|
In addition our staff interviewed the motor and battery Gurus at Associated:
Mike Reedy and Sean Cochran; and the R&D Manager at Trinity: Rick Hawks.
Both Trinity and Associated have several months of testing on the new Panasonic
cells and probably have more experience with Nickel Metal Hydrides in general
than anyone else in the country.
First we asked Associated and Trinity what classes most benefit from Nickel
Metal Hydrides. Both agreed that any class where run time is an issue and the
batteries are being dumped in the allotted racing time, the higher capacity of
Nickel Metal Hydrides will be an advantage. Those classes include:
In several classes the choice is not so obvious. While 3000 Nickel Metal
Hydrides offer greater capacity allowing hotter motor winds or taller gearing,
Sanyo 2400 NiCads offer higher voltages. In the following classes racers are
experimenting with the higher voltage NiCads vs. the higher capacity 3000NiMH:
Pickin' the pack
Okay, Panasonic, Sanyo or Powers? Which is best? Opposite is a
graph comparing the 20 amp discharge rates of the old Panasonic 3000
NiMH, the new stock Panasonic 3000 NiMH, Sanyo 3000 NiMH, Sanyo's 2400
NiCad and Powers GT3000R. We've talked with several pro racers that have been testing/ racing
all three types of NiMH cell. They all agree that at this point it's a
toss up. The Powers cells have the highest capacity but the lowest
voltage. These batteries require a slightly taller gearing or hotter
motor to make up for the voltage loss. The Sanyo cells are most
popular for 1/10-scale modified touring, but they have also been the
easiest to get. The new Panasonics are just now becoming available and
the numbers sure look good on the machines plus on the track they
don't fall off at the end of the run. Compared to Nicads Nickel Metal Hydrides are environmentally
friendly and many industry leaders believe that NiMh is the way of the
future.
|
||||||||||||||||||||||||||||||||||||||||||||||||||||
We asked both Trinity and Associated their recommendations for getting the
best performance and life from Nickel Metal Hydrides. Both agreed that it's
important not to over charge the cells. When reaching a full charge, NiMh
batteries have a soft peak meaning that the battery's voltage drop at full
charge is small compared to a Nicad which has a hard peak. Because of this it's
important to use a charger that can be adjusted for a low Delta Fallback (the
amount of voltage drop before the charger shuts off). Novak's Millennium or
Competition Electronics Turbo 35 are favorite choices of racers. It's important
to not let the cells get hot during charging. A charge rate of 4 to 5 amps is
recommended and when the cells reach their peak you'll notice that the heat
builds up rapidly. Associated recommends not exceeding 125* f during charging.
If possible, time your charge to end just minutes before your race. Sometimes
that's just not possible and in those cases re-peaking just before a race is
recommended. Just be sure not to overheat the cells.
Most importantly don't over discharge the cells. Discharging below .9 volts
per cell can cause permanent capacity and voltage loss. At the end of a race
day, discharge the cells no lower than .9 volts per cell before putting them
away.
Nickel Metal Hydrides can be used up to three times per race day. Just be
sure to let them fully cool before recharging. Usually a rest period of 2 to 3
hours is recommended.
Both Associated and Trinity warned against storing the cells for long periods
without cycling the cells. In Rick Hawks' words, "use em or lose em".
If there is more than two weeks between races it's
recommended that the cells be cycled. Once every two weeks is about right. A 4
to 5 amp charge with a 20 amp discharge to .9 volts per cell is recommended to
maintain the performance of the batteries.
The old Blue Label Panasonic cells were a bit finicky and would lose capacity
over a season no mater how well they were taken care of. The Sanyos and the new
Pansonics are proving to be a more consistent performing cell with better
longevity.
We asked both manufacturers what effect zapping NiMh cells had and both said
that zapping increases the voltage and decreases the internal resistance only
slightly in some cells. While the effect is beneficial it's not as big a
difference as found with Nicads.
We asked Rick Hawks why the new Panasonics were called Stock Nickel Metal Hydrides when modified classes seem to have the greatest benefit. He said that the first prototype samples had the same capacity as the Blue Label Panasonic cell but with a greater voltage. When the production cells came in, the new cells not only had a higher voltage but a significant increase in capacity. Both Associated and Trinity agree that the new Panasonic's will be better than the old style in all applicable racing classes