Unify with solar panel - too hot for charging

WisBlock
1

We are using RAK4631/Arduino with RAK19007 and Li-Ion 18650 battery, in a Unify 150x100x45mm enclosure with integral solar panel.
On sunny days (in Houston) the RAK1901 temperature sensor reports 60C inside the box - this is dangerously high for charging Li-Ion batteries, which can suffer thermal runaway and catch fire if they are charged at temperatures above 50C.
Questions:

  1. Has anyone had a similar overheating problem with these solar Unify enclosures, and if so, what was your solution?
  2. Due to our low power consumption, the battery is invariably at 100% by the time the box gets above 45C. Does this mean that the charger chip on the RAK19007 effectively halts the solar charging current anyway, perhaps eliminating the danger? Or is it still forcing charging current through the hot battery? Or maybe it is dumping unneeded solar power as heat, and thus adding to the heat problem?
2

Welcome back to RAK forum @greigmj ,

60degC is a bit high. It can be that this is reached the ambient temperature is high and the battery is being charged on the maximum charging current.

If the battery is already full (4.2V), the charging will be stopped until the voltage reach around 4.0V where the charging will start again.