E39 OEM Battery Maintenance

Prepared by VietSB
Modified 01.14.04

NOTE: Perform these steps at your own risk. All P/N's listed are a "best guess", so please double-check with your local dealer. These mods and repairs were performed on my US-spec 1997 540iA (11/96 prod date, M62 engine) but there is no guarantee they will work on other E39's. These instructions are provided for entertainment purposes only!

BACKGROUND: They say it's maintenance-free, but some folks on the board check and top-off their battery cell levels yearly, especially before summer climate arrives. I'll let you decide...

Also, if you drive your E39 only on "select" Sundays, you might want to look into a battery maintainer/charger. Lack of use will eventually drain a battery and with replacements going from $100 (Douglas OEM) to $180 (OEM), proper fluid maintenance and charge level is a very good idea.

Required Parts:

Required Tools:

1. Disconnect the negative lead of the battery if you don't trust yourself. I chose to leave it connected since I'm lazy.

2. Remove the 13mm bolt and nut holding the battery brace in place. It's the yellow metal bar in the pic above. If you have a newer E39, the cell towards the front of the car might be obscured by the positive battery lead. Use the 10mm or 13mm socket to carefully remove the lead.
3. Carefully peel back both stickers.
4. Unscrew the cell caps one at a time. Fill with distilled water till the fluid touches the very bottom of the internal black plastic depth indicator coming down from the top of the battery cells. Do not overfill! Use a sports bottle w/ flexible straw or turkey baster to fill the cells with minimal spillage. Unscrewing the cap near the positive terminal might be difficult, but it is possible. They might be fairly tight the first time around, so if you decide you need to use hand tools, please follow my advice about disconnecting at least the negative terminal.

5. Ensure all the cell caps are back on to their original tightness, put the stickers back down, reattach the battery brace, and carefully reconnect the battery leads.
For charge level maintenance, I looked at the following:

Questions? Comments? E-mail me: .

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