Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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The IBC is rated to handle ~36v. It will take voltages a bit higher than that, but you need to allow for the fact that freshly charged 36v packs will come off the charger at a higher voltage than their rated voltage.
For an *equivalent* amount of power, its better to make it with a higher voltage and less amps, than a lower voltage with more amps, since voltage doesnt produce heat in the IBC, but amps do. The power dissipation of the IBC's Fets is directly related to the amps passing through them, whereas an increase in voltage doesnt bother it at all (provided you stay under the rated voltage).
So in that respect, if you want more power, you are better off overvolting 12.4v drills to 24v than you are taking 9.6v drills to 18v say. In both cases, you are doubling the volts (and hence the amps), but one nets you more power..
As an example (ignoring efficiencies for now) if you were using 10amps at 12v on a drill motor, thats 120 watts of power (watts=volts x amps), and you double the voltage to 24v, you now flow 20 amps of current for 480 watts of power, or an extra 360 watts for an increase of 10 amps of extra load (heat) on the controller.
If you are running a 9.6v drill that produces 120 watts (the same as above) of power, that must be using 12.5 amps (more amps for the same power), which is immediately heating the controller more, and we now double the voltage to 18v, the current doubles to 25 amps but we are only getting 450 watts from the motor but putting an even higher stress on the controller. To get 480 watts of power at 18v you need to be using 26.6 amps or more than 6amps extra than you would at 24v.
Thats a little vague I know, but the bottom line is that higher voltage lower current motors will produce more power with less stress on your controller than lower voltage higher current motors will.
Running higher voltages and lower currents have other benefits as well with small voltage drops along your wiring and connections causing less of a power loss than they would at lower voltages and higher currents.
Also, the lower current demmands on your batteries will mean they will last longer than lower voltage batteries being asked to put out more amps will.
The main drawback of higher voltages is of course you need more cells to produce it, and you need motors that will take the voltage without melting down..
for anyone interested in fiddling about with this osr tof thing, the team tentacle torque/power calculator at
http://4.47.235.131/tcr/torquecalc.htm
can be very informative. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
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