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Battery for Portable Freezer
#1
Hello,

It is time for me to stop lurking and try my hand at recycled 18650's.


Looking to build a battery to power our portable freezer at the Farmers Market. It is currently being powered by a 12 volt deep cycle lead/acid that is hooked up to a solar panel to keep the battery charged.

The freezer is able to run also at 24 volts so was thinking to build a 8S 20p battery which if my math is correct would give around 44 amp hours, and be about 26 volts. The freezer pulls 2.5 amps at 24 volts so that should give me around 17 hours of run time. Is that correct or am I looking at it incorrectly?

Any suggestions are welcomed as nothing is in stone yet, and this will my 1st project dealing with 18650’s.

Thank you for your suggestion
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#2
Hi

You should go 7s if you plan for LiIon?

That is a range between 21 to 29.2V. 8s goes all the way to 33.6 (If you utilize full range)

You are basically correct in your calculations.

Just build it. Either you get a solar panel with close to same voltage as the battery and use a BMS with charge and discharge port separated. (Its uggly hack to charge but works) or even better get a MPPT charger in smaller format and hook up.

The later with MPPT charger is 10x more recommended. Dont forget the BMS to protect from over and under voltage on the setup.
Happy build!

This from my chan could potentially give you some ideas. https://www.youtube.com/watch?v=-IWKTDYjKZo
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#3
Thanks Daromer for the reply. I had thought about 7s and in a lot of ways make more sense so I am going to change to that. 

Any suggestions for a Small form MPPT? 

Also since the output range of 7S is between 21 to 29.2v will I need to include a converter to maintain 24 volts?

Thanks again for the suggestions.
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