Battery health testing

Hi

My Defender 300TDI wouldn't start after been sat for days due to low battery.
Got the battery tested at local car shop. They used a Durite battery tester and it said replace batter as state of health is 39%. Battery is 10 years old so bought new, fitted it and it starts again.

Looked at Battery Analyzers online and bought a Topdon BT20 for under £20. Charged the old battery indoors and tested it with the BT20 and result said state of health 87%

Thats a big difference and wondering why. Is it because battery is room temp + full charged or is the Topdon not precise?
Reviews online says they are good quality. Could it the the shops Durite meter thats rubbish? Just had another thought could it be the difference of CCA and EN settings in the tester? Think shop said 740 CCA and when battery was out I seen its 740 EN.

Does anyone on here have experience with battery analyzers?

How long did you leave the battery after charging before testing?
I bet when it is loaded up it will read low SOH again.

I have an ebay cheapy I use at work, pretty accurate.

lynall said:

How long did you leave the battery after charging before testing?
I bet when it is loaded up it will read low SOH again.

I have an ebay cheapy I use at work, pretty accurate.

Click to expand...

About a day from fully charged to the battery tester arrived and did the test.
Guess the battery in knackrd as the fully charged voltage is 12.60. To stress the battery I ran the test 3 or 4 times and the results were v similar, resting voltage dropped to 12.57
Still feel the SOH is too high

Know a scrappy so might take meter there and test known faulty batteries and compare

UsInWorld said:

About a day from fully charged to the battery tester arrived and did the test.
Guess the battery in knackrd as the fully charged voltage is 12.60. To stress the battery I ran the test 3 or 4 times and the results were v similar, resting voltage dropped to 12.57
Still feel the SOH is too high

Know a scrappy so might take meter there and test known faulty batteries and compare

Click to expand...

Them modern testers do not stress the battery like the old style drop testers.

You could always chuck it back on the car for a day or two, with the new one in the boot just in case.