the camper on 12v (hot air furnace, on-demand hot water heater, water pump, and lighting. Refrigerator is propane).

 

[Plasa]

Hello everyone!
Thank you for the responses. I plan to build the "house" with 24V, to keep the cables small and to low down the current in hole system. But now it's time for waiting, the truck will be ready for delivery only end of the year. In Europe / Italy it's difficult to build a home made mobilehome, too many regulations and laws...
So let's hope the best!

Thanks and cheers from Italy

Christian

 

[Terra1936]

Anyone have the diagram for 2 battery hook up?

 

[Ronmar]

Anyone have the diagram for 2 battery hook up?

Remove the two forward batteries, or the two rear batteries. Take the connections from the batteries you removed and move them toward the front or rear and re-attach them…

 

[RRaulston]

By the way, I just bought 2 group 31s at Fleetpride. First time orders get 25% off!!

 

[RRaulston]

Concerning a battery balancer, are the $50 Chinese balancers worth the price/risk for what they do? Or wail to get Bussman??

 

[coachgeo]

Concerning a battery balancer, are the $50 Chinese balancers worth the price/risk for what they do? Or wail to get Bussman??

IMHO if your leaning toward swapping to a commercial 200amp alternater..... get a bussman....... but.... take some time if you got it and watch ebay. They pop up at real good prices few times a year.... if your diligent you can save some funds.

 

[Ronmar]

Actually got one of the small(~5A) balancers and it did what it said it would. I put a 12v solar charger on the 0-12 batt where the A0 vampire draw is, and the balancer would keep the 12-24 batt within .1-.2v of what the 0-12 batt was floating at.

 

[Third From Texas]

Actually got one of the small(~5A) balancers and it did what it said it would. I put a 12v solar charger on the 0-12 batt where the A0 vampire draw is, and the balancer would keep the 12-24 batt within .1-.2v of what the 0-12 batt was floating at.

Yeah, I was doing the same. Then one week of bad weather I didn't drive the truck. With the balancer on I forgot to hook up the charger. Yeah, won't be forgetting the charger again. Flattened both my bats. I have a pile of like dead 6TLs in the garage (but only three of them that I personally killed).

So yeah, balancer is good. As long as you're charging. It's bad when the vampire shows up and you're not charging, though....

 

[Ronmar]

Yeah, I was doing the same. Then one week of bad weather I didn't drive the truck. With the balancer on I forgot to hook up the charger. Yeah, won't be forgetting the charger again. Flattened both my bats. I have a pile of like dead 6TLs in the garage (but only three of them that I personally killed).

So yeah, balancer is good. As long as you're charging. It's bad when the vampire shows up and you're not charging, though....

Oh yeah, you must have a power source…

 

[tgreening]

Since someone else revived this Zombie thread, I dont have to feel guilty so.....

Its giving me a headache. My supposedly new 6TLs took a dump. I'm still trying to work out which of the 4, if any, are still viable but in any case will drop down to a 2 batt config. At least for now.

Ronmar: In your diagram up above you have 2, 2, 1, 1. I assume this signifies the number of connections at that specific terminal? And how exactly do you determine which cable is the 12V?

I have 4 cables coming from the truck. Two + connect to the + terminal of the forward inboard battery, jump to the + aft inboard, and jump again to the Nato plug. The other 2, a short and long, are connected at the - terminals of the inboard and outboard aft batteries. The long jumpers to the - of the outboard forward battery, and to the Nato plug. The short connects to the - terminal of the aft inboard battery and jumpers to the + aft outboard, - forward inboard, and finally + forward outboard.

1998 A0

 

[Third From Texas]

Bet you a dollar that it's the 12v battery (outboard forward iirc).

These trucks are notorious for a 12v vampiric drain when parked. It will suck the 12v side down (typically pulling that battery down). And when one of the four drops below 12v and the truck will not start.


Suggestions:

1) on an A0 truck, drop to dual batteries
2) install a battery disconnect switch (and USE it at all times that the truck is not running)
3) get a maintainer on the two batteries

 

[Third From Texas]

Here's what I recommend for charging:

1) search eBay for "24V PulseTech Battery Solar Pulse Charger w/Mounting Kit"



or beter yet

2) charge your dual batteries via shore power (I prefer this over solar because the vampires come at night when the sun is down)

https://www.amazon.com/dp/B08G3STB1N

But as I'm sure someone has mentioned, the 100a alt in the A0 and A1 trucks is anemic as ****. The 12v side is only 50a and so much is pulling on the 12v side with just the OEM stuff (add more lights. radios, etc and it just gets worse). S&S terribly under-sized the alt (or oversaized the battery bank, depending on your perspective).

Factor in the vampiric drain on the 12v side, and....truck no go.

But if you insist on quad batteries, get two of the NOCO's listed above. Plug in when not in use. /done

 

[Third From Texas]

You can also throw an equalizer/balancer into the mix (two if you run quads).

Just remember that if not on the charger/maintainer the vampire will suck them all down equally if a balancer is in the equation.

https://www.amazon.com/gp/product/B09GLMCNXK

 

[Ronmar]

No, the 1 and 2 indicate battery 1(gnd to 12v) and battery 2(12v-24v). In your pic the outermost batts are grnd-12v(batt 1 in my diag). The innermost are 12-24v (batt 2).

The connections near frame are 24v. One to the starter, one to the 24v batt term on the polarity box and one to the nato plug.

Tge connection where inner and outer batteries meet is the 12v line to the 12v batt terminal on the polarity box.

The connections furthest from the frame are ground, one to the inst shunt and one to tge nato plug...