Battery Life

[Omega]

You are lucky! maybe it will not be the same after replacement of your old batteries, as Christoph explained above.

My batteries were both dead after 2 years. Probably one defective and the other one drained because they are connected in parallel.

Based on input from this Forum, I changed to one single battery operation (100 Ah), but I kept a second one (70 Ah) as spare, and intalled a switch. This is just in case I forget to switch off the lights.

I never operate both in parallel. Most of the time running on the large one, only occasionally on the small one to keep it loaded.


Just be sure to never switch batteries while the engine is running!

[Andrzej]

I use a charger and the barries are still fine after 9 years.

Same by me! Both batteries are over 9 years old and still ok. I charge both together every two months via charging poles under the bonnet with sc smart charger

[Danilo]

...
For this reason I have equipped my 850 with only one battery, which has a larger capacity of 100 Amp/hour.

...
Many greetings

I also did this Mod a couple of years ago and never regretted

[DickB]

I use a charger and the barries are still fine after 9 years.

[Christoph]

Hello David,

we have some 8 series drivers in the forum who have big problems with the starter batteries available today. These batteries have very low internal resistance and if you connect two of them in parallel, they often get drained or even break down very quickly.

For this reason I have equipped my 850 with only one battery, which has a larger capacity of 100 Amp/hour.

This prevents mutual breakage and also works for several years with no problems.

Many greetings

[Reiser]

In the past, I have replaced the batteries of my 8 series every 5 to 6 years and I never had any problems. The battery in my F11 series BMW is going to be 8 years old and is still working perfectly, modern batteries seem to last longer ...

[dhwayne]

In the years I have owned my 93 850Ci I have gone through batteries every 3 years in spite of keeping it on a battery minder when in the garage. Has anyone trued deep cycle or marine batteries to get longer life?