Battery keeps dying / draining / discharging

[JonsE30]

Hi everyone, my battery keeps dying and i think i have a battery drain but i do not know where or how else to test. It dies after sitting 24-48 hours. Here are the things i've tried:

1) removed after market radio, just left the wireness harnes and antenna hanging - still died

2) removed 6 button obc/clock - still died

3) made sure that no dome lights are left on - still died

4) i jumped started it to those portable black and decker jump starters and it started up just fine - can this rule out the starter?

5) i drove it around at all different rpm ranges and then parked it and turned it off. i unplugged both battery terminals and measured the voltage at 11.87 volts, in 48 hours it dropped to 11.67 volts. i plugged back the terminals and it started fine - can this rule out the battery? this is the 2nd battery i got from pep boys, it has a sticker date of 04/2019 but bought it maybe 2 weeks ago.

6) while the car is running, what i did notice was when i started the car all the bottom dash lights were still on, then after i revved it once, they all went off. - does this mean the alternator is going bad? or maybe needs more tension?

7) the battery looks like it is being charged by the alternator. the voltage was up to 12.9-13.0 volts, but the voltage increased while the car is running so the alternator is still working right?

8) i turned off the car and the voltage read at 11.87 volts and left it plugged in. in 30 minutes it dropped 11.67 volts. the next morning maybe 18 hours later, it dropped to 10.46 volts which isnt enough for the starter to turn over.

[Vincenze]

You should disconnect the negative cable from the battery, set you multimeter to 10A, and measure the amperage between the negative cable and the negative battery post.
The amperage should be close to 0.035A.

Then you can disconnect the fuses one by one and check the amperage again.
Essentially, only the fuse 21 should have power.

The voltage should be closer to 12.5V. You can bring it to Pepboys, they will fully charge it.

[cheffy30]

sounds like you have a wasted battery sent from hell using Tapatalk

[JonsE30]

0.05A is what i am reading between negative lead and negative battery post, What does this mean?

i jumped it again and while the engine is running, the voltage of the battery is hovering around 13.1volts.

if the alternator is bad, wouldnt the the battery light on the dash be light? because right now it is not lit.

is it supposed to stay at 12.5V at rest? is 13.1 volts while engine is running good?

[Vincenze]

I think the charging voltage should be in the 13.5-13.9V range. Did you change and adjust the alternator belt?

0.05A shouldn't discharge your battery in a day.
Try to remove the fuse #21. Will the amperage drop significantly? If not, find the fuse that causes this drain.

If it's the fuse #21, the drain can be caused by the SI batteries in the instrument cluster.

[JonsE30]

Vincenze i didn't just change it, but i was retensioning because i saw some slack in it.

i retested it again and with 21 fuse it was .06, without fuse it was .00-.01

SI batteries in the instrument cluster, meaning, i need to take out the cluster and solder new batteries in or replace it altogether? can the car be driven without fuse 21?

at this point, is the battery salvageable?

[Vincenze]

You should have the battery warranty from Pepboys.
Try to bring it there, they will test and recharge it.

You should replace the SI batteries. There are 2 types.

You can remove the fuse 21 after a drive. Without it, the speedometer won't work, maybe something else.

These are the newer SI batteries.

Cluster removal.
It's a good idea to change the odometer gears too.

[reelizmpro]

These cars are 30-35 years old. In that time, things like alternator, power/ground cables, instrument cluster/SI board all have lost efficiency over the years due to breakage, corrosion, wear and tear, etc. I once tracked a low voltage problem to corrosion at the battery junction under the hood (battery in trunk). These are things you should look into. You have two problems, a draw and your charging system is weak. Anything under 13.5v while running is low. It should be between 13.5-14.4 to run your accessories and recharge the battery. Battery resting voltage should be >12.3. Any less than that and the battery is around 50% charge. If you're getting less than 12v then the battery isn't being adequately charged by the alternator. Wait too long and you can degrade the battery. First thing I would do is inspect or upgrade the wiring, clean up the junctions/grounds and inspect/replace the voltage regulator with a fresh higher voltage regulator. Find out what's causing your draw but even with the draw, you would be fine as long as you take care of the charging system.

[JonsE30]

should i wait to warranty exchange the battery after i get the SI batteries replaced?

[Vincenze]

should i wait to warranty exchange the battery after i get the SI batteries replaced?

Pepboys won't exchange your battery because you think it's bad.

It will test and recharge it.

[tomstin]

Are you sure its the cluster? Or something simple like the trunk or glove box light remaining on?

[JonsE30]

tomstin i took the bulbs out of the trunk and glove box light and all the dome lights.

reelizmpro the battery junction under the hood looks clean of corrosion ( i am assuming the block located on the passenger side where the batteries in euro cars come in?), i've never maintained an alternator, just usually replaced it. i will look into what's involved with testing the voltage regulator. i have a battery charger at home and i was able to recharge it over night. it now reads as 13.2v with no leads connected to it. this is a healthy reading right since its more than 12.3v?

i removed the gauge cluster and inspected the si board and it looks pretty straight forward from the youtube videos. i ordered a soldering kit and the SI batteries online.

[JonsE30]

so its been 24 hours since i took it off the charger and it went from 13.2v to 12.9 volts, is that normal loss?

[locar]

I just want to add that I had this issue and I replaced my SI battery board and the issue went away. I used the programma SI batteryless board which was a good cost compromise vs getting a reman board.

EDIT: I should follow that up to say that only certain models of the e30 can use the batteryless board. Make sure yours can if you want to go that route.

[reelizmpro]

so its been 24 hours since i took it off the charger and it went from 13.2v to 12.9 volts, is that normal loss?

Yes, a fully charged 12v car battery should be 12.7 volts. When you charge it, it will go higher though. If you charge it at a higher voltage too long you can degrade the battery that's why there are smart tenders and chargers these days.