Dual Batteries

[WVAiredales]

The 92 7.3 I recently bought has dual batteries, is this a factory deal or an aftermarket job? And if I need to replace them what would the knowledgeable people suggest for batteries?

Thank you
Shawn

 

[Kizer]

Dual batteries are factory. Please read "stickies" at the top of the forum to learn a lot about your new truck. And congrats. on the truck.
I have used AGM and lead acid group 31's. My personal opinion is that group 31 batteries work great for the $ spent. You know how opinions are.

 

[franklin2]

You have two batteries, but think of them as one large battery. That's how they are hooked up electrically, they just did not have enough room for one large battery. So make sure when you replace a battery, you replace both batteries at the same time with the same type. If you replace one battery, the new battery is going to only be as good as the older one it's mated to.

 

[icanfixall]

The above is true but one needs to understand why.... Think of an older used battery and a new battery tied together as you may tie together two tanks of water. So lets say one tank is 85% as full as the other tank that is 100% filled. Soon both tanks will not be full when they are connected. Same thing happens when we replace one bad battery with a new good battery. the other battery may not be as good on charge as the new one so it gets drawn down to the old batteries level. then you will NEVER have two batteries with a full charge or power level. If you for cost reasons need to replace only one battery make sure you can test the old battery for charge and power level. then and only then can you safely replace onlt one battery and still come out ahead. I realize most over the road truckers will not replace a complete bank of batteries when only one in that bank goes bad.

 

[chris142]

I only run AGM batteries. They don't corrode the cables like a flooded battery will. Mine are group 65's from A-Zone and they work fine.

 

[Macrobb]

I've done literally everything wrong you can do wrong with batteries; as long as your starter is in good shape, your wiring is good, and your alternator is charging properly, you can get away with all sorts of things.

I've run a single battery I got at the dump for a while(works fine, just has less 'cranking time' before it runs down), I've mixed and matched(make sure you don't have one battery with a dead cell, otherwise you can get away with it[1]).

[1] Note that while in /theory/ if you have two batteries of different capacity, they won't take a charge properly, in /reality/ the system isn't quite like that.
Your alternator simply puts out 14.0-14.5V DC, which is more than a 12V battery needs for optimal charging. Each battery will draw current from the alternator based on it's level of charge, and they will both "end up" being fully charged to their own capacities. Remember, an alternator doesn't 'shut off' like a quality charger does, it simply puts out a given voltage. Batteries will end up slightly overcharged over time, instead.

Anyway, that's just my 2c. I know it's not the 'correct' way of doing it, but I've never been one for doing things correctly.

 

[IDIoit]

. So make sure when you replace a battery, you replace both batteries at the same time with the same type.

agreed you should replace both.
disagree on staying with the same type.
group 31's for me.
largest battery cables.
and a powermaster starter.
never worry about starting again.

 

[franklin2]

By same type, I meant both batteries need to be the same type. If you want to put group 31's in there, they both should be group 31's.

I also have run mine all summer long with one battery, and mixed up batteries also. But that was being cheap getting by with used batteries. Once I buy new batteries, I buy both at once , same brand same size. They will last the longest that way.

The poor battery against the better battery is not just theory, it's a fact. When batteries are hooked in parallel, even though they are charged above their normal voltage, when the engine is turned off, one battery will hold less charge than the other, and they will tend to equalize sitting there over time, ending up not as good as the better battery, and not as bad as the worst battery.

 

[Macrobb]

The poor battery against the better battery is not just theory, it's a fact. When batteries are hooked in parallel, even though they are charged above their normal voltage, when the engine is turned off, one battery will hold less charge than the other, and they will tend to equalize sitting there over time, ending up not as good as the better battery, and not as bad as the worst battery.

I really suggest you look into battery theory some more.
If I installed 1 group 31(850CCA) and 1 Lawn & garden battery(200CCA), the lawn and garden battery /will not/ discharge my group 31 battery to "equalize".
Remember that a 12V battery is made up of 6 cells, each cell being 2V nominal. Whether a tiny little lawn and garden battery, or a massive semi truck battery, they both are the same chemistry and each cell is 2V... The only difference is the size of the plates in each cell.

