I have a Harbor Freight 100 amp battery load tester that went bad. It won't apply a load to the battery anymore. I think the switch is bad. I wondered if it actually pulled 100 amps from the battery and I didn't think to try my clamp-on ammeter until after it died. Oh well.
I decided to replace it with a conductance tester I found on Ebay for $40 with free shipping, the KAL KM8100. This appears to be a new-old-stock discontinued model--the copyright date in the manual is 2001. Supposedly it was about $180 back then.
The KAL KM8100 doesn't have an LCD display. What it does have are three LEDS: Orange for "ready", green for "battery OK", red for "battery bad", two buttons "TEST" and "COLD TEST" (for testing a battery under 32F) as well as a dial to select the CCA of the battery in 25CCA increments from 350CCA to 900CCA.
To use it you set the dial to the CCA of the battery you're testing, hook up the cables, and push the TEST or COLD TEST button. If the battery is good the green light will come on. If it's marginal both the red and green lights will come on. If it's bad the red light will come on.
If you're wondering how good or bad the battery is, you can turn the dial until either the red or green light stays on.
For $40 it seems like a good tester. It seems accurate in that it can tell the difference between the 700CCA, 2-year-old battery in my Saab and the 650CCA, 3-year-old battery in my Mustang. The Saab battery is actually putting out 800CCA according to the test, while the Mustang's battery is only putting out 700CCA. (It's apparently normal for a battery to test above it's CCA rating when it's good).
Unfortunately, neither conductance testing nor load testing can give you an idea of the battery's reserve capacity, which is how long it can power a load without the engine running. It seems the only way to test that is to actually drain the battery down and see how long it takes.
There is only a weak correlation between a battery's CCA and it's reserve capacity. It seems very common for a battery to lose reserve capacity, yet still test OK for CCA.
I decided to replace it with a conductance tester I found on Ebay for $40 with free shipping, the KAL KM8100. This appears to be a new-old-stock discontinued model--the copyright date in the manual is 2001. Supposedly it was about $180 back then.
The KAL KM8100 doesn't have an LCD display. What it does have are three LEDS: Orange for "ready", green for "battery OK", red for "battery bad", two buttons "TEST" and "COLD TEST" (for testing a battery under 32F) as well as a dial to select the CCA of the battery in 25CCA increments from 350CCA to 900CCA.
To use it you set the dial to the CCA of the battery you're testing, hook up the cables, and push the TEST or COLD TEST button. If the battery is good the green light will come on. If it's marginal both the red and green lights will come on. If it's bad the red light will come on.
If you're wondering how good or bad the battery is, you can turn the dial until either the red or green light stays on.
For $40 it seems like a good tester. It seems accurate in that it can tell the difference between the 700CCA, 2-year-old battery in my Saab and the 650CCA, 3-year-old battery in my Mustang. The Saab battery is actually putting out 800CCA according to the test, while the Mustang's battery is only putting out 700CCA. (It's apparently normal for a battery to test above it's CCA rating when it's good).
Unfortunately, neither conductance testing nor load testing can give you an idea of the battery's reserve capacity, which is how long it can power a load without the engine running. It seems the only way to test that is to actually drain the battery down and see how long it takes.
There is only a weak correlation between a battery's CCA and it's reserve capacity. It seems very common for a battery to lose reserve capacity, yet still test OK for CCA.