[RE-wrenches] Trickle Charging?

[Ray]

Lots of questions this season..... I'm winterizing a cabin for a 
customer that will not be there for the next 8 months (summer use only). 
Inverter and loads will be off. The rooftop array will probably be 
covered with snow for extended periods of time, and he has a brand new 
800 AH set of AGM batteries.  I've read that AGMs can handle sitting for 
longer periods of time, but my experience is that they are a bit 
finicky.  I'm planning on adding a small wall mounted array on a small 
Morningstar PWM controller that's sole purpose is to trickle charge the 
batteries and off set the self discharge in heavy snow.  What is the 
minimum size array needed?

I've calculated self discharge rates from 2% to 5% /month, and I'm 
seeing a very small array would offset that.  Even at 5% monthly losses, 
and 4 hrs of sun/ day, I'm seeing a 10 watt array could meet that.  My 
current plan is a pair of 30 watt modules wired in series for the 24 v 
battery.  Is that too small? Or should I not even worry, because enough 
sun will creep through the snow to the main array?

Thanks,

-- 
Ray Walters
Remote Solar
303 505-8760