wlfk
12-16-2007, 12:57 AM
Apologies to any of you who may have read this thread on the other forum. I thought I'd post it here to see whether any of you can shed light on the matter:
Everybody raves about high-voltage setups - whether it's 4s on a T-Rex 450 or 10S on a 600...
Now basic maths would suggest that a 3s 2100mAh pack would weigh about the same as a 4s 1575mAh pack; that it would store the same energy; that it would provide the same power (assuming an identical 'C' rating). So why the difference?
~~~~~~~~
One explanation I've heard is that the wiring and connectors can be less heavy-duty at high-voltages, thereby saving weight. I'll admit I'm sceptical about this - after you've installed a slightly beefier ESC I can't see that the difference is more than a few grams.
On the other hand, you have to run a lower KV motor to make use of the higher voltage. Low-voltage motors need more copper turns which I assume means the ratio of copper:insulator goes down, which can't be good.
I can see how, weight for weight, a smaller motor running at higher RPM might be able to put out more power - in the same way as a high-frequency transformer can be made smaller than a low-frequency transformer. So perhaps what we really want to do is to aim for smaller sizes of pinion and run motors closer to their RPM limits? On the other hand, I assume this also reduces gear-efficiency to some degree.
:)Are the differences people are seeing simply down to the fact that they're actually carrying a heavier pack and can therefore run at higher power levels?
:)Is it that people are running lower governor settings, so there's more headroom to prevent bogging under power?
:)Is there any theoretical basis for deciding on the best voltage/amperage ratio - given that you can choose the other components to match?
:)Are higher-voltage setups really so great?
I'm asking this question mostly on a theoretical level, though I do have a specific interest: a Mikado Logo 600dx. At the moment I'm tending towards 7s2p A123 with a Z-Power 1150kV motor. But I could go all the way up to 10s2p if I thought it was worth the trouble and expense. Or even 14s1p - which I think would reach the limit of a Jazz ESC.
K
Everybody raves about high-voltage setups - whether it's 4s on a T-Rex 450 or 10S on a 600...
Now basic maths would suggest that a 3s 2100mAh pack would weigh about the same as a 4s 1575mAh pack; that it would store the same energy; that it would provide the same power (assuming an identical 'C' rating). So why the difference?
~~~~~~~~
One explanation I've heard is that the wiring and connectors can be less heavy-duty at high-voltages, thereby saving weight. I'll admit I'm sceptical about this - after you've installed a slightly beefier ESC I can't see that the difference is more than a few grams.
On the other hand, you have to run a lower KV motor to make use of the higher voltage. Low-voltage motors need more copper turns which I assume means the ratio of copper:insulator goes down, which can't be good.
I can see how, weight for weight, a smaller motor running at higher RPM might be able to put out more power - in the same way as a high-frequency transformer can be made smaller than a low-frequency transformer. So perhaps what we really want to do is to aim for smaller sizes of pinion and run motors closer to their RPM limits? On the other hand, I assume this also reduces gear-efficiency to some degree.
:)Are the differences people are seeing simply down to the fact that they're actually carrying a heavier pack and can therefore run at higher power levels?
:)Is it that people are running lower governor settings, so there's more headroom to prevent bogging under power?
:)Is there any theoretical basis for deciding on the best voltage/amperage ratio - given that you can choose the other components to match?
:)Are higher-voltage setups really so great?
I'm asking this question mostly on a theoretical level, though I do have a specific interest: a Mikado Logo 600dx. At the moment I'm tending towards 7s2p A123 with a Z-Power 1150kV motor. But I could go all the way up to 10s2p if I thought it was worth the trouble and expense. Or even 14s1p - which I think would reach the limit of a Jazz ESC.
K