Model Forum / Radio Controlled / Water Models / December 2008

NIckel-Metal Hydride rechargable batteries.They were the most popular
and efficient rechargable battery before the invention of the LiIon
(Lithium Ion) batteries which last longer and don't suffer from battery
'memory' which shortens battery life.

When people get beat-up at the National Institute of Mental Health.

A nickel-metal hydride battery, abbreviated NiMH, is a type of
rechargeable battery similar to a nickel-cadmium (NiCd) battery. The
NiMH battery uses a hydrogen-absorbing alloy for the negative electrode
instead of cadmium. As in NiCd batteries, the positive electrode is
nickel oxyhydroxide (NiOOH). A NiMH battery can have two to three times
the capacity of an equivalent size NiCd. However, compared to the
lithium-ion battery, the volumetric energy density is lower and
self-discharge is higher.Common AA batteries (penlight-size) have
nominal charge capacities (C) ranging from 1100 mA·h to 2900 mA·h at
1.2 V, usually measured at a discharge rate of 0.2×C per hour. Useful
discharge capacity is a decreasing function of the discharge rate, but
up to a rate of around 1×C (full discharge in one hour), it does not
differ significantly from the nominal capacity.The specific energy
density for NiMH material is approximately 70 W·h/kg (250 kJ/kg), with
a volumetric energy density of about 300 W·h/L (360 MJ/m³).

'en.wikipedia.org'
(http://en.wikipedia.org/wiki/Nickel_metal_hydride_battery)

battery made out of nickel metal. they are a type of plate that have
ability to absorb a lot of power via recharge and you can charge them a
lot more than the old acid batts. Only problem is they have no memory so
they lose charge faster if they are not being used. THe good thing is
you get more power from NiMH and they can be recharged a lot more
times.

Nickel-metal hydride batteryModern, high capacity NiMH rechargeable
batteries Energy/weight 30–80 Wh/kg Energy/size 140–300 Wh/L
Power/weight 250–1000 W/kg Charge/discharge efficiency 66% [1]
Energy/consumer-price 2.75 Wh/US$[1] Self-discharge rate 30%/month
(temperature dependent)[2] Time durability Citation Needed Cycle
durability 500–1000 Nominal Cell Voltage 1.2 V A nickel-metal hydride
battery, abbreviated NiMH, is a type of rechargeable battery similar to
a nickel-cadmium (NiCd) battery. The NiMH battery uses a
hydrogen-absorbing alloy for the negative electrode instead of cadmium.
As in NiCd batteries, the positive electrode is nickel oxyhydroxide
(NiOOH). A NiMH battery can have two to three times the capacity of an
equivalent size NiCd. However, compared to the lithium-ion battery, the
volumetric energy density is lower and self-discharge is higher.Common
AA batteries (penlight-size) have nominal charge capacities (C) ranging
from 1100 mA·h to 2900 mA·h at 1.2 V, usually measured at a discharge
rate of 0.2×C per hour. Useful discharge capacity is a decreasing
function of the discharge rate, but up to a rate of around 1×C (full
discharge in one hour), it does not differ significantly from the
nominal capacity.The specific energy density for NiMH material is
approximately 70 W·h/kg (250 kJ/kg), with a volumetric energy density
of about 300 W·h/L (360 MJ/m³).

'en.wikipedia.org'
(http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery)

Dude! I don't know, why don't you google it?

They use a combination between nickel and another metal alloy, thus a
hybrid battery. They are similar, but better than NiCd (nickel-cadmium)
batteries. Still, lithium-ion batteries are the best.

'en.wikipedia.org' (http://en.wikipedia.org/wiki/NiMH)