23LikesRunning a speedo without a capacitor?
08-28-2021 | 09:36 PM
#31
Suspended
iTrader: (1)
Joined: Jun 2008
Posts: 561
To pressure test the resistance aspect, let's consider a super-old 45 amp hobbywing esc, and consider that a worst-case scenario.
https://www.amainhobbies.com/hobbywi...qztswqlcqxactz
Its resistance is listed as 0.0006 ohms.
Voltage drop = current * resistance, let's assume it's operating at its max 45amp capacity.
Vdrop = 0.0006 * 45 = 0.027 volts
At my club, we charge 2S batteries to 8.4 volts.
0.027 / 8.4 = 0.3%.
So let's say a very expensive ESC can deploy twice the FETs to lower resistance by half.
We'd be talking about a 0.15% improvement.
I seriously don't think human perception feel changes that small. And even if it theoretically does improve lap times, surely there are better ways to chase laptimes per dollar?
https://www.amainhobbies.com/hobbywi...qztswqlcqxactz
Its resistance is listed as 0.0006 ohms.
Voltage drop = current * resistance, let's assume it's operating at its max 45amp capacity.
Vdrop = 0.0006 * 45 = 0.027 volts
At my club, we charge 2S batteries to 8.4 volts.
0.027 / 8.4 = 0.3%.
So let's say a very expensive ESC can deploy twice the FETs to lower resistance by half.
We'd be talking about a 0.15% improvement.
I seriously don't think human perception feel changes that small. And even if it theoretically does improve lap times, surely there are better ways to chase laptimes per dollar?
08-29-2021 | 01:45 AM
#32
Tech Lord
Joined: Aug 2007
Posts: 14,051
From: Holland
To pressure test the resistance aspect, let's consider a super-old 45 amp hobbywing esc, and consider that a worst-case scenario.
https://www.amainhobbies.com/hobbywi...qztswqlcqxactz
Its resistance is listed as 0.0006 ohms.
Voltage drop = current * resistance, let's assume it's operating at its max 45amp capacity.
Vdrop = 0.0006 * 45 = 0.027 volts
At my club, we charge 2S batteries to 8.4 volts.
0.027 / 8.4 = 0.3%.
So let's say a very expensive ESC can deploy twice the FETs to lower resistance by half.
We'd be talking about a 0.15% improvement.
I seriously don't think human perception feel changes that small. And even if it theoretically does improve lap times, surely there are better ways to chase laptimes per dollar?
https://www.amainhobbies.com/hobbywi...qztswqlcqxactz
Its resistance is listed as 0.0006 ohms.
Voltage drop = current * resistance, let's assume it's operating at its max 45amp capacity.
Vdrop = 0.0006 * 45 = 0.027 volts
At my club, we charge 2S batteries to 8.4 volts.
0.027 / 8.4 = 0.3%.
So let's say a very expensive ESC can deploy twice the FETs to lower resistance by half.
We'd be talking about a 0.15% improvement.
I seriously don't think human perception feel changes that small. And even if it theoretically does improve lap times, surely there are better ways to chase laptimes per dollar?
And there comes the stupidity of more than 90% of the drivers thinking that they can buy laptimes to get to the top while getting close to the top is for 99% with the skils of driving and the setup of the car.
08-29-2021 | 04:19 AM
#33
Got my work done (so my boss is happy) and got some chores done (so my other boss is happy) and after a nice Sunday night dinner, got out the scope to zoom in a bit:
The double-sided cap board does a better job of keeping ripple down, but voltage sag is close to 20mV in both cases, so really, nothing to really worry about. Yes, the standard cap does dip a bit more, but we're in single digit mV territory. I've got one other idea to try, but will take a few days for some parts to arrive...
FWIW - the quoted resistance in ESC brochures can be taken with a grain of salt. As gigaplex points out, software and overall design are crucial and they cost money.
The double-sided cap board does a better job of keeping ripple down, but voltage sag is close to 20mV in both cases, so really, nothing to really worry about. Yes, the standard cap does dip a bit more, but we're in single digit mV territory. I've got one other idea to try, but will take a few days for some parts to arrive...
FWIW - the quoted resistance in ESC brochures can be taken with a grain of salt. As gigaplex points out, software and overall design are crucial and they cost money.
08-31-2021 | 11:57 AM
#35
Very cool exercise PDR! Keep that data coming! :-)
I was wondering the exact same thing. What if you put a serious load through the system. 3.5T is maybe overdoing it a bit but 5.5T or 6.5T would be very interesting.
I was wondering the exact same thing. What if you put a serious load through the system. 3.5T is maybe overdoing it a bit but 5.5T or 6.5T would be very interesting.
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