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Battery & Charging System Question

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MGTF1250Dave

MGTF1250Dave

Jedi Knight
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Aloha All,

Recently the starter motor is acting anemic, turning the engine over slower than normal. The starter is a gear reduction replacement type. I attributed this to driving the car infrequently and only for short trips and thinking perhaps the battery was not fully charged. Yesterday on a short trip to the store, the ammeter showed a strong charge at driving revs (above 2000 RPM), about 15 plus amps. This is normal on start up in my experience, however it usually drops down to a few amps after about 5 minutes. Now, the ammeter continues the high charging rate constantly, not dropping off. The ignition warning light bulb does work, and once the car is started does not come on.

Today I'll start checking into things, but I wonder where to start. The battery is a few years old so it may be the problem, no longer capable of holding a full charge or have an internal problem causing the continual demand for a high charging rate. Does this theory seem reasonable?
 
If the battery is significantly discharged, it will take a long time (easily 3 hours) to fully recharge it @ 15 amps.

I would do two things :

1) Check the voltage at the battery with the engine at fast idle (15+ amps on ammeter) to be sure it is not over 14.4 volts. If so, you have a control box problem (and very likely a bad battery as a result).

2) Shut the engine off, briefly turn on the headlights, then turn them off and check the battery voltage again. If it is less than about 12.0, most likely the battery is bad (shorted cell). A shorted cell will cause the symptoms you describe.

Many auto parts stores will do a more comprehensive battery test for free, so if either of the above tests fails, I'd take the battery to O'Reillys or similar for testing. Otherwise, I'd just keep driving and/or charge the battery with an AC charger.
 
Mahalo Randall,

I checked on voltage to the battery at about 2000 RPM and it was about 13 or so volts. While reving the engine that is when I noticed the ground cable on the battery vibrating. I've tightened up that connection and am now charging the battery.

Before putting on the battery charger, I also ran the headlight test you recommended. It was satisfactory as the battery voltage was 12V after the lights were turned off.

I'm off for a test drive so hopefully the loose terminal connection was the only fault.
 
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