Scientific Operations Bellum Gratia Artis

Power

This page contains information about power topics.

Possible USB-C PD to barrel jack adapter: https://www.amazon.de/-/en/dp/B07PBG4GY6 (from this forum post

FIXME: a non-Amazon source would be nice, as well as purchasing options for other countries.

Batteries

Background

The Reform relies on a set of eight LiFePO4 lithium-ion cells to provide battery operation. It presently suffers from an issue wherein significant power is drawn while the unit is switched off. This presents a situation where leaving the machine sitting on a couch powered off for a week or two without the power adapter attached drains the batteries.

If LiFePO4 cells are over-discharged, they can be damaged. Furthermore, the Reform, as well as many dedicated chargers, will refuse to charge them if the cell voltage dips below a certain threshold (2.5 V?). Combined with Reform's lack of low-voltage cutoff, this presents a situation where leaving the machine sitting on a couch powered off for a week or two without the power adapter attached drains the batteries to the point where the laptop cannot charge them up again.

There has been some discussion on IRC about methods for recovering cells that have been subject to this. One method is discussed in the Recovery section.

Installation/Removal

Due to a handful of reports of smoked motherboard components when doing this in the opposite order, it is recommended to remove the battery pack connectors before removing individual cells from the packs, and likewise to insert individual cells into the packs before plugging in the battery pack connectors. The cause of this phenomenon has not been knowingly investigated.

Recovery

Stable, current-limited (e.g. "bench" or "lab") power supplies can be used to recover lithium-ion cells that have been sufficiently drained that chargers refuse to touch them. This method was used to successfully recover stock Reform LiFePO4 cells with voltages reading as low as about 150 mV.

Materials needed:

Procedure:

  1. Remove the cells from the computer. See Installation/Removal.
  2. Configure the power supply. The power supply's constant-voltage threshold should be set to the cut-off charging voltage of the cells (3.65 V for stock Reform cells) or slightly less. The power supply's constant-current threshold should be set to a value much less than the maximum charging current of the cells (250 mA was used for stock Reform cells; ≤ 500 mA is recommended). The intent here is to be gentle with the cells (how much this matters has not been investigated). Ensure that the supply's output is switched off.
  3. Insert a cell into the holder.
  4. Wire the holder to the power supply. Wire the multimeter to the holder if you are doing so. Double-check all connections.
  5. Switch the power supply on. It should start in constant-current mode, delivering the full current you programmed in. The cell is now charging.
  6. Take temperature measurements every few minutes to ensure that the cell is not becoming uncomfortably hot. Consult the datasheet of the cells to determine your comfort level for this. Also, keep an eye on the cell voltage as read by the multimeter. At 250 mA, the cells barely heated up above ambient temperature during the recovery.
  7. Once the cell voltage increases to 2.5 V, the Reform can handle charging from there. Once you are satisfied with the voltage, switch off the power supply and then remove the cell from the holder. Keep in mind that cell voltage will decrease slightly when the charging supply is removed. The power supply's constant-voltage mode will not become active unless you choose to charge the cell nearly all the way up with this method. This is not necessary.
  8. Repeat steps 3 through 7 with the next cell. Do this until all cells are recovered.
  9. Insert the cells back into the computer. See Installation/Removal. The Reform should be able to finish charging them itself.

Replacement

If the cells have been damaged past the point of a realistic recovery, you might choose to replace them. A US source for replacement cells can be found here.