Hi there,

The patient is GP T-jet from 2008. Today the battery warning light came on for a couple of seconds after I drove off from work, never came back, I could not hear the belt slipping or anything. No other symptoms. Checked the battery - solid stationary 12.6V. Checked charging - solid steady 14.2V (I never seen higher on this car). The battery is 4.5 years old. The alternator is from new I believe, 165 kkm driven. One other thing, it was really wet all day.

I am inclined to think that this is the alternator starting to play up, despite the healthy charge voltage. But I'd need a way to confirm / rule it out before I go into the trouble of ordering it and changing it in this pissing weather.

You really need to check the battery with the dedicated tool (under load)!! There is also a way to monitor the charging/discharging CURRENT, but this requires to slightly modify the wiring. I can tell how, should you be interested ...

BRs, Bernie

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Thanks for the hint about the tester, these are ~40€ here, I shall consider it. Meanwhile I will check the internal resistance and see what happens under load with the voltage.

I should perhaps add that the previous battery died instantly at around 80kkm and age of 5.5 years, this one is younger time wise, but has done some more km than the 80kkm. So all in all it would not be surprising if it is the battery.

EDIT: My multi-meter would not pick up the internal resistance on any setting, shows infinity all the time. However, today, the stationary no load voltage is 12.4V, with the lights on 11.92V, with high beam on 11.88V. According to some Internet guides this makes the battery pretty much done, no? Especially that it had a perfect occasion to fully recharge on Sunday during a 650 km trip. I will recheck it later today right after some driving.

Also check your earth connections from battery to the motor or to the chassis.
High resistance there can also make charging difficult.
11,94V with lights on is not really bad.