It does climb back up pretty quickly. I'll be giving it more of a test today as I drive around doing errands for a couple of hours. I only wish that it was a HUD so that I'd keep my eye on the road too .
Measuring how well it keeps the battery charged up is yet another matter. I guess that the only way of doing that is to put the charger on when I get home and note the time to when it says "fully charged" and see if that changes in a material way from day to day. It will always take some charge but there shouldn't be a gradual drain.
I read about someone who was traveling in an RV whose alternator died during the trip ... he then ran his generator with a charger back to the battery in order to get home. That would work with my X5 and a generator on my hitch-rack, but difficult with the M5 .
Luckily I have no long distance trips planned with the M5 in the near future.
Late last year my battery I had replaced in 2008 was dead (after the original one lasted 7 years). I vowed to buy a maintenance charger, but I hooked up my 2/10/50 charger on 10A just to see the response -- it was poor. I wrote off that battery and bought a new one. Two weeks later it was dead too. Back on the charger and it charged right up. Maybe a month later after a long drive, as it was idling in the garage, the interior lights were dim and occasionally flickering, etc. Battery was almost dead after a long drive.... Checked all connections, ground connection to chassis, etc, all were perfect with zero corrosion (car is a garage queen, hasn't hardly ever been in rain, etc).
I know the tech at my local dealer very well, and so had him test out the alternator -- all the BMW tests showed that it was fine. I replaced it anyway, and I've had zero issues since then (5 months). There was no core charge on the old alternator, so I kept it to have it rebuilt.
The net of it is that my alternator was "testing" fine when presented for evaluation, but it was evil and hiding its fun for when it was most inconvenient for me I suppose. It's now in a box waiting its uncertain future...
2001 M5 LeMans Blue/Silverstone Dinan: springs, Konis, rear sway bar, monoball bushings, and exhaust;
Ground Control camber plates, Stoptech front BBK, Brake ducts opened,
Evolve AlphaN tune,
OE 9.5" rear wheels all around & 275/35-18 Pilot Super Sport
2011 M3 sedan 6MT Silverstone, no sunroof!
2006 330i sport 6MT Electric Red/Black
2001 Audi S4 6MT -- it's back
1996 Volvo 850R wagon
Late last year my battery I had replaced in 2008 was dead (after the original one lasted 7 years). I vowed to buy a maintenance charger, but I hooked up my 2/10/50 charger on 10A just to see the response -- it was poor. I wrote off that battery and bought a new one. Two weeks later it was dead too. Back on the charger and it charged right up. Maybe a month later after a long drive, as it was idling in the garage, the interior lights were dim and occasionally flickering, etc. Battery was almost dead after a long drive.... Checked all connections, ground connection to chassis, etc, all were perfect with zero corrosion (car is a garage queen, hasn't hardly ever been in rain, etc).
I know the tech at my local dealer very well, and so had him test out the alternator -- all the BMW tests showed that it was fine. I replaced it anyway, and I've had zero issues since then (5 months). There was no core charge on the old alternator, so I kept it to have it rebuilt.
The net of it is that my alternator was "testing" fine when presented for evaluation, but it was evil and hiding its fun for when it was most inconvenient for me I suppose. It's now in a box waiting its uncertain future...
CSBM5 - It seems that they can test fine producing enough voltage but do not produce the amperage to charge the battery up.
Perhaps, yeah. I really don't know what its problem is as I didn't spend a lot of time trying to figure it out once I decided it was done as far as I was concerned. I plan to get it rebuilt and then just hold onto to it for the distant future. FWIW, my car has 61k miles on it now, and it will be 11 in July this year (07/01 build date).
So ... here's what I found. 35 minutes out and 45 minutes back. On my way out, I had some city and then onto the highway. The voltage reading behaved itself fairly well, fluctuating a little between 13.5 and 13.7, probably with the A/C cycling, and with the application of the brakes, down to 13+ and then back up to 13.7. So far so good.
On the way home, I took an arterial route, rather than the highway, with plenty of stop and go. I observed greater fluctuation for the first half, 13.8 flickering a couple of times, never getting down lower than 13. The A/C was already on and then I added the headlights, fog lights, seat heaters (it's 90+ outside, so this was not great !), and the rear defroster. Stopping at a light, idling down, I was getting 11.8. Driving along, with all that on, I was getting a fairly consistent 13.
I'm definitely thinking that the alternator isn't keeping up at this point. It might last me a while driving around during the day but with any night driving, it's not putting out enough juice. Aren't these things rated t 120 amps ?
Comments ? I should check to see if my X5 has the same voltage display and see how it does with everything on. Hmmm.
More findings -- with my X5 3.0i, it's reading around 13.0 with all the same things turned on and rpm at 2000+. However, with it idled down, the voltage is still reading 12.9.
So ... here's what I found. 35 minutes out and 45 minutes back. On my way out, I had some city and then onto the highway. The voltage reading behaved itself fairly well, fluctuating a little between 13.5 and 13.7, probably with the A/C cycling, and with the application of the brakes, down to 13+ and then back up to 13.7. So far so good.
On the way home, I took an arterial route, rather than the highway, with plenty of stop and go. I observed greater fluctuation for the first half, 13.8 flickering a couple of times, never getting down lower than 13. The A/C was already on and then I added the headlights, fog lights, seat heaters (it's 90+ outside, so this was not great !), and the rear defroster. Stopping at a light, idling down, I was getting 11.8. Driving along, with all that on, I was getting a fairly consistent 13.
I'm definitely thinking that the alternator isn't keeping up at this point. It might last me a while driving around during the day but with any night driving, it's not putting out enough juice. Aren't these things rated t 120 amps ?
Comments ? I should check to see if my X5 has the same voltage display and see how it does with everything on. Hmmm.
Go have a different parts store test the alternator. Sure sounds bad to me! It should be able to handle that load better (as you saw with my test at idle, sitting in the garage)
More findings -- with my X5 3.0i, it's reading around 13.0 with all the same things turned on and rpm at 2000+. However, with it idled down, the voltage is still reading 12.9.
I will suggest you look at your accessory belt and/or belt tensioner. Look for cracks or other signs of wear. But all that aside unless you have a belt gauge it is truly hard to tell if the belt is worn to the size of the V in the pulleys. If the belt is well polished and is bottomed out they slip without squealing. Not saying it is not the alt but the symptoms are not the usual ones. Without the usual symptoms you want to rule out all other possibilities.
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. Checked all connections, ground connection to chassis, etc, all were perfect with zero corrosion (car is a garage queen, hasn't hardly ever been in rain, etc).
Good post.
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