12-04-2020, 11:10 AM
Well, the plot thickens, as it might have been expected. In a few words, improvements to the SoC cooling will have to be made in parallel to the PineBook Pro's power circuitry improvements. Below is a more detailed explanation.
Once the CPU cores are all kept at 100% utilization for an extended period of time (20+ minutes), the heat soak from the SoC affects the battery charging IC (i.e., TI BQ24171), which goes into thermal shutdown. As a result, battery becomes rapidly discharged because the loaded SoC uses a lot of power and there's atually no charging at the same time. Turning the laptop upside-down and providing additional coolling to the back of the laptop turns the previously mentioned 20 minutes into about an hour, but the BQ24171's inevitable thermal shutdown happens anyway.
I'm already evaluating a few possible solutions, including gluing a thin copper sheet to the inside of the back cover, using thermal epoxy. The back cover seems not to conduct heat very well, which causes a hot spot where the SoC touches it. Another possible solution being evaluated is gluing flat copper heatpipes to the inside of the back cover. In addition, gluing a small heatsink to the BQ24171 IC should help a bit.
Once the CPU cores are all kept at 100% utilization for an extended period of time (20+ minutes), the heat soak from the SoC affects the battery charging IC (i.e., TI BQ24171), which goes into thermal shutdown. As a result, battery becomes rapidly discharged because the loaded SoC uses a lot of power and there's atually no charging at the same time. Turning the laptop upside-down and providing additional coolling to the back of the laptop turns the previously mentioned 20 minutes into about an hour, but the BQ24171's inevitable thermal shutdown happens anyway.
I'm already evaluating a few possible solutions, including gluing a thin copper sheet to the inside of the back cover, using thermal epoxy. The back cover seems not to conduct heat very well, which causes a hot spot where the SoC touches it. Another possible solution being evaluated is gluing flat copper heatpipes to the inside of the back cover. In addition, gluing a small heatsink to the BQ24171 IC should help a bit.
