Batteries.... ?

[BLK HMMWV]

Will a LiFePO4 battery with the following description work for the battery in an Hmmwv:

(It is listed as 24V 300Ah LiFePO4 Battery Built-in BMS Lithium Iron Phosphate Cells.)

Product details:
Delivery date: 2023
Battery type: 3.2V Lifepo4 battery
Fixed amount: 300AH
Nominal voltage: 25.6V
Maximum charging current: 50a
Instantaneous discharge current: 200a
Continuous discharge current: 100A
Life: 6000 cycles or more
Size: 535*215*207mm (+/-10mm)
Charge temperature: 0 to 45 ° C
Discharge temperature: -20 to 60 ° C
Storage temperature: -20 to 65 ° C
Operating voltage range: 20V to 29.2V
Electrical voltage: 29.2V
Overload protection voltage: 29.2V / 0.05 V
Protective voltage for overload: 20V / 0.05 V
Protect the battery temperature: 60 ° C Plusmn 5 ° C
Output and Parameters: High Current Positive / Negative Connection column (red positive, black).

Short answer NO

 

[Coug]

Will a LiFePO4 battery with the following description work for the battery in an Hmmwv:

(It is listed as 24V 300Ah LiFePO4 Battery Built-in BMS Lithium Iron Phosphate Cells.)

Product details:
Delivery date: 2023
Battery type: 3.2V Lifepo4 battery
Fixed amount: 300AH
Nominal voltage: 25.6V
Maximum charging current: 50a
Instantaneous discharge current: 200a
Continuous discharge current: 100A
Life: 6000 cycles or more
Size: 535*215*207mm (+/-10mm)
Charge temperature: 0 to 45 ° C
Discharge temperature: -20 to 60 ° C
Storage temperature: -20 to 65 ° C
Operating voltage range: 20V to 29.2V
Electrical voltage: 29.2V
Overload protection voltage: 29.2V / 0.05 V
Protective voltage for overload: 20V / 0.05 V
Protect the battery temperature: 60 ° C Plusmn 5 ° C
Output and Parameters: High Current Positive / Negative Connection column (red positive, black).

Slightly longer answer, the specs above list it as max charging of 50a, and even the oldest HMMWV has at least a 60 amp alternator, and newer ones can have up to 400 amps.
The starter is also going to draw more than 200a.

That battery appears to be a deep cycle version, not a starting battery, so it isn't designed for heavy loads like a starter, but rather a smaller, longer discharge. Trying to use it in a starting application may result in fire or explosion.

Plus for the price you could easily buy multiple 6TAGM batteries and a top of the line charger for them.


Some info from the BatteriesPlus website:

Starting
When you hop in the car and turn the key, the starting battery needs to release a very large amount of current to get the starter motor spinning to crank the engine. This extremely large amount of current, even if it only lasts for a second or two, will activate the battery management system (BMS) in the lithium iron phosphate battery, rendering the battery useless requiring a replacement battery to be installed.

https://www.batteriesplus.com/blog/power/lithium-starting

 

[Mogman]

Welcome to the SS forum!!

 

[Mullaney]

Will a LiFePO4 battery with the following description work for the battery in an Hmmwv:

(It is listed as 24V 300Ah LiFePO4 Battery Built-in BMS Lithium Iron Phosphate Cells.)

Product details:
Delivery date: 2023
Battery type: 3.2V Lifepo4 battery
Fixed amount: 300AH
Nominal voltage: 25.6V
Maximum charging current: 50a
Instantaneous discharge current: 200a
Continuous discharge current: 100A
Life: 6000 cycles or more
Size: 535*215*207mm (+/-10mm)
Charge temperature: 0 to 45 ° C
Discharge temperature: -20 to 60 ° C
Storage temperature: -20 to 65 ° C
Operating voltage range: 20V to 29.2V
Electrical voltage: 29.2V
Overload protection voltage: 29.2V / 0.05 V
Protective voltage for overload: 20V / 0.05 V
Protect the battery temperature: 60 ° C Plusmn 5 ° C
Output and Parameters: High Current Positive / Negative Connection column (red positive, black).

