Would like to know the accurate way to test vehicle battery

eddieguy

Hero Member
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Dec 1, 2006
Messages
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Make
Toyota
Model
Rav4
Year
2003
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186,000
Engine
2.0 liter 4 cyl
My vehicle sat for over 2 weeks without starting the engine I was in the hospital with covid-19 pneumonia so the vehicle wouldn't start after sitting that amount of time I jumpstart the battery and it started all right.

I'm very happy to be out of the hospital and able to breathe and doing a whole lot better I'm just trying to determine the health of my vehicle's battery accurately.

I have had some auto parts stores test my battery and they would hook their equipment up to it and they would tell me that way then there's been times I have removed my vehicle's battery taking it to the auto parts store so they could put a full charge on it and then tested under load.

I guess my question here is can they accurately tell me the condition of my battery by hooking their little equipment up to it or does it need to be bench tested have a full charge put on it and tested under load
 

Mobile Dan

wrench
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Mar 1, 2002
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"in the car" with clip-on tester is not very accurate, but is the best choice for an older battery.
"load testing" is more accurate but each test reduces the life of the battery.
I've seen lots of "parasitic drain" problems which are actually due to an internal short in the battery. Testing usually won't point that out. Best test is to fully charge the battery, then disconnect negitive cable, wait overnight or several days, then reconnect cable and see what happens. If the battery discharged while disconneted from the car, the battery must have an internal short.
 

billr

wrench
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I'm going to disagree with Dan a bit. What he described would be good for detecting an internal parasitic load, but would not be a sufficient test of the over-all battery condition. You must also have a load test done, something drawing significant amperage (about 300A or more)
 

grcauto

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Load test is the best way to test. As for shortening the life of the battery it doesn't do more than a normal start.
 
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