HyperSpeed
Well-Known Member
- Joined
- Jan 21, 2009
- Messages
- 117
- Reaction score
- 8
I find the following to be an interesting topic--as for all of the technology we have available--I have yet to see anyone actually confirm the power being used in cordless electric-powered devices or R/C vehicles which use brushless motors.
When it comes to electric power systems consisting of lithium battery packs feeding power through an ESC and into a brushless motor powerplant; sure, we have ratings on lithium packs that make claims they can output X number of amps. Then we have ratings on the ESCs too, stating they are rated for X amount of continuous amperage and can handle X amount of burst-current for so many seconds. Yet how can we actually verify what is really happening when the devices are being pushed? How do we know we really need the 300A ESC and not the 200A ESC? Sure, the batteries make claims of C-ratings they can deliver, but what do we need to do if we want to see the cold hard data in graphical form from conditions during use, to actually know how many kW a motor is sucking up?
On the other hand, let's say that we have somewhat of a blind system; for example, a power tool like a brushless chainsaw. We may know how many volts the pack is capable of supplying--we may even have looked inside the pack to see what kind of cells it is wired together with internally, and based on manufacturer specs we can also know what those cells are capable of outputting as far as current, but finally we arrive at an enigma of what kind of limiting logic the unknown ESC in the system is programmed with to feed an also unknown specification of brushless motor in such a system. In the end, the best most of us can do is to know that there is a given voltage of battery available, yet we really have no clue as to the kW power the system is actually working with, and as such we really have no idea what device is using that voltage to make any form of comparable power level between them. It seems to be a very crude form of making worthwhile comparisons between products, other than stating the obvious: "The system in competitor A is a 40V system, the other system in competitor B is a 56V system, and competitor C uses an 80V system". That's pretty much it--there's no HP/kW breakdown between them to make a more relative comparison with.
With all of that being said, I would like to take the required steps to figure out how each system is using the available energy to actually produce a real-world power figure. I would like to know what I could potentially gain by using a different ESC in the system, for example.
So let's hear it; what does one need to do to know how they can potentially modify a power system to unlock more available energy from the cell pack?
I had an idea that is rather crude, but straightforward in the general sense, I believe. Use a hi-amp meter with a shunt rather than a fuse, and install short, heavy gauge power wire between the pack and the ESC input side, then run the device under maximum expected load in use, and record peak amperage levels witnessed. Then repeat the test while monitoring the voltage levels from the pack as they sag under the same device loads. Take the standard calculation for wattage, V*I, and the wattage levels before efficiency loses will then be known. The only problem here is this doesn't tell us the power made by the system, but rather the power used by the system. I don't know how efficient most brushless ESCs are in delivering this power to the motor, but I would assume it would at least tell something about the system power for a start, which is a lot better than knowing nothing at all.
I would like to upgrade the ESC and motor in one of my power tools, as from a first glance, it is probably heavily limiting the potential power being fed to the brushless motor--probably for the sake of run-time and user safety. I have made this assumption by first noticing the small-gauge power wires between pack and ESC, as well as between ESC and motor. If this were an R/C car, there is no doubt that those wires would be much heavier to minimize as much resistance as possible. This is why I feel there is probably much power to be gained from the tool I seek to gain more power from. Let's face it, chainsaws are probably the number one tool out there that users seek more power from.
When it comes to electric power systems consisting of lithium battery packs feeding power through an ESC and into a brushless motor powerplant; sure, we have ratings on lithium packs that make claims they can output X number of amps. Then we have ratings on the ESCs too, stating they are rated for X amount of continuous amperage and can handle X amount of burst-current for so many seconds. Yet how can we actually verify what is really happening when the devices are being pushed? How do we know we really need the 300A ESC and not the 200A ESC? Sure, the batteries make claims of C-ratings they can deliver, but what do we need to do if we want to see the cold hard data in graphical form from conditions during use, to actually know how many kW a motor is sucking up?
On the other hand, let's say that we have somewhat of a blind system; for example, a power tool like a brushless chainsaw. We may know how many volts the pack is capable of supplying--we may even have looked inside the pack to see what kind of cells it is wired together with internally, and based on manufacturer specs we can also know what those cells are capable of outputting as far as current, but finally we arrive at an enigma of what kind of limiting logic the unknown ESC in the system is programmed with to feed an also unknown specification of brushless motor in such a system. In the end, the best most of us can do is to know that there is a given voltage of battery available, yet we really have no clue as to the kW power the system is actually working with, and as such we really have no idea what device is using that voltage to make any form of comparable power level between them. It seems to be a very crude form of making worthwhile comparisons between products, other than stating the obvious: "The system in competitor A is a 40V system, the other system in competitor B is a 56V system, and competitor C uses an 80V system". That's pretty much it--there's no HP/kW breakdown between them to make a more relative comparison with.
With all of that being said, I would like to take the required steps to figure out how each system is using the available energy to actually produce a real-world power figure. I would like to know what I could potentially gain by using a different ESC in the system, for example.
So let's hear it; what does one need to do to know how they can potentially modify a power system to unlock more available energy from the cell pack?
I had an idea that is rather crude, but straightforward in the general sense, I believe. Use a hi-amp meter with a shunt rather than a fuse, and install short, heavy gauge power wire between the pack and the ESC input side, then run the device under maximum expected load in use, and record peak amperage levels witnessed. Then repeat the test while monitoring the voltage levels from the pack as they sag under the same device loads. Take the standard calculation for wattage, V*I, and the wattage levels before efficiency loses will then be known. The only problem here is this doesn't tell us the power made by the system, but rather the power used by the system. I don't know how efficient most brushless ESCs are in delivering this power to the motor, but I would assume it would at least tell something about the system power for a start, which is a lot better than knowing nothing at all.
I would like to upgrade the ESC and motor in one of my power tools, as from a first glance, it is probably heavily limiting the potential power being fed to the brushless motor--probably for the sake of run-time and user safety. I have made this assumption by first noticing the small-gauge power wires between pack and ESC, as well as between ESC and motor. If this were an R/C car, there is no doubt that those wires would be much heavier to minimize as much resistance as possible. This is why I feel there is probably much power to be gained from the tool I seek to gain more power from. Let's face it, chainsaws are probably the number one tool out there that users seek more power from.
Last edited: