checking the battery voltage correctly

[shogun]

You can unlock your OBC (TEST #9) to see if the problem may be stemming from your alternator or from the battery. Test #9 with the ignition in position 1 will give you an idea of the battery's health...Test #9 with the engine RUNNING will indicate what the charging system is doing.

The battery should be consistantly around or above 12 volts. At 11.89 volts...the battery is at 0% state of charge. With the engine running...Test #9 should consistently read around 13.6 volts (give or take a few).

Removal of surface charge:

If the battery has been just recharged, or the car has been driven, eliminate any surface charge by one of the following methods:
-allow the battery to sit for 2-3 hours
-turn the headlights on high beam for 5 minutes and wait for 5 minutes after turning off.
-with battery load tester, apply a load of 1/2 the battery's CCA for 15 seconds, then wait 5 minutes.

State-of-Charge Test
http://www.bimmerboard.com/members/q...f%20Charge.jpg

[whiskychaser]

Thats one of the best bits of info I've seen! Could I just add that a wiser man told me if your alternator fails, be sure to charge the battery before you fit a new one. Otherwise the new alternator is likely to go mad trying to charge the duff battery and fry itself. Apparently, its the number one cause of new alternator failure

[525i winter driver]

Thats one of the best bits of info I've seen! Could I just add that a wiser man told me if your alternator fails, be sure to charge the battery before you fit a new one. Otherwise the new alternator is likely to go mad trying to charge the duff battery and fry itself. Apparently, its the number one cause of new alternator failure

oh gee that's a couple weeks too late for me... shewt, hope mine makes it. actually i was just using test#6 to see how many amps the system uses and with the car running and everything switched off i'm running 72 amps which seems really high to me but i don't know - what do you guys get?

[whiskychaser]

oh gee that's a couple weeks too late for me... shewt, hope mine makes it. actually i was just using test#6 to see how many amps the system uses and with the car running and everything switched off i'm running 72 amps which seems really high to me but i don't know - what do you guys get?

Some mistake somewhere. You cant be running 72 amps with everything switched off! You would be welding something. More like 72 milli amps?

[525i winter driver]

Some mistake somewhere. You cant be running 72 amps with everything switched off! You would be welding something. More like 72 milli amps?

maybe mA - i thought that was pretty up there now i'm scared a bit help? - with the engine off it reads 0.0 T:ADC with the engine running it varies from 71.5 ('T:ADC') with everything off to 75.0 with everything on. the rest of my obc readings are good. alternator runs at 13.7 v down to 12.8 with everything inc defrost on. sorry - i've hijacked this thread...

[whiskychaser]

maybe mA - i thought that was pretty up there now i'm scared a bit help? - with the engine off it reads 0.0 T:ADC with the engine running it varies from 71.5 ('T:ADC') with everything off to 75.0 with everything on. the rest of my obc readings are good. alternator runs at 13.7 v down to 12.8 with everything inc defrost on. sorry - i've hijacked this thread...

Its got to be milli amps. 65 amps is a cranking voltage If you were losing that you wouldnt have a battery after ten minutes. Your alternator readings look just fine. Perhaps I should have worded my original response better. My own apologies for intruding on a very good thread

[525i winter driver]

Its got to be milli amps. 65 amps is a cranking voltage If you were losing that you wouldnt have a battery after ten minutes. Your alternator readings look just fine. Perhaps I should have worded my original response better. My own apologies for intruding on a very good thread

thanks man. sorry again... but i'd feel a whole lot better if somebody would post something like "that's exactly what i get all the time when i use test#6" i'm stressing about this i just replaced the alternator myself which i haven't done before and just had an electrical meltdown in the sword and right now i drive around with a fire extinguisher.

[whiskychaser]

thanks man. sorry again... but i'd feel a whole lot better if somebody would post something like "that's exactly what i get all the time when i use test#6" i'm stressing about this i just replaced the alternator myself which i haven't done before and just had an electrical meltdown in the sword and right now i drive around with a fire extinguisher.

Ok I just checked mine. Its got a brand new battery on it so this may affect the figures a bit. Anyway I get:
Test no. 6
Ignition off - Zero
Ignition on - 38.5 to 39.5 TADC
Running at 1000rpm - 38.5 to 39.5 TADC
Test no. 9 (system voltage)
13.85 down to 13.77 volts UB at 1000 rpm.
Hope that helps

[525i winter driver]

Ok I just checked mine. Its got a brand new battery on it so this may affect the figures a bit. Anyway I get:
Test no. 6
Ignition off - Zero
Ignition on - 38.5 to 39.5 TADC
Running at 1000rpm - 38.5 to 39.5 TADC
Test no. 9 (system voltage)
13.85 down to 13.77 volts UB at 1000 rpm.
Hope that helps

oh ... i mean thanks

[525i winter driver]

LMAO ok after tearing the dash apart yesterday i did some subsequent research and the info on this page http://home.iae.nl/users/bts/obc.htm would appear to be misleading. this page looks more like it... so WC how much gas do you have in your tank right now would you say... half a tank give or take? holy heart attacks 70 amps!

previous expletive deleted mega apologies!