m936A2 battery upgrade help

[sweetk30]

looking to replace old led acid us 6tmf batterys that are mad in 2010 and been left dead a few times . there the lead acid with the 6 vent caps .

looking to go simple and free up space in cab . read up some guys in the past have moved them down to the pass side tool box area .

is there any good writeup threads on this ? and how to do the wiring ?

I am more a 12volt guys stuck doing this 24volt military job .

I have BIG crimpers down to 4-OO battery cable size . so making new ends or cables is not a problem .

from some bqasic search reading looks like you guys like the 8d big boy batterys .

this truck lives in the north east rust belt / snow country . . . and needs to be fire up ready when the call comes in .

thanks guys have a good day and easter holiday .

 

[74M35A2]

Two group 31's is all you will need. Especially with an 8.3L in good state of tune. No crimping needed. Frees up a ton of underseat room. Make sure charging system works well, replace them every 5 years, and you'll never need to lift the seat.

 

[Brutacus]

A pair of 8D's will do the trick, and they are very easy to wire up. Here is how I wired mine up. These two provide plenty of cold cranking amps. Whatever you do, make sure you wire up your glow plug(s) on the 12 volt. Everything else should be 24 volts. If you look in the pictures, you can see I have my glow plug wired on 24 volt by mistake. I have since corrected that.

 

[simp5782]

A pair of 8D's will do the trick, and they are very easy to wire up. Here is how I wired mine up. These two provide plenty of cold cranking amps. Whatever you do, make sure you wire up your glow plug(s) on the 12 volt. Everything else should be 24 volts. If you look in the pictures, you can see I have my glow plug wired on 24 volt by mistake. I have since corrected that.
View attachment 675847View attachment 675848View attachment 675849

M939 NHC250s and 8.3s do not have glow plugs.

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[74M35A2]

Too many amps.

 

[Brutacus]

M939 NHC250s and 8.3s do not have glow plugs.

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I didn't know that. I was thinking in terms of my NHC 250.

 

[Brutacus]

too many amps.

haaa!!! :-d

 

[simp5782]

An 8.3 doesn't really need 8D's. It can get by with 31s.

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[74M35A2]

An 8.3L with an air tight fuel suction system doesn't even need two group 31's. But, it is one of the most economical ways to get 12v @ $100 each.

 

[sweetk30]

cool info guys thanks .

looking around the 31 seems to be a much more instock option .

interstate 31-xhd is 12v x 1000cca @ 0* temp .
napa bat-7234 is a 12v x 1125cca @ 0* temp .

the owner has a charge account at napa and he has had good luck with them in others so that's prob the option we will go .

I will whip up a good hold down for them in the side box for sure .

I have been charging them and 3 of the 4 draw the charger down when turned on the 4th is doa I think as he does nothing . . . so we know he is drawing the others down and dead .

 

[simp5782]

Check your local freightliner dealer. The Group 31s they have are around $65 each here in Memphis. If you at set on 8D's. Duracell batteries at batteries plus @ 1720/1400 amps are around $148 each if you talk to em down. I run 8D's cause I am on the road a lot and if something happens I want to be able to get a little bit of distance before they die.

 

[Csm Davis]

Too many amps.

No such thing!

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[simp5782]

No such thing!

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Famous last words of "Too many amps" when one day you may have to jump start a C130 on your way to Dollar General

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[74M35A2]

...or a mighty NHC-250 wound up in string, with a sprinkler box taped to its head.

 

[74M35A2]

No such thing!

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That was from an unmentioned member, one of my favorite lines here.

 

[Buffalobwana]

A pair of 8D's will do the trick, and they are very easy to wire up. Here is how I wired mine up. These two provide plenty of cold cranking amps. Whatever you do, make sure you wire up your glow plug(s) on the 12 volt. Everything else should be 24 volts. If you look in the pictures, you can see I have my glow plug wired on 24 volt by mistake. I have since corrected that.
View attachment 675847View attachment 675848View attachment 675849

that black wire is supposed to be wired as 12v, as you learned, but I thought it was the low setting on the heater fan.

 

[74M35A2]

Correct

 

[Buffalobwana]

See, even a blind hog can find an acorn every now and then.

 

[sweetk30]

so what is the basic deal with the 4 batts 2 12v's to make 24volt and then a whole second bank . . .

 

[simp5782]

so what is the basic deal with the 4 batts 2 12v's to make 24volt and then a whole second bank . . .

Just starting power. A cold NHC250 will kill four group 31s or 4 6TLs in about a minute of cranking time. LESS cranking amps means more plates and increases battery life. Hawkers will last 10years or more. Where as a group 31 may last 2 to 4.

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