Science of batteries, speedcontrols, and motors
11-23-2008, 03:08 PM
#2
The resistance value on the batteries tells you how quickly a cell will give up it's energy. The lower the resistance, the more power you can get at once (more punch). This is especially important in spec racing where everyone runs the same motor. This helps boost power to motors at low rpm where current draw from the motor is VERY high maxing out the cells capability to supply power.
The average voltage value tells you how strong the cell is under the specified load (typically 35amps). A higher average voltage will give more power throughout the entire run. This helps later in the run where lesser cells voltage will drop reducing overall power.
Runtime tells you how long, in seconds, the cell is capable of running at the specified discharge amperage (typically 35amps) until the voltage drops too low to produce power. A longer runtime is important for high power motors that use the entire pack in one run. It allows you to gear higher run the motor hotter, or even switch to a more powerful motor...
A good ESC is important because it needs to allow the motor to draw all the power it can from the cells. If the ESC has high resistance, it lets less power through to the motor. Also the motors rated current spec is important. The more current it handle, the cooler it will operate. Also a high current ESC can run hotter motors...
The average voltage value tells you how strong the cell is under the specified load (typically 35amps). A higher average voltage will give more power throughout the entire run. This helps later in the run where lesser cells voltage will drop reducing overall power.
Runtime tells you how long, in seconds, the cell is capable of running at the specified discharge amperage (typically 35amps) until the voltage drops too low to produce power. A longer runtime is important for high power motors that use the entire pack in one run. It allows you to gear higher run the motor hotter, or even switch to a more powerful motor...
A good ESC is important because it needs to allow the motor to draw all the power it can from the cells. If the ESC has high resistance, it lets less power through to the motor. Also the motors rated current spec is important. The more current it handle, the cooler it will operate. Also a high current ESC can run hotter motors...
11-23-2008, 05:30 PM
#3
Ok, I understand a bit more, but what about the Mah rating on the battery? Does this number have to do with more power or more run time, or both? is 3800mih battery better than 5000mih. Back in my days of electric, you'd want the lowest mah rated battery that could make 5 min qualifiers because those batteries usually provided more punch. Is this the case still?
11-23-2008, 09:08 PM
#4
The usual rule is higher is better. The milliamp rating refers to the cells capacity. More milliamps means more runtime. All things being equal, a higher milliamp battery will have higher average voltage at the end of a run. This means it will hold it's power longer than a battery with lower milliamp rating. But of course not all things are created equal. Currently the best racing nimh cells seem to be IB, EP & Ener-G 4600mah...
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