[SuperSound]

Originally Posted by Glen e

You are checking the battery with the engine running .....I also have been marine systems for 20 years. You are reading the charging system ,not the battery

Car batteries resting voltage is maxed at 12.7, once surface charge is removed. Educate yourself here : http://www.batteryfaq.org

Agreed. Most batteries will still start cars even in the high 11s on voltage, but not likely in cold climates. Never seen a 12V battery resting above 13.0Vs unless maybe in an overcharged (damaged) situation.

[MovieGuy]

Originally Posted by SuperSound

Agreed. Most batteries will still start cars even in the high 11s on voltage, but not likely in cold climates. Never seen a 12V battery resting above 13.0Vs unless maybe in an overcharged (damaged) situation.

They will boil over before they will overcharge that much. I was a locomotive electrician for 39 years. I dealt with 64V systems. So Glen can be more precise on what to look for on 12V systems. But I completely agree with him when he says if you check the battery while it is running you are checking the charging system and not the battery. Whence my earlier comment about looking at what the battery is doing DURING the starting process. On locomotives, we would put the meter across the battery switch, if the voltage went below 46 volts we knew the batteries were bad. I have seen batteries read 64V and not be good. It can be that they need a charge but it can also be a bad cell.

[eurostyle]

Originally Posted by Glen e

You are checking the battery with the engine running .....I also have been marine systems for 20 years. You are reading the charging system ,not the battery

Car batteries resting voltage is maxed at 12.7, once surface charge is removed. Educate yourself here : http://www.batteryfaq.org

No, the engine was not running and the battery shows 13.76
Per the owner manual the car has an Absorbed Glass Mat (AGM) 12 volt battery. When using a 12 volt battery charger on the 12 volt AGM battery, some chargers have an AGM battery setting on the charger. If available, use the AGM setting on the charger, to limit charge voltage to 14.8 volts.
In other words the chart shows 12.7=100%. My battery shows 13.76 and I have charged batteries up to 14.8. If my battery would show 12.7 like in your chart it would be a dead battery. 1 volt difference on your chart shows a dead battery, 12.7-11.7, 1 volt difference on my battery and I would not be able to start the car.

[burnningice]

This actually just freaked me out. I've never seen a car that rests at 12v while running. Has always been. 12.6 off and 14.4 on.

[Glen e]

Originally Posted by eurostyle

No, the engine was not running and the battery shows 13.76
Per the owner manual the car has an Absorbed Glass Mat (AGM) 12 volt battery. When using a 12 volt battery charger on the 12 volt AGM battery, some chargers have an AGM battery setting on the charger. If available, use the AGM setting on the charger, to limit charge voltage to 14.8 volts.
In other words the chart shows 12.7=100%. My battery shows 13.76 and I have charged batteries up to 14.8. If my battery would show 12.7 like in your chart it would be a dead battery. 1 volt difference on your chart shows a dead battery, 12.7-11.7, 1 volt difference on my battery and I would not be able to start the car.

No you are not correct. You are reading a false surface charge at 13.76. Google "AGM charge chart" and you get a bunch of hits like this. In order to read a battery correctly you need to put a load on the battery of 1 to 2 minutes of something strong like your headlights or something else, then read it after 15 minutes with a voltmeter. Also a Battery Tender is fine to use with an AGM, and it will automatically shut off and go to a float mode (i.e. it's 100% charged, at 12.6) battery chargers limit the top end of the charge on an AGM.

No battery, no matter what type, that's ever used in a car, is dead at 12.7.

Yes, SLIGHTLY diff, but certainly not avresting voltage at 13.76:


See the third paragraph here:

https://www.solar-electric.com/deep-...at%20Batteries

[fastball]

Keeping this simple from an electronics/biomed technician who has installed and repaired more than a few car stereo and vehicle security systems going back to the 90s.......

Ever since the 1950s when the electrical standard for all North American production cars changed from 6v with a generator to 12v with an alternator, its remained essentially the same: a fully charged battery with the engine/charging system off will read 12-13 volts, and NO MORE.

When the engine/charging system is on it will read 12-14.4 volts.

If you measure your electrical system in those states and your readings fall within those parameters in those states, your battery and charging system are operating properly.

This applies to every car, truck, van, SUV you can name that was ever produced for the North American market since 1958.

[LtColumbo]

I was taught that charging voltage should be between 13.8v-14.2v.

The static charge on my battery showed 12.8v

I would assume that anything less than that while driving would indicate a DISCHARGE condition.

For the past several days, I have had the voltage displayed on my 1LT. Sometimes it reads 13.8v. Sometimes it reads 12.1v.

A reading of 12.1v while driving is very disconcerting. Even a "float charge" is 13.5v from what I remember.

So is our voltage monitor showing that the alternator is only charging 12.1v back into the battery? Wouldn't an AMP gauge be more useful?

And really, what is the point of that information as opposed the what is actually going on AT the battery, ya know, like it's been all along?

The owners manual does not fully explain this "smart charge" or "EPM" as they apparently call it.

[Glen e]

Originally Posted by LtColumbo

I as taught that charging voltage should be between 13.8v-14.2v.

The static charge on my battery showed 12.8v

I would assume that anything less than that while driving would indicate a DISCHARGE condition.

For the past several days, I have had the voltage displayed on my 1LT. Sometimes it reads 13.8v. Sometimes it reads 12.1v.

A reading of 12.1v while driving is very disconcerting. Even a "float charge" is 13.5v from what I remember.

So is our voltage monitor showing that the alternator is only charging 12.1v back into the battery? Wouldn't an AMP gauge be more useful?

And really, what is the point of that information as apposed the what is actually going on AT the battery, ya know, like it's been all along?

The owners manual does not fully explain this "smart charge" or "EPM" as they apparently call it.

Correct, it USED to be that way.....BUT .the new smart systems will turn off charging and resort to no charging when it deems the level adequate /full so the resting voltage is above about 12.4. Remember when the engine is running, you are watching the charging system, not the batt voltage. Resting, engine off, wait an hour and 12.6 is 100%.

[LtColumbo]

I just went to my car and put it in "service" mode. The voltage read 12.5v without the engine running. So if the voltage reading is "charging" voltage, and the engine was OFF, it should have read 0.0v?

But you're saying that somehow the gauge knows the difference between whether the engine is running or OFF?

[Glen e]

Yup .....service mode actuates the gauges to read, so you get the resting voltage. Start the car, which starts the batt to read what's coming in from the alternator, so it reads >13.....

This is ford but GM is same:

http://www.valeoservice.com/data/mas...E6E8714173.pdf

[cellsafemode]

I guess what we need is an update to the firmware so instead of a voltage it just says "good, low, bad".

[SuperSound]

Originally Posted by cellsafemode

I guess what we need is an update to the firmware so instead of a voltage it just says "good, low, bad".

That's exactly why many cars don't have any gauge.

Sent from my SM-G950U using Tapatalk

[Glen e]

Originally Posted by cellsafemode

I guess what we need is an update to the firmware so instead of a voltage it just says "good, low, bad".

Actually prob just "charging/no charging" would prob do.....LOL

[LtColumbo]

OR maybe and alternator icon OR amp gauge instead of a battery icon!