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A friend has a 12V 40Ah battery, and asking if he could use it for solar. He needs to light DC two 9W lamps and charge four Galaxy phones. I told him he needs to buy a 10amps PWM CC. What size of a 12V PV panel to buy? (A 12V 100W panel would be enough?) (Sun hours are five). Thanks in advance for your help.
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How long will those 9W lamps be used a day and what is the estimated watt hour usage for each of those 4 galaxy phones?
A 40Ah 12volt battery can provide a little over 100 watt hours without discharging it below 80%. It can provide more if you discharge it more but there is a possibility you will shorten it's life.
A 100watt battery panel should generate just over 5 amps at peak sunlight which is the right amount for that 40Ah battery. I would also determine the worst case amount of sun hours available. 5 per day may be during the summer but more than likely not the winter. -
If he wants back up power, get a dedicated battery charger for that battery and plug it in. The battery will not get cycled unless power fails and you can have a few modern conveniences for short blackouts.4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrfComment
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Agree, if the site commercial power just get a AC charger and appropiate sized battery.
No way to answer your question directly as you have not stated how many Watt Hours are required in a day/ Best guess is the battery is not large enough based on 2 9-watt lights. That battery can only support the 2 lights for 5 hours per day.
Secondly I doubt you have 5 full Sun Hours in a day. Very few places get that much sun especially in short winter months.
Only thing I can tell you for sure is a 12 volt 40 AH battery with PWM needs a minimum panel wattage of 45 watts and no higher than 75 watts. That does not mean it will work. A 75 wat panel on PWM is just less than 5 amps.Last edited by Sunking; 02-08-2016, 03:52 PM.MSEE, PEComment
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Dears SunEagle, Logan005, Sunking,
Thank you all. Total watt/ hrs= 76.Yemen has 5 sun hours min for sure. (My friend can't afford a deep cycle battery.)
Thanks again for your help.Comment
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If he wants back up power, get a dedicated battery charger for that battery and plug it in. The battery will not get cycled unless power fails and you can have a few modern conveniences for short blackouts.Comment
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what? word for word? copy and paste?
4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrfComment
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I think it's a baby account, they build some relationship before they spew danish ham4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrfComment
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It is a Spammer waiting to strike.MSEE, PEComment
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