I'm charging my battery while it's in the trunk on my 2000 SL500.

You can - but it is not a good idea. When batteries are charging, you want as much air circulation as possible to reduce any danger of gases.

Thanks Mark, that's what I was thinking and had to ask to be sure. Time to buy a new battery. I had this one trickle charging for two days and still does not show a complete charge. It's an easy fix for $139.99 - 10% for a Delco Gold. Piece of mind is worth $130.00.

That's a good price for the 500 battery. Most are 160 and up.