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I am building a portable A/C (really it's just a box with a fan and ice packs) and I want to use a 200CFM case fan. It's rated 12V 1.6A. I was hoping to direct connect this to a solar panel and keep it running (with a slower speed during cloudy conditions), but from what I've researched, I'd need a 25W-35W panel and the one I found was relatively huge in comparison to my cooler box. So now I'm thinking I'll just use a battery and charge the battery at night. So if I have a 30000mAh battery with 2 5V 2.1A port and 1 5V 1A, is there some way I can hack it to 12V 1.6A? Or should I just Amazon a 12V 1.6A drill battery? Any suggestions are welcomed, even negative ones.

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  • \$\begingroup\$ I'd bet 100 $ that the "30000 mAh" 2 USB port "battery" has less than 20% of the stated capacity. \$\endgroup\$
    – jms
    Sep 29, 2016 at 12:03
  • \$\begingroup\$ Considering that it's a no-name brand battery pack from Amazon, I won't be taking that bet :) \$\endgroup\$
    – bosscube
    Sep 29, 2016 at 12:35

3 Answers 3

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I'd use a surplus automotive battery, but for portable weight a LiPo box 72W 132WH 12V/11000mAh $65

For a fan , dual VW Passat turbo fans with Buck Reg speed control using 15A 50kHZ PWM choke, 10Amp ripple cap. to run it quiet at slow speed with a mini vortex maniform to get rid of eddy current (fan blade interface) noise

Surge current on a 1.6A fan is at least 10A and if you stepped up from 2.5V to 12V that becomes at least 4x battery surge current... or as much as the boost reg can handle without overheating.

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  • \$\begingroup\$ And this is where I lack the experience to have any idea what your 2nd paragraph means. Which is a good reason why I should stay the hell away from modifying any battery packs :) So the 11000mAh pack you linked should be sufficient to run the fan for how long, approximately? \$\endgroup\$
    – bosscube
    Sep 29, 2016 at 11:50
  • \$\begingroup\$ 11000mAh=11Ah then /1.6A = ~6 hours ( usually rated for 20h discharge time and if faster , slightly less) \$\endgroup\$ Sep 29, 2016 at 12:35
  • \$\begingroup\$ Fans make less noise inside a round duct rather than on safety screen interface. \$\endgroup\$ Sep 29, 2016 at 12:42
  • \$\begingroup\$ you are extremely welcome.. hot season is over here.. are you down under? \$\endgroup\$ Sep 29, 2016 at 12:45
  • \$\begingroup\$ I once did a DVT using a picnic cooler and dry ice with a 15 CFM 2W fan to get the D.U.T. down to -40'C in 30 minutes. \$\endgroup\$ Sep 29, 2016 at 15:56
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There's a few caveats here.

Are you sure the battery is 30Ah? If it's cheap and less than about a kilo (based on lithium's specific energy; Wikipedia gives a pretty wide range of values), chances are that it's not really 30Ah, and that's not even including a case, charge management and output boards, etc.

Do you care if it runs at full power? The 30Ah pack has a higher capacity in Wh, but is apparently limited to ~10W on its output, per channel. Your fan, would, at full load, draw approximately 20W. It may be possible to parallel the power bank's outputs, but this is dependent on how the pack is constructed. Even so, the pack may have a protocol or sorts for charging at the full 2.1A, usually dependent on data line voltages.

Given that you still want to use this battery, the item you're looking for is a boost converter. It will take 5V and "boost" it to 12V, but drawing proportionally more current at the 5V side, plus a bit for losses. The good news is that these are dirt cheap (>$1). eBay and Aliexpress have a wide selection, and for a low power load like a fan, these will suffice.

More data on the 30Ah battery would help us help you make a better choice.

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It might be a single 3.7V "30Ah" cell which translates to about 20Ah at 5V and much less once stepped up to 12V - ideally, 8Ah for 5 hours operation at 1.6A.

But even if its internal boost convecter can supply more than 5V 2A (which will translate to 12V 0.8A), that'll reduce its capacity further.

Another latent problem is that fast charge and discharge will shorten the life of cells not designed for it - you may reduce the life from several hundred cycles to tens of cycles.

Every few days someone has the bright idea of using these under-priced, over-spec'ed products that are cost-engineered to keep a cellphone charged, imagining they can power a golf cart, small motorbike (or today, an AC unit). It's going to be disappointing.

Use a battery pack designed to run a motor in the first place. It might cost a little bit more, but there's a reason for that.

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