This question is part of a long-winded way of working out the maximum working-under-duress current-load on a 3S Li-Ion battery from a 10.8v/12vMax Dewalt Drill.
The replacement motor for the drill is a Mabuchi RS-550VC-8518. I've hunted high and low for a data sheet but the motor seems too old to have one available. Various listings I've found for these specific motors on E-Bay and the like list the stall current at any where from 3.0 Amps to 10 Amps (with no torque figures given…), while the closest wind I can find on Mabuchi's site (RS-550VC-7525) is rated at a wooping 85A/549nM.m stall and a similar Kysan motor (RS-550SH-7524) is rated at 32.4A/117.6nM.m stall.
Firstly, can both the figures for the RS-550VC-8518 and RS-550SH-7524/7525 be correct? ie: is there something about DC motors at this scale that could account for such a huge difference in stall current with that amount of difference in wind spec? (I'm more used to 130/180 sized motors…)
If not, which figure is more likely to be correct? 3-10A or 32A or 85A?
Best Answer
If you are searching a replacement motor, then you should firstly check if the dimensions match.
The second importan thing is that you may have already discovered is that the same size motor can have different specification, how come? It's because of the different windings, that motor is built for.
Same size means almost same nominal power, but different nominal working points are possible.
How you'll find almost equal motor? By choosing one with same motor constants kt- torque constant or kv-voltage constant. Note: these two constants are the same, just fliped arround, so if you identify one of them you are done.
kt - torque constant A/Nm.
Mabuchi:
At the stall point the kt tends to be lower due to core saturation, so compare whatever you have for equivalent.