Two batteries, one tray.

[TechnoWeenie]

I have 2 group 31s (950CCA) on the battery tray closest to firewall.

 

[MarcusOReallyus]

Cool! No mods to the tray? They just fit?

 

[MarcusOReallyus]

I love my Group 31 Exides from Tractor Supply. $100 each and still going strong. Just started my M1031 after sitting for two months outside in freezing temps, fired right up without hesitation.

Nice! Hard to beat buying at TSC.

I like the idea of being able to just drop the batteries in, and maybe fab a hold-down for them.

OTOH, I've got three other vehicles that take 34s, and being able to swap this way and that sounds nice, too.

 

[TechnoWeenie]

Cool! No mods to the tray? They just fit?

Yup. Ratcheting tie down strap to secure them.

 

[tvguy]

Here's my setup using the factory rear battery mount as a base . . .

 

[Skinny]

Yup. Ratcheting tie down strap to secure them.

This probably wouldn't be my preferred method. I have seen batteries come out on the trail even with a factory tie down. An Optima will actually work after you run it over.

 

[TechnoWeenie]

This probably wouldn't be my preferred method. I have seen batteries come out on the trail even with a factory tie down. An Optima will actually work after you run it over.

The tie downs are rated for 1k lbs. I got in the engine bay and kicked the batteries as hard as I could, and I'm no small guy. Didn't budge.

If I'm flying inverted at -4 Gs, then I have more important things to worry about than my batteries..

 

[True Knight]

Here's my setup using the factory rear battery mount as a base . . .

Is that the dual battery tray that optima makes?

 

[tim292stro]

Group 31 will fit, I like the Odyssey 31M-PC2150, but Optima has the D31A/T. The Odyssey battery has a metal case rather than plastic, and has the equivalent performance to the 6TL/6TMF Military battery you would be replacing.

Battery Type/Model	6TL	31M-PC2150	YellowTop D31A
Width	11.875"	13"	12.875"
Length	10.5"	6.8"	6.5"
Height	9"	9.39"	9.375"
Weight	73lbs	77.8lbs	61lbs
20Hr-AmpHr	120	100	75
CCA	825	1150	900
Warm CA	1010	1545	1125
Reserve Minutes	215	205	155
Retail New (quick web search)	$295	$350	$250

If you look at the "length" value you'll note that it's nearly half what the width is on the standard 6TL ordinance battery. Some key things I noticed however are the reserve minutes and amp hours. I read somewhere (and I can't remember where now) that the military minimum acceptance for 6TL is 100Amp/Hrs and at least 200 reserve minutes. From my memory (shaky at best), the amp hours affects how long you can run a light load and then be able to start your vehicle, and the reserve capacity affects how long it takes to recover from running a load to being able to serve a cranking load.

I also like the cranking power of the group 31 batteries, however I have a personal caution about the Optima batteries. I had the D31T in my bus, and the D34-78 in my pickup truck. Both vehicles had battery failures after 4 years (which sucks), but the real warning was the way they failed. My truck's battery started the truck, and got me to the middle of no-where (no cell signal), then when I stopped to take some pictures the dome light came on when I left the truck, but didn't when I returned. Key-in and turn... nothing . For the bus, it started the bus well for fours years then one day at a gas station, it did nothing.

The batteries "failed partially open" while the vehicle was running, then as the battery cooled, it failed the rest of the way open - no warning what so ever. No externally visible damage, no burning or warm plastic, no smells, not difference on the volt meter or ammeter during charging. I've seen a lot of internet chatter about various failure modes of the Optima batteries (nearly catching fire, failing open with no warning, not accepting a charge after a deep-cycle...).

One thing that's very interesting is the warranty page for the Optima batteries. If you use these things in a series string (24V/12V CUCV original system) with a "battery management system" (basically charges each battery with the correct voltages, two alternators do this, and a "Vanner" does too), the warranty is only 12 months. If you use it with a 24Volt alternator like in a Deuce or 5-ton with "no battery management system" (batteries may charge unevenly), the warranty is only 1 month.

The Odyssey Group 31 being a BCI size, gets a 4 year warranty in engine start applications, no mention of stipulations on series strings - but I'd still recommend a Vanner or dual alternators, since they are pretty strict about the charging voltage range (14.0-14.7V per battery).

Also a point that Odyssey likes to point out, is that cute 6-pack layout wastes a ton of space vs a flat-stack:

 

[tim292stro]

I should note that I've been told that the Sears DieHard Platinum batteries are Johnson Controls re-packaged Odyssey batteries (they sure look the same). This Group 31 model has the exact same specs as the 31M-PC2150 I mentioned above, but no metal case - it's $100 cheper than the Odyssey, making it competative with the Optima YellowTop D31T/A.

 

[Nathanater]

 

[MarcusOReallyus]

Well, I went with a couple of Group 31s from Tractor Supply, Exide heavy duty farm batteries. I just popped them in in the standard config, one per tray. The standard hold-downs fit them fine.

I'll get around to making a larger tray and hold down one of these days, so they can just fit on one tray.

Thanks all!

 

[Keith_J]

Reserve capacity is the minutes the battery can support a 25 amp load with voltage above 1.75 volts/cell. For 12 Volt nominal battery, that is 10.5 volts. This IS the important characteristic for a glow plug diesel battery.

Capacity on the 20 hour, amp-hour test is a longer capacity test than the RC. Basically, it is the amp-hour rating over a 20 hour load. 20 hours is 1200 minutes so a battery with an RC of 1200 would have a 20 hour amp hour rating of 500 (25 amps for 20 hours). That would be a monster. The 6TL battery has a 20 hour rating of 120 amp-hours so 120/20 is 6 amps. It supports a 6 amp load for 20 hours before the voltage drops to 10.5.

Now a 6TL also has an RC of 215 minutes which at a 25 amp load is only 89.58... amp hours!! Wait, that is far less than the 120 amp-hours on the 20 hour test!!! Well, that is the nature of Peukert's Law, capacity of a battery is an inverse of discharge rate. Which works in charging too, faster discharges and faster charges cause the battery to heat because conservation of energy is a law, not a good idea.

This is why you need heavy batteries in a glow plug diesel.

 

[av8rnik]

Anyone have any experience with Die Hard Platinum batteries group 35 (http://www.sears.com/diehard-platinum-automotive-battery-group-size-35-price/p-02851035000P)? I have a pair of 31M's that are a little too big to have them both up on the front battery tray, which i need to do to make room for a turbo install.

 

[MarcusOReallyus]

Anyone have any experience with Die Hard Platinum batteries group 35 (http://www.sears.com/diehard-platinum-automotive-battery-group-size-35-price/p-02851035000P)? I have a pair of 31M's that are a little too big to have them both up on the front battery tray, which i need to do to make room for a turbo install.

Here's the correct link: http://www.sears.com/diehard-platinum-automotive-battery-group-size-35-price/p-02851035000P

Nick, when you put that )? on the end of it, you broke it.


If I were you, I'd stay with the 31s and just add a little bigger shelf to the front tray.

 

[av8rnik]

Thanks for the correction, didn't notice it. That is how I am leaning but wanted to get other folks' opinions as well.