Battery temperature too low warning

Hi, I’ve been seeing these warnings lately when hiking with the phone outdoors. The temperatures never dropped significantly under 0 °C.

I was trying to find some environmental ratings for FP4 that would specify what is the operating temperature range, but haven’t found any (I looked at the eshop page). Has anyone found these details?

And what is the behavior of the phone with this warning displayed? Is it only a warning telling me the battery doesn’t like the temperature, or is there a premature shutdown/lockdown to save the phone? And can’t the phone turn on one of its pretty efficient heaters to heat up the battery? :slight_smile:

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Did you already see this thread? FP4 battery issue? Low temperature alerts, sudden switch-offs, won't charge
Do you only see the the warning or does it behave as strangely as mentioned in the thread above?

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Yes, I’ve seen it. My phone only alerts me when the temps are really low (below 0).

Just a note.

When batteries go from warm to cold environments the dampness in the sir will condense in the phone, keeping it a plastic pouch will not stop that and can make it worse in that there is no air circulation.

My idea is to keep the phone as close to my body as possible to keep it warm.

I keep mine in a microfiber lined leather pouch when I’m outside in the snow, that keeps it warm and dry and adds another layer of protection. Has worked great for my previous phone and so far no problems with the FP4 as well.

Just a note, when I tried to get the FP4 to charge / discharge as fast as possible I kept it running on a icepack for almost an hour and the battery temperature never dropped to zero degrees.

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I also think maybe it’s the humidity. Does anybody know where exactly the battery temperature sensor is located in FP4?

Apparently the battery temperature sensor is inside the battery (at least according to this SO question).
Makes sense, even the shrinkwrap around the pack would probably mess with your readings.

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Wonderful. That gives me hope only the battery might need replacement in my case, not the whole phone :).

The battery may just be helped with a #kickstart in a warm atmosphere.

Hi peci1,

Your phone and battery is behaving totally normal. Any Lithium based rechargeable battery must never ever be charged at temperatures below 0 °C. During the charging process of Lithium based batteries small amounts of water can build up inside the cell as part of the chemical processes during charging. The water built-up later is reversed.

BUT: At temperatures below 0°C this temporary built water can freeze, destroy the cell and even lead to blow-up or fire. For this reason manufacturers implement a temperature sensor to stop charging a few degrees above 0°C (usually around 5 °C).

My FP2 for example does not present this message but simply stops charging. Of course it’s just a matter of software to present some message or not. But the general principle is (or should be!) the same on all devices with Lithium batteries: No charging below 0°C.

You can use the phone normally, just charging isn’t possible below 0 °C. However, it might be a good idea to keep the phone near to Your body to keep it warm, as batteries tend to loose capacity at low temperatures.

Best Regards



Thanks for the insight. This warning showed during use, not during charging. So does it just inform me that I should not connect a charger until I heat up the battery?

Hi peci1,

I don’t see a specific reason to present this message without connecting a charger, but it’s a matter how developers implement it. So, yes, take it as an informative message.

Happy hiking.


I’m not sure if the buildup of water is really the correct reason for not charging under 0°C and I have never heard of that specifically. The limitation is real, though. Some information can be found here, for example: BU-410: Charging at High and Low Temperatures - Battery University

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For some detailed info on Li-ion batteries see below.

As far as the water goes I have no research to confirm that.
However as Li-ion batteries are used on the Mars land rover at temps that can be as low as -120° C then clearly this issue with water is not an issue for some batteries.

Also note the working temp of 'this ’ battery is down to -20°C so I doubt water is and issue.

It’s just that charging a t very low temps is very slow and difficult to manage with ‘off the shelf’ chargers etc. ~ so it is advised not to charge below 0

For even more detail see


How’s your phone been doing?


Fine. I took it to a few more outdoor trips and sometimes it did show the low temp warning, but I never had a practical problem. But I did not try to charge it out in the cold.

The battery seems to be working pretty well generally, the phone usually lasts 3-4 days on a single full charge. I even had one streak with 5 days of battery life (and no, the phone was not off or in airplane mode :slight_smile: ).


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