Certainly you guys have heard of replacing the old wet cells with the dry cells. I make the new boxes for them. They attach to the fire wall in the same spot. No more battery service needed. No more acid vapors and a nice weight reduction of about 10 pounds. Odyssey is the brand name of the battery. I sell the new boxes for $70.00. The battery is pma'd but the installation requires an A&P sign off. Up here in Alaska most small planes have all been switched over to the dry cells.
It sounds like this mod could be made for just a little more than the price of a used old box. I think the se batteries only cost $200.00
