Nickel Metal Hydride - NiMH|
Nickel Metal Hydride
(NiMH) is the next generation of rechargeable batteries that emerged after NiCd.
It uses hydrogen absorbing alloys in its negative electrode (anode) and nickel
oxide in its positive electrode (cathode). Sanyo first released its version
of NiMH, Twicell, in 1990.
NiMH batteries are more
environmentally friendly than NiCd, and offer much greater battery capacity
per volume than NiCd. Another major advantage of NiMH over NiCd is their ability
to accept a charge at any time without suffering from the "memory effect"
(described under our section on NiCd). The memory effect does exist in NiMH,
but the extent is a fraction of that in NiCd. A good way to charge NiMH batteries
is either with the "burp" charging described in our NiCd section,
or with a negative Delta V terminating charger. Before charging your NiMH battery,
check with the charger manufacturer to make sure their charger can handle NiMH.
NiMH batteries should not be left in a charger for more than 30 hours.
- more than 500 charge/discharge
- 1.2 volts is the nominal
voltage of one cell
- high volumetric energy
density, generally lasting twice as long as NiCd
- quick charge rates
possible with controlled charging
- temperature range of
-20°C to 60°C
- sealed configuration
with gas release vent
- more environmentally
friendly than NiCd
- less memory effect
- many size configurations
availabe including AA, AAA, C, D, 9v, and many sizes in between