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BEST BATTERY PLACEMENT PRACTICES 195

5 cell 6 cell
(special order)

Shorted thru
empty cell
Figure 19- 5 Create your own
Front Back
“odd- number cell” battery holders
by bridging across the terminals
6 cell of one of the cell pockets. This
double sided
maintains electrical continuity for
the holder but lets you use one
Shorted thru
empty cell fewer batteries.

prefer the fastener approach when a permanent installation is required and I want to make
sure the battery stays put.

BATTERY HOLDERS FOR “IN- BETWEEN” VOLTAGES
Sometimes you may want an in- between voltage. Just use an odd number of cells. For
instance, five rechargeable cells provides 6 volts; five nonrechargeable cells, 7.5 volts. While
they do make battery holders for odd numbers of cells, they’re not always easy to find, and
they tend to be more expensive.
One alternative is to use a standard even- cell holder and “bridge” one of its cell “pockets”
to produce an odd- cell voltage. A four- cell AA holder provides 6 volts— too much for electron-
ics designed for 5 volts. By removing one cell from the holder, the voltage is reduced to 4.5
volts, which is within the normal operating range.
Figure 19- 5 shows the concept of bridging a cell pocket in a six- cell holder, which is com-
monly available in both single- and double- sided versions. You can bridge the pocket tempo-
rarily by using a jumper clip. For a permanent job you’ll want to solder a length of wire
between the battery posts in the last cell pocket.

ON THE
There’s more about batteries, battery holders, and battery packs on the RBB Online Support site
(see Appendix A for more details).
W E B
Best Battery Placement Practices

For obvious reasons, the battery in your car is intentionally mounted for easy access. The
same obvious reasons apply to robots. When possible, the battery holder or pack for your bot
should be located where it affords quick and reliable access.
One ideal location for the battery pack or holder is on the underside of the robot. This
assumes there is enough ground clearance between the robot and the floor. Mounting on the
bottom allows for quick access to the cells, either for replacement or recharging: just turn the

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