.
Welcome to the Outfit!

Don't take it personal when everybody answers up with a NO to your question. That is what this place is all about. Ask a question, Get an answer. Sometimes it isn't as "cut and dried" as this one - but we all enjoy being able to help and steer folks in the right direction.

Welcome to the group and post us up a few pictures...

.

 

[Eddy1947]

Thank you all for your quick answers. I am not put off by a quick "no" as that is exactly what I needed to hear. The answer with all of the details that followed will help me make a wise choice going forward. Again, thank you all.

 

[lynchmob15]

I need to replace the batteries in my M998 and I was looking at Group 24M's. they are deep cycle marine batteries, would they work in the truck?

 

[Mullaney]

I need to replace the batteries in my M998 and I was looking at Group 24M's. they are deep cycle marine batteries, would they work in the truck?

.
That should work. Be sure to verify clearance between the bottom of the seat and the top of the battery. The regular 24 series should fit with no problem...

 

[Coug]

Short answer:

there is no real advantage to using marine batteries unless they are the only ones available or you're getting a major discount on them compared to the automotive version.



Long answer:

Deep cycle marine batteries have different charge and discharge rates than an equivalent 24F (Flooded lead acid) or 24MF (Maintenance Free) type battery.
Also they rate the cranking amps differently. MCA is measured at 32°F whereas CCA is at 0 °F
Also the deep cycle part in the name is because it is designed to discharge further and last longer while doing so, but in exchange it gives up cranking amps and overall life expectancy for cranking.

The only real advantage to using a marine battery vs a standard automotive battery is if you use the battery power a lot when the engine isn't running.


This answer over on Quora gives a lot more detail

https://www.quora.com/Are-there-any-issues-with-using-a-deep-cycle-marine-battery-on-a-car

Yes — you can use a deep‑cycle marine battery in a car, but there are trade-offs and some installation/charging considerations. Below are the key points to evaluate before making the swap.

Performance and suitability

• Cranking vs. cycling design: Automotive (starting) batteries are optimized for very high cold‑cranking amps (CCA) for short bursts to start the engine. Deep‑cycle marine batteries are designed to deliver lower current for long periods and tolerate repeated deep discharge. A deep‑cycle will start most cars fine but typically provides lower CCA than a similarly sized starting battery.
• Reserve capacity: Deep‑cycle batteries often have higher reserve capacity (useful for accessories when engine is off) but slower cold starts.
• Life under starting duty: Repeated use as a starter battery (frequent cold starts, short recharge cycles) can shorten a deep‑cycle’s life compared with a purpose-built starting battery.

Charging and electrical system

• Charging profile: Car alternators and on‑board chargers are tuned for lead‑acid starting batteries. Most deep‑cycle lead‑acid types (flooded, AGM, gel) accept the same nominal charging voltages, but:
  • Gel batteries are sensitive to overvoltage; they require lower float/absorption voltages.
  • AGM deep‑cycle tolerates higher charge rates and is often the easiest deep‑cycle to use in cars.
• Alternator capacity: If the battery has a much larger capacity than stock, the alternator will take longer to restore charge after starting or accessory use. That’s not harmful per se but can lead to more engine run time needed to recharge.
• Charge algorithm mismatch: Repeated partial charges from short drives can reduce battery life. Smart charging (DC‑DC charger or multi‑stage regulator) mitigates this.

Physical and safety considerations

• Size and fit: Marine deep‑cycle cases (group sizes) may differ. Confirm physical dimensions and terminal locations; ensure secure mounting and proper venting for flooded cells.
• Venting and hydrogen: Flooded deep‑cycle batteries vent hydrogen during charge; they must be installed in a ventilated area and terminals protected. AGM and gel are lower venting risk but still require care.
• Weight: Deep‑cycle batteries are often heavier, which can affect handling if replacing multiple units or using a much larger battery.

