M939A2 5 Ton 6TN 6TL Battery Replacement

[BOXBUILDER6971]

Hello to all who was like me in trying to find a replacement for the Military 6TN / 6TL battery. I am new here and know there are more POST about batteries. I just wanted to show everyone out here how I added 2 more batteries to my truck. I hope this may help someone else, maybe a newbie like myself to Military Trucks.
Here Is How I redone my battery box on my M932A2 5 Ton BMY. I got ripped off when I got my truck. It only had 2 batteries, with no tie downs. I read on here where a lot of people used different car batteries. I researched several options before choosing these. I first measured my battery compartment. It was basically 21" X 32". My 6TN Hawker batteries were a hair over 11" wide. I searched the web to find the biggest battery I could find to fit my box. The 8D commercial batteries had the most power, but I could not fit 2 beside each other. The 4D commercial batteries were a bit smaller but would fit. I used the truck batteries not the SOLAR Deep Cycle batteries. I used the Duracell Ultra SLI4DA with 1290 Cranking AMPS and 1050 CCA with 290 minutes reserve. Here is the link from batteries + Bulbs. https://www.batteriesplus.com/productdetails/sli4da I used the coupon CDP10011 for 10% OFF online orders For a total of $275.29 before tax for 2 batteries. I went to store and picked up. First removed the 6TN batteries to have room for the 4D batteries. They weigh right 100lbs each. I removed the boards under the 4D batteries and stacked between the 4D's for spacers. I then bought some stainless flat bar 2" wide and 3/8" thick. I cut it 13 1/2" long. I drilled a 3/8" holes through each end, and 3/4" center from each end. This gave me 12" centers between holes and used the original J hooks. I used 3/8" stainless lock nuts with nylon inserts. I used rubber belt under the stainless bar to spaces and to be more secure. You should use the vent less batteries with no caps on top. the caps will get in the way of the stainless flat bar. I used new 2/0 welding cable and crimped new ends on to make custom cables. Used heat shrink to make look neat and protect the cable. Found a diagram on the web to wire correctly. Finished connecting the cables together, checked voltage with a digital meter to make sure correct. Flipped the main switch, turned to run a moment to power the truck. Tapped the starter and about a second started like a brand new car. For all out there who want the keyed kill switch. Just remove a few boards and there is still enough room between the batteries to install the switch and cables.

 

[Ue413]

Nice set-up. I have the same issue on one of my trucks (two car batteries) and need to eventually address.

 

[smittyjr355]

. Flipped the main switch, turned to run a moment to warm glow plugs.

You have glow plugs on this truck??

 

[BOXBUILDER6971]

Thank you if I am wrong. Like I stated this is all new to me. I will fix the original post.

 

[BOXBUILDER6971]

​Thank you. Ue413 I hope this gave you some ideas.

 

[74M35A2]

The 8.3 fires so quickly, I ripped out my 4 great working 6TL's and sold them to smittyjr355 for $10 each. Dropped down to 2 group 31's to gain much wanted dry storage cab space. I'd drop down to even one battery if they were 24v each! Still fires up great in cold MI winters.

It sounds like your truck was cranking slow to begin with? If so, your batteries were likely just old, probably did not need the added battery capacity, but, overkill is kind of the going thing on this site.

 

[Ford Mechanic]

Man that makes my back hurt just looking at it. We have several or the 4d and 8d batteries in generators around town. Hope you had a soldier B to help putting them in the cab.

I just have 2 of the 6tn's in mine. I moved then to the box under the cab. Much easier on my back that way. I'll also be replacing them with 31's when they croak. 31's have a plenty to run the 8.3 on, and easier on the back.

 

[98G]

Mixing old and new batteries strikes me as a bad idea.

2 batteries have always cranked adequately to start even the nh250, even in the cold. Although I can see wanting 4, especially in cooler climates.

 

[lindsey97]

All batteries in the series have to be replaced at the same time, because of different internal resistance in the older batteries.

Basically, when only one battery is replaced, the others try to equalize it and drain the newer one.

They form a circuit and become "one" when connected together, and when there is a weak link in the middle, you cannot produce energy when needed.

Batteries can also show good high voltage after charging , but yet be dead when installed in a vehicle and put under a heavy load, such as starting or winching. A load test is the only true way to determine a battery's ability to produce energy.

When I acquired my first M923, I argued quite a bit with 98G over the trucks needing 4 batteries versus 2, but after the 3rd truck and few recoveries, I now agree that 2 good batteries with clean connections and good cables will start a nhc250 and will certainly be more than adequate for the 8.3l Cummins.

