E34 M5 Battery - The Unofficial BMW M5 Messageboard (m5board.com)

garry_lay · 5th April 2000, 22:06

My battery is slowly dying (i.e. slower cranking speed in the morning). This battery is made by Interstate and I have it for 4+ years now. Does any body knows who else in the US manufactures battery for this car? How about Sears DieHard, AC Delco batteries? Should I go back to the BMW dealer and buy OEM battery?

JON · 6th April 2000, 15:19

There are a few different batteries that you can get for your M5. Interstate, Die-hard etc. are all good although there is a whole new world out there in the automotive battery industry. I have a 91' E-34 M5 and when my battery took a hike, I looked into the Silcon-suspended Totally sealed cells. Thermo-dynamics makes one, they were originally designed for aircraft use ex. SR-117 stealth. They are wide-spread, some of Nascar, NHRA, and some other race leagues have them in the high performance race cars. What the battery is: Completely sealed, dry cell battery; the electrolyte is suspended in silicon pressed between the cells. This battery has been proven to be fully operable after these types of conditions! A hole shot strait through it, still works, a Race-car set fire the casing of the battery was melted, pulled it out of the car- placed it in antoher and started up right away. Not only that but this thing can push some amps- 750ca constant 10,000Amps at 30 seconds max discharge. If you are interested in the battery e-mail me and I can give you the info to get one your self. You can leave your headlamps on for a whole day and it will still crank up at that night. In other aspects, the battery is very small, the old battery in the M5 was about 11x8x7, the Reactor Power Cell is only 8x5x7 on top of that the whole casing is actually blue, looks neat too. If anyone wants to know more about this really remarkable battery just e-mail me.

Thanks,
Jon

Ken Semak · 6th April 2000, 22:44

The OEM battery for the E-34 in the U.S. is made by Douglas. You can find the exact same battery sans the BMW Logo at most battery stores. I found out about Douglas batteries while I was at a dealer and noticed the Douglas Battery truck delivering OEM batteries to BMW. I inquired at the parts counter, who confirmed my assumptions. When my battery went out, I located the EXACT same battery (they even will put in the overflow adapter that connects to the overflow hose) at less than $100.