I' thinking DC/DC converter, rather than "power supply." The input is batteries, not wall A/C. The battery chemistry is typically LiPo, sometimes LiFePO4, and very unlikely to be NiMH or SLA these days.
So, problems I've solved myself because I couldn't buy ready-made solutions for them:
- Input is 4S LiPo, so between 12.8V and 16.8V. Output is 19V +/- 5%. Output current is 3.5A max.
- Input is 4S LiPo. Output is 12V +/- 5%. Output current is up to 30 A.
- Input is 3S LiPo, so between 12.6V and 9.6V. Output is 12V +/- 5%. Output current is up to 10A.
- Soft/remote on/off for up to 30 A.
Things I like, in general:
- High-efficiency switching converters. 90% is needed; 95% is good.
- High current capacity! Motors draw lots of power, as do high-capacity computers.
- Wide input range -- anything from 2S to 6S LiPo would be ideal. If you can't get sufficient efficiency with buck/boost or CUK or similar topology, step-down-only is acceptable.
- Constant current limiting -- rather than hiccupping, and resetting my entire system, letting the voltage drop and emit a warning when current draw goes over the design limit.
- Robust -- should be able to run at stated capacity in an indoors environment for an hour without overheating; this includes running in current-limited mode for an hour.
- Matching to particular power needs. 12V is common in industry, but 19V is also common for laptops/computers and not readily available off the shelf.
- LiPo power awareness -- warn when voltage is at 3.4V per cell, and turn off when voltage is at 3.2V per cell.
- Latching remote off (and, ideally, on.)
- Adjustable output voltage. In some designs, allowing any output voltage between, say, Vbat/2 and Vbat, isn't that hard to design in, and would be a useful feature.
- High-current connectors. Dean-style T-connectors, or XC-60 bullet connectors would be great. Screw terminals are good, too, if they're rated for sufficient current.
Some of these requirements are a bit conflicting -- especially the connectivity and supply range versus weight ones. I'd rather go for an open frame converter with bare solder holes, and add whatever shield/cabling is needed myself, than find myself with a steel-encased, screw-clamped supply that adds half a pound of extra weight.