B&B Electronics Parallel Printer Card PIOC Manual do Utilizador descarregar pdf (Página 33)

A pack or cell powering a load can be approximated by a voltage source in series with a

resistance, delivering power to a load, such as a motor. Ohm’s Law

Voltage (volts) = Current (amps) x Resistance (ohms)

tells us that current will decrease when resistance increases. Lower current means in turn

a lower voltage delivered to the motor, which means less power delivered to the wheels.

So, it follows that one important way to compare packs is to measure it’s actual internal

resistance.

It’s called actual internal resistance to distinguish it from relative internal resistance,

mentioned elsewhere in this manual.

In the T35-GFX, actual internal resistance is measured by briefly altering the current at a

predetermined time during the discharge process, and recording the voltage. Having

voltage and current for two different currents, the actual internal resistance can then be

calculated.

From Ohm’s law:

So it follows that:

This is the basic math used by the T35-GFX to calculate actual internal resistance.

The T35-GFX presents actual internal resistance in milliohms. Lower is always better.

Below discharge rates of 5 amps, actual internal resistance measurements cannot be made

with the T35-GFX.

Other Features

Viewing the Discharge Graph

While the discharge cycle is in process,

pressing the MODE button will toggle

back and forth between the main

discharge screen and the real-time

discharge graph. More will be said

about the graphing feature later in this

document.

Figure 15. Typical discharge graph.

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B&B Electronics Parallel Printer Card PIOC Manual do Utilizador Página 33