Optima technology batteries have been used in large boats for many years. They are great for use where they are drawn way down overnight, and then charged up.

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Bill Streep
San Antonio
'57 190SL (toy)
'08 S5500 (mine)
'09 CLK550 (wife's)
'06 SLK350 (daughter's)
'11 GLK350 (daughter's)
'03 CLK310 (spare)