Is BMC V4 really more efficient than V2?

I was curious and compared latest V2T (with V4 clutch and doubled phase wires) and V4T side by side, ran only a few tests, wouldn't say my testing was thorough, because not all planned tests were completed (different amps, load, rpm, etc...), but according to the data I was able to collect, there doesn't seem to be any difference. Seems V2T and V4T is the same motor only V4T is more expensive. But if higher top speed motor is desired, there is no other choice than V4C or S because V2S (similar to V4C) and V3 (similar to V4S) have been discontinued.

Tests were conducted up a quarter mile hill with varying grade, used Lyen Mark2 controller limited to 30A, 16S LiFePO4, 26" wheel, big dummy frame, CA with datalogger. Here is the data from CA datalogger:

http://www.ebikessf.com/sites/default/files/images/endless-sphere/V2t-vs-V4T-hill-30A.xls

I will run more tests with torque, cruiser and speed motors, but suspect claims of up to 10% increase in efficiency are false.

Yeah, I've been wondering if there were any significant changes. Unless they actually changed the stator or mechanical layout. It would appear to be the same motor. They screwed up with the V3 wind by having too low of a resistance and went back to the V2 it seems. You can only push that motor so far unless a total redesign is implemented which seems unlikely. The V2 series were already optimally wound. It seems more of a marketing ploy, but it's nice to see bigger phase and better components to handle the power, making the windings more the failure point. Your going to still have to watch the power levels.

I would like a side by side comparison of the internals. All the hype on the new motor is just pushing sales.

Mmmmmhm... i did suspect that these claims were false as soon as hi-power cycles mentioned them.
A 10% efficiency increase in any hub motor does seem very unrealistic.

What i'd like to see is if there is actually more copper in the motor as stated.

I do think that the limits of the MAC/BMC motors was reached long ago & all the little upgrades since then have just been a way to justify skyrocketing neo magnet prices. What we need is the crystalyte 5xxx equivalent of a geared hub, don't you think?

neptronix said:

I do think that the limits of the MAC/BMC motors was reached long ago & all the little upgrades since then have just been a way to justify skyrocketing neo magnet prices. What we need is the crystalyte 5xxx equivalent of a geared hub, don't you think?

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the beauty of BMC is the weight , only 4kg..
But yes i was also wondering why not try doing huge geared hub motor at 10kg or so !!!

BMC, MAC, of all generations.. between 3.8-4.0KG

Not a lot of improvements in the geared world, other than better gears. We've definitely been neglected :/

neptronix said:

BMC, MAC, of all generations.. between 3.8-4.0KG

Not a lot of improvements in the geared world, other than better gears. We've definitely been neglected :/

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Yes I hear ya.... clutch and composite gears seem to have been the focus of improvments of these geared hubbies for a while until the V4 appeared with its (supposedly) beefier phase wires.

Still... I'll take an 7.8 pound BMC, MAC motor that freewheels any day. Might not seem like a big weight difference from 12-13 pound DD motors I used to run but that weight really does make a difference. I also luv to pedal so I luv that freewheel. It's perfect for my purposes in making a commuter ebike (not e-motorcycle) mainly for the street.

ebikes-sf said:

I was curious and compared latest V2T (with V4 clutch and doubled phase wires) and V4T side by side, ran only a few tests, wouldn't say my testing was thorough, because not all planned tests were completed (different amps, load, rpm, etc...), but according to the data I was able to collect, there doesn't seem to be any difference. Seems V2T and V4T is the same motor only V4T is more expensive. But if higher top speed motor is desired, there is no other choice than V4C or S because V2S (similar to V4C) and V3 (similar to V4S) have been discontinued.

Tests were conducted up a quarter mile hill with varying grade, used Lyen Mark2 controller limited to 30A, 16S LiFePO4, 26" wheel, big dummy frame, CA with datalogger. Here is the data from CA datalogger:

http://www.ebikessf.com/sites/default/files/images/endless-sphere/V2t-vs-V4T-hill-30A.xls

I will run more tests with torque, cruiser and speed motors, but suspect claims of up to 10% increase in efficiency are false.

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Ilia,

Thanks for sharing your test results. Is there anything you observe about the V4 when it's running that would indicate that the wider composite gears and clutch are any better than the V2? Like does the V4 growl any less than the V2 at slow speeds <5mph?

