Myth busting- Batteries

[Ajax MD]

I have the standard, military style AGM batteries installed in our truck.
I have the 200 amp alternator, and the 3L80 3-speed transmission, so nothing is tapping the rear battery for 12v. I have added ZERO 12v accessories to the vehicle.

Is it true that over time, the rear battery doesn't ever quite equalize and the batteries should be rotated, or is that some kind of myth?
Follow up question: What steps should be taken to protect the smart-start box from damage when charging the batteries with a charger? Should I unplug it? Disconnect the batteries from the vehicle? Is this a mythical worry also?

 

[TOBASH]

It is true, and is a big discussion in places like IH8MUD where the Diesel motors use 24 Volt systems.

A "solargiser" will help.

On this site, milcommguy sells 'em. So do many site sponsors.

milcommguy's prices are super reasonable, if he still has them in stock.

Prices on FleaBay are high.

 

[Milcommoguy]

It is true, and is a big discussion in places like IH8MUD where the Diesel motors use 24 Volt systems.

A "solarizser" will help.

On this site, milcommguy sells 'em. So do many site sponsors.

milcommguy's prices are super reasonable, if he still has them in stock.

Prices on FleaBay are high.

All Solarizers have been sold.

All things being equal, as in both batteries production dates/ lot numbers and one or the other hasn't been abused, they should look like one big 24 Volt battery. Equal charging, equal discharging they are in the same bank. There is no reason the battery connect to the 24 Volt lead gets voltage first or some other voodoo thinking that the one in the rear discharges first.

A bit of history... I worked in the telecommunication. Our sites had 52-56 volt battery banks and some 120 volt systems made up of 2.25 volt cells to meet the terminal voltages above. These types of systems are a 100 year old designs in most every phone company central office. Never had the problems described going on in a hUMV. Like I say below.

Mix and match unknowns batteries and all bets are off, CAMO.

 

[chrisross]

so on a 4LE80 you need to rotate the batteries for realz ?

 

[frank8003]

You will never see the Ma Bell backups or powerplant battery cells to the DC bus and the ones in all the worlds' diesel and nukes. The Subs battery that would always be tested and changed out one for the other sequential order.
Ma Bell is once a month, USN Subs check is every few hours, Powerplant is once a day, My truck once a week.
Battery is battery.................................... How the heck you think subs go under?
One can weld with a battery without Truck running, useful.
One must treat them nice for longevity.
There is the huge amount of information I assure You that You Can not get to.
But what is available to You would be enlightening.
Work study work work and study some more.

 

[juanprado]

I have experienced the stated failure twice since I got mine. Don't know why as I am also m998 stock with 60amp and no 12v accessories. I do have a solargizer.

Just a few months ago, I replaced the bad battery and rotated.

Maybe I just had bad luck ....

 

[frank8003]

Maybe I should post all my battery stuff and let everybody else figure it out.
This will take a couple of whiles.

 

[glcaines]

You will always have one battery fail before the other. The chances that both batteries will give up the ghost simultaneously is very remote. When I have one battery fail, I replace both of them at once. I keep a 24 VDC battery minder on mine all the time when not in use. I routinely get ~9 years out of 6TL batteries.

 

[NDT]

glcaines nailed it. Put a pair of BatteryMinder 2012-AGMs on your Hawkers and they may last forever!! I have a pair of 2008's that are going strong being kept warm and happy and defibrillated by the 2012's.

 

[Milcommoguy]

Not going to go head to head on battery fails or the history. There is a TON of information. Mostly engineering and standard practices going back 100 years.

When one follows the book and with routine operational maintenance batteries can last a very long time. I have seen signal batteries used in railroad applications 60 years old before being removed for the latest and greatest only to fail six years out.

Lead acid wet cells types, using them in general, in a HumV... hot, cold, bouncing and bumping, charging and discharging and that time or two when "left the switch on" is going to be the death of one or both. As closely as they are manufactured they seem to have individual personalities. Note there are 6 cells each, times two.

In my simple world, It's not going to be 6LT's , military style, AGM, red or colored tops, over price, over engineered batteries. Little 60 Amp alternator to charge. Starter spins up the tuned engine, glow plugs a working, no problem. Two each Costco $90 buck batteries. Coming up on five years. My HumV isn't getting $400 dollar each for batteries.

It is completely possible, more than likely and at anytime, one of the 12 cells fails.. and then it's down hill from there. Time to remove and replace... both as your on borrowed time for a new matched set. IMO

Now where's that Costco receipt, CAMO

 

[Coug]

So the theory goes that the first battery in the string will charge more than the second battery in the string over time. Something about the first battery possibly pulling more of the amps/current/whatever before it gets to the second battery in the string.
This in and of itself isn't a big deal, except that the voltage regulating system in this system is pretty dumb. All it really cares about it how much voltage vs current it's putting out.
So over time, if one battery has a higher charge level than the other, you start to have issues. It's more of a cumulative effect, that one battery can slowly get higher over time, which means the other just doesn't see as much voltage to charge up.
Even within a single battery you will see individual cells that aren't at identical states of charge, and one cell will usually fail first.

