RAM (Reusable Alkaline Manganase) are rechargable cells with many advantages: are cheap, have no autodischarge and no memory efect, work fine in higher temperature. Number of charging cycluses vary widely (25-600) and depends on degree of discharging. It is recomended to charging them as frequently as possible. RAM batteries are a good choice for everybody who frequently use AC adapter for power of HPLX.
RAM cells have to be charged by constant voltage 1.65 V per cell and when the charge current decreases below cca 10 mA, charging is completed. Unfortunatelly, charging subsystem in HP100/200LX is designed for use of NiCd cells, which are charged by constant current.
I use two sets of RAM cells and external charger. Cells are changed and charged when the voltage reaches cca 2.45 V. I am full satisfied with this system of HPLX power.
More informations can you found on sites of RAM producers f.e. Pure Energy or Grandcell.