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The AC-DC power supply load appears to draw 40W of power, so we can subtract that from all of our findings to get a base power consumption + whatever overhead is associated with the DC load.
There's two screen adjustment pins. The ambient light sensor gives a 100W range and the backlight adj pin gives a 175W range. With DPMS on and screens/fans off, the board itself appears to draw about 10W.
This means that there's a base-level operation at the lowest light setting of about 60W to about 340W at the highest level with the ~280W fluctuation being controlled by the various backlight control pins.
The CPU board has 7 GPIO pins + ground which do 3.3V peak and can do PWM. We can allocate 3 pins in parallel with an RC circuit to get to a 0-9.9V range so long as we can interface the GPIO directly.
We need a way to address thermal runaway through emergency shutdown. The current systems have low and high temperature with hysteresis and a separate fan speed setting ranging from 10-100. The load variations between the settings appear to be about 5W. There's a temperature sensor connected to one of the screens that manages this. However, the system is self-contained and can only modulate fan speeds. It cannot, for instance, do any kind of emergency shutdown if the temperature raises past a threshold.
There's usb surface mount connectors on the board itself so the supplier could put a usb connector on that board so the host (CPU) can read the temperature and fan speeds. The current shipment can use 3rd party add ons that detect both temperature and humidity over usb, as a secondary sensor (such as https://www.alibaba.com/product-detail/SSN-20-35-80-Celsius-degrees_60094009267.html?spm=a2700.7724838.2017115.233.74f046d4XgDeID or https://www.alibaba.com/product-detail/China-USB-in-transit-temperature-recorder_60680351762.html?spm=a2700.7724838.2017115.332.74f046d4XgDeID). A usb extension cable can be used to affix the device to wherever the reading is desired.
Any secondary battery should have a data cable so that the host can monitor such things as the current temperature of the battery, the current load, and the remaining capacity.
The current batteries have to be redesigned to accommodate for this need. They also appear to be using a variation of lithium ion that has high capacity, low cost, and a dangerous thermal profile. This needs a fundamental redesign and is unacceptable in its current state.