Service Interval light batteries [Archive] - M42club.com - Home of the BMW E30/E36 318i/iS

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john318isau
03-29-2006, 10:08 PM
Most E30 owners have heard about problems with the batteries on the Service Interval (SI) board where batteries have leaked causing instrument problems but fortunately this doesn't effect some of our 318is's.

The problem is caused by the use of rechargable Ni-Cd batteries but of the 318is's I have seen all have used non-rechargable Li (Lithium) batteries which are not prone to leaking like the Ni-Cd's.

However, this means that the Lithium batteries will eventually require replacement as they have a limited lifespan (7 years was suggested but mine have been in there 15+ years). They can be replaced fairly easily if you are a handy with a soldering iron.

You can identify which batteries you have by looking for the words Ni-Cd/Ni-Cad/Nickel-Cadium or Li/Lithium on the batteries themselves.

For those that have Ni-Cd batteries, according to an electronics technician I discussed this with the Ni-Cd's leak because they are often being over-charged.

If you have had battery acid leak on the circuit board for a reasonable amount of time you can probably fix the board by cleaning it with circuit board cleaner and repairing any tracks that have been eaten away by the acid (with bits of wire soldered on to replace missing track), then protecting the circuit board with a circuit board lacquer. And of course you would need to change the Ni-Cd batteries. And you can't swap them for Lithium batteries as they are not rechargable.

ak96ss
03-29-2006, 10:11 PM
Another option is to solder in leads to a remote battery pack to use the Lithium batteries. Then, you only have to remove the cluster (for that) one time. Leave your battery pack more accessible, and when it is time to swap, you can just pull the old ones and stick new ones in there.

Febi Guibo
03-29-2006, 10:25 PM
The lithium batteries (3 volt, with three prong 'feet') for our boards are available here:
http://www.tselectronic.com/dantona/comp7.html

Can somebody provide a definitive list of everything that goes wrong when your batteries are out?

- service interval lights?
- what else?

M42boy
04-07-2006, 10:46 PM
The lithium batteries (3 volt, with three prong 'feet') for our boards are available here:
http://www.tselectronic.com/dantona/comp7.html

Thanks for the link. I have a connection and going to try to get a batch of these for free just for M42Club members. I'll see what I can do.

shellback
04-08-2006, 10:10 PM
How do you remove the old batteries from their socket. I mean, these things are jammed in there - is that glue?
Anyway, I realy don't look forward taking that dash apart again! I broke one of the two "A" tabs on the top already!

Febi Guibo
04-09-2006, 10:47 AM
To remove the batteries, you have to carefully de-solder them. The glue on the top of the batteries is just hot melt glue to keep them from vibrating.

You can get a little suction style 'bulb' at radio shack to help with the desoldering... but basically, just use a soldering iron to heat up the solder where the batteries are mounted to the pcb, and eventually, they will come free.

shellback
04-09-2006, 01:34 PM
got it - thanks,

Chris