Easy M939 Group 31 Change-Over

[74M35A2]

I changed over to two group 31 batteries in order to make more room under the seat. I was able to fab a super easy hold-down if anybody needs: Just a single 14" long piece of Unistrut, and one existing hold down bolt. On the base, I ditched the factory wood in exchange of two 20" strips of 1"x4" from a pallet, in order to reduce the standing terminal height. Was fast, easy, low cost, and secure. Starts great, even in MI winter. The batteries are 1175CCA each.

 

[R Racing]

It looks good !!! Maybe put down a bit of baking soda to neutralize any left over battery acid?

 

[Artisan]

Good idea w/ the Unistrut. I run 2 DieHard Gold batteries for my NTC Cummins 400
and it spins it FAST w/o issue ever.

I was perusing Unistrut fittings just yesterday trying to get into my mind
what all hey have to offer, SO I CAN MAKE IT MYSELF instead of paying
the large $ they want for some of the stuff...

(If anyone is making Unistrut fittings let me know)

 

[74M35A2]

It looks good !!! Maybe put down a bit of baking soda to neutralize any left over battery acid?

Yep, did it. Lined the bottom of the box with insulation also for the heater relocation, playing soon at theaters near you.

 

[74M35A2]

Good idea w/ the Unistrut. I run 2 DieHard Gold batteries for my NTC Cummins 400
and it spins it FAST w/o issue ever.

I was perusing Unistrut fittings just yesterday trying to get into my mind
what all hey have to offer, SO I CAN MAKE IT MYSELF instead of paying
the large $ they want for some of the stuff...

(If anyone is making Unistrut fittings let me know)

It is a 14" piece of stainless Unistrut leftover from a project at work. I'd be happy to cut and mail a piece for free for anybody who is going this path. Please have honest intentions of using it, I don't want be doing it just to sit on somebody's garage shelf. The height is only proven to work correctly with a 1"x4" at the base, group 31 batteries, and the factory hold down J bolt. On your own for any other combination.

 

[Baradium]

Do you know offhand if 4 group 31s would fit under the seat? I've been meaning to measure, but I'm almost afraid to mess with stuff when it's 40 or 50 below... so easy to break things. With the temps I deal with sometimes, you can never have too many CCA.

 

[74M35A2]

You can very easily fit four group 31's, you may even be able to do more than that. Your CCA will obviously double once you go from two to four batteries, hence you would reach 1175CCA x 2 = 2350CCA @ 24VDC (56,400 Watts of starting power!).

 

[swbradley1]

Those are my preferred NAPA batteries.

 

[74M35A2]

Those are my preferred NAPA batteries.