The only way you get one battery discharging into the other is if:
A. One is discharged(at which point the battery /voltages/ will equalize, with the dead battery charging off the good one - a small dead battery won't drain as much as a large dead one will).
B. One battery has a shot cell. If one of the cells is shorted(something that ends up happening in a lot of batteries that 'die'), it will have a nominal 10V, peak 11.5V or so.
Because that is lower than the nominal 12V, peak 13.5V from a 'good' 12V battery, that battery will charge the 'dead' one, which can't actually accept the current(as each of it's 5 good cells is already fully charged), and so it ends up electrolyzing the water in the cell until the voltages equalize... around 11.5V.
This is at the 'dead' point of the good battery.

As such, you have to keep a shot battery away from a good one, if the shot one has a dead cell. If they both read 13.0+V after charging and letting sit for an hour, even if one barely has enough capacity left to light a bulb, it won't discharge the good one... the bad one just won't do anything when you go to use it.

 

[mblaney]

^^+1 I think the E series came from the factory with different size batteries (one was not a lawn mower battery though )

I stuck with stock size batteries from Costco (Kirkland brand). -20C this morning and fired right up, no block heater, batteries are three or four years old. Good price, excellent warranty, and most important - one of the top rated batteries.

Remember battery maintenance (if they are not sealed) - top them up with distilled water.

 

[icanfixall]

Distilled water is the ONLY water our batteries should get. Not the reverse osmosis type pure water. Get the true steam distilled water.

 

[mblaney]

Distilled water is the ONLY water our batteries should get. Not the reverse osmosis type pure water. Get the true steam distilled water.

or vodka?

 

[BDOGONE]

I pulled that skinny "lawn mower bat" out of my van, bought a pr. Of 31c's, fully expecting to do lots of surgery to install the one. Surprise it shimmied right in there no cutting! Don't get me wrong, it's tight.....


Sent from my iPhone using Tapatalk

 

[The Warden]

^^+1 I think the E series came from the factory with different size batteries (one was not a lawn mower battery though )

Maybe it was different in later years, but the '84 IDI E-350 I used to own had two batteries that were the same size, CCA, etc.

 

[franklin2]

I really suggest you look into battery theory some more.
If I installed 1 group 31(850CCA) and 1 Lawn & garden battery(200CCA), the lawn and garden battery /will not/ discharge my group 31 battery to "equalize".
Remember that a 12V battery is made up of 6 cells, each cell being 2V nominal. Whether a tiny little lawn and garden battery, or a massive semi truck battery, they both are the same chemistry and each cell is 2V... The only difference is the size of the plates in each cell.

The only way you get one battery discharging into the other is if:
A. One is discharged(at which point the battery /voltages/ will equalize, with the dead battery charging off the good one - a small dead battery won't drain as much as a large dead one will).
B. One battery has a shot cell. If one of the cells is shorted(something that ends up happening in a lot of batteries that 'die'), it will have a nominal 10V, peak 11.5V or so.
Because that is lower than the nominal 12V, peak 13.5V from a 'good' 12V battery, that battery will charge the 'dead' one, which can't actually accept the current(as each of it's 5 good cells is already fully charged), and so it ends up electrolyzing the water in the cell until the voltages equalize... around 11.5V.
This is at the 'dead' point of the good battery.

As such, you have to keep a shot battery away from a good one, if the shot one has a dead cell. If they both read 13.0+V after charging and letting sit for an hour, even if one barely has enough capacity left to light a bulb, it won't discharge the good one... the bad one just won't do anything when you go to use it.

A battery doesn't have to be "shot" to lag behind and drag down and hinder the performance of a good battery. It's not all about cell voltage, it's also about the internal resistance of the battery. This internal resistance increases as the battery ages. So when you ask the battery for high output, the older battery will have a higher internal resistance, so it contributes less when paired to a better battery with less usage cycles on it.

Here's a little bit of reading about it. They say sulfation and corrosion are the main culprits making the internal resistance rise in a older battery.

http://batteryuniversity.com/learn/article/rising_internal_resistance