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Help with Cheap Power bank?

Todes320

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Oct 28, 2021
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Hi I am new to all of this and need some help. We race karts and use a generator for our power needs at the track. Since becoming interested in solar for my home I was thinking what about a battery bank for the trailer. I have no clue how to calculate our power needs, we typically run a fan for hours its 120 watts rated. and a heat gun that is 1500 watts to run intermittently for 10 minutes at a time multible times thorughout the day. I was looking for help to set up a cheap batter bank with lead acid to run this equipment for the day at the track off grid and I can just charge the day before with a plug in charger on the grid. Down the road I would like to add a solar panel on the roof of the trailer to keep the batteries always charged.

If its possible would also like the option to maybe run a portable AC unit I think it draws around 1300 watts.

I don't even know where to start, how many batteries? how to tie them all together? what inverter to get? just want a cheap simple system so I can stop breaking my back moving the generator around and no noise at the track.

Thanks! for any help!
 
Watts * hours = Wh - a unit of energy

1500W heat gun * 10/60hr = 250Wh/use

120W fan * 4 hours = 480Wh use.

Repeat the above for all devices used and their frequency. Add them all up. Convenient spreadsheet energy audit here:


Once you have added up all the Wh, you divide that by 12V and then you have the number of Ah of capacity you need at 12V. To make sure the lead-acid batteries last, you need 2.4X the calculated capacity as you never want to run them down below 50%, or their life will be severely reduced. The extra 0.4X is to account for inefficiencies in converting DC to AC power.

Example:

Assuming 4 heat gun uses & 4 hours of fan, that's 1480Wh of use. At 12V, that's 123Ah. 2.4X is about 300Ah. That's about $500 for 2X Trojan T-1275 batteries - plus the inverter needed to power your items and the charger to charge the battery in a reasonable time frame.

You'd need a pair of those for about each hour of A/C run, i.e., $500/hour of A/C run time.
 
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Don't forget the old "fast, good, cheap, pick 2" saying. In solar it's more like "simple, good, cheap, pick one". Just read these forums, they're absolutely full of people who chased the cheapest deal and are now trying to figure out how to deal with the consequences. The truth is that consumer solar is rife with scam artists making ridiculous claims and taking advantage of the uneducated.

I can't give you specifics, but in general it's going to cost a lot more than you think it is to build something safe and reliable that will last you for a reasonable period of time, but buy quality a bit at a time and upgrade when needed, it will be cheaper and simpler in the long run. Start with the energy audit, then figure out how to reduce your demand which is a LOT cheaper than increasing supply, then start sourcing components.
 
Will prowse has several videos building systems that do exactly what you are asking for. He even has videos where he builds a battery bank with solar, and an inverter in a trailer to test equipment, and such.
Also, at the top of the forum pages, there is a link to his diagrams page with links for parts etc.
Also, he has a book to learn the ins and outs of solar.
 
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