Garmin Tactix Delta stops solar charging when it gets too hot

Most charging circuits have thermal protection built in, so it wouldn't surprise me...

SocalHiker said:

left it in my car instead of outside

SocalHiker said:

my watch was really hot to the touch.

Why do you do such experiments? You are dealing with a Li-Ion battery here. This technology has a very high energy density. If things go badly, the battery catches fire and gasses out. A burning car could be the result.

First i didn't expect it to get that hot. Second I've not heard one story with these watches catching fire. It's a solar charging watch so why wouldn't it be able to be in the sun for long periods of time? Third, your response was off topic but thank you for your concern.

But when worn and in activities, it will have cooling from air currents etc. Putting in in a hot car, not moving, with no cooling would trip any thermal protection. Li-Ion batterys have high energy density and a malfunction due to heat could kill the watch.

Per the manual, the solar charging temperature range is 0-60 degC (32-140 degF) so I guess yours got hotter than that.

Thank you very much. This was an answer that i was looking for. I appreciate it.

SocalHiker said:

Is this normal for the watch to stop solar charging when it gets too hot or do I have an issue?

I'm not sure, but it could also be that the car windows absorb parts of the sunlight (UV radiation) that are important for generating electricity in the solar cell of the watch, and that's why the battery isn't charged. The IR light passes through the car window and that is why the watch gets warm, but the UV light is absorbed. And if the watch contains an UV solar cell, then it will not charge.

For example, if you have eye glasses with photochromic lenses, then it will not darken in the car because the car windows filter the UV radiation.

I totally understand what you're saying but the solar graph shows that it was taking in solar energy for hours inside the car but then just immediately stopped while still being in the car in the same position. 

bluefish said:

Why do you do such experiments? You are dealing with a Li-Ion battery here. This technology has a very high energy density. If things go badly, the battery catches fire and gasses out. A burning car could be the result.

Unlikely due to the small size of a watch battery.

But you raise a good point with larger devices, which is why most li-ion batteries have thermal protection circuits.

mcalista said:

which is why most li-ion batteries have thermal protection circuits.

Yes, that is correct. However, this protection only stops charging when the heat is too high. However, even a protection cannot prevent dangerous outgassing of the battery when the external heat is too high.

mcalista said:

Unlikely due to the small size of a watch battery.

This has nothing to do with the size. There are nice videos on Youtube with Li-Po batteries, like the one in the watch.