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I'm charging my Li yard lights below freezing!

45North

Let it shine!
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Jan 2, 2020
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For the past 2 years - including winters - I've been using my Li yard lights despite all the warnings about not charging Li below freezing.
Daytime temps here in Ottawa are consistently below freezing for weeks (months?) on end. Yet they continue to light up every night if there's been enough sun in the daytime.

Yes, I knew I was ignoring the warnings but figured I'd risk it anyways. (I wouldn't be doing this experiment with a big $1000 Li battery!)
So, what's up? Have I just been lucky? Or have I killed them and I just don't know it yet.
 

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Do you notice on the label where it says "Li-ion", and NOT LiFePO4?
It's my understanding that no Lithium batteries can be charged below freezing.

And technically LiFePO₄ is one of several specific types of Li-ion battery chemistry.
 
Not really. At below about 32F the charge rate (amps) needs to be really low. I believe your iddy bitty solar panel qualifies as "low rate"
It still manages to light up for a few hours every night - especially now that the winter sun has started getting a little higher.
 

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It still manages to light up for a few hours every night - especially now that the winter sun has started getting a little higher.
This is actually the light from 2 spots. I double up in the winter for the display.
 
It's my understanding that no Lithium batteries can be charged below freezing.

And technically LiFePO₄ is one of several specific types of Li-ion battery chemistry.
Actually there is apparently one special type of Li batteries that can be charged below freezing - but they cost even more!
 
I have a couple of those cheap lights on my property. The battery quality is so bad that they almost always stop lasting through the night after 18 months. My current ones cut out at about 3am. My thinking is that these batteries are like an old banged up pickup truck. You won't notice a new dent, scratch or rattle until it's the one that makes it stop running. Your putting in so little charge that the damage is just adding little bits onto an already half dead battery.
 
See this video I did:


Because of the cold, the internal resistance goes up, and this in itself already prevents the battery from taking in any meaningful current. This prevents a lot of the damage that can occur. That is, at normal charging voltages. If you were to crank up the voltage, you would be able to increase the current and you'd destroy them.

Also, I assume you get very little light in winter just like I do, so you'd barely be charging those anyway... Discharging below freezing is fine, be it with diminished available capacity.
 
See this video I did:


Because of the cold, the internal resistance goes up, and this in itself already prevents the battery from taking in any meaningful current. This prevents a lot of the damage that can occur. That is, at normal charging voltages. If you were to crank up the voltage, you would be able to increase the current and you'd destroy them.

Also, I assume you get very little light in winter just like I do, so you'd barely be charging those anyway... Discharging below freezing is fine, be it with diminished available capacity.
Brrrrr!
My hands were getting cold just watching this!
 
Many LiFePO4 cells can be safely charged below freezing.

It’s an internet myth that they can’t.
 
Citation needed

I’ve attached the specs for the BYD Blade LiFePO4. Note the working temperatures.

Any decent LiFePO4 will be able to operate in frozen conditions - some cheap crappy ones may not.
 

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Any decent LiFePO4 will be able to operate in frozen conditions
There's no debate that LiFePO₄ can be stored and discharged below freezing. The question is only about charging.

It is interesting that the spec sheet states the charge range is -10ºC to 50ºC (14ºF to 122ºF).
 
There's no debate that LiFePO₄ can be stored and discharged below freezing. The question is only about charging.

It is interesting that the spec sheet states the charge range is -10ºC to 50ºC (14ºF to 122ºF).

There is no debate about LiFePO4 being able to charge and discharge well below freezing. There are a few morons on the internet that think they know what they are talking about - and many more that parrot their misinformation.

Good LiFePO4 cells can be charged well below freezing, as per the BYD spec sheet. (keep in mind the BYD Blade is based on LiFePO4 tech that is at least 5 years old - there are far more capable LiFePO4 cells available)

The real question you should be asking yourself is why you blindly believed someone saying you can’t charge LiFePO4 below freezing (which is clearly incorrect), and yet you have such trouble believing the correct fact that there is no issue with any quality LiFePO4 cell being charged well below freezing.
 
Many LiFePO4 cells can be safely charged below freezing.

It’s an internet myth that they can’t.

With a caveat that it's only possible at reduced charge rates, mostly enforced by its internal resistance rising significantly as per the video I did. EVs also have to pre-heat their batteries for example to be able to receive maximum power.
 
With a caveat that it's only possible at reduced charge rates, mostly enforced by its internal resistance rising significantly as per the video I did. EVs also have to pre-heat their batteries for example to be able to receive maximum power.
Perhaps re-posting the video would help?
 
With a caveat that it's only possible at reduced charge rates, mostly enforced by its internal resistance rising significantly as per the video I did. EVs also have to pre-heat their batteries for example to be able to receive maximum power.

Yes, for sure the IR limits charge acceptance. The higher quality the cell, the higher charge rate.

Many people wrongly assume that all LiFePO4 cells share the same chemistry.
 
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