Kingsong to Gotway power conversion factor?

[chrisjunlee]

A while back @US69 mentioned Gotway inflates their power values by reporting the current behind MOSFETS, while Kingsong doesn't (I still don't understand why that would matter).

How do you convert between the two? Is there a way to calculate a common amperage/power draw, let's say, from a common point (e.g. the battery)?

[meepmeepmayer]

Who cares?

But ride up the same hill at the same speed and compare the power numbers. Then you have your factor.

Not that it matters

[Chriull]

1 hour ago, chrisjunlee said:

How do you convert between the two? Is there a way to calculate a common amperage/power draw, let's say, from a common point (e.g. the battery)?

Yes. But its not really easy and one has to know various wheel parameters. Here and the following posts are the details:

 

[chrisjunlee]

5 minutes ago, meepmeepmayer said:

Who cares?

But ride up the same hill at the same speed and compare the power numbers. Then you have your factor.

Not that it matters

Because data. If you don't care, it's not something I can explain, nor does it matter to you 

@Jon Sternhow would you explain this without sounding condescending? 

[chrisjunlee]

16 minutes ago, Chriull said:

Yes. But its not really easy and one has to know various wheel parameters. 

My question is simpler: How does Kingsong and Gotway measure current differently? 

@US69specifically said Gotway measures right behind MOSFETS, and that explains the 10x differences in current readings. That makes no sense to me.

[Chriull]

41 minutes ago, chrisjunlee said:

My question is simpler: How does Kingsong and Gotway measure current differently? 

@US69specifically said Gotway measures right behind MOSFETS, and that explains the 10x differences in current readings. That makes no sense to me.

All the wheels measure the motor phase currents - normally 2 of the three phase currents, as their sum is always zero. They need it for the self-balancing algorithm.

It is assumed that Gotway reports somehow these phase currents. The meaningfull value to calculate power would be the effective value (true rms) of these three phase currents.

Noone knows by now (at least i did not read about any tests/investigations/etc) regarding which value (with which error factor) is reported exactly by GW wheels.

@US69 got from Kingsong technicians that KS wheels measure directly the battery current.

As described in more detail in my above link U_battery * I_battery = U_motor * I_motor (not regarding the losses in the electronics). If one is interested in the output power of the motor this would be U back emf * I_motor = (U_motor - R coil*I_motor) * I_motor (mechanical power, not regarding internal motor losses like ferromagnetic losses, etc or the motor inductance - just ohmic losses at the coils regarded, with U back emf as the generated Voltage by the motor = kv * rpm).