Battery or Alternator

[Student12]

This may be a Longshot but...

I've had the un-pleasant experience of the dreaded auxilary draining the main battery.

For those who have experienced this situation,
I'm curious to know how amps does your alternator have.

I see the Gladiator alternators are 180 or 240 amps

My altinator is 180 amps

Could it be the quality of the alternator ?

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[OVERLORD]

Easiest, get your batteries load tested. Free at most Auto Parts stores.

 

[Lost1wing]

No!

How do know your aux battery is the problem? What testing have you done? What symptoms or messages do you have?

 

[Lost1wing]

Easiest, get your batteries load tested. Free at most Auto Parts stores.

And before you start yanking out your batteries, know that you have to be careful with the cable ends, or we will be talking in depth about batteries and fuses.

 

[Student12]

No!

How do know your aux battery is the problem? What testing have you done? What symptoms or messages do you have?

I never use the stop start feature. Battery charge screen would continuously drop to around 12 volts.

Came out to start up the truck, brake pedal wouldn't budge. Got it tested, needed multiple jumps and still wouldn't crank. Replaced the main battery.

 

[Lost1wing]

I never use the stop start feature. Battery charge screen would continuously drop to around 12 volts.

Came out to start up the truck, brake pedal wouldn't budge. Got it tested, needed multiple jumps and still wouldn't crank. Replaced the main battery.

I don't use ESS either, but I do look at the ESS page for clues. Much better than the voltmeter display. Don't get me wrong I look at the voltage display too, but the ESS battery charging message remaining on is a big clue that you have a problem. Start Stop unavailable or stop start not ready on for long periods are also clues.

Your Aux could be bad, that it dropped your main battery to cause a no start. If it was the problem your new main may not be new very long. I would look at replacing it or at least charging it and having it tested.

 

[Mr._Bill]

I never use the stop start feature. Battery charge screen would continuously drop to around 12 volts.

Came out to start up the truck, brake pedal wouldn't budge. Got it tested, needed multiple jumps and still wouldn't crank. Replaced the main battery.

Whether or not ESS is used has no effect on charging or battery life.

The average life expectancy of the batteries is three years. If the truck is not driven enough to keep the batteries charged, they will fail faster.

The batteries are paralleled together all the time, except during the startup test and during ESS restarts. When it is time for replacement, both batteries need to be replaced at the same time and fully charged before installation.

The system voltage will climb up to the 14.6 range when the batteries need charging. When the batteries are charged it will drop to the 12.8 range. The output from the alternator is not constant, it is varied based on system demand.

 

[Deleted member 52902]

Your new Main battery is already getting trained by the old Auxiliary battery in how to die a premature death. Replace that Aux battery now.

The alternator quality is fine. Its amperage output @ 180 amps maximum is fine too. A higher output alternator, or generator type (just a different internal design used for same purpose) is appropriate when the demand to recharge the starting battery, the Aux battery that maintains power for electronics, and additional demands on the electrical system from some or added devices, and perhaps a towed trailer with its additional lighting and in some larger trailers, electric brakes; then a higher output alternator may be necessary to keep up with the demand. Why isn't the 240 amp always included? It costs more. That additional current (amperage) capability is normally paired with a more robust coolant system handle additional heat with additional overall system (powertrain and electrical) loads. You can replace your 180 amp alternator with the 240 without a change in the cooling system but I don't see the point in most cases, without considering the other components which might even include wider axles and make sure a high mounted winch isn't blocking air flow on hill climbs with a heavy tow, to provided best overall results. Including best rear axle ratio.

You might not have this complicated matrix to need anything more than the original 180 amp alternator. But you really should change out that Aux battery at the same time as the Main (starter) battery every time an actual battery issue is in play.

Or you can change the system to use only a single, larger capacity battery. But in reality , there is nothing wrong with the two battery system provided by JEEP. Depending on how the JEEP is utilized, an extended off-road demand for current might make the expense of changing out the little Aux batteries capacity, to a larger battery. But then you have to consider where to locate that battery. Which also requires longer, and larger wire for the additional current. Because, resistance increases with distance, so that has to be taken into account. This approach should be an engineered solution. Fortunately, there are kits made to do this sort of upgrade.

Meanwhile.... Unless your JEEP is festooned with a fairly robust increase of concurrent, electrical-current demand. You can stick with the 180 amp alternator. Ditto for the factory size of the battery pair.

 

[sharpsicle]

I’m kind of confused here.

You replaced the main, and everything works? I’m assuming the main was tested and proved to be bad? Was the aux tested at that time? If not, why not?

