NiCd battery active material from the board of positive pole composed by nickel oxide powder and graphite powder, graphite does not participate in chemical reactions, whose main role is to enhance the conductivity. Active material from the board of negative electrode composed by cadmium oxide powder and iron oxide powder, the role of iron oxide powder is to cadmium oxide powder have a higher proliferation, prevent clotting, and increase the plate capacity. Active substances were wrapped in perforated steel, the compression molding was turned into positive and negative battery plate. Between plates separated by alkali-stick hard rubber or hole PVC corrugated plates. Electrolyte is usually potassium hydroxide. Compared with other batteries, NiCd batteries self-discharge rate (that is the battery loses charge rate when not in use) moderate. In the use of process NiCd batteries, if not completely discharge before another charge, when discharge next time, you can not release all the power. For example, release 80% of the electricity and then fully charged, the battery will only emit 80% of the electricity. This is so-called memory effect. Of course, a few full discharge / charge cycles NiCd battery will resume normal. For NiCd battery memory effect, if not fully discharge, you should discharge to below 1V per session before charge the battery.

NiMH battery positive plate material is NiOOH,  absorption hydrogen alloy for negative electrode plate material. Electrolyte is usually 30% KOH solution, and add a small amount of NiOH. Membrane using porous non-woven or nylon non-woven fabrics, etc. NiMH batteries are cylindrical or square.

NiMH battery has a good low-temperature discharge characteristics, even in -20 ℃ ambient temperature, using a large current (in 1C discharge rate) discharge, release of electricity can reach more than 85% of nominal capacity. However, when in high-temperature (40 ℃ above), the electrical storage capacity will drop 5 to 10%. Such self-discharge (the higher the temperature, the greater the self-discharge rate) causing capacity loss is reversible, and several charge-discharge cycles will be able to return to maximum capacity. NiMH batteries open circuit voltage is 1.2V, the same as NiCd batteries.