I need to power a 10 W device to operate 16 hours a day on a 50% use capacity. So 10 W device running 8 hours a day I guess. I need to run this device from a battery pack as no AC is available. How many days can I run on what size of battery? Ideal is 14 days before recharge, how big a battery will I need?
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Do you have any access to sunlight, so solar can help top-up the battery across the daytime ? – Criggie Dec 08 '23 at 02:23
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10 W * 8 hours/day * 14 days = 1120 Wh battery.
Do yourself a favor and get a larger one than you need. Especially lead-acid suffers from deep discharge so a two times overrating would be advisable. Lithium-ion is less sensitive, but ideally you would dimension to operate between 20-80 % SoC, implying a 1.4 overrating factor.
winny
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Definitely oversize your battery. Especially if it has to survive under less-than-ideal temperature conditions as well. In winter, it's not uncommon to see commercial-grade Lithium-ion solutions hold 30% less charge, which means you need to over-engineer your battery to hold at least 143% of what you think it should under ideal conditions. – Mast Dec 07 '23 at 20:45
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1Then there's durability of a battery. How many months/years should it survive? Depending on the battery you get, expect 5-15% degradation each year. – Mast Dec 07 '23 at 20:46
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Simply multiply the numbers together.
10 W * 8 h * 14 = 1120 Wh.
Justme
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And realize that a lead-acid or gel battery can deliver perhaps 50% of the nameplate rating. Lithium is better under ideal conditions, but suffers much more from cold (unless it has built-in heating, which also impact actual Ah delivered). – Jon Custer Dec 07 '23 at 22:34