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LiPo Batteries Outside
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Please be positive and constructive with your questions and comments.

LiPo Batteries Outside

by czuvich on Wed Apr 24, 2019 11:44 am

I'm working on my outdoor project that will be in the sun and use small solar panels to recharge the small (500mAh) LiPo batteries attached to the nRF52840 Express chips.

I'm using a NEMA rated outdoor enclosure with small vents to keep everything protected

https://www.polycase.com/wc-31
https://www.digikey.com/product-detail/ ... ND/7898284

I live in Central Texas where things can get pretty hot. Everything I'm reading tells me that LiPo batteries are volatile in hot temperatures; however, I only see LiPo solar chargers available. I see the LiPo batteries on here are rated at around 140F which I think the enclosure shouldn't get that hot even exposed to the sun.

Should I continue using the LiPo batteries in my outdoor projects, or should I try looking for alternatives? I don't want my batteries to suddenly all fail (I have several of these running), but I don't really see alternative battery chargers for Arduino (besides LiPo). I have to believe if LiPo chargers are that popular, then people are using LiPo batteries outside in enclosures without failure.

czuvich
 
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Re: LiPo Batteries Outside

by adafruit_support_mike on Wed Apr 24, 2019 2:31 pm

LiPos are rated to operate between 20C and 70C, or about 60F to 160F. You’ll see some effects from higher temperatures, like things operating at higher current, but everything should be safe.

If you decide you want to use something else, take a look at sealed lead-acid (SLA) batteries. They’re similar to car batteries, but safer. They’re often used for solar applications like electric fences and wildlife cameras. There extremely durable.

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Re: LiPo Batteries Outside

by czuvich on Wed Apr 24, 2019 6:07 pm

That is great news! I think my outdoor project will be fine (short of freezing weather). I've called polycase, posted on Arduino, and here... and the general consensus for my project is that it "should work fine", but keep it shaded and monitor your temps.

The jump from a 3.7V 500mAh battery to a 6V 1ah battery is significant. My circuit is only using 3mAh at MOST, and I'm using a solar charger with a very small solar panel (2") to replenish the battery. Maybe this design will fail horribly in a production environment, but so far so good in my backyard. If it does fail, it is likely due to protecting the battery and not the circuit itself.

czuvich
 
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Re: LiPo Batteries Outside

by sam_moshiri on Thu Apr 25, 2019 5:28 am

Yes, it is safe, but probably the higher temperature will shorten their lifetime

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Re: LiPo Batteries Outside

by czuvich on Thu Apr 25, 2019 10:09 am

How would you generally keep an outdoor project cooler (primarily battery) if it needs to be in direct sunlight (backyard garden)? My enclosure is only about 2”x2”x2”. I’ve considered putting it inside of a small sprinkler valve box, but those only come in black.

czuvich
 
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Re: LiPo Batteries Outside

by adafruit_support_bill on Thu Apr 25, 2019 10:21 am

Outdoor enclosures for electronic equipment (e.g. railroad signal equipment) are often painted white or silver to reflect solar energy. Weather resistant venting at the top and bottom will allow for some convective air-flow to moderate temperatures also.

There is not much room for venting in a 2" cube. But if your enclosure is already somewhat weather resistant, you could put it inside of a larger ventilated box that would shield it from direct sun and rain.

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Re: LiPo Batteries Outside

by czuvich on Thu Apr 25, 2019 10:35 am

I purchased a few of these to try and vent the small enclosure. I’ll put one on top and bottom. Hopefully this works!

https://www.digikey.com/product-detail/ ... ND/7898284

Thanks for the great information.

czuvich
 
Posts: 109
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Please be positive and constructive with your questions and comments.