I’ve done motor spreadsheets before, but now I’m considerably smarter. If you don’t believe me, just ask me. I’ll tell you. Honest I will.

Anyway, what with all this noise I’ve been making about dual motors and such, it’s come to my attention that it’s a pain in the butt to set up a dual PMDC motor array with a single controller in parallel. You, at the very least, need to have matched motors (which makes perfect sense, when you think about it), and then need to further tune them to keep them from burning themselves up. Running two controllers gets things a little easier to balance, but you still have to have the motors pulling the same, and now you’ve added another controller system, adding weight and more stuff.

So, this begs the question. What about just putting on a bigger motor, rather than doubling up a small motor? Which begs a spreadsheet.

Here are the motors I’m considering- the Motenergy ME1003, the ME0709, the ETEK, two ETEKs, and, just for yuks, that badass new AC motor that Zero has modified.

Motor Type | Cont. | 30 sec. | Voltage range | Amps Cont. | Amps Peak | Max RPM | Weight | Notes | |

Brushed DC | |||||||||

ME1003 | Brushed PMDC | 11.5 KW | 23 KW (1 min) | 12 to 72 VDC | 200 | 400 (1 min) | 5000 @ 72V | 39lbs | Radial air gap |

ME0709 | Brushed PMDC | 6 KW | 13.4 KW | 12 to 72 VDC | 125 | 300 (30 sec) | 3200 @72V | 36lbs | Radial air gap |

ETEK | Brushed PMDC | 7.2 KW | 21.6 KW | 72 VDC* | 100 | 300 (30 sec) | 5000 @ 74V | 21lbs | Axial air gap |

2x ETEK | Dual Brushed PMDC | 14.4 KW | 43.2 KW | 72 VDC* | 200 | 600 (30 sec) | 5000 @ 74V | 42lbs | |

Agni 95R | Brushed PMDC | 12 KW | 30 KW (1 min) | 12 to 72 VDC | 230 | 400 (1 min) | 6000 @ 72V | 24lbs | Axial air gap |

2x Agni 95R | Dual Brushed PMDC | 24 KW | 60 KW (1 min) | 12 to 72 VDC | 460 | 800 (1 min) | 6000 @ 72V | 48lbs | Axial air gap |

AC | |||||||||

ME0913 | 3-phase PM Synchronous | 12 KW | 30 KW | 0 to 96 VDC | 125 | 420 (1 min) | 5000 @ 96V | 35lbs | Axial air gap, internal temp. sensor |

**rated at 48 VDC, but typically overvolted to 72 VDC*

Huh. Interesting. At the published specs, the ETEKs don’t hold up. At these specs, they look pretty impressive… the million dollar question being, how long do they last at these loads? Wait. Sounds like we need to do a little blowing up of motors maybe. (Who says Mythbusters has the corner on the blowing up of stuff market?)

The ME1003 holds it’s own against the Agni, but at more weight (and half the price). The ETEK doesn’t hold up too well against the Agni, an interesting point, since the designs are so similar… so dual ETEKs ≠ dual Agnis. The solid ol’ ME0709 looks pretty conservative in this company.

…

*(disclaimer: specs are the best I could find. If you have better ones and feel these are not accurate, feel free to comment with links. kthnx.)*

Agni 95R is 12-16kW cont and 30kW peak http://www.agnimotors.com/home/index.php?option=com_content&task=view&id=5&Itemid=60

Also the etek on 72V will give higher cont and peak numbers.

72V*300A = 21.6kW peak

72V*100A = 7.2kW cont

I think it makes sense to compare all the motors at 72V which is the pack voltage you run I believe. You could just multiple 72V by the cont amp and peak amp to get cont and peak power values. Eff will be a little bit different, but doesnt matter too much in this simple comparision.

-Kyle

Thanks, Kyle! I’ll update it asap.

I do want to add… I’m not at all confident that the ETEK can withstand 300amps at 72V for even 30sec. But I did update the specs with those numbers, since it’s commonly held belief.

Yea it seems keeping the RPM below 5000 (~72V) is a must for the etek, but the losses at that RPM may overheat the motor…

Good etek data here http://www.thierry-lequeu.fr/data/Briggs/EtekSpecs.htm and this link on that page http://www.thierry-lequeu.fr/data/Briggs/EtekSpecs.htm#Page4

Nice work! I would though replace the Amps column by torque; Amps alone mean nothing and comparing different motors. I have data for these motors:

eTek: 0,129 Nm/A

ME708: 0,132 Nm/A

ME709: 0,192 Nm/A

ME909: 0,119 Nm/A

ME1004: 0,127 Nm/A

Lynch 170-127: 0,12 Nm/A

Perm132: 0,178 Nm/A

Most values I found by graphically finding as accurately as possible the derivative of the Amps motor curves provided by the manufacturers. The value for the eTek is stated 0.13Nm in B&S motor datasheet, but converting from ft.lbs, the original measuring unit, is 0.129 Nm/A (and matches the graph analysis). I collected this info to do calculations to help me pick a motor for my bike conversion, which is all we can do without actually testing the things…

Sorry, I meant “Amps alone mean nothing when comparing different motors.” . And my suggestion is then to multiply current by the torque constant; then the different sets are comparable. You can play with the gearing to find a torque – max speed equilibrium. In my comparison I use a max value (can be used to start) and a continuous value.

Yes, I think there has to be some mention of torque… Thanks for the information sir! I’ll take a look at improving this information.

Hi, I was just thinking about the probs with running two PMDC motors in parallel and I thought, ‘what if you connect them to the drive shaft through a differential?’. Then, if one has slightly more RPM per volt, it won’t matter as long as they’re putting out pretty much the same torque and, as torque increases as you slow the motor down under load, they should equalise…Yes? No? Maybe?… Anyone tried it?