Other: Battery/Charging System

[Al from Eatonville]

1953 Commander with 232 V8. 6 volt positive ground electrics. The battery has not been holding a charge and will drain out after even a short drive. Will recharge quickly enough on a charger, but I can't go anywhere and depend on it restarting to come home. So it's been a constant hassle for a couple of months now. In an effort to determine if the battery is the culprit or if something else in the charging system is at fault, I removed battery from car one week ago. Then charged the battery fully. I then checked the voltage with my multimeter. Charge reading was 6.75. Checked it today (7 days later) and reading was 6.31. I then reinstalled battery in car. Started the car and, while running, the charge reading was jumping all over the place (going from .08 to 8.3, but constantly jumping all over the place in between). I have had my generator rebuilt by the best shop in Tacoma, and I have replaced my voltage regulator with a brand new unit from SI. Battery only about 18 months old, but I suspect it is just not doing it's job and needs to be replaced. Any thoughts or suggestions are greatly needed and welcomed. My goal is a dependable daily driver - like I used to have. Thanks so much in advance for your help.

[StudeRich]

A jumping ammeter is most often sticking and bouncing Points in the Regulator, it can also be issues with the Generator.
Never assume New is perfect, have the Battery Gen. and Reg. all checked by an Auto Electric Shop.

I think a load test on the battery may show it is weak.
Have you checked the Date code on the battery ?
The Alpha Letter is the Month, the Number is the year, on the small round sticker on one of the two Ends of the Batt.

[Commander Eddie]

I just replaced the battery in my Ford truck after only 13 months. The charging system checks out so it was a bad battery out of the box.
If you don't drive your car often I would invest in a 6-volt battery tender that can be attached to your battery to keep it charged up between uses. Batteries can go bad just sitting. Even new ones. I use Battery Tender brand on all my vehicles (except the truck). That has changed and it is plugged in now.

[Ross]

I have found that digital voltmeters often don't like reading generator systems and jump all over the place. I keep an old analog voltmeter just for that purpose and it is a good thing to pick up at a yard sale. At a good fast idle you should get oh, 7 to 7.4 volts.

But in the meantime, what does your ammeter on the dash say? Does it show a charge whilst you are driving? Cruising along at anything over 30mph it should stay on the charge side when you flip your headlights on. As the battery approaches full charge the needle should go to the center but never show discharge at cruising speed.

Most importantly, when you get home and shut everything off the needle should be at dead center. If it shows a discharge something is shorted or hooked up wrong. If it shows a heavy discharge then the cutout relay in your regulator is stuck and will drain the battery in no time.

Another simple test is to ground the field terminal of the generator whilst the engine is running at a high idle. The voltage should jump way high (and your ammeter will jump to a heavy charge) when you do this and shows that the generator is good. Do this test only briefly.

[Jeffry Cassel]

Ref : my somewhat embarrassing 'spun bearing' post. Just because a battery is new doesn't mean it is OK. In my case I had load tested it and Theo had load tested it. In both instances a false negative test was obtained. By the time Tristan load checked it, it was far enough gone to give him a positive reading. If your ammeter reads a charge, your battery is the problem. You disconnected it for a week but then charged it! Disconnect it for a week and check state of charge - voltage and load test. Any battery will self discharge over time. A good battery will take quite some time to do so, but a failing battery will go down in just a few days.

[BRUCESTUDE]

I have found that laying my digital volt meter on the fender while the engine is running will cause the reading to jump all over the place. If I hold it in my hands while taking a reading ( I use 3 hands) it gives a steady reading.

[altair]

I made a mistake once, I charged a dead battery backwards and the needle was jumping all over the place. The battery tested good had lots of power and started smartly, what could be the problem?