04-16-2013, 06:56 AM
My estimate of 3 hrs sunlight per day is based on many things but is essentially a WAG. Of course I get 12 hrs/day of SOMETHING like everywhere else, but it being Eden Roc, and for the purpose of estimating based on full power output, etc. I know the sun (when there is any) bores into the panels from 10am to 1pm since my roof faces SSE. The rest is gravy.
IMO around here an MPPT charger is a must have to make the most of the variable solar resource.
I went straight to a 48 volt system because I got a 48 volt UPS for my inverter for free. I am sure the UPS was worth every penny I payed for it and perhaps considerably more. So far so good. I can't really take credit for the choice of 48 volts but there are a lot of benefits to going with higher voltage and I am glad I did it. Theoretically you can hook batteries up in parallel to get more amp hrs but in practice there are problems with uneven charging and discharging of parallel strings. If you stick with series only then as your system capacity goes up you naturally move to higher voltage. There is a certain symmetry to that and it all works out well except for buying a new inverter.
The Costco batteries have 220 amp-hr capacity. If I wanted to go to larger I would either have to go to two parallel strings or go to the next size larger of batteries. I think they are called L-16s and have about 400 amp-hr capacity. A quick search shows them available from Amazon for $350 each but I shudder to think what the shipping would be. Being the cheapskate I am I would probably go with the parallel strings of golf cart batteries, doing my best to wire the two strings to reduce uneven current flow.
I got a 120' coil of #4 wire second hand at Hawaii Re-Store for $80. I think I could still get a 500' spool of #2 for $250 but that is overkill. I bought 250 volt fused air conditioner disconnects to disconnect my power. Fuses really perform in terms of interrupting current, but in some respects I wish I had gotten proper DC rated circuit breakers. I also got a 30' #10 extension cable having the connectors on it that matched those on the panels. I cut it in the middle and wired the cut ends into my panel disconnect to make the actual connection of panels to the rest of the system. Also bought crimp on lugs for the wiring. Boy it really adds up and I may have been too optimistic at only $200. The simple pull-out fused disconnects were sure economical though. The fuses are rated for 125 volt DC. I am assuming that the fuse holder is good for a similar amount DC. DC is harder to interrupt. AC stops 120 times a second on it's own.
IMO around here an MPPT charger is a must have to make the most of the variable solar resource.
I went straight to a 48 volt system because I got a 48 volt UPS for my inverter for free. I am sure the UPS was worth every penny I payed for it and perhaps considerably more. So far so good. I can't really take credit for the choice of 48 volts but there are a lot of benefits to going with higher voltage and I am glad I did it. Theoretically you can hook batteries up in parallel to get more amp hrs but in practice there are problems with uneven charging and discharging of parallel strings. If you stick with series only then as your system capacity goes up you naturally move to higher voltage. There is a certain symmetry to that and it all works out well except for buying a new inverter.
The Costco batteries have 220 amp-hr capacity. If I wanted to go to larger I would either have to go to two parallel strings or go to the next size larger of batteries. I think they are called L-16s and have about 400 amp-hr capacity. A quick search shows them available from Amazon for $350 each but I shudder to think what the shipping would be. Being the cheapskate I am I would probably go with the parallel strings of golf cart batteries, doing my best to wire the two strings to reduce uneven current flow.
I got a 120' coil of #4 wire second hand at Hawaii Re-Store for $80. I think I could still get a 500' spool of #2 for $250 but that is overkill. I bought 250 volt fused air conditioner disconnects to disconnect my power. Fuses really perform in terms of interrupting current, but in some respects I wish I had gotten proper DC rated circuit breakers. I also got a 30' #10 extension cable having the connectors on it that matched those on the panels. I cut it in the middle and wired the cut ends into my panel disconnect to make the actual connection of panels to the rest of the system. Also bought crimp on lugs for the wiring. Boy it really adds up and I may have been too optimistic at only $200. The simple pull-out fused disconnects were sure economical though. The fuses are rated for 125 volt DC. I am assuming that the fuse holder is good for a similar amount DC. DC is harder to interrupt. AC stops 120 times a second on it's own.