posted on May, 26 2020 @ 11:29 AM
Make sure all leads are tight and not corroded. If not, then it's most likely bad cell, like already mentioned.
If you want to do some diagnostics on it, you can get a cheap clamp style no-contact capacitive load tester online that will tell you all kinds of
When everythings off, put around hot from battery to see if there is a parasitic drain/short somewhere.
Then observe voltage gain when you start it on same positive lead wire to test stator/alternator output.
Test with DC amp load setting.
You can just clamp tester around wires throughout the ignition system to see if relay or whatever is bad, just follow down the line from battery,
through relay, to starter testing each segment for Amps as you go.