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Robot Battle Battery Packs and 1/2 D Cells

No longer available, sorry
Galactic Power PowerStream has developed custom NiCad cells for warrior robots.
Size Capacity Internal Resistance Weight
1/2 D RW 33 dia x 37 mm 2.5 AH 7 mOhms 81 grams
Ordering Info Single Cells Solder Tabs Single Cells Flat Top 12 Volt Packs
Part Number PST-halfD-ST PST-halfD-FT PST-halfD-10cell
Half D cells custom engineered for battle robots.

Custom design and manufacture of state-of-the-art battery chargers, UPS, battery packs and power supplies for OEMs in a Hurry

Do you want 40 amps from an 81 gram, 1.2 volt cell?

Ours do 98 amps!

Do you want to charge fast?

How About 15 minutes? Go to charging curve (latest tests show no degradation in performance and only slight temperature rise at a charge rate of 4 C. Further tests continue.)

We have asked our factory to develop a custom-engineered ½ D cell for high current capability specifically for the battle robot industry. These are nominally 2.5 AH capacity.

We were getting 98 amp pulses before all the MOSFETs in our constant current load blew out. Unfortunately this data wasn't logged.

Current Discharge
(amp Hours)
Percentage of
Nominal AH
2 Amps C/1.25 2.47 100% Continuous
10 Amps 4C 2.45 99% Continuous
20 Amps 8C 2.15 87% Continuous
30 Amps 12C 2.40 97% Pulsed
40 Amps 16C 2.37 96% Pulsed
50 Amps 20C 2.35 95% Pulsed
60 Amps 24C 2.16 87% Pulsed
70 Amps 28C 2.00 81% Pulsed

This is the significant data. As you can see, even at high currents the battery retains a significant proportion of its nominal capacity. Pulsed means 2 seconds on, 8 seconds off. We did the measurement this way because we didn't want to damage our constant current load.

Note that even though the capacity in Amp Hours is maintained, the cell voltage is not. The following curves give the data. The data below were taken from the same 10 cell pack, charged at about C/3. Cells were allowed to cool before charging.

This curve is a C/1.25 rate, and still has 100% of the rated capacity.

The 10 Amp, or 2.5C discharge curve, showing 99% of rated capacity..

Battle Robot Batteries at 20 Amps discharge

This curve shows an 8C discharge rate. Capacity to 0.9 volt per cell is 87% of rated.

This curve shows the discharge and voltage swings under 30 amp pulses. The duty cycle is 20%, consisting of 2 seconds on and 8 seconds off. As can be seen, the voltage swings are about 0.2 Volts per cell for most of the discharge, but towards the end of the test the voltage drop increases. At a bottom voltage of 6 volts the test was cut off because the temperature rise changed slope, indicating that something new was happening. There are 129 pulses above 9 volts, and 142 pulses above 6 volts.

This is the first 5 pulses of the 30 amp pulse test, showing the shape of the pulse and the recovery level.

This curve repeats the pulsed data for 40 amp discharge. In this case the voltage sag starts off to be about 0.3 volts per cell. There are 78 pulses above 9 Volts and 105 pulses above 6 volts.

The first 6 pulses of the 40 amp pulse test.

At 50 amps per pulse the voltage sags about 0.4 volts per cell. There are 44 pulses above 9 volts, and 83 pulses above 6 volts.

The first 5 pulses of the 50 amp test.

The first 5 pulses of the 60 amp pulse test.

The 70 Amp pulse test shows a swing of about 0.5 volts per cell. There are 51 pulses above 6 volts.

The first 5 pulses of the 70 amp pulse test.
Charging curve at 10 amps terminates at about 93 degrees F.
Charging at a 4 C rate works very well. There are some subtleties about terminating when charging at this rate, so contact us for more information. Charging at higher rates should be possible. The charge terminates at 18 minutes, with the final cell temperature at about 93 °F.
For a chart of the sizes and weights of cylindrical batteries click here: Battery size chart
For more battery engineering resources click here: Battery Engineering Resources

Note: We don't inflate our specifications as many companies do. The capacity in amp-hours is guaranteed, and will be exceeded most of the time. "Usable cycles" is unknown under these abusive conditions

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