Page 103 - Build Your Own Combat Robot

Build Your Own Combat Robot
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D-cell NiCad should always have a capacity greater than 4Ahr, yet many
name-brand D-cell NiCads can be found with Ahr capacities of less than 2.5Ahr.
Virtually all brand-new rechargeable batteries will have a higher energy capac-
ity after going through a few charge/discharge cycles. The minimum recom-
mended break in period is three cycles, although capacity will increase during the
first ten charge/discharge cycles.
For all battery types, if you want to increase voltage, just add the batteries to-
gether in series. From any battery type, you can build up as high a voltage as
needed. All the batteries in series must be the exact same type of battery in voltage
and capacity. If you want to increase for current capacity, add battery packs with
the equal voltage and current capacity together in parallel.
Figure 5-1 shows two battery packs wired together to increase the voltage or
current. When connecting batteries together in series, the voltage is added together
and the current capacity is the same as a single battery pack. When the batteries
are wired together in parallel, the voltage remains constant but the current capacity
is added together.

caution Remember that each battery pack must have identical total voltage and current
capacity or you will damage the batteries.

Preventing Early Battery Death
With proper care, most combat rechargeable batteries can run through 200 to
1,000 charge cycles. Under battle conditions and extreme current draws, the ac-
tual figure will be closer to 200 than 1,000, though. If you do a lot of practice driving,
you should consider getting new batteries after two or three competitions. To get the
maximum amount of charge cycles, you must pay attention to the following areas.
First, follow the proper care and charging guidelines for your particular re-
chargeable battery. All rechargeable batteries require about 5 to 50 percent more
charge placed into them than is taken out of them. Improper charging by either
overcharging or undercharging is probably the biggest killer of rechargeable bat-
teries. An automatic charger specifically designed for your particular battery type
is the best defense against harming the battery by improper charging.
Second, rechargeable batteries can become severely damaged by being deeply
discharged. While the battery is in hard use, and whenever the battery charge is be-
low 80 percent of the rated charge, it is possible that some of the cells within the

FIGURE 5-1
Batteries in series
and parallel.