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OffGridKindaGuy · 04-04-10, 08:16 PM

Quote..
"I have a Harbor Freight 45 watt system charging."

Let's figure from here..

According to the specs, the "working" voltage is 14.5/15 volts. The system is rated at 45 watts. The total amperage of this system is 3 amps @ 15 volts.

During perfect conditions and correct angle, 15 aHr. could be collected during a day. (5 hr. peak charge period) Your battery shouldn't be much larger than 4 times this amount (60 aHr.) to achieve full charge in a days time. Your total usage should be kept within 15 aHr. in a 24 hr. period. The energy collected before 9:30 am and after 2:30 pm will cover the internal losses in the battery. (20%)

"I have it powering ONLY the yard light which is pulling 37-39 watts per Kill A Watt."

Houston.. We have a problem..

We'll round to 38 watts @ 120 v.a.c. = .316 amps

@ 12 volts = 3.16 amps (Through the inverter)

If you are only using the Harbor Freight system to charge with, you can only operate your outdoor light "safely" for around 5 hrs. max.

If you have more than 60 aHr. reserve of battery, you'll never gain full charge which will destroy your batteries over time. If you have all of those batteries connected, that's not a good thing. I would only use one of the 75 aHr. batteries by itself..

04-04-10, 08:16 PM	#8
OffGridKindaGuy Hi-Tech Hillbilly Join Date: Mar 2010 Location: Ohio Posts: 97 Thanks: 1 Thanked 16 Times in 15 Posts	Quote.. "I have a Harbor Freight 45 watt system charging." Let's figure from here.. According to the specs, the "working" voltage is 14.5/15 volts. The system is rated at 45 watts. The total amperage of this system is 3 amps @ 15 volts. During perfect conditions and correct angle, 15 aHr. could be collected during a day. (5 hr. peak charge period) Your battery shouldn't be much larger than 4 times this amount (60 aHr.) to achieve full charge in a days time. Your total usage should be kept within 15 aHr. in a 24 hr. period. The energy collected before 9:30 am and after 2:30 pm will cover the internal losses in the battery. (20%) "I have it powering ONLY the yard light which is pulling 37-39 watts per Kill A Watt." Houston.. We have a problem.. We'll round to 38 watts @ 120 v.a.c. = .316 amps @ 12 volts = 3.16 amps (Through the inverter) If you are only using the Harbor Freight system to charge with, you can only operate your outdoor light "safely" for around 5 hrs. max. If you have more than 60 aHr. reserve of battery, you'll never gain full charge which will destroy your batteries over time. If you have all of those batteries connected, that's not a good thing. I would only use one of the 75 aHr. batteries by itself.. __________________ If it don't, I'll always think it shoulda..