Aa Batteries In Instrument Cluster - BMW Forum

ben_t · 03-31-2005, 07:10 PM

What do the AA batteries in the instrument cluster do? Are they just for the SIL?

billB · 03-31-2005, 08:59 PM

memory backup?

MrAlfonze · 04-01-2005, 09:30 AM

Quote:

Originally posted by ben_t@Mar 31 2005, 07:10 PM
What do the AA batteries in the instrument cluster do? Are they just for the SIL?

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The book states the the 2 AA NICADs on SLI board are back up for Service indicator array and functionality, this is for battery removal or depleted battery, although it does not look like it is protected from short, i.e. battery cable/s touching even if battery is not connected or hot cable disconnected and touching ground. The stock Varta's are 2x 1.2 Volt 1700ma, you can usually find 1700ma AA with solder tabs from any hobby shop, Radio Shack also sells 1.2Volt but they are 1200ma, only difference would be, how long they would last running back up, the IC draws about approx 50ma and the is a 500ma difference between batteries used, there is about a 10 hours more battery life with the 1700ma at that rate (all are just approx calcs), and just FYI there are 2200ma and 2400ma versions of 1.2volt AA NICADs.