Anyone run one of the "new" DieHard Group 31 AGMs? Can't tell if the posts are on the right side (at least they appear to be closer to the edge), but that's a helluva good price (even better after coupons).

I was gonna say I'm sure its the same as the Autocraft AGM I got when I picked up my 4runner but I did some research and it turns out they are made by EnerSys not johnson controls like the regular line.

I have heard good things about the Odyssey batteries so maybe that is a good thing?

I also considered a Duracell battery from Sams Club as they are made by East Penn who has a very good reputation but as you stated the coupons at advance are very good. I always get 25% when I order from there.

Not all AGMs are built equal… the DieHard Group 31 AGM would still be classified as a starter battery, just a AGM variant.

If deep cycle performance is important you would still be better off with an Odyssey

Unless the battery is being installed in the interior of the car, I find it hard to justify the extra premium over a standard $100 5 Year starter battery.

I just got the 24F version DieHard AGM. Pretty good full replacement warranty at 36mo. It is Hecho en Mexico, but hopefully will end up being fairly reliable. After tax and core, with coupon, total was $160, which is barely above most other batteries nowadays. At these prices I might buy another size 34 for a dual battery setup and install it behind the air intake.

I regularly run a fridge, so AGM makes a lot more sense than a regular starting battery.

Yeah, I'm assuming Enersys is still making them like they did for Sears, it just looks a little different now?

I looked at the Duracells, but it seems like the posts are on the far side on the 31Ms and on the wrong side for their 27Fs (also seems low on the CCA/amp hour size vs something like the X2/Northstar).

True, but isn't this the same marine EnerSys battery everyone raved about back when it was sold at Sears (pre-AA buyout)? If so, isn't this just a rebadged Odyssey?

This would be used for powering a 12v fridge, not just for fun. Otherwise, my old Johnson Controls Interstate/Costco battery has been just fine and I could just keep that.

I was also wondering if I could get away with the standard 24F size for a fridge. I really like the 27F size, but the options there are pretty pricey!

I am pretty sure I know what you are talking about... there was a point in time back in the day when it was a OEM of a high end deep cycle, but that relationship stopped like over 5 years ago IIRC.

I remember this pretty well because I went to different Sears locations and learned I missed the boat by a few months and never got one for myself.

The AGMs that replaced it were primarily a starter variant which is also in line with how it is currently priced. That is not to say it won’t work fine for a fridge. I don’t run a fridge full time, but my 2nd battery is a regular Costco Interstate starter battery… I set my low voltage disconnect in the high 11’s (11.7v to 11.9v) and haven’t had a single issue in the lats 5 years. If I need the power ill set it lower, but if you don’t cycle to deep regularly, it actually lasts and works just fine.

Keep in mind that your charging system will never keep an AGM battery fully charged. Somewhere on the label it should tell you the recommended charging voltage, usually 14.2 - 14.4 v for AGM.

On my 08, the alternator output never exceeds 14.1, and even then, only for a short period. Usually, it runs in the high 13s.

It’s a fair statement given what we know about deep cycle AGMs, but that rule of thumb does not apply to all AGM batteries. Always check manufactures recommendations for charge voltages.

A starter AGM is pretty much a direct drop in without much worry about. You might see a small difference in voltage requirement but nothing significant.

The 3 most common charging profiles would be Normal, AGM, and AGM+ which is generally what something like an Odyssey would use. The difference between Normal and AGM might be about 0.2VDC

Ah, I see. These news ones are apparently made in Mexico and are not te same type, gotcha.

I wouldn't be running a fridge 24/7, more like for trips/camping. I was worried my Costco battery would eventually fail from "deep" cycling but maybe my fears are unfounded. I could just try running a fridge as-is and reassess if I actually even need an AGM. My choices thru research seem to be narrowed down to a factory size Costco 24F (unsure if this Interstate model is a "starter" or "dual purpose?") or the X2Power (Northstar) 27F (dual purpose) - again, only if a normal lead acid really doesn't hold up for my use.

Are you running a diode to boost the voltage? Mine runs ~14V cold start then drops off as it gets warmed up.

Are you talking about a single battery setup or dual? I run a dual with two starters.

Not going to sugar coat it... the Northstar is by far a better battery than the Costco Interstate, but it also cost 3-4x more money.

The Costco Interstate is a standard run-of-the-mill starter battery. Really no different than the others found in that price class.

For occasional deep cycle use, I still standby my statement that using a cheap starter battery is fine. For the money saved, I can still nuke it 3 times and be ahead. I gets me through the occasional weekend camping trips just fine and simplifies maintenance because I dont have two different types of batteries in the same system. (I use an ACR, not a DC-DC)

I would only buy a deep cycle if I was cycling it daily, and needing to be able to discharge it deeper. You will get more usable capacity from a deep cycle AGM without causing damage to the battery.

If I was going to run a single battery setup, I would probably spend the extra coin for a Northstar or Odyssey and do the diode booster.

I wonder if these new ones will be good as the originals?

Still running a set of DIehard Plat originals, primary is group 35 and other my secondary is group 31M. I keep both batteries on maintainers to keep them healthy.




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Lotta Tacoma guys run fridges and their stock battery is the 24F. Specs on this DieHard 24F is 70AH. Most fridges average about 1amp/hour through 24 hours, so you could run this 1.5 days without starting and only draw your battery down about 50%.

Even the Northstar/X2 27F AGM everyone raves about only has 92AH spec, so for a 50% draw-down, that's only another 11 hours.

Carry a jumper pack and don't worry about it.

Single. I figured - the jump in price seems to spell it all out lol. At this point I guess my plan should be to bite the bullet on a X2 29F battery and install the GM diode fuse.

Thanks for all the input man, appreciate it!

Yeah, but I'm assuming I need to go with a decent deep cycle/dual use AGM if I go this route.

A Noco lithium jumper lives in the truck, so I'm good to go there. If I find a decent enough fridge, I'd figure the built in low voltage protection should keep me from having to use the jumper - but it's always there just in case.

In that case, absolutely get the AGM. IIRC the Odyssey (Northstar is similar) is rated for something like 400 cycles at 80% depth of discharge. You would most certainly toast a starter if it was used in the same manner. I do no more than an occasional (couple times a month) 50% discharge, with the starter.

The built in LVD on the fridge is pretty reliable, that should be enough. My ARB had 3 different voltage levels for LVD so you have some control over how much power you want to keep in reserves.

Since I have the V8, I definitely don't want to be stressing a starter beyond its normal limits - not looking forward to that job!

Good to know, looks like I have a little plan in place - thanks for all the input!