Sacman Ilia is opening a new shop and doesn't get time to follow, but you can email at ebikessf.com.

999zip999 is right, ilia is super busy with his new shop and I went his new shop yesterday. I can see him busy with the organize around the shop while I installed on my Yuba's MagicPie motor with a new DNP freewheel in his shop.

Just email ilia and he will respond to your email.

I am thinking rid MPIII motor to BMC V4T for the hilly climb capability.

Really? Ilia is moving out of the 2nd floor loft workshop with the nice window view of the SF Bay? Well that's good I guess I hope his new location works out well. Thanks for the info guys. I'll email him directly.

Yep, it was too small loft and too narrow stair hassle carry any packages or bicycle such cargo bike so ilia moved new location (I guess). It really NICER spacious room and comfortable place. I like the new location bit father out the SF downtown.

Just adding an extra piece of information to the thread that may support the claim the BMC V4 may be more efficient than the V2, (at least the V2S vs V4S) .

I've just recently got a hold of a couple of cooked BMC motors, a V2 and the other a V4

After opening both motors up it quickly became obvious the V4 stator is quite different to the V2. Both stators are 36 teeth, but the V4 has 2mm longer stator teeth, so has more copper. The second difference is the V2 has 0.5mm laminations versus 0.35mm laminations for the V4 (may not be clear from the picture as the V4 has an unusual stamping pattern)



The efficiency differences between the motor would only probably become more apparent in the V4S compared to the V2S, where iron losses would start to take effect at higher electrical rpm.

Interesting! thanks for the info!!
Cell_man also is selling the MAC motors with an upgraded stator, but there is no indication on how it is upgraded. Maybe the same way.

Given the high pole count plus high RPM of these motors, i can see how thinner laminations would be beneficial.
Especially if you are running a wheel size lower than 26".

Just 1-2% more efficiency can mean for less heat created, which is what these geared motors really need since all geared designs shed heat poorly.

10% better efficiency was always going to be a physical impossibility.

We are talking a maximum difference of about 1%, you are likely to see a much bigger (practical) efficiency difference just by choosing the right gearing or winding for the speeds you travel at.

We are talking a maximum difference of about 1%

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Hi Architectonic , The V4 BMC stator teeth measured 10% longer than the V2 BMC stator teeth, and so copper fill is correspondingly more. Brian is just trying to clear up that not all BMC's have .35mm laminations (a perceived advantage over, the less than half the price Mac motors) and It appears only the V4 has this advantage of the thinner laminations. Stator dimensions are 130mm OD by 20mm stator length. So has some potential for single reduction kart chain etc. The bare motor was approx 2.2 kg (by my beer smeared memory?) And i thought it had 36 teeth Brian? If you are going to volt up the $35 extra over the V2 seems well spent. But they are probably not $335 more motor than Cell Mans Mac's.
Brian stop pissing around with sinister siamese surgery plans and other dud motors, get that Joby going!
Zappy

.

zappy said:

And i thought it had 36 teeth Brian?

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ah yeah, one too many beers methinks 32 pole 36 teeth

yep, much better to piss around with the Joby!

It's very hard to properly field test for efficiency. So many extra variables. I'm sure the right test would stall one motor, while the more powerful motor doesn't quite stall. Bingo, 10%. Clearly, a motor that stalls less on a given hill is the more efficient one, for that particular grade. So go ride where there is only one kind of hill and you are good to go.

I have two ways to instantly know if a motor is less efficient, at a particular moment.

1 It makes me go faster.

2 It gets hotter, gets hot faster.

Either one can easily add up to much more than 10% Once cruising at a set speed all the motors in the test are capable of, on similar bikes, in similar weather, I find measuring any difference very hard to do. The difference has always been very small with the motors I've experienced. Measuring how efficient stops and starts are is easier, but still requires about 10 miles of stop and go riding for the difference to really show.

Mostly, I find the slower windings to be the better efficiency, for the particular kind of riding I tend to do. But only if they are ridden in their efficient rpm, just like any motor. Hop em up to 30 mph, and they don't seem so efficient after all. (reason 1) Less heating climbing hills, but you can still make enough heat to melt one on a big enough steep enough hill. Or slog through enough deep sugar sand.