From: ham789@netzero.net   
      
   On 7/19/2014 8:16 PM, danny burstein wrote:   
   > I picked up a used 48VDC Sears lawnmower a couple of years ago.   
   >   
   > It uses 4 12V batteries in series, each one a nominal 9 amp hour   
   > rating, so (at nameplate maximum) I'd have 48 times 9 => 450 watt-hrs.   
   >   
   > Reality, of course, is a bit less and I have my own back/movement   
   > issues, but I get a reliable 15 minutes (and then some...) out of it.   
   >   
   > It uses a 120VAC charger which plugs in, takes about 65 watts   
   > from the outlet (measured with a KAW) for an hour or three, then   
   > down to 25 or so, then trickle charges at 2.   
   >   
   > (I don't have an easy way to measure the DC output that   
   > goes into the assembly).   
   >   
   > I'd like to hook up a solar panel and charge it that way.   
   >   
   > So my key question is... anyone have a recommended charge   
   > controller to pump in at the higher rates, and then   
   > shift downward as the batteries get full?   
   >   
   > I'd really rather not waste the expense and energy in   
   > doing a (nominal) 50 volt-from-the-array conversion ->120VAC   
   > and then the regular charge cord...   
   >   
   > Thanks for all suggestions.   
   >   
   sorry, but I have more questions than answers.   
   Most importantly, why bother???   
   Costs you a nickel to charge it.   
   say 26 charges/year, that's $1.30/year in electricity.   
   How much can you build for $1.30?   
      
   Why do you care about efficiency?  What are you gonna do with   
   the energy that you didn't waste?  Consider tapping that source.   
      
   Ok, OK, so everybody has to have a hobby.   
   The biggest problem with solar is that it varies a LOT.   
   Most circuit designs you'll find depend on some relatively   
   stable input.  They will go all crazy when the input fluctuates   
   below what they want.   
   Stabilizing the input is harder than regulating the output.   
      
      
   You're gonna need a custom design.   
      
   IMHO, you'd save far more energy by building some solar storage   
   facility that converts to 120VAC and using that for your infrequent   
   mower charge.  Then you could actually use all the rest of the   
   energy collected for other purposes.   
   Solar panels are expensive.  Use all you can get out of them.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)