Battery Voltage question

[Brahmajoe]

When I come to a stop and my auto stop engages, my voltage shows 11.9. Does this mean one of the batteries is going low? When it kicks back on it goes to 14v

Sponsored

 

[Mr._Bill]

How old are the batteries?
How often/far is the truck driven?

I saw similar behavior around the time my Main Battery needed replaced.

 

[Brahmajoe]

How old are the batteries?
How often/far is the truck driven?

I saw similar behavior around the time my Main Battery needed replaced.

It’s a 2022. I drive it daily. I just noticed that it drops like that at a stop start event

 

[Brahmajoe]

How old are the batteries?
How often/far is the truck driven?

I saw similar behavior around the time my Main Battery needed replaced.

At least 30 miles a day. Back and forth to work

 

[Mr._Bill]

I would disconnect the negative cables and separately charge each battery with a good quality AGM charger. Disconnect the IBS from the negative post of the Main Battery for about twenty minutes to reset it. The head unit will reboot from power loss and take up to 24 hours to fully recover.

The average life expectancy of batteries in the JT is about three years. Some go longer, some die sooner. Driving it regularly, like you do, helps to extend the useful life of the batteries, but the quality of the factory units is not the best available.

 

[Brahmajoe]

I would disconnect the negative cables and separately charge each battery with a good quality AGM charger. Disconnect the IBS from the negative post of the Main Battery for about twenty minutes to reset it. The head unit will reboot from power loss and take up to 24 hours to fully recover.

The average life expectancy of batteries in the JT is about three years. Some go longer, some die sooner. Driving it regularly, like you do, helps to extend the useful life of the batteries, but the quality of the factory units is not the best available.

I don’t have a charger. Does the dash show the main battery voltage?

 

[kevman65]

I don’t have a charger. Does the dash show the main battery voltage?

There is a way to switch it from Charge Mode to Status Mode.

The problem is, the two batteries are tied together, so you're getting an average across the two.

 

[Brahmajoe]

There is a way to switch it from Charge Mode to Status Mode.

The problem is, the two batteries are tied together, so you're getting an average across the two.

So should I just check the main first with a multimeter? Should the negative post be disconnected if I do that for a true main battery reading

 

[kevman65]

So should I just check the main first with a multimeter? Should the negative post be disconnected if I do that for a true main battery reading

Yes, separate the negative cables from the main, then read across the posts.

 

[Brahmajoe]

ok and i should be reading around 12.4 or better correct?

 

[PW45]

if your ESS is still working there's nothing to do. ESS not working is the first symptom everyone is having that the battery might be going bad.

you're reading a voltage drop when the engine stops because the meter is no longer feeling the alternator contribution to the felt voltage but there's still electronics operating that will cause a voltage drop to appear on your reading.

 

[Mr._Bill]

ok and i should be reading around 12.4 or better correct?

Fully charged should read around 12.8 volts. Below 12.4 indicates that the battery needs some help, or possibly replacement.

Separate the negative cables, one is the Aux battery, the other is the connection to the frame. The reading from there to the positive cable is the Aux battery. The reading for the Main battery can be taken from the posts. You should get two different, but similar, voltage readings. If one is significantly lower than the other, it indicates poor health for that battery.

 

[BaliMawr]

if your ESS is still working there's nothing to do. ESS not working is the first symptom everyone is having that the battery might be going bad.

you're reading a voltage drop when the engine stops because the meter is no longer feeling the alternator contribution to the felt voltage but there's still electronics operating that will cause a voltage drop to appear on your reading.

This isn’t always the case. My ESS never quit, but a week ago, the truck wouldn’t even turn over- two dead batteries.

Sponsored