battery cluster light indication behavior (not explained in manual)

[BaltimoreBimmer]

Hi. I've done a fair amount to my e30 as of late, one of which includes replacing the battery. According to my POs it looks like the battery has been replaced several times over the past 7 years (3+ times, mine being the 4th).

I noticed the other day that when I turn off my car, the battery indicator on the cluster will briefly illuminate. I cannot recall if it did this before I replaced the battery or not. Is this typical behavior or some sort of warning? The manual did not say anything about this behavior.

I'm curious if there is an underlying alternator issue causing the battery to go bad.

Something else of note, the battery when brand new (about one month ago) was reporting 12.2 volts when the car is off. I have heard 12.6 is where a new battery should be.


More interested in what you guys have to say about the indicator illuminating for 1 second when turning off the car. The battery light does not come on when driving the car. Is that normal?

[jlevie]

I have never seen that happen, but I can imagine a fault in the voltage regulator causing it. Or perhaps something more obscure is powering the cluster briefly after the ignition is switched off. Does the CEL or hand brake light also briefly light up?

[BaltimoreBimmer]

I have never seen that happen, but I can imagine a fault in the voltage regulator causing it. Or perhaps something more obscure is powering the cluster briefly after the ignition is switched off. Does the CEL or hand brake light also briefly light up?

The CEL or hand brake lights do not light up, just the brake light. I have replaced my SI board with a digital voltmeter courtesy of george graves. So that will certainly help in diagnosing the issue.

Here is a start after having the car off for maybe 4 hours.

https://www.youtube.com/watch?v=e_T17KYpO3w&feature=youtu.be

here is a start a few seconds later, notice it doesn't dip to red and goes right up to 13v when running.

https://www.youtube.com/watch?v=vWXpJUtDz3U&feature=youtu.be

Red = 10v, Yellow = 11v, Green 1 = 12v, Green 2 = 13v, etc, etc. Ideally, I should be at Green 2 when the car is running. Interestingly enough, it will often be around 12v running and then pop up to 13v a bit later (like in the video). It will stay at 12v if I have a bunch of crap turned on, or even pop up to 13v when I hit the brake to cut the CEL. Thoughts?

[TobyB]

I'm with Jim on this- something funky is going on in your alternator.

I typically get 5-15 years per battery. Check to see if the alt has a slow
drain on the battery, maybe?

t

[Das Delfin]

my battery light stays on for about a second after shutting off the car. It's been like this since I bought the car and I've never had a problem with my battery (aside from when the alt died and killed it! Which means I got a new alt and battery 3 years ago)

I always thought it was tripping because when you turn the car off the alt is slowing to a stop and isn't putting out as much voltage as it should, which is what trips the light before the motor comes to a complete stop and the magnetic field created by the alt collapses in its entirety.

My car is an early model 325i but with a motronic 1.3 computer

Possibly related: my SI board had its NiCd batteries replaced with lithium at some point in its life.. possible that the lithiums hold this instantaneous charge longer? I'm not sure. Trying to draw comparisons if no one else says their battery light behaves like this.

Either way car batteries in regular daily driver use consistently last about 5 years.

It would be worth your while to grab a volt meter and put its leads directly on your battery while the car is on. It should read at least 13.5V. The alt outputs 13-14V when the car is on. A fully charged battery (as in just after you shut the car off, and having driven around for a few hours) should be at least 12.7V. 12.2 means the battery either isn't charging (completely or at all) or is old enough to give up its charge easily, or there is a constant draw somewhere on the battery (which will weaken the battery overtime and cause a premature failure, especially if the car is left sitting).

You can test if there's a draw by disconnecting the negative terminal to the battery and putting an ammeter between the battery's negative and the car's negative lead. They also make those cool ones that clip around the ground cable and give you a reading without having to disconnect anything. It should read something low, like 28mA. It's kinda fun to then turn on stuff like your radio or headlights and see how much amperage is drawing on the battery with those things turned on. For example my LED low beam headlights draw 8 amps!

[Das Delfin]

I like George's stuff but I'm not a fan of his SI board volt meter because it doesn't show decimals as honestly as a volt meter with an LCD readout. I'm saving up for the one made by jaywood :P Though you should be able to figure this stuff out with a $5 multimeter from harbor freight

[george graves]

I like George's stuff but I'm not a fan of his SI board volt meter because it doesn't show decimals as honestly as a volt meter with an LCD readout. I'm saving up for the one made by jaywood :P

What? Saving up? He charges like $10!

I like Jaywood - he's good people! But he'll be the first to tell you that it's a $2 ebay voltmeter, with a plate you're expected to super glue into place. It's awesome for what it is. And hats off to him for making them. For the price, totally pick one up. Just be sure to add a fuse to it, because the wires tend to fall off and can cause a short.

You are right though. My Si voltmeter doesn't so decimals. I made it to be more of a stealth version of an idiot light, that tells you much more than just a battery voltage(batt voltage, charging volts). And looks 100% factory. So, yea.

[Das Delfin]

lmao I meant that - that's how broke I am atm! An glimpse inside Brian's wallet. Thanks for the insight too

[jeffnhiscars]

I've had batteries last 6-7 years then had replacements that struggled to survive their 2 year warranty. Despite there only being 3 mfgs who make most of the batteries out there, I suspect they are not all built to the same standards (think Walmart).

I'm also thinking voltage regulator but dont rule out crap batteries.

[BaltimoreBimmer]

Though you should be able to figure this stuff out with a $5 multimeter from harbor freight

I've got one and did readings when I first put in my battery and was concerned they were a bit low. I'll recheck and see what's what.

Concerned b/c I'm not positive if i have my receipt from the autostore :\ but I think I do.

I'm also thinking voltage regulator but dont rule out crap batteries.

things keep coming up and I don't have time to check my voltage regulator, even though it takes two seconds. I'll do it today, I swear!

[BaltimoreBimmer]

Though you should be able to figure this stuff out with a $5 multimeter from harbor freight

I've got several and did readings when I first put in my battery and was concerned they were a bit low. I'll recheck and see what's what.

Concerned b/c I'm not positive if i have my receipt from the autostore :\ but I think I do.

I'm also thinking voltage regulator but dont rule out crap batteries.

things keep coming up and I don't have time to check my voltage regulator, even though it takes two seconds. I'll do it today, I swear!

edit: holy double post batman, why dis happen

[Das Delfin]

I've got several and did readings when I first put in my battery and was concerned they were a bit low. I'll recheck and see what's what.

Concerned b/c I'm not positive if i have my receipt from the autostore :\ but I think I do.

if they asked for your name/phone number they'll have it on file