E30 Zone

1986 324i Cab

The section in the Wiki about SI batteries, talks about the old rechargeable NiCad type & replacing them with rechargeable NiMH both 1.2v although not the same physical size. (& not to mix the two types).
I replaced my cluster PCB many years ago, possibly 20yrs, with a brand new unit from BMW. This has Lithium batteries 3v. Nowhere on these batteries does it say “rechargeable” I need to replace these batteries, I’ve found they are CR14250SE & tagged for 8mm PCB mounting. & found these which are advertised for E30 cluster. Again nowhere on these does it say rechargeable. Rechargeable Lithiums are branded & labelled as Lithium-Ion.
So my question is are my original Lithiums rechargeable, & are these Lithiums advertised as suitable for E30 cluster, which are clearly throw-always, really suitable?
Cheers

That would be 325i. !

The early circuit boards used the 1.2 volt rechargeable Ni-cads which I have in mine. Later cars used the 3volt non rechargeable Lithiums. These Lithiums have a lifespan of 20 years roughly while the Ni-cads only last about half that. So you would have the correct battery. The great Brian Moore had a piece on this so you may take it as Gospel.

Ah…..my suspicions confirmed. My SI board plus batteries are around 20yrs old.
Thank you very much.
I’ve not seen any posts from Brian Moooore for a long time, is he still involved?
Cheers & thanks again

So my batteries arrived today.
Seem to fit quite well.
I’ll put it back tomorrow and see if it works!

Very good. Therapeutic sort of work.

It works !! Including the Rev counter All back together Happy days
Cheers

Well done!

Brianmoooore wrote: ↑

Sun Oct 01, 2023 7:29 pm

Well done!

Welcome back Brian, you had us all worried for a while, good to see you back

Jumping on the back of this thread, because same board and replacement batteries. I replaced my SI batteries recently - it took a few drives before the various instruments came back to life. Is that normal, or is that a sign of a poor connection somewhere? It also seems like my tacho is reading a little low - when driving the revs sound higher than the reading suggests.

I don’t think that is normal, certainly with mine after the battery change everything came back to life straight away.

Where did you procure those FDK units?

I bought them on eBay.
Search with this in the address bar on eBay and lots will come up.
CR14250SE 3V Battery L14250 CR14250 PCB TAGS BMW INSTRUMENT CLUSTER E30 8mm pins
Cheers

Mmm I thought the lithium si batteries were rechargeable
I've had my e30 for almost 19 years and I've never had any problems
Until
I'd taken the car off the road to rebuild the motor, took me all summer to sort it out
So the car was off the road for about 4 months and after I'd put the car battery back on and tried to reset the service lights I couldn't
700 miles later the battery warning, abs, brake pad warning lights all glimmered on a few times and wondered if the si batteries are well past there best and not charging because they had been left with out the main battery on for a time
Strangely another 200 miles later and all's well again
I should also say the car has been in constant use in the time I've had it , except for this summer
As I write this the motor has covered 900 miles and is pulling lovely, loosing up nicely
Got to love an m20

The Lithium SI battery’s are throw-aways not rechargeables. They have a life span of about 20yrs.
As you are having all the classic problems of end of life SI’s, I would suggest you change them. I think yours are showing an end of life burst of energy, probably the hot summer we’ve had.
Changing them is not a difficult job but does need patience. I actually found it quite therapeutic sitting out in the sunshine with my soldering iron.
Cheers

The AA SI board batteries are rechargeable and have a 'life' of about 10 years. They're not exactly stressed in their E30 application, so even though they've deteriorated, they might continue to do their job for another ten. A sure way to finish elderly ones off is to disconnect them from the main car battery.
The shorter batteries that later boards had are not interchangeable with the AA sized ones and are not chargeable. As long as the car battery is connected, no current is drawn from this type, and they will last a very long time, but if the car battery is disconnected, they will start to run down, and once exhausted will have to be replaced.

Thank you for the replies
I've never touched the batteries but when I first got the car 19 years ago the bulb for the speedo was out
When I took the cluster out to change it I noticed every screw had been mangled with the wrong screw driver
At the time I put this down to someone doctoring the recorded mileage
Maybe they have been looked at in the long past but not by the last long term owner, he was driving it into the ground by the time it came my way it was in a very neglected state
As it is the car is behaving it's self nicely
Another question,
Does the motronic ECU take a reading for the ICV from the rev counter in some way to control the engine speed?
Thanks for reading everyone

The ECU takes the signal from the crank position sensor and processes it into a signal for both the rev counter and the ICV.

Thanks Mr Moore
Sometimes the the idle takes a moment to smooth out but only when the engine is stone cold
Started to wonder if my very old si batteries play some part in that
I've run the car for many years without resetting the service lights having never had any problems with the clocks themselves that I was aware of
I wonder if the old but seemingly functional but not si batteries are causing gremlins elsewhere
I have a spare si board now, so I'll change the batteries on it and see what happens
Thanks

Great to see you on the zone Brian, making your invaluable contributions, you never cease to amaze me.
I’m sure I speak for many on here in wanting to thank you for all your help over the years.
Good luck & cheers.

minesapint wrote: ↑

Fri Oct 10, 2025 10:57 pm

Great to see you on the zone Brian, making your invaluable contributions, you never cease to amaze me.
I’m sure I speak for many on here in wanting to thank you for all your help over the years.
Good luck & cheers.

Absolutely

minesapint wrote: ↑

Fri Oct 10, 2025 10:57 pm

Great to see you on the zone Brian, making your invaluable contributions, you never cease to amaze me.
I’m sure I speak for many on here in wanting to thank you for all your help over the years.
Good luck & cheers.

Here Here

Mart.