From D Batteries to Group 31?

[Glennman]

I am having problems with my (2) huge D series batteries and if I need to replace them I'm thinking about trying (2) Group 31 size batteries in my 2002 MCI D 4500. Anyone have any advice on that? Thanks in advance!

[muldoonman]

31's. Half the size and half the juice.

[Iceni John]

Group 31s can have quite high CA/CCA ratings, but compared to 8Ds they have much lower Reserve Capacity.   If you live in a cold climate or at higher elevations, this could be a problem if you need to crank your engine a lot before it fires.   I changed from 8Ds to 31s, but I can now also connect my house batteries to the starter to give me the same (or better) RC as 8Ds.

John

[Glennman]

Thanks John, I plan to have them tested this week. I do live in a cold climate AND we're surrounded by mountain passes. Looks like I'll be forking out a few more bucks, but the last thing I need is to have cranking problems in the cold.

[Gary Hatt - Publisher BCM]

I replaced my two 8D batteries with three Group 31s in my Eagle.  The Group 31s were a fraction of the cost and were much easier to handle for an old man like me. I also had problems with my Interstate 8D batteries lasting more than a couple of years before not charging properly.

[dtcerrato]

We used to have shorter life spans with our 8D batteries until we upgraded our charging methods to four stage charging  now we get 8+ years out of them. We stayed with the two 8D start batteries and have five grounp 31 batteries in the house bank. All the batteries are wla hybrid deep cycle and can be joined or chosen for which bank serves what including the inverter. It works great for us.

[Dave5Cs]

2Grp31's never a problem even in the winter which can get down to-30 degrees. A lot lighter and smaller. We also use a Delco MT-39 starter which takes less power. But my 31's are 1200CCR from Napa.

[Glennman]

My '74 MCI with the 8V-71 has (2) group 31's and I've never had a problem with them even in the winter. However, they have been reinstalled in the rear engine compartment opposed to the side battery compartment. I figured that since the wires to the starter are shorter, then that helped with having the smaller batteries. Maybe that's not a thing.

[dtcerrato]

IMO if yout engine is in good condition and starts quick even in below freezing weather one wouldn't see a difference in 31 vs 8D. But if ever there was a need for extended freezing cranking time - the basic difference would show, sooner than later.

[Van]

What no block heater? 24volt system, 2 8D's or 4 group 31's. Either way COB, pay the money then cry the blues in private like the rest of us😉 Don't forget some quality chargers.I use Victron smart bluetooth chargers, 24v for my 4 31 chasis and a 12 volt for my 2 8D lifeline house and 1 for my genny batt.

[Gary Hatt - Publisher BCM]

2Grp31's never a problem even in the winter which can get down to-30 degrees. A lot lighter and smaller. We also use a Delco MT-39 starter which takes less power. But my 31's are 1200CCR from Napa.

My bus has wheels.  It never goes anyplace that gets below 40 degrees.  Just sayin'. 

[Dave5Cs]

Don;t need 4 just 2, 31's  smart charger 4
8,6 volt deep cycle AGM for house, 1500 watts on roof house panels and victron CC
1, 31 for 7KW genny connected to smart charger and solar charger if needed.
4024 Magnum hybrid with 1oo amp smart charger.

[Glennman]

Thanks for all the help everyone! As it turns out, one of my (2) 8-D batteries has a bad cell, so I will be replacing just the one. I don't like having batteries of different ages being used in pairs, but under the circumstances, I certainly will not be tossing a perfectly good one just to satisfy my OCD.

[luvrbus]

2Grp31's never a problem even in the winter which can get down to-30 degrees. A lot lighter and smaller. We also use a Delco MT-39 starter which takes less power   my 31's are 1200CCR from Napa.

Yep with the MT 39 starters 2 lawn more batteries will start the series 60 in a MCI with 2 group 31 you do lose the reserve of the 2-8D's is the draw back,4 GP31 are about the same reserve with that comes more cables to deal with

[Dave5Cs]

Nope I lose nothing. even when it is cold starts right up and the starts no longer run anything else. House batteries take care of ever thing else.