Group 27 Batt, a fridge and a JKU

Crossfaced

Observer
Just an FYI a GR27 battery fits perfectly in a JK. The only mods was to remove a plastic piece from the bottom of the tray and to relocate the little canister next to the battery.. the name of it eludes me.

With this battery and my Whynter 65 set at 38 and ambient temps ranging from 60-76 I got 3 days out of the battery before it hit 12.37 but still fired up with zero hesitation....absolutely no problem.

The battery I used was an X2 Power GR27 AGM battery part #SLI27FAGMDP . I believe it's a Deka made product.

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Dan Grec

Expedition Leader
Wow, that's great.

Any idea how many Amp hours (Ah) that battery is? I'm impressed it lasted so long!

-Dan
 
I recently tackled this same exact issue. I have a 2015 JKU with a Engel M45 plugged into the rear power outlet which was modified to be on full time. The OEM battery would die overnight with the fridge setting on 2. I need it to last 2-3 days without starting for my purposes. I did a bunch of research on dual battery setups and based on what I saw (mostly) this is overkill for my scenario.

I then turned my focus to high powered single batteries. I started with Optima since all I had ever heard was great things in the past - I just couldn't afford them. But what I learned was they moved their operations to Mexico and since that time the Optima quality has been called into question. I then learned about the Odyssey brand of batteries and their high regard amongst the off-road crowd. My research showed that the largest capacity battery that would fit my 2015 JKU is the following;

https://www.amazon.com/gp/product/B00249CSS2/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1

I made the purchase. The posts are on the wrong side of the top so I had to do some minor modification to the power and ground leads by way of snipping connectors that attached the wire harness to the firewall and various other locations. It's a tight fit but I was able to make it work with very limited mechanical abilities.

After owning the odyssey for about a month now I'm happy to report that the battery easily meets my demands. I've let this jeep sit over s number of weekends and it reliably fires up with authority on Monday morning. This is with leaving the fridge on max cool over the weekend. It has worked great for me so far and I'm completely satisfied with the purchase.

Hopefully this is helpful to others. Best of luck.
 

vtsoundman

OverAnalyzer
Great job on the install. However I am pretty this only works on 2012 and newer Jeep's. Some have gotten a group 31. I was able to squeeze in a group 31 in my 07 with a modded aftermarket dual batt tray.

I was wrong, reserve capacity is 195 ah.

Reserve capacity is quoted in minutes, not hours...so likely 195 min. No way you got a 4D under the hood of a Jeep....really I wish we could, but a 4D battery is huge!

Group 24 70-85 Amp hours
Group 27 85-105 Amp hours
Group 31 95-125 Amp hours
4-D 180-215 Amp hours
8-D 225-255 Amp hours

Group 27 is typically 90ah.
Group 31 is typically 100 to 105ah

Reserve Capacity*(RC) is the number of minutes a fully charged battery at 80 o F (26.7 o C) is discharged at 25 amps before the voltage falls below 10.5 volts. To convert Reserve Capacity*(RC) to Ampere-Hours at the 25 amp rate, multiple RC by .4167.

sent via the cone of silence
 
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vtsoundman

OverAnalyzer
I recently tackled this same exact issue. I have a 2015 JKU with a Engel M45 plugged into the rear power outlet which was modified to be on full time. The OEM battery would die overnight with the fridge setting on 2. I need it to last 2-3 days without starting for my purposes. I did a bunch of research on dual battery setups and based on what I saw (mostly) this is overkill for my scenario.

I then turned my focus to high powered single batteries. I started with Optima since all I had ever heard was great things in the past - I just couldn't afford them. But what I learned was they moved their operations to Mexico and since that time the Optima quality has been called into question. I then learned about the Odyssey brand of batteries and their high regard amongst the off-road crowd. My research showed that the largest capacity battery that would fit my 2015 JKU is the following;

https://www.amazon.com/gp/product/B00249CSS2/ref=oh_aui_detailpage_o08_s01?ie=UTF8&psc=1

I made the purchase. The posts are on the wrong side of the top so I had to do some minor modification to the power and ground leads by way of snipping connectors that attached the wire harness to the firewall and various other locations. It's a tight fit but I was able to make it work with very limited mechanical abilities.

