Charging voltage question?

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Mr.FT

Mr.FT

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Since I added a volt gauge to my 72 Demon 340 I noticed my voltage at Idle is @ 13.6 v. Now my question is as I accelerate the voltage climbs to 14.9 or so. Is this normal? as I back off the voltage drops again. Should I be concerned about this ?

Thanks
Tom
 
Yes. That is not "real high" and I've had some guys try and tell me that it should be higher. But with the VR and battery warmed up and normal voltage "optimum" should be 13.8--14.2. My personal limits on a properly working system is not below 13.5 and not above 14.5

The MOST COMMON cause of high charging in these girls is one or both of two things......voltage drop in the ignition harness, causing low voltage to the voltage regulator, or poor ground path from the VR to the battery negative, which amounts to the same thing
 
For now, I would watch for battery sides swelling and/or dampness on top of the battery. Defective batteries and/or cycling battery discharge and recharge in Chrysler or any brand is what rotted away battery trays.
 
RedFish said:
For now, I would watch for battery sides swelling and/or dampness on top of the battery. Defective batteries and/or cycling battery discharge and recharge in Chrysler or any brand is what rotted away battery trays.
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Thanks for the heads up, would the fact that the battery is an AGM battery matter??
 
Get a test voltmeter and check the voltage at the battery while you rev the engine and also at idle. Dash gauges are not the most accurate, so it may just be off.
 
How accurate is your voltage gauge? Check it with a good reading hand held voltage gauge, to see if your cars gauge is off. I find some manufactures are not that precise on the voltage readings from there gauges. Your cars gauge could be reading high!! AMG battery will not change anything.
 
AGM batteries have a different charging strategy. There are three steps in a charge profile, it involves voltage, current, and temperature controls. Using standard regulator for flooded battery, will shorten battery life.

Correct AGM regulators are found for marine applications, and are expensive.
 
KitCarlson said:
AGM batteries have a different charging strategy. There are three steps in a charge profile, it involves voltage, current, and temperature controls. Using standard regulator for flooded battery, will shorten battery life.

Correct AGM regulators are found for marine applications, and are expensive.
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I've been using a AMG (Optima) batteries in my cars for the last 10 years and they have worked great. I have never had to change regulators to make them work or last, as long as the charging system in your car is working right, it will keep the battery charged. You have to use special AMG battery charger for storage and when you have a dead AMG battery.
 
Cooler Canadian weather is a blessing.

This is recommended maximum float voltage vs battery voltage, not ambient temperature. AGM battery systems typically incorporate battery temperature sensors.

AGM.PNG


While 13.8V at 77F is typical for well maintained Mopar, I doubt they cut back to 13.44V at 104F. I am also guessing that under hood battery temperature will exceed 104F, on a regular basis.

More information here: AGM Charging : Technical Support Desk
 
I just had a chance to get the car out for a run today. I noticed that the charging voltage is "hi 14.8 or so" but after I run around for 15 min. or so it drops to @ 13.5 -13.8 is it normal for this to happen?
Thanks
 
YES
Say you're sitting in a diner having coffee.Think of the battery as your coffee mug, and the regulator as a waitress.
See, you get down to the bottom half of your mug, and the girl comes around and tops it up. As she pours, she pours hard at first, and as the glass gets full, she backs off, and then it dribbles a bit and then off she goes
 
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And it is good. The OEM regulator has temperature compensation, as it gets warm the charging drops off. The assumption is the battery has similar temperature or less than regulator. The compensation is for flooded lead acid, not AGM.

If you monitor the battery temperature and the voltage, and it fits within table, that is good. But, that is only part of the story.

AGM are maintained by float voltage, but full charging happens at constant current, to meet a voltage per a different spec, followed by an absorption period. This type of charging takes a smart charger or regulator, for optimal performance. The OEM Mopar regulator does not measure, nor control current. It controls only float voltage for flooded batteries.
 
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I have used the same Red Top Optima battery for 10 years and it is on its second car. Never had to charge it during 10 summer car seasons, it has always held its charge while use in my cars. I use a AMG battery charger during the winter storage and that's it.
 
Mr.FT said:
I just had a chance to get the car out for a run today. I noticed that the charging voltage is "hi 14.8 or so" but after I run around for 15 min. or so it drops to @ 13.5 -13.8 is it normal for this to happen?
Thanks
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Uuuhhh.... no, not this much. There is some drop as the alternator's diodes and windings heat up, but not 1 to 1.3 volts.
 
nm9stheham said:
Uuuhhh.... no, not this much. There is some drop as the alternator's diodes and windings heat up, but not 1 to 1.3 volts.
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Had a chance to get out again today and this time the voltage remained high. It was between 14.7 and 15.1, I stopped every once in a while and checked the voltage at the battery just to verify. Every once in a while it would drop to @ 13.6 or so just for a minute or so and then back up. I'm starting to think maybe time to change the VR and see if that helps, any suggestions ??
 
The VR itself is temperature compensated. If you look back in any early seventies service manual, there's a chart showing colder VS warmer voltage output target of the VR
 
Mr.FT said:
Had a chance to get out again today and this time the voltage remained high. It was between 14.7 and 15.1, I stopped every once in a while and checked the voltage at the battery just to verify. Every once in a while it would drop to @ 13.6 or so just for a minute or so and then back up. I'm starting to think maybe time to change the VR and see if that helps, any suggestions ??
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I would be going through all of the systems connections with a fine toothed comb, and cleaning them first. That includes all ground connections, bulkhead connections, and ignition switch connections.
 
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