Actually, the battery for a E39 M5 is quite different than anything I've
seen before. First, it huge and designed to fit in a tight space in the trunk.
The battery is vented and has two handles on it. What I found was that
there were only two or three replacement batteries that would even fit
in the battery compartment properly. Other batteries may work, but they
don't fit without adding risers and spacers to position and hold the battery
wanted $405 + HST or $458 CAD for the battery, they
did not offer any refund for the old battery core and this did not include
any cost for installation.
I ended up purchasing a battery from Advance AutoParts in Niagara. They
had an exact replacement battery (Made in Germany) for $162 USD. I
ordered it online for pickup at the store. During checkout, they had a
promotion going on for $30 off purchases over $150, so in the end the
battery cost me $132+tax or $143.00 USD. And they gave me $5.00 back
for the old battery core and offered free installation if I wanted.
The battery fit perfectly, and has a 3 yr full replacement warranty and
is prorated after that.
AUTOCRAFT GOLD 95R/H9 950 CCA
Here is a shot of the battery sizes. I got this off the E39 list. My battery
is exactly the same, only has a 6/2011 date.