I do strongly prefer to use 2 Interstate MTP65 batteries when dropping down to 2 batteries in our M939 series trucks. Interstate has an excellent warranty, and I have personally seen them live 6-7 years on heavy equipment with high vibration extreme heat conditions. My Caterpillar D4c has 2 MTP65's installed with custom cables, and there is no comparison to the 4D battery they replaced. And I don't have buy batteries for the dozer every 18 months.

My father owned a garage/auto parts supply store from 1977 to 2006. We were a Interstate battery dealer during that time and sold a lot of them with virtually none ever returned or defective. Try that with your Wal-Mart batteries.......

 

[Madderoftime]

Just had a alternator take out all 4 of my batteries. Killed one cell in 2 batteries, 2 cells in one and 6 cells in the last one. Will be replacing today with 2 8D AGM. Will post a picture when done. I have a battery equalizer and a 3K inverter installed too.

 

[jasonjc]

All batteries in the series have to be replaced at the same time, because of different internal resistance in the older batteries.

Basically, when only one battery is replaced, the others try to equalize it and drain the newer one.

They form a circuit and become "one" when connected together, and when there is a weak link in the middle, you cannot produce energy when needed.

Batteries can also show good high voltage after charging , but yet be dead when installed in a vehicle and put under a heavy load, such as starting or winching. A load test is the only true way to determine a battery's ability to produce energy.

.

They also need to be the same size and type. They will not charge right , do to the different capacity. That set up will be short lived.

 

[Madderoftime]

They also need to be the same size and type. They will not charge right , do to the different capacity. That set up will be short lived.

Using just 2 8D batteries would be short lived? If I was using the same alternator I would agree since the original one had a voltage regulator that was set to work with Hawker batteries. I am not using that type of alternator again. Plus the use of the inverter is actually better to use the AGM type since it will handle the deeper discharge.
In your setup originally listed I would recommend a battery isolating device to keep the new ones from fighting the old ones. I've made the isolaters myself. A bit different as I was working with multiple charging sources.

 

[jasonjc]

Using just 2 8D batteries would be short lived? If I was using the same alternator I would agree since the original one had a voltage regulator that was set to work with Hawker batteries. I am not using that type of alternator again. Plus the use of the inverter is actually better to use the AGM type since it will handle the deeper discharge.
In your setup originally listed I would recommend a battery isolating device to keep the new ones from fighting the old ones. I've made the isolaters myself. A bit different as I was working with multiple charging sources.

What??????

I'm referring to the OP's using 2 old used 6tl AGM's and 2 new 4D's. Or other combos of old and new, big and small , AGM lead acid.

 

[KaiserM109]

You do nice work; I'm impressed with the rewiring. You say that you're new here, well welcome. Your post added some new information, thanks.

PS Where did you get the discount coupon?

 

[KaiserM109]

Answered my own question:

 

[MyothersanM1]

Put a couple of these...


...into my M818 this past January after installing an M915 style battery box http://www.steelsoldiers.com/showthread.php?148460-M915-Battery-Box-on-M809-series


Plenty of power.

 

[Madderoftime]

Got the 2 8D batteries in there. 160+ lbs a piece it was a task for sure. The ones I got are a bit wider at the bottom and makes it so they sit on top of the hold down bolt loop. So I had to lift the batteries up with a 1/2" board all across. That made the posts just a bit too tall. To fix this I will be adding 3/4" to the top of the box and moving the hinge up that far. Will take me a couple weeks to get the material and make this happen. SO tempted to just make a new box entirely.

 

[turnkey]

Sorry to hear about the battery cook out....so what does the new set up look like ...???

 

[BOXBUILDER6971]

You do nice work; I'm impressed with the rewiring. You say that you're new here, well welcome. Your post added some new information, thanks.

PS Where did you get the discount coupon?

Thank you. I use to work on fork lifts and batteries. Yes maybe it was a bad idea to use 2 6TN batteries and 2 4D. It is an easy fix. All I have to do is unhook the 2 wires connecting the 6TN and 4D's. Like I said this is all new. I just thought I needed 4 batteries. That is another reason I posted on here. So many people want to help other people not just make fun of them like some other places. I do want to thank all of you for the comments and ideas. I am not so hard headed that I will not take your advice. I want to learn all I can about my truck. If I would have know I only needed 2 batteries I would have went with the 8D or 4D truck batteries only. The 4D's are a bit shorter than the 8D's maybe less chance of a short from the seat bolts. As for the back breaking lifting of the heavy batteries. I used the forklift in my picture and a pallet to raise and hold the 4D batteries to the height of the door. then just slide them over not as much lifting. Any other ideas you may have please let know.

 

[VPed]

Just an FYI for others since you already bought, but two group 31 batteries have worked well for many on here including me. I have them on an A1 truck with the big Cummins and have not had any problem starting, even down to 25 degrees F. The are significantly lighter than the 8Ds and leave tons of room in the battery box.