Switching large currents

disconnect your alternator leads.

Reply to
M Philbrook
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does not matter, the diodes in the alternator are knonw to form a leakage current. One day it'll become a much more leakage current.

Those alternators will charge a battery in most cases..

Do don't discount that.

Jmaie

Reply to
M Philbrook

You're sure about the 50mA continuous? You may have to let the car sit with doors closed and keys out for a few minutes to see the actual continuous drain.

Charging the battery properly once, using an external charger, can restore function in a flakey battery, if your alternator can't do it. Check the battery's warrantee - it may still be in effect. The higher priced ones carry replacement warrants for many years....

RL

Reply to
legg

OK, well I've re-checked it and my memory was playing tricks. It begins draining at 330mA for the first minute or so, then drops down to 210mA where it remains, from what I can see, indefinitely. So ~4X as much drain as I'd originally claimed; sorry about that.

Here's the spec off the label:

12V 110Ahrs 680A cold-cranking capacity (limited time obviously!)

I will. In the mean time I'm going to try what some here have suggested - that the alternator may be the source of the problem...

Reply to
Chris

You haven't disconnected the alternator to see if that stops the drain?

Reply to
gray_wolf

It was a hell of a job to get at, but I've now managed it. Yes, it was the alternator at fault. Thanks, all.

Reply to
Chris

Since you do not drive the vehicle on a regular basis, you would still be better off if you get a float changer. Harbor Freight often has them for 5 or 6 dollars.

Dan

Reply to
dcaster

A friend of mine ran a test on one of the inexpensive Harbor Freight float chargers, and was not impressed. It didn't reduce the charging voltage to a suitable long-term float voltage, after the battery was topped up. As a result, it would tend to overcharge the battery and "cook" it, reducing its lifetime significantly.

I picked up one of the Deltran "Battery Tender Jr." floaters and ran a few cycles of test, using a GPIB-connected voltmeter to monitor its behavior. It did a nice job... current-limited charge (750 mA) for as long as the battery was drawing that much, then a voltage-limited charge of around 14.8 until the battery reached full charge (current being drawn dropped below a threshold) and then dropped to a float voltage of around 13.6. Much safer for the battery.

Reply to
Dave Platt

Yes, I rather liked someone's suggestion of a solar float charger. Seemed an elegant solution.

Reply to
Chris

He wants to drive a car, not collect on the fire insurance. lol.

--sp

(sorry)

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Best regards,  
Spehro Pefhany 
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Reply to
Spehro Pefhany

Well I have two of the Harbor Freight float chargers. Just went down to the garage and measured the battery voltages. The one on the lawn tranter was 13.49 volts. The one on the other battery was 13.00 volts

Harbor Freight often sells items that look identical but made by different manufacturers. Maybe my chargers are made by a different manufacturer than the one your friend tested. But it would be easy to add a 7812 to limit the voltage.

Dan

Reply to
dcaster

You could just add a diode in series to drop the voltage by about 0.6-0.75 volts depending on current and temperature..

Paul

Reply to
P E Schoen

By dropping the voltage you greatly extend the charge time for a battery that is significantly down. But if you only need a float charger, a diode should do it.

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Rick C
Reply to
rickman

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