After owning the odyssey for about a month now I'm happy to report that the battery easily meets my demands. I've let this jeep sit over s number of weekends and it reliably fires up with authority on Monday morning. This is with leaving the fridge on max cool over the weekend. It has worked great for me so far and I'm completely satisfied with the purchase.

Hopefully this is helpful to others. Best of luck.
Agreed...a single group 31 working as starting works great for just a fridge. I've run without my solar and aux group​ 31 with just the fridge for several days without starting. Jeep fired right up. Once the Jeep wouldn't crank - I left my driving lights on by accident. I used my lithium jump starter and she fired right up.

For full disclosure:
I now use my main group 31 starter battery to run one of my radios, a small secondary aux fridge (occasionally). I have a 2nd sealed VRLA group 31 aux battery (plus solar) under the rear seat that runs my main fridge, laptop, comms, and other stuff...I work remotely quite frequently. If I didn't have all that other crap, I'd be running a single big battery under the hood and a smaller solar setup.

sent via the cone of silence
 

Vanhalo

Member
Is the single Group 31 battery fairly common for folks only running a 12v fridge?
I am trying to pair it with a Dometic PLB40.
What I want to do is have the PLB40 take over when the Jeep is off.
When the Jeep is running it should be charging the PLB40.
Not sure if I should be bypassing the PLB40 when the Jeep is running.
 

vtsoundman

OverAnalyzer
Is the single Group 31 battery fairly common for folks only running a 12v fridge?
I am trying to pair it with a Dometic PLB40.
What I want to do is have the PLB40 take over when the Jeep is off.
When the Jeep is running it should be charging the PLB40.
Not sure if I should be bypassing the PLB40 when the Jeep is running.
If you have the Jeep running , charge all your batteries...transfer all loads to the vehicle bus and charge the batteries. The Jeep alternator is a very capable unit.
 

Yarjammer

Wellreadneck
Two things on the on the Odyssey battery...

  1. For 2012+ JKs, you want to by the "R" version that already has the reversed posts (if I ever meet the engineer that decided to do this ?)
  2. The JK alternator will never fully recharge it as it requires more amps than it puts out to reach a full state of charge. You'll want to pick up one of their recommended chargers (not cheap) to do a restorative charge every now and again to keep your Odyssey happy and healthy. I balked on this recommendation and realized a couple years later they weren't kidding with my the ones in my DBS.
 

Vanhalo

Member
If you have the Jeep running , charge all your batteries...transfer all loads to the vehicle bus and charge the batteries. The Jeep alternator is a very capable unit.

I have since learned quite a bit about batteries. I took the cranking battery out of play. I keep the fridge on the dometic 24/7 then I plug it into shore power at home. Going to add solar to the dometic. If my needs become greater I am going to upgrade to a BattleBorn.


Sent from my iPhone using Tapatalk
 

jeep670

Adventurer
Two things on the on the Odyssey battery...

  1. For 2012+ JKs, you want to by the "R" version that already has the reversed posts (if I ever meet the engineer that decided to do this )
  2. The JK alternator will never fully recharge it as it requires more amps than it puts out to reach a full state of charge. You'll want to pick up one of their recommended chargers (not cheap) to do a restorative charge every now and again to keep your Odyssey happy and healthy. I balked on this recommendation and realized a couple years later they weren't kidding with my the ones in my DBS.
I have the R version and it's indeed a drop in.
I read people recommending a charger but from my experience is not needed. I've checked my battery a few times and it measured at 12.8-12.9V which tells me the jk alternator does the job well.
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