Starter Motor.

[Pingu]

Only really applies when the starter is working, and the original post was a non-starter. And in the right hands a tester isn't that scary, just got to know what you're doing.

If you don't think short-circuiting a battery is scary then fair enough. I was less worried when I was cutting up bullets with a hacksaw than I was when I was whacking the probes onto a truck battery.

If the starter is not working, true, but the starter was working and was probably drawing 80% of the current needed to start it.

 

[Pingu]

I'm sure I've seen signs outside motor factors, workshops etc advertising free battery checks. Don't halfords do it? Obviously hoping to sell you a battery.

I've always assumed they'd use that kind of tester. Do they?

I think they use a super-dooper version that tests the battery in a wide variety of conditions. You can tell a lot about a battery's condition if you have the right kit. They all work in the same way. Add a resistance then measure the voltage and the current. The clever bit is interpreting the results. We would have to look up charts and do many different tests. Their expensive tester will just have red, amber and green lights to show the user if the battery is good or bad. It might also show if the battery has been allowed to drop below 10.4v, as this causes a chemical reaction inside the battery, and the battery can never be fully recovered.