The point of rotating the batteries is so that they both see equal incoming current over time.

Almost every backup battery system I've worked on either has some type of charge equalization modules on it, or the charger has an equalization setting, where it pretty much overcharges the entire battery bank to make sure they are all brought up to an equal level from time to time.

If you don't want to swap them back and forth, then putting a good charger (I like the NO.CO brand) and do a charge on each individual battery to bring them back to as close to identical states of charge as you can.

And as Milcommoguy said, anytime one cell or battery fails, you should replace everything in the system. (Though I'm into mine for $300 each)

Sure, you can replace just the failed battery, but you'll be putting an increased load on it compared to the remaining battery, and cutting the life of the new battery short. Not so big of a deal on a $100 or less battery, but much more important if you're putting actual money into it.

 

[Ajax MD]

Thanks for the insights. I'm not experiencing any problems, I just want to be proactive. It seems that if I buy a 24v battery tender, I can avoid rotating the batteries.

 

[Coug]

Thanks for the insights. I'm not experiencing any problems, I just want to be proactive. It seems that if I buy a 24v battery tender, I can avoid rotating the batteries.

Only if it has an equalizing function. It's much better to charge them individually rather than together otherwise, so 2 12V battery tenders would be better.

Battery tenders are more for maintaining than charging, so it would take a while to bring the battery with lower state of charge up to an equal charge as the higher; their purpose is more just to maintain a fully charged state, rather than do any actual charging. They do charge up batteries over time, but they don't usually have enough current to correct any issues (you'd need a charger with an "equalize" or "repair" function for that)

 

[Ajax MD]

Only if it has an equalizing function. It's much better to charge them individually rather than together otherwise, so 2 12V battery tenders would be better.

Battery tenders are more for maintaining than charging, so it would take a while to bring the battery with lower state of charge up to an equal charge as the higher; their purpose is more just to maintain a fully charged state, rather than do any actual charging. They do charge up batteries over time, but they don't usually have enough current to correct any issues (you'd need a charger with an "equalize" or "repair" function for that)

On the topic of charging with a charger, this is another myth I'd like busted or confirmed-

People have posted that the Smart Start boxes have been damaged by external battery chargers. Perhaps some initial surge during connection of the battery charger causes this, I don't know. Is it important to disconnect the batteries from the vehicle prior to using an external charger to protect the Smart Start box or is that a myth?

 

[Milcommoguy]

If that was the case.... What good would the slave connector be used for?

And as to the smart start box... Just plain dumb over kill in a combat truck. IMO

Answer: Jumping and charging, CAMO

 

[Coug]

On the topic of charging with a charger, this is another myth I'd like busted or confirmed-

People have posted that the Smart Start boxes have been damaged by external battery chargers. Perhaps some initial surge during connection of the battery charger causes this, I don't know. Is it important to disconnect the batteries from the vehicle prior to using an external charger to protect the Smart Start box or is that a myth?

This is one I've never heard before. I suppose it might be possible to damage the box, but I don't really see how if the start switch is turned off and the batteries are connect AND you didn't do something stupid like hook up a dumb charger backwards or something. The batteries should act as a buffer for any voltage/current when the charger is hooked up.
I dunno, all my chargers are smart chargers that run some sort of test cycle before actually applying any charging to the system.

 

[Retiredwarhorses]

It’s not chargers that cause issues, it’s salve starting that can cause issues.

 

[Ajax MD]

It’s not chargers that cause issues, it’s salve starting that can cause issues.

Ah, ok. That's interesting to know.

Well, I don't have a 24v charger right now. If I had to externally top off my batteries, I'd need to split them and charge them individually.
I do want to get a battery minder of some sort.

Right now, the truck is being driven once per 1-3 weeks for about 30 - 60 minutes. It'll never be a daily driver for commuting but as I finish a few things such as CV boots and locking spindle nuts it'll probably get driven more often.

 

[frank8003]

Oh, about batteries ..........
Start with Alessandro Giuseppe Antonio Anastasio Volta

Alessandro Volta - Wikipedia

en.wikipedia.org

That will start you on the long trip. Way before you get to submarine battery and Power Plant and Ma Bell battery take a small side trip to the art and science of actually making and selling a lead acid battery that is predicted (guaranteed) to fail at a specific time in use in the future. Make a few hundred million bucks because It gets treated like a consumer item.