[NSRCA-discussion] NSRCA-discussion Digest, Vol 41, Issue 28

[Bob Richards]

Roger,
 
Don't have any data regarding pilot usage, etc. But I do have a few pointers from having used 12v batteries in RVs.
 
First, the best batteries are golf-cart batteries. The plates are thicker and will not die from sulfation as quickly as others. They typically are 6v batteries, but you just hook them in series to get 12v. Marine batteries are a compromise between a true deep cycle battery and a starting battery, so stay away from those. AGM batteries are good and are maintenance free, but are really expensive, the most bang-for-the-buck will be from the golf cart batteries but will require a little more maintenance.  Keep the electrolyte levels topped off, and check the specific gravity occasionally to determine the charge state. Don't top off a battery that is discharged!!
 
When calculating capacity, don't count on using the bottom 30% or 40% of the capacity, nor the top 10%. This means you should only count on using 50% of the capacity of the batteries, on average. The reason is that using the bottom 40% or so of the capacity of the batteries is what shortens the life the most.  Filling up the last 10% of the capacity takes a very long time, maybe more than a day. This will depend somewhat on the charge controller that you use with the solar panels.
 
A problem that I see is that you will most likely be using the capacity at the same time the sun is shining, so you may not be able to maintain the charge of the storage batteries at the same time everyone is flying. Instead of a daily useage and recharge cycle, you might be looking at a weekly cycle. In other words, you might have to have enough storage battery capacity to get you through a weekend of flying, with the rest of the week left for charging back up.
 
The windmill idea sounds like a good one. :-)  No reason you can't have both.
 
Bob R.
 


--- On Wed, 4/29/09, Roger Hammel <skitimberlakespartava at yahoo.com> wrote:







 
 
Any data and experience would be appreciated.  Need data on :
a) the number of anticipated electric pilots and expected average weekly capacity used per pilot from existing solar powered systems  
b) the size & type of the battery (deep cycle) used to store power - e.g. number of Mah and type - wet cell, gel cell or AGM, and the typical max discharge % anticipated; 
c) - the recharge time (days or hours) to recharge the storage battery from normal max use drawdown; 
d) the number and size of the solar panels used; and power output (amps) at say 16-17v range
e) the capacity of the charge controller used.
 
 
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