And can you compare results with KONNWEI KW208?

I can't say that I have. But I did notice that despite kelvin clamps I never managed to get exactly the same measurement once I removed the clamps and re-attached them. What I mean is that if I run the same test twice without touching the clamps, the values were very consistent. But taking the clamps off and on again and I got more differences. I also found it us not easy to connect the probes to real battery terminals (at least for my car) I can well imagine that crime and oxide on the connections can play a role there. For what its worth, since making this video I was approached by TOPDON to review one of their testers. I just finished testing their AB101. The video will come out tomorrow. When comparing the readings for the BM550 and the AB101 for my VW Golf car, the values were very close to each other. Having played with the TOPDON tester, I think for 12V car lead acid batteries, the AB101 is better than the BM550 simply it tests more stuff, like cranking. But I will keep the BM550 because it does other voltages which the AB101 does not,

I can understand the trouble with the kelvin clamps, they seem to be a little to small which makes it hard to apply them. I too was offered the AB101 and did a review. The AB101 is quite a bit better for 12V car batteries, but if you need a tester that can do more than 12V, the BM550 beats it

There are tables from various places that list AH and CCA, Google should find. Some folks use AH*7.6 = CCA for medium batteries but it is usually not quite so linear for small or big batteries. Its a complex issue because AH and CCA are different in what they mean and so any correlation is always just approximate

Not directly. You could run the engine/alternator for a while and see if the state of charge increased. Better, check the battery voltage before starting the engine and after. If the voltage is higher, the alternator is charging the battery.

​@@TheHWcave Thank you.

Generally, alternators either work or they don't work. You can test the alternator using a multimeter (voltmeter). Just put the probes on the battery, measure (let's say 12.5V)... leave them connected, start the engine, and check again. If the voltage is about 14V (or 2V higher than a "flat" battery), then the alternator is working. You can test the charging current using a DC Clamp meter, but you have to get enough load on there to test it. That generally means starting and stopping the car a number of times to get the battery voltage down close to 11-12V, and then running the engine and as many other ancillaries as possible. High beam headlights, etc.

​@@johncoops6897 Thank you John very much!