91.5 Charging Voltage too high

[Ncostello]

I've not been driving my truck lately... and knew I wouldn't. So a few months ago I bought a tiny charger at Harbor Freight that is supposed to maintain 13. 1V for long periods of time... with a max output of 500mA. I took the charger off today and noticed it was keeping the battery around 13. 5 volts.

After starting it up I left the voltmeter on the battery and noticed it was charging at 15. 5V... then began coming down after about 15 minutes of high idling. But it never went below around 14. 7 volts... and kept jumping back up to 14. 8 or 14. 9. Wasn't holding very steady on the meter. Either I have a voltage regulator problem or the battery is now messed up from long term use of that charger (that was made for long term battery protection... go figure).

Either way I'm not driving it like this. I suppose I should start by having the alternator tested... and the battery tested. It's a 2009 DEKA Group 31 with little usage on it. But it will settle down to 12. 5V if I let it sit for a few days. So I'm thinking the battery is OK. I'm certain all of my wiring is clean and secure. I know the grounds are good as are the body grounds.

If the charger takes the battery up to 13. 5V... shouldn't the alternator basically not send any charge to the battery after I crank it over? Certainly it shouldn't be trying to maintain 14. 5 volts.

 

[Bob4x4]

The old regulators are not as smart as the new ones. What does your ammeter show?

 

[DVolk]

It should charge at 14 volts when running, renember this is supplying the whole truck and the regulator shuts down the voltage if the batttery needs more how ever the volt guage should read 14 volts

 

[mysteryman]

Normally a short to ground on the field/stator winding is what causes this. I see you live in Indiana. The heart of the rust belt ! The road salt will often break down the insulation on the stator windings. This will cause cross shorts in the windings which will cause voltage spikes. Also check that the quick connector plugs are clean. High resistance at the plugs for the field wiring will also cause high output. Especially the the dark green field wire !

After starting it up I left the voltmeter on the battery and noticed it was charging at 15. 5V... then began coming down after about 15 minutes of high idling. But it never went below around 14. 7 volts... and kept jumping back up to 14. 8 or 14. 9. Wasn't holding very steady on the meter. Either I have a voltage regulator problem or the battery is now messed up from long term use of that charger (that was made for long term battery protection... go figure).

Either way I'm not driving it like this. I suppose I should start by having the alternator tested... and the battery tested. It's a 2009 DEKA Group 31 with little usage on it. But it will settle down to 12. 5V if I let it sit for a few days. So I'm thinking the battery is OK. I'm certain all of my wiring is clean and secure. I know the grounds are good as are the body grounds.

If the charger takes the battery up to 13. 5V... shouldn't the alternator basically not send any charge to the battery after I crank it over? Certainly it shouldn't be trying to maintain 14. 5 volts.

 

[Bob4x4]

A field wire shorted to ground will full field on one brush or take out fuselink on the other... ... ...

 

[tempforce]

looks to be charging normal to me… the battery will always need more voltage to charge than if you just check it without a load or charge going to it. . most batteries will show between 11. 7 and 13. 5 static… so a 1 volt higher charge rate would not be anything to worry about. 14. 7 is where most charging systems are set to float at. . i. e. . battery at full charge, engine running… anything over 15 or under 12 and you have a problem.

 

[Ncostello]

Thanks all. For now I'll rule out corrosion. There truck has never shown much of anything in the way of corrosion... like some vehicles I've seen. I'm around highway plows and bridge de-icing tanker trucks at work so I'm very familiar with what salt and calcium chloride liquid can do to the vehicles we have. Plus, about two years ago I semi-restored the engine compartment. Part of that process involved removing the wiring harness all over the engine and transmission. I checked (found one chaffed wire too in a loom!) everything, cleaned and re-wrapped to look original. All the connections were clean and didn't have any signs of corrosion as it was. Fuse links are all good... and the battery cables are new. The body and engine were all grounded well with new straps. This is not to say the alternator hasn't suffered something internally. So I will at least have it tested by some folks I trust.



I still have to assume I have a problem however because it will charge over 15V on what I believe is a 100% charged (over charged) battery, and no load on the system (no lights, no heater motors running etc). I've not checked amp draw while running. Bob4x4... if by ammeter you mean the guage on the dash it's showing in the "normal range"... somewhere between 8 and whatever the high end is. Isn't that a voltage guage?



I better start with the alternator and try a different known good battery. I have this weird feeling this cheap little Harbor Freight charger has ruined the battery. I've had a few of those and some keep the batteries topped off well above 14V constantly. Max output is supposed to be 13V.



It's almost as if my battery started out at 12V measured... the charging voltage would be perfect. But my battery is starting out at 13. 5V after unplugging the long term "maintainer"... and the alternator still want's to put another 2. 5V +/- on top of that. So 12V becomes 14. 5V... and 13. 5V becomes nearly 16V.

 

[DVolk]

Stop by some battery place and have it checked most will check them for free . Are you seeing singns of the battery boiling over ? If you dont its fine id say your guage is weirding out , does it drop with the lights on and all the accessorys on ?

 

[Ncostello]

No signs of boil over. It's a "sealed" DEKA. Which are pretty good in my opinion. My multi-meter is a good one. So I don't believe it's showing wrong voltages. It's correct on everything else. My back-up cheapo meter reads the same.



If I turn my brights on, heater fan and everything else... it doesn't drop really. My lights are pretty bright during all this... so I'm too high on voltage. I don't wanna ruin some of my 12V items so I'm not going to run it like this until I test the alt and battery. This weekend I will. I'll report back. I may see if I can have the battery run on a conditioner or something to discharge and recharge properly.



Word to the wise... don't use cheapo tenders for your battery. Spend the money and buy quality products. That's my guess for now.

 

[DVolk]

Im not a huge fan of digital volt guages they have a tendicy to jump around a littel .
have you checked any type of other battery to see if they both read the same ? no matter if its a 9 volt battery or
what ever if its the type that can read 110/120 volt check that and see what it says , the 2 meters i got will read voltage even when you hold on to both wires and there not the cheap brands either

 

[B.G. Smith]

Disconnect the charger for a few minutes and check the battery voltage. Bet you won't see 13. 5V. Really sounds normal to me. When you crank the truck you pull the battery "surfasce charge" off and the alternator/regulator is doing what it supposed to do. Some of the older systems had a charge rate of 13. 8 to 14. 5 where they had a seperate regulator. If I remember correctly, the Auto Lite system were a little higher. 12 volt battery fully charged has about 2. 2 volts per cell which would be 13. 2 volts after the surface charge is gone. You are not going to do much charging at 13. 5 volts. Per the questioon above about amps, you would have to connect a meter capable of handling at least 140 amps or so in line from the alternator(big wire on alternator)to the PDC. bg

 

[ENafziger]

Have you tried changing the voltage regulator? Summit has original Mopar. The last couple I bought were made in USA too.