Battery Voltage Diagnosis - Helpful Reference Chart

The attached chart has helped me diagnosis battery issues in the past, so I'm sharing it.

Hats off to my buddy Doug for putting this together.

 

i like!!

gonna shrink it and print it onto a sticky Avery label, the stick it to my toolbox.

 

load test
1/2 cca for 15 secs shouldn't drop below 9.6v. Make sure no surface charge.

 

Redneck alternator test:

Turn on heater fan to high, high beams, hazard lights, wipers to high, and measure voltage at 1500-2000 rpm. It shouldn't be much lower than when the loads are switched off, 14 - 14.5V

Redneck battery load test:

Measure battery voltage while cranking ( pull EFI relay). If it drops below 10 V, when your battery was 80% charged or more (table above), you have a weak battery, or possibly a high starter amperage draw. The first is MUCH more common.

Proper test equipment far exceeds these for accuracy, but for a backyard guy trying to get by, they work most of the time. That said, if you don't get clear results, get a proper test done.

 

Thanks for the info. Printed it off. I have a pod mounted gauge, now I have something to measure the volt meter reading to.