Will a Bad Battery Manifest into Trans Issues
 

Continuation of my original thread

https://xoutpost.com/bmw-sav-forums/...-failsafe.html

For sure, I have a Bad Battery. After 3-4 stops/starts and about 10 mile drive, I think the alt MAY be okay and it's my battery

What is weird is when I test drove the car with a good donor/test battery, it was still showing trans issues. This test drive with donor battery was very very limited. I just drove around the block.

Anyhow, original battery charged and rested overnight.
Resting voltage showed 12.7 in the morning.

Had both alt and battery load tested at autozone. Maybe 3/4 mile drive from Autozone. Their tester says *replace battery-whatever how that is interpreted*. It was at 12.4 when they load tested the battery after the 3/4 mile run.

The entire drive showed alternator hovering mid 13's , with only dips down to 12.3-12.7 when decel/throttle off.

Extended test driving, buying a new battery, etc. Probably put like 10 miles in total watching alt voltage.

For the most part, alt hovers at mid to high 13's. I do see it dip as low as 12.3 when decel.

The transmission still feels like it's in limp, and when accelerating from stop or just 1-2, it is jerky. Even jerky when decel.

WILL the bad battery literally cause all this I am feeling in the tranny ?

Got new battery on float charger. Will swap when I get home tonight to do another round 2 of testing.

YES

at least for me. My alternator gave up and came home from the gas station and left maybe 10 minutes later and driving out of the neighborhood i got trans fail safe then ac cut out etc eventually I stopped turned it off and waited and tried to start it started but was not happy. at the time i had extended warranty. Dealer flat bedded to have it serviced and said the alternator was not charging properly and therefore battery was under performing and was near is end of life so they replaced both.

The battery to me is starting juice and supplemental once on...
So assuming/presuming the alt voltage is looking fairly good, I'm not correlating right now the limp mode with good mid-high 13's V, with a ~known bad battery~.

New battery is@home charging, so I guess I will see if it was just the battery and nothing more ?

This doesn't seem right - I NEVER see mine dip below 13.8 - at any point.

If your BC voltage reading is showing low 12s your alternator is not doing anything - that just the battery voltage.

Others can (and will) chime in here - the more info. the better - but I think your alternator is suspect. :(

You are right in that the alternator should do its job after but ive seen where power draw will spike and thats were the battery comes in and help provide the juice. In my case i have currently 200K with a rebuilt transmission that needs to have the sonnex sleeves installed in the valve body any way in 200K alternator was replaced 1 time and im on my 3rd battery first 2 the dealer paid for. but only time i had trans fail safe was when the alternator was not able to provide the juice...

my cousin has a ford f550 and he had issues with limp mode i went and tested batteries etc and they were sitting with the truck off at 12.7 and 12.5 not bad but doing the alternator test i noticed times it was charging 14v and times it was sitting at 12.9 and spike to 13.5. Told him to take it to the dealer and have then verify my findings and i was right alternator was going out and was putting the truck in limp mode which would go away at times but in got to the point where it was happening and at that time it wouldnt go away.

so in your case it might just be the alternator thats going out.....you can try buying a regulator for the alternator idk the cost on the reman but ive always kept my alternators on my other cars and just replaced the regulator on the back which is where the brushes are and the part that actually wears away *so does the shaft but not as fast as the brushes.

I've never driven watching the V on cluster to date so I have no delta on what is normal or not. Mid to highs 13's. With the momentary dips to 12.3 then watch it go to 12.7 and the bounce back to the 13's

Ah. Gimme a mechanical gremlin anyday. I hate electrical gremlins

How did you measure your resting voltage?

With a multimeter?

Still connected to the vehicle?


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Charged, floated and checked back 12 hrs later. Granted I think technically from what I understand, Surface Voltage can be a couple days if I take a deep dive in my former battery troubleshooting. ---- Battery off car

My battery light on the dash came on as I pulled into my driveway January 2017. Checked voltage with vehicle off measured 12v. Started the 2002 x5 4.4 and measured voltage was 10.5v. That was my clue as to the status of the alternator. After replacement running voltage was measured at 14.4v. I never had any errors leading up to the battery light.


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wpoll -

I really should measure at the batt. terminals to see what .X V difference it might be on the BC.