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?
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.
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.
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
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 ).