Practical outcomes by typical scenarios

• Occasional use in daily driver: Acceptable if the battery’s CCA rating is sufficient for your engine and you understand potentially reduced cranking in very cold weather.
• Heavy accessory load / audio systems: A deep‑cycle (or dual‑purpose starting/deep‑cycle) can be a better choice than a pure starter battery because it handles deep discharge for accessories.
• Long idling, marine trailer vehicles, or vehicles used off‑grid: Deep‑cycle is advantageous for powering loads when engine is off, especially when paired with appropriate charging systems.

Recommendations

• Pick the right chemistry: AGM deep‑cycle gives the best compatibility with car charging systems; avoid gel unless your charger/alternator is compatible.
• Match CCA for cold climates: Ensure the chosen deep‑cycle provides sufficient CCA for reliable starting in expected temperatures.
• Use a dual‑purpose battery if unsure: Starting/deep‑cycle (marine dual) batteries are engineered to provide higher CCA and more cycling tolerance — a good compromise.
• Upgrade charging if needed: Install a multi‑stage alternator regulator, DC‑DC charger, or a smart external charger if you frequently run accessories or have long charge recovery needs.
• Secure and ventilate properly: Fit battery in an approved tray, secure terminals, and vent flooded cells to avoid hydrogen buildup.

Bottom line: A deep‑cycle marine battery will work in a car for many uses, and can be preferable for accessory-heavy applications, but expect lower cranking performance, possible shortened life under pure starting duty, and pay attention to chemistry, charging profile, physical fit, and ventilation.

 

[Mogman]

I need to replace the batteries in my M998 and I was looking at Group 24M's. they are deep cycle marine batteries, would they work in the truck?

I always use AGM batteries, because the batteries are in the passenger compartment (read chance of acid burns in an accident) and because they are in a rather sealed box which can pose an explosion hazard due to hydrogen accumulation, regular lead acid batteries off gas hydrogen during normal operation.
They also have a longer life under normal conditions and tolerate being idle much better that lead acid batteries as they are not as susceptible to sulfication.
But of course they cost more....

 

[TOBASH]

I always use AGM batteries, because the batteries are in the passenger compartment (read chance of acid burns in an accident) and because they are in a rather sealed box which can pose an explosion hazard due to hydrogen accumulation, regular lead acid batteries off gas hydrogen during normal operation.
They also have a longer life under normal conditions and tolerate being idle much better that lead acid batteries as they are not as susceptible to sulfication.
But of course they cost more....

I’ve heard this before. No particular disagreement.

This is why I’m considering moving my batteries and hold downs to the passenger side under the hood area. Not hard to plasma cut and then weld up some 1/4” steel plate to make a battery tray, and attach to support pillar. Then just extend some wires and shorten some others. Either that or make a battery box for the bed and extend wires and such.

 

[SmartDrug]

I always use AGM batteries, because the batteries are in the passenger compartment (read chance of acid burns in an accident) and because they are in a rather sealed box which can pose an explosion hazard due to hydrogen accumulation, regular lead acid batteries off gas hydrogen during normal operation.
They also have a longer life under normal conditions and tolerate being idle much better that lead acid batteries as they are not as susceptible to sulfication.
But of course they cost more....

What size AGMs are you running?

 

[Mogman]

I’ve heard this before. No particular disagreement.

This is why I’m considering moving my batteries and hold downs to the passenger side under the hood area. Not hard to plasma cut and then weld up some 1/4” steel plate to make a battery tray, and attach to support pillar. Then just extend some wires and shorten some others. Either that or make a battery box for the bed and extend wires and such.

I am Petty lazy, AGMs are allot easier., besides that right front fender well is where I run the Air Dog fuel preporator

 

[Mogman]

What size AGMs are you running?

Well I am running one 6T size Odyssey for the main (12V) system and 2 smaller (51R IIRC) AGMs for the 24V system.
If I was running a normal HMMWV I would just use 2 group 24 AGM batteries, I have gone the 2 Odyssey route but they are stupid expensive now.

 

[TOBASH]

I’m tending towards rear bed batteries for several reasons.

I’ve installed Robotech power tools and I want the NATO plug near the batteries and easy to access to fix my rig and the rigs of those around me. I also want to place the 24-220 Volt sine wave inverter in that box for welding purposes. (I carry a 220 V flux core welder while off roading).

