Eric...
These old threads may help...
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http://www.iceinspace.com.au/forum/s...ead.php?t=1640
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http://www.iceinspace.com.au/forum/a...wse.php?a=6091
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http://www.iceinspace.com.au/forum/a...achmentid=1484
Mine is still going with absolutely no maintenance req'd at all.
I used a similar set-up for my "equipment/eyepiece" box.
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http://www.iceinspace.com.au/forum/a...wse.php?a=6090
Just use an "On/Off" switch.
The heaters & my Magellan 1, run all night off a 12 Volt 7 AH Gel-cell.