Comment by pengaru

Comment by pengaru 4 days ago

I've gone through a dozen or so LiPo-utilizing portable devices at my property in the Mojave desert. All it takes is a single season for many of these batteries to swell up to such an extent the enclosures split open.

Ostensibly they contain charge controllers and temperature sensors, yet they're unable to prevent this outcome when the ambient temperature exceeds 110F day after day while the device stays on in a hot attic w/usb-c pd connected.

Fortunately I haven't had any burst into flames yet, but after a few years of seeing this pattern repeatedly I stopped deploying anything containing LiPo batteries at the property.

YMMV - but IMHO it's prudent to exclude these batteries from such unattended, powered 24x7 devices.

jeffbee 4 days ago

This has nothing to do with being near full charge and everything to do with the temperature.

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pengaru 3 days ago

Leaving such devices plugged in 24x7 unattended creates opportunities for such ambient conditions to develop unnoticed.
These mobile LiPo-using rechargeable devices simply aren't ideal for being left powered while unattended, day after day, year after year. All it takes are some sunny days with normally closed blinds left open and you may slowly be cooking that device you forgot about that Just Works but is a ticking time bomb after the 10th day it spent an hour in direct sunlight while charging.
AIUI the high temperatures are particularly damaging to the SEI (Solid Electrolyte Interface) layer, which is the layer preventing dendrite growth. If that layer breaks down enough for dendrites to grow, you're in internal short / fire-risk land.

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The_President 4 days ago

Excellent advice. Did you swap any of the cells with a different chemistry?

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pengaru 4 days ago

Not really, there was a brief excursion in kludging a ZTE MiFi device to use a DIY NiMh pack of AA cells when it refused to stop self-destructing its OEM LiPo batteries every summer. (I use a MiFi hotspot for a cheap security camera network)
It worked as a stop-gap but I've since replaced it with a GL.Inet X300b ruggedized hotspot without any batteries.
There's no UPS for now... if I went the route of wanting uninterrupted power at the property I'd probably put a battery bank underground outside to power the entire building. It's not worth risking anything rechargeable inside the place given how hot it can get, and how long I sometimes go without visiting.

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- The_President 4 days ago
  
  Cheers, Thanks for the info.
  
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  pengaru 4 days ago
  
  I'm not sure how generally applicable it is. When you have several acres of undeveloped land full of sand at your disposal it's relatively trivial to dig a pit, mix some concrete from the sand you excavated, and pour a subterranean cellar to house a battery bank and other hazardous infrastructure. Nobody would even notice it happened/exists.
  The situation is far more complicated for folks in apartments or high density housing.
  
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