battery and charging system test

[shogun]

Winter time = battery problem and engine starting problems. Have found a nice info from Patrick, which is quite useful for an easy check, even without removing the rear seat (E32 has the battery under the rear seat and a plus pole under the hood) or open the hood:

I tried OBC test #9 before but still prefer to measure the voltage the old sure way because my OBC for some reason measures a voltage 0.2V lower than a calibrated DMM. (=digital multi meter)

Find a digital multimeter (a useable one can be had for $15) and stick the probe into the cigarette lighter socket in the center console.

The following are the detail figures I use for my own evaluation:
With key out of ignition switch, should see 12.4V or above. 12.0 V is getting low.
With key inserted and turned to position 2 (don't start car), should see 12.0V or more. 11.6V would be too low.
Crank car, catch the lowest voltage reading during that couple of seconds. Should see 10.0V or above. 9.5V would be marginal.
The above just consider the health of battery itself.
Car running at 1500 RPM or more, should see 13.7 to 14.3V, 13.6V or below means the charging system is weak.

As you know, there can come up weird signals from the CEL in case of low voltages too.

[Paul in NZ]

rrrrr....rrrr rr ..click click=battery weak


rrrrrrrrrrrr...vrooomm..=battery a ok

[shogun]

20 years later I use for this a Dual USB Car Charger, 12V to USB Outlet with Cigarette Lighter Voltage Meter LED/LCD Display Battery Low Voltage Warning