Howdo these car battery testers work?

[dog80]

Tester here: http://www.cadex.com/products/spectro-ca-12-ga

I have a cheap knockoff I bought from dealextreme.com and have tested various batteries and seems to come pretty close to the actual CCA value.

How does it work?

[grumpydoc]

Wild guess:

1) Measure battery voltage - gives state of charge
2) Apply know load of at least a few A for a couple of seconds - measure drop and from that the ESR of the battery
3) See how long the voltage takes to recover to that measured in 1 - will give some idea of the state of the plates.

I assume CCA is not far from the short circuit current which you will know if you know the ESR

But, as I said, wild guess.

[Paul Price]

Nah, not the way mine's work.

Mine reads capacity, CCA, and state-of-charge of a starter battery in a 15-seconds test using electrochemical impedance spectroscopy (EIS) and genetic algorithms(GA). Capacity is the leading health indicator of a battery, and my capacity estimation is possible by expanding on battery-meter telepathy and adding an esoteric algorithm that completes an otherwise lengthy test of 40 million computer instruction cycles in 15 seconds.  My device should not to be mistaken with impedance testing that reads internal battery resistance only. Batteries have improved and resistance-related failures are isolated. My circuit uses a genetic matrix that outsmarts most starter batteries trying to hide their potency, yet operation has been verified by psychics and so gives a pass/fail on capacity.

[duskglow]

I just built a BS detector, and I applied it to that last post, and, well, you've fried it.  I hope you're happy.

[Galaxyrise]

It's also a quote from the aforementioned link.

[Paul Moir]

That's the funniest thing I've heard in a while. 

[ConKbot]

I'm sure Cadex is blowing smoke out their ass and they dont know much about batteries 

[grumpydoc]

Mine reads capacity, CCA, .....My circuit uses a genetic matrix that outsmarts most starter batteries trying to hide their potency, yet operation has been verified by psychics and so gives a pass/fail on capacity.

LOL