charging battries with a PV array

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charging battries with a PV array

Postby Alt on Tue Sep 23, 2008 7:05 am

If i have a battry bank already, I am not sure of my amp hours a day, what is a good way to estimate the number of pannels needed to charge my battry bank on a daily basis i have reversed my calculations but i just want to see if any one else has any better ideas.
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Re: charging battries with a PV array

Postby DennisM on Tue Sep 23, 2008 8:28 am

Tell us more about your battery bank. Overall output Voltage - single battery voltage & Amperage - batteries per string. Where in the world (approximately) are you located ?

Dennis
FW1000 2-FX3648's 2-FM80's FNDC Hub10 Mate2 RTS X240 48v-900Ah Rolls Surrette S600 battery bank 2 arrays of 3X3 Sharp 216's (3888W stc) 10kW Isuzu genset Separate water system Gundfos 6SQF-2, IO101, CU200 control, powered by 2 Sanyo HIT200's in series
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Re: charging battries with a PV array

Postby tallgirl on Mon Dec 15, 2008 5:29 pm

Average insolation, average cloudy / foul weather days, average number of bad days in a row, target depth of discharge, how willing you are to run a genny.

Is that what you used?
Julie in Texas

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Re: charging battries with a PV array

Postby crewzer on Tue Dec 16, 2008 6:06 am

alt,
I am not sure of my amp hours a day,

You’ll need to know this in order to find your answer.

Assuming a 12 V system, 90 Ah/day net use, and 90% coulombic efficiency (Battery Ah out/Ah in), the PV system will need to generate 100 Ah/day. If the combination of array orientation, mounting style, and location is good for a minimum average of 4 hrs/day of “full Sun”, the system will need to be rated at 100 Ah/day / 4 hrs/day = 25 A. Assuming modules rated at 17.6 Vmp STC, the array rating will have to be rated at 17.6 V x 25 A = 440 W STC. YMMV.

4 hours/day example: Austin, TX, December, South-facing array, tilted up at latitude, average. See: http://rredc.nrel.gov/solar/old_data/ns ... /13958.txt

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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