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every where i look it says take your watts divided by volts. so if i have a 100 watt light i take 100 divided by 120. i get .8333333 so less then 1 amp? so if i have a 240ah battery bank i could use that light bulb for 240 hours? or 120 hours so i don't go below 50% ... that is my math but when i look every where online people say i can run a 100 watt bulb for only 20 hours on a 240ah battery bank. Am i just not doing things right in my head?
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1. You should only run on the top 20% of the battery.
2. You're not accounting for system inefficiencies. You will have loss in inverting from DC to AC.
100 watts divided by 12VDC = 8.33 Amps. 240AH/8.33 = 28.8
WWWLast edited by Wy_White_Wolf; 02-02-2016, 10:02 AM. -
Your light is running on 120Vac whereas your battery is just 12V (assuming). 120Ah x 12V = 1440Wh 1440Wh / 100W = 14 hours Always do your math with the labels attached and you won't confuse the wrong numbers.BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installedComment
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ok thanks. i knew i was missing something. this whole solar powered camper van is giving me a headacheComment
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im new but ill give you my 2 cents on this. i got a computer monitor that runs at 19 volts. when i use it straight off the battery thru a step up dc converter, i use 1.36 amps pretty constantly. but when i use the 400 watt pure sine inverter and use it's ac adapter that came with the monitor it use 3.4 amps is watt the watt's up meter says. so for you being in a van i would run every thing dc instead of using and inverterComment
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ok yeah my laptop runs at 19v.(could just use the car charger?) and my tv has a 12v plugin in the back i could use as well. only other thing i will be using sometimes is my superslim playstation 3. which does not use much energy...im safe too assume they will use less amps hooked up through 12v because im not using the inverter? i picked up 4 of these http://usbattery.com/products/6-volt...s-2200-xc2-lf/ 2200 xc2 6volt 232 amp hours. sooooo 232ah x 12v 2784WH 2784 WH /100 w 27 hours run time.
geez you would think 4 batteries could run a little 100w draw for more than 27 hours lol sorry if my replies are all over the placeComment
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If you use all 4 batteries at once, you will NOT have 232Ah @ 12V. You will either have 232Ah @ 24V (4 in series) or 464Ah @ 12V (2 strings of 2 in parallel).
And remember, you aren't going to go below roughly 50% of the total battery bank capacity. You didn't take that into account in your last post - so your replies are a bit all over the place at this point, in your words. However, you get the same answer using my 50% since you double the capacity, but use half of it.
I am not sure what you are asking about "less amps". Basically, if you eliminate an inverter (if possible), you would eliminate inverter inefficiency. Look at it that way. That is what will result in a bit less current - whatever the efficiency of the inverter is, which varies with load. Maybe it is 85%, in which case your amp draw would be about 15% less by eliminating the inverter.Last edited by Living Large; 02-02-2016, 09:49 PM.Comment
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kk thanks. so much. yeah i was using your 50% already with the 232ah
i am going to have 2 100w solar panels as well so i guess that will charge them up enough during the day that i shouldnt drain them too much. again thank you for being so helpful.
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as opposed to using a 100 watt light bulb, consider an LED 100 watt equivalent that only uses about 10 watts.4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrfComment
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