I want the front passenger seat compartment to act as an additional hidden tool storage area.

I’m considering placing an off-the-grid radiator fluid heat exchanger right front under-hood area to allow for warm showers while camping. (I respect Spartans BUT I prefer warm showers while Winter camping). Also considering installing active CTIS. I rebuilt an old Hummer H1 CTIS controller back in the day. The old water fording valve hole will be repurposed as a valve gauge for tire pressures. Fairly easy (haha) to plop it in.

I’ll post these things on the custom forum once they get done over the next many months.

 

[Dave2018]

Is anyone running anything OTHER than 6TLs? My truck should be here shortly and I will need batteries. I am looking at possibly group 24s or group 34s. I know there are group 31s but I don't want to run those.

And before saying "just get 6TLs" there was a post back in the LMTV forum that said something like " We should export 6TLs to all unfriendly nations. ".

I am am cheap and don't want to spend the $$$$ for 6TLs and they are simply not needed. I have been running group 24s in my LMTV for years and haven't had one issue. I bought blems that where 29.00 each. Of course that was before the Biden inflation and I am sure they are well north of that price today.

So back to my question what other sizes are you having luck size wise.

Words of wisdom on 6TLs

Source for 6TL Battery

Thanks to some research by tnmogger, we've been able to order NAPA Part BAT-7256 and come up with a 6TL battery. Cost is around $200/ea, but they gave me 20% off with the "bucket sale" I spent $195 out the door including tax and three tubes of grease. It it is a US Dept of Commerce and State...

www.steelsoldiers.com

My hmmwv has been running the same batteries for 19 years. The original hawker, what a quality battery. They even wrote the year they put the batteries in service. ...So it seems that staying in a vehicle in ga away from much freezing weather and not being used much but a charge kept is the ticket. Its a 2008 with 1700 miles original. Looking for another 10 years. Woo Hoo.

 

[juanprado]

19 years even for a hawker is impressive. There was a scrapper in Hattiesburg when the flood of M939's were being surplussed that was scrapping the trucks after pulling what he could flip easily. He had pallets of hawkers and excide wet cells but already had cut a deal to scrap for lead. I wish i could have gotten some above scrap price

 

[Dave2018]

19 years even for a hawker is impressive. There was a scrapper in Hattiesburg when the flood of M939's were being surplussed that was scrapping the trucks after pulling what he could flip easily. He had pallets of hawkers and excide wet cells but already had cut a deal to scrap for lead. I wish i could have gotten some above scrap price

For sure, standby's.

 

[MarkM]

Nev

My hmmwv has been running the same batteries for 19 years. The original hawker, what a quality battery. They even wrote the year they put the batteries in service. ...So it seems that staying in a vehicle in ga away from much freezing weather and not being used much but a charge kept is the ticket. Its a 2008 with 1700 miles original. Looking for another 10 years. Woo Hoo.

Never ever have I had batteries last much more than 10 or so years and most would last a lot less. Living in NE with the winters do I real number on batteries.

My 2015 Kia tosses a battery every 5 years like clockwork.

I had a pair of Hawkers in my M998 and they made it to 11 years old. I've had really good luck with the Optimas.

Mark

 

[Coug]

I have seen batteries that lasted less than 1 year.
I have seen multiple batteries last 12+ years in standby generators.
My dad's 96 ford ranger had the original battery last 17 years.
All of these were flooded lead acid, and pretty much ignored their entire lives (never topped up with fluids or cleaned terminals or anything)

Better quality brands you are more likely to have a battery last longer (which is why the manufacturer is usually willing to put a longer warranty on them)

It's all a matter of figuring out how much quality you require, and how much you are willing to spend.

I have several paragraphs saved on my computer that I usually end up posting on threads on facecrook every month or so when people ask about batteries.
Short version, if you never leave pavement or cell coverage, buy whatever battery works and is cheap.
If you go off roading, use the truck for work, or are often out of cell coverage, invest in better batteries. The up front cost usually pays for itself by not having to pay later in either recovery fees or lost paycheck.