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I'm new to this list, but I know quite a bit about batteries and charging systems (http://www.killacycle.com)
At 10:41 PM 3/23/2004 -0500, you wrote:
Guys,
I'm getting really frustrated with my (stock 3rd gen) alternator. I'm seeing
13.2v on the buss when the engine is running, but the charge light is still
on (even with the diode).
>>>> Alternator voltage <<<<<
At 13.2 volts, the battery is being charged. How much it is being charged, and is it the correct charge is the question. You really need to measure the current to be certain. If you don't know that alternator current, or at least the battery current, all you can do is take wild guesses as to the health of the charging system. If you can borrow a DC clamp-on ammeter, you can know the entire picture.
If the battery is discharged, it will draw a lot of amps and reduce the bus voltage. There is only so much amperage that alternator can put out at an idle. If the battery is drawing hard along with everything else, the bus voltage will be low and the alternator light could come on, even though the alternator is working correctly.
When the battery charges up completely, and the electrical loads are light, the bus voltage should come up to something like 14.5 volts. This may not happen at an idle.
>>>> Battery voltage <<<<
A room-temperature, healthy, fully-charged Absorbed Glass Mat (AGM) lead-acid battery will have an open-circuit (no load) voltage of 12.8 to 13 volts. At 13.2 volts, it is taking some degree of charge. If the battery is fully charged already, 13.2 volts is close to the "float charge" voltage. That is, the battery is taking a tiny trickle charge to keep topped off. A severely discharged battery may have a voltage as low as 11.7 volts, even taking a substantial charge current.
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