HOW MANY AMPS?
Now, we know what you’re thinking: “If more amps is better, why not get a 30A charger
and blast that battery full in just five minutes?” ;at makes sense math-wise, and
serious racers do exactly that. However, they also retire their batteries after 30-40
runs, while the rest of us would rather get 300-400 runs out of our
batteries. Charging at lower amperages will extend your batteries’ lives—
that means more recharges before the pack no longer performs well
enough to be worth keeping. For maximum life, charge LiPo packs at the
same rate as their capacity. For example, if you have a 4000mAh LiPo
battery, charge it at 4A. If you have a 5500mAh battery, charge it at 5.5A.
And so on—just take the battery capacity and divide by 1000. In the lingo
of battery charging, this is known as charging at a rate of “1C,” or
“capacity multiplied by one.” If you want to speed things up, charging at
higher rates up to “2C” (twice the battery’s capacity; for example, 8A for
a 4000mAh pack) is fine, but do most of your charging at a lower rate
whenever you can.
LIPO BALANCING: WHAT IT IS AND WHY YOU SHOULD DO IT
When a pack is “balanced,” it means the cells have the same voltage. For example, a 2-cell, 7.4-volt pack is balanced if both cells have 3. 7 volts. If you don’t
balance the cells, their voltages may drift after a few charge/discharge cycles. Why does this matter? Because LiPo cells don’t tolerate being over-discharged well. And while your speed control’s low-voltage detection system (see “Caring for Your Batteries”) will prevent the pack’s total voltage from
dropping past a certain point (let’s say it’s 3. 3 volts per cell, or 6. 6 volts for a 2-cell pack), the speed control only “sees” the total voltage of the battery, not
the voltage of each individual cell. So, if the pack is unbalanced, that 6. 6 volts might not represent 3. 3 volts per cell; you might actually have one cell at 3. 6
volts, and another at 3V—that cell will be over-discharged, and now your pack is compromised or even ruined. Balancing ensures the cells always have
equal voltage. Happily, balancing is easy to do; in most cases, all you have to do is make certain the pack’s balance plug is plugged into the charger.
CHOOSING A CHARGER
Now that you’re set up with batteries, let’s talk chargers. First and foremost,
make certain that you get a NiMH charger if you have NiMH batteries, and a
LiPo charger if you have LiPo batteries. It is vitally important to get that right.
If you use both types of batteries, there are chargers that can be set for
either battery type. If you go that route, be sure to set the charger for the
correct battery type before you hit the “start” button. As for charger features
to look for, the most important (after determining “Is it the right type for my
battery?”) is amperage. ;e higher the charger’s amp output, the faster it
can charge your pack. ;e math is easy: just divide battery capacity by
charger output. Let’s say you have a 5-amp charger and a 6000mAh battery.
6000 milliamp-hours equals 6 amp-hours. Divide 6 by 5, and you get charge
time in hours: 6 ÷ 5 = 1.2 hours. ;e higher
the amp rate, the quicker the charge time.
Racers use high-powered chargers like this MaxAmps Hyperion EOS 0840i
to blast their batteries at 30A or more. ;is type of charger requires a
separate DC power supply, and a complete setup can cost over $300.
You don’t need this level of gear for fun-running.
Traxxas’ EZ-Peak iD chargers
automatically detect battery
type, cell count, and capacity
when used with Traxxas iD
Some chargers have balancing ports built into the case. ;e small white connector you’ll find on most LiPo packs
is the balance plug. It’s wired so the charger can read each
cell’s voltage individually and charge accordingly.
Chargers designed for packs with more than three cells
typically include a balance board to accept the balance