As for the brake pedal thing, that has nothing to do with battery voltage. The brake system stiffen up when the truck sits for a while, you just have to push harder. This reads as though a stiff brake pedal that you didn’t push hard enough to allow the truck to start caused you to replace the battery? What’s going on here?

 

[Student12]

I’m kind of confused here.

You replaced the main, and everything works? I’m assuming the main was tested and proved to be bad? Was the aux tested at that time? If not, why not?

As for the brake pedal thing, that has nothing to do with battery voltage. The brake system stiffen up when the truck sits for a while, you just have to push harder. This reads as though a stiff brake pedal that you didn’t push hard enough to allow the truck to start caused you to replace the battery? What’s going on here?

Definitely had the main battery tested.

What prompted me to change the main battery was not even being able to enter the vehicle via the fob. Once I used the key to get in, I tried to start up the truck & it was a no-go. Pair all of that with the stiff brake pedal and a good key fob battery, that's when I figured that this is a battery issue.

I ended up going with a dual battery setup.

 

[brsnow2585]

I'm tentatively researching an aux battery delete. When it's cold and/or I haven't needed to drive in a few days I randomly get a message like ' battery low, aux buttons not available' something to that effect, to me that seems like a circuit routing issue. I've got auto start/stop disabled, leading me to think the computer monitors and the aux switches run through the aux battery before/instead of the main battery.

 

[sharpsicle]

I'm tentatively researching an aux battery delete. When it's cold and/or I haven't needed to drive in a few days I randomly get a message like ' battery low, aux buttons not available' something to that effect, to me that seems like a circuit routing issue. I've got auto start/stop disabled, leading me to think the computer monitors and the aux switches run through the aux battery before/instead of the main battery.

That message is not a sign of a bad aux battery. Common misconception. The system uses both in parallel for aux switch functions, and most occurrences actually end up with the main needing replacement instead.

 

[brsnow2585]

That message is not a sign of a bad aux battery. Common misconception. The system uses both in parallel for aux switch functions, and most occurrences actually end up with the main needing replacement instead.

Hmm... Good to know, do you know if they are isolated from each other? Ie: if one gets weak or a fault dragging the other down too, maybe even the alternator? I've never had the slightest inkling that the main battery is hurting, always cranks strong, I watch the off-road pages regularly and the alternator reads all expected and consistent. I do winch occasionally, that's obviously fat wired directly to the main battery posts(with cutoff switch that stays off until I need or suspect I might). I'm thinking to pull the aux and factory main battery and replace with the biggest dual purpose deep cycle I can find that fits the battery tray. Thoughts, counter thoughts always welcome, that's why I came here, if I'm thinking stupid or backwards tell me, that's why I'm asking. I did get the max tow package and the diesel, both which have the bigger alternator(which might get switched up bigger in the future, just not right now). Mine is a '22 so I'm figuring the battery is going to be due for a change here sometime, I subscribe to the 3-5yr life expectancy rule of thumb for standard batteries not being tortured. I've definitely used mine, but not abused it.

 

[sharpsicle]

Hmm... Good to know, do you know if they are isolated from each other? Ie: if one gets weak or a fault dragging the other down too, maybe even the alternator? I've never had the slightest inkling that the main battery is hurting, always cranks strong, I watch the off-road pages regularly and the alternator reads all expected and consistent. I do winch occasionally, that's obviously fat wired directly to the main battery posts(with cutoff switch that stays off until I need or suspect I might). I'm thinking to pull the aux and factory main battery and replace with the biggest dual purpose deep cycle I can find that fits the battery tray. Thoughts, counter thoughts always welcome, that's why I came here, if I'm thinking stupid or backwards tell me, that's why I'm asking. I did get the max tow package and the diesel, both which have the bigger alternator(which might get switched up bigger in the future, just not right now). Mine is a '22 so I'm figuring the battery is going to be due for a change here sometime, I subscribe to the 3-5yr life expectancy rule of thumb for standard batteries not being tortured. I've definitely used mine, but not abused it.

Honestly, I think there’s a lot of reading you should do on the battery and electrical systems in these modern trucks. Considering things like smart alternators are in the mix, you really need to know and understand how they work and the voltage you should expect to see.

The cliff notes is that the batteries are always in parallel, they only separate when it’s cranking during an ESS event. Otherwise, it’s like one big battery system. The alternator will only output the voltage needed to maintain the system, so if it’s always at 14 V, then it’s trying to charge constantly. Healthy systems see the voltage drop down into the high 12s or low 13s for maintenance of healthy batteries while running.

 

[brsnow2585]

Electrical engineer here, but before this ESS crap started to be a thing. What you said about parallel make perfect sense, but on starting if there's a cutoff to the aux battery as you alluded to, there's another element in the loop, as well charging 2 very disparate size batteries in parallel is just asking for problems

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