MintyBoost Sweat Battery
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MintyBoost Sweat Battery

by mishawagon on Wed Apr 10, 2013 1:56 pm

Hello,

I am creating a sweat battery phone charger to use with my Mobile Sauna http://dsinstitute.com

I am wondering how many primary batteries to wire into the MintyBoost. Can I wire in like 5.8 V into it, or does it need 3V to match the two AA batteries? Each sweat cell primary battery is .5 to .6 V, and I want to have 9 of them wired in series.

Thanks,
Misha
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Re: MintyBoost Sweat Battery

by john444 on Wed Apr 10, 2013 7:32 pm

Hi Misha,

I did not see anything about "Sweat Batteries" on the link.
That's ok, but I am not sure how they would work.
So, a couple of questions:
Do you connect 9-people in series? or how do you get 9-cells connected together on the same person?

A Minty Boost pulls lots of mA's from AA cells when operating.
Will you be able to supply enough current from your "Sweat Batteries" to run a Minty Boost?

mishawagon wrote: Can I wire in like 5.8 V into it

The Minty Boost wants less than 5-V to operate properly.
You might check out http://www.ladyada.net/make/mintyboost/power.html.

John444
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Re: MintyBoost Sweat Battery

by Disco Dan on Wed Apr 10, 2013 7:36 pm

Could you not just put a large solar panel on the roof of it and construct a small 'charging station' outside? Unless you encase ALL the electronics in resin or seal in a waterproof box it won't work.
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Re: MintyBoost Sweat Battery

by mishawagon on Sun Apr 14, 2013 1:10 pm

Hello,

Thank you very much for your replies. The sweat would be donated by volunteers after sauna use. The sweat will serve as the ion transport inside aluminum air batteries. We can wire then to give up to 5 volts but not more, however I am worried about the current. Thank you for pointing that out. It looks like each primary cell will only output like a mA. I think we need like a thousand of them! It seems like from the power guide we need at least 1000mA, or even 2000mA !

Misha
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Re: MintyBoost Sweat Battery

by mishawagon on Sat Apr 20, 2013 1:06 pm

Hello,

I have a question about this line in the power document:

"Many devices now charge at 500mA or higher rate, which translates into a 1000 mA draw from the batteries (because the voltage is boosted, the current is also boosted!)"

The line "voltage is boosted, so the current is also boosted" is a bit confusing to me, sorry if I am missing something obvious. Is this because 3V of batteries are used and mintyboost kicks it up to 4.5 or 5 volts? If my batteries are 4.5v then I can in theory get away with only 500mA draw from batteries?

Thanks!
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Re: MintyBoost Sweat Battery

by adafruit_support_bill on Sat Apr 20, 2013 5:35 pm

Power is volts times amps. If you cut the voltage in half on the input side, you need twice the amps to produce the same power on the output side. And that is assuming that your boost converter is 100% efficient. In reality, it is typically in the 80% ballpark.
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Re: MintyBoost Sweat Battery

by mishawagon on Wed Jun 05, 2013 5:17 pm

Hello,

In the end this worked out beautifully. We made a sweat battery out of about 150 cells! We evolved the aluminum air battery design to use a sweat-soaked paper towel instead of a vat of sweat. We grouped our cells in secondary groups of 8 to get the voltage up to about 5v, and then put 19 groups in parallel. The first day of the exhibition we had about a whole amp of power coming out! The half life of the power is about a day, mainly because of the evaporation of water from the paper towel. We rehydrated the primary cells and got the battery to power the mintyboost and charge cell phones during the whole weeklong exhibition.

It was great, thanks for this excellent kit! Big props for making the board perfectly sized for Altoids smalls tin instead of the big one.

Photos and how-to pdf with drawings of Baghdad batteries and our batteries on our blog here: http://dsinstitute.com/archives/130

Video interviews with us about our presentation at the Ideas City festival put on by the New Museum here:
http://dsinstitute.com/archives/135
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Re: MintyBoost Sweat Battery

by adafruit_support_bill on Wed Jun 05, 2013 5:23 pm

Awesome! Thanks for posting this. This looks like one for the blog :D
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