Chris Harper wrote in a message to Ian Woofenden:
 IW> Go with true deep cycle batteries NOT car batteries.
 IW> That's a good question, and not an easy one to answer. 4-7 days of
 IW> autonomy is common. But you also need to figure in your depth of
 IW> discharge.
 CH> Thanks for the advice! Is it better to discharge "deep" with 
 CH> deep-cycle batteries, as it would seem to indicate? 
No,  it just means that they're capable of such cycling,  but you're better 
off to keep them as charged as you can for as much of the time as you can.  I 
can recall one bit of training material that talked about golf cart 
batteries, and they compared the overall number of cycles you'd get out of a 
set if they were charged after every 9 holes or after 18...  The former 
lasted a *lot* longer.
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