Simple Solar Setup ?

[ericlp]

you never want to run Lead Acid Batts into the ground. Only pull 20-40% Max... But if you can keep it at 20% discharge you'll reap greater benefits.

You only get 3 hours of sun? Yeah, there is a dude on CL selling 240 Watt Panels for 250 bucks. Basically a dollar a watt.

If you're putting together your own system the main thing is... you want to start out with a decent Charger and Inverter since being able to add batteries and more panels is always a good thing. I went from 2kWh a day to 3... But I want to factor in for at least a 5K watt system maybe even a 6K watt since no one can really account for all the cloudy days ... The beautiful thing is ... RIGHT now you can buy solar panels for a buck a watt so even with that it's only gonna be around 3-5K buck in panels. Since you should be able to get 3-4 hours of sunlight here well in my area anyway. So even if you only had 2 hours sunlight at 8 240 watt panels will produce about 4-9K watts average I would think around my area. So that would be about 4K bucks in Panels.

Hey mark, only 200 bucks in wiring? What gauge of wire you got going to the batteries? So costco battery about 100 bucks a pop, how many amp hours for them?

[David M]

I would agree. Basically everything will work around the inverter, all the other pieces can mix and match, upgrade, but if you have a quality inverter it is key. I definitely stay away from 12 volt systems, 24 and 48 are better. My first was a 12 which I eventually upgraded to 24, but that involved the expense of a new inverter. Simply rewired the panels, and batteries, changed the charge controller settings. My current house system is 48v, last year I added panels, but because I had planned on future expansion it was a simple matter of wiring into to existing charge controllers. For the cost os panels, racking, and a little wire I increased my capability by 1/3 - very happy.

David

Ninole Resident
Please visit vacation.ninolehawaii.com

[MarkP]

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.

[ericlp]

Thank Mark for the detail message. I should swing by one day and check out you setup. Sounds pretty cool...