Odyssey 6TL Battery Mounting Question. Anyone tried swapping to 8D AGM batteries?

[coachgeo]

That's exactly why I wanted to do this swap. Do you do what the poster above described, basically hook up the two 12v in series to get 24 and just use the terminals on one of the batteries for 12v?

The truck in question is a SD Brazos with Cummins engine. Aside from that difference, it's mostly identical to the FMTV. Battery setup looks the same to me.

as has been mentioned..... this can be done but it is not ideal for the uneven draw on the battery that is drawn from in both the 12v and 24v state, thus it will wear it prematurely. There in lies the hmm??? what is the reality of "premature". Have read for example; a battery with 24v and 12v draw may last say 6 years instead of its warranted 8yrs. To some that may not be such a big deal, except best is to have two cells in a battery bank equal so you would need to replace both battery when the time comes.... buy one, one replaced via warentee?

Buttt... If understand correctly from what have read; since wired like this creates an imbalance in the 24v bank's two batteries, might result in the 24 charging working your alternator harder and wearing it out potentially prematurely too? Not too clear on that. "FMTV sales" am sure has more accurate info than I do on this

 

[Johno176]

?

 

[DiverDarrell]

Coachgeo, I believe the battery issues come when your only charging with a 24v alternator. Our trucks with the dual alternators should prevent issues. Think of it like the 12v alt keeps the battery up. It’s not like a 24v alt charging one battery at 14v and the other is at 11v. The dual alt keeps things equalized. It’s no different really than the stock 4 batt system. For the truck systems I’m not worried about it.

 

[coachgeo]

Coachgeo, I believe the battery issues come when your only charging with a 24v alternator. Our trucks with the dual alternators should prevent issues. Think of it like the 12v alt keeps the batter's up. It’s not like a 24v alt charging one battery at 14v and the other is at 11v. The dual alt keeps things equalized. It’s no different really than the stock 4 batt system. For the truck systems I’m not worried about it.

Much thanks. Better understand how the alt works on these now. good info for us less clueless (probably just me lol)

 

[aleigh]

Lol what. Last time I needed batteries I just went down to oreilley's - literally - and bought some 6TLs. Took 15 minutes to swap all four.

 

[Hard Head]

Kinda makes you wonder how much they will charge you for Blinker Fluid .

It sounds like they are trying to tack on a extra $500 or so to change the batteries, that most likely have to be removed during the RV build anyway.

I want a larger image of that mystery fluid lol.

 

[Hard Head]

I bought 8 platinum AGM's two and a half years ago from advanced auto for my 939 and two 804 generators. I had 2 fail load test analysis in January. They replaced them since their batteries have a 3 year no hassle warranty! I analyze each battery every 3 months when in the last year of warranty. Just something that I feel is worth doing since AGM batteries are expensive. If you can show them they are bad, they replace them.

 

[Smike740]

Looks like one of my 4 6TL batteries is bad. They are the lead acid type and all four have 2009 date codes so I should be happy they lasted this long.

I am in the process of checking the other 3, so far the second one I checked is still good

I have reviewed a bunch of old battery threads researching the options.

Assuming 3 of the batteries are good is there any benefit of running 3 batteries over 2.

I would run two in series and feed the 24v off these. I would then run the 12v off the 3rd battery instead of tapping the 12v off the center positive of the 24v series bank that most have done when running two batteries.

Has anyone run this configuration? Any feeling on whether this will result in a better charge balance between the 2 batteries on the 24v side?

 

[Aernan]

The batteries are parallel serial configuration. You only need 2 batteries to run the truck the other two just increase capacity. The batteries are designed to last 10 years so yours should have been usable until 2019. When you do change the batteries it's best to do it as a complete "pack" so they all have the same total capacity. Also I have been told not to mix flooded cell with AGM but I did it anyway to get the truck back on the road. I had a very long chat with the Hawker rep. on the phone. The Odyssey batteries are made by the same company but won't fit due to extra battery posts. You can buy NEW hawker batteries directly from Hawker if you want real 6T AGM Batteries.

To save you a bunch of digging here are the testing instructions:

Take all batteries out and take them to "batteries plus" (retail store) and ask for a load test to measure cold cranking amps. Should all be over 1100. Battery is a 6T but the meter probably won't have that setting so use a "group 31" option.

I opted for the lowest cost option. I went to NAPA and bought some 6T flooded cell batteries. They are dry stored and you must add 6 Liters of acid to them. Then bulk charge them overnight. Without core I think they are ~$250 each.

Another thread they found some giant batteries that are basically two 6TL side by side. They are called the 8D
https://www.steelsoldiers.com/showt...ion-Anyone-tried-swapping-to-8D-AGM-batteries

If you don't mind modifying the battery box you can use a typical Group 31 battery and you will be able to fit at least 6 of them in there. They are cheap and common.

Likely the most simple option is to buy 6T AGM Hawker batteries directly from Hawker NEW for a bit over $400 each. As long as you start/run your vehicle once a week you will get 4-10 years from a set.

To make the batteries last as long as possible either use a trickle charger or a solar panel. Many members have old Solargizer chargers. They are still available and in production. Check amazon for "24-Volt Solargizer Model 150"

 

[Smike740]

Aernan thanks for the info, 3 of the 4 batteries check out ok, the forth is bad not sure why only this one failed, the CCA is very low, not sure there is any way to recover.

I know it is recommended to replace the batteries together so I will probably just run 2 for now and potentially switch to the 8D batteries later.

If anyone has pictures of the installed 8D please share them

 

[Aernan]

The reason lead acid batteries go bad as they age is the "sulfide". It's like rust on the plates and it doesn't conduct electricity well. You can use a de-sulfiding charger. I have one but it can only reverse some of the aging. https://smartercharger.com/
I think the layout of the batteries causes one of them to never quite charge or generally work harder. You can certainly re-arrange and put the worst battery in the rear left until you get a new battery or swap to 8D.