How much is too much?

2 Posts
Aug 18, 2013 07:43 pm
How much is too much?

I currently have 8 - 200 watt 24V Sharp panels wired in parallel /series with them being in pairs, giving me 48V going into an Outback 60 charge controller. During the summer months their is no problem meeting my energy requirements in a 1000 sq. ft structure, including a full blown woodworking shop. However December and January up here in Canada is cold and we only get 4-5 hours of sunlight, and it was tough to keep the battery bank charged to more than 65%. I would like to add more panels to my system, but how many is too much, considering what the Outback 60 can handle, and my Xantrex SW4808 inverter?
 
97 Posts
Aug 20, 2013 12:11 am
Re: How much is too much?

Hi Ken.  I am in a similar situation located just south of Manitoba with a 48v system, and limited solar power during the winter months.  Do you have the option of using wind power?  I get most of my electrical power from the strong NW winds in winter and the wind turbines often produce more power than I need to maintain battery charge.  I simply dump the excess power into heating of the residence.  Perhaps increasing your battery capacity would help?  I have doubled my battery bank and found that it helps to reduce the depth of discharge.  I also use a backup generator for extended "down" times of wind and solar energy resource.   Jon C. 
 
2 Posts
Aug 20, 2013 09:57 am
Re: How much is too much?

Thanks for the tip. I have tried the wind turbine route, and it was not particularly successful as we are quite sheltered with trees and bush. We would have to install a fairly high tower to get above the tree line, and we are in an area that typically does not get the winds needed to sustain any appreciable amount of generated power. We have a backup generator that we used last winter, which cost us a fortune to run, so we were hoping that adding either more panels or more batteries would be a solution. If we add the panels, would the amperage be too high for the charge controller to handle? If we add batteries, would not the small amount of charge we get during the few hours in winter be spread proportionately among the cells, and therefore not fully charge the system?
 
97 Posts
Aug 20, 2013 12:10 pm
Re: How much is too much?

Ken, there are many variables here, but if I understand the parameters correctly, you have a solar panel power source of 8-200 watt panels which yields 1600 watts of power in full sunlight.  This would produce 33 amps of current at 48 volts.  Since your charge controller is rated at 60 amps, you could almost double the number of solar panels.  Keep in mind that there are surges in panel output when going from cloudy to full sun condition as the panels cool and then reheat (cloud effect), so you might want to add only two more of the same type of panel, instead of four and risk an overload of the charge controller.  Batteries, in my experience, are only 50-75% efficient in returning usable power to your system, but by increasing the number of batteries in the array, you increase their efficiency by drawing less power from each cell under normal load conditions.  So, in my experience, even though you are distributing a smaller charge current to each cell, and requiring more time to produce a full charge condition, you are also drawing less power from each cell and increasing the battery efficiency.   I wish you good fortune with your system.  :-)  Jon C.
 
97 Posts
Aug 20, 2013 12:43 pm
Re: How much is too much?

Ken, I made an error in the last post.  I intended to suggest adding only half the amount of additional panels, or four panels, not two.  This would theoretically produce 50 amps of charging current for the battery bank, and not overload the 60 amp charge controller. 
 

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