"Fast charge circuits for NiCad batteries." 4 pages.
At four pages, this app note is the shortest one ever. It discusses using temperature measurement to determine the charging status of a NiCad battery pack (which was previously discussed in Figure 3 in App Note 6). This approach is still a good idea: I've been witness to some spectacular battery-pack failures, and I fully appreciate the need to prevent them!
In this app note, two thermocouples are used to compare the battery-pack temperature to ambient temperature and to taper the charging current. Figures 2 and 4 use an LT1006 precision single-supply op amp to measure the temperature and drive a 10-amp Darlington transistor to charge the batteries. (Appendix A discusses the construction of the necessary low-resistance shunt to measure the transistor current in the charging circuit.) An op-amp offset-trimming resistor is included in the schematic because the type-K thermocouples only produce 40 microvolts per degree Celsius.
Figures 5 and 6 use switch-mode drive to reduce the power dissipation in the charging transistor. I'm not a battery expert, but I've been told that this approach is a bad idea. Rechargable batteries really prefer constant charge (and discharge) rates, and charging (or discharging) with pulses of current will shorten the battery pack's lifetime. Am I misinformed?
Best quote (on page AN37-1): "Excessive internal heating degrades the battery and can cause gas venting to the outside atmosphere." Yep.