Help Me install BPM axle

[d8veh]

The controller has a pair of white wires for speed limit. Did you leave them disconnected?

You can get a bit more speed by connecting the black and green wires on the three-speed switch connector.

Your speed calculation is correct.

Your controller will give 30 amps when starting and hill-climbing. That's much too much for a 10aH battery. Expect it to cut-out on hills. It shouldn't affect top-speed, because the current goes down to zero as you approach top-speed. The KU93 would be a better controller for that battery, but at 22 amps, it's still a little high. A 15aH battery would've been better.

When I mounted my plate, the fixings put it under tension so wasn't quite straight. It made the battery a tight fit so that it didn't rattle. I had to adjust the bolts to get the right curve in the plate because with too much curve, you can't get the battery in. You could try adding additional struts to the back of the plate. If you make them a little too short, when you tighten the fixing screws, it'll induce the right curve in the plate.

 

[Beagle123]

Hi Dev8:

As usual, you're exactly right. I was thinking about bending the plate to eliminate the rattle, but I didn't know if it would work. I may just try denting the edges to make it tight. Its nice to know that I'm not just wrecking my new battery.

I checked the white speed-control wires already. They're disconnected.

I will try to see what happens by connecting the black and green wires.

That's much too much for a 10aH battery. Expect it to cut-out on hills.

Actually, it doesn't seem to stress at all. Everything is slowwwww and smooth. It gently accelerates to 16mph and stays there. I'm very happy with the quiet smooth performance of the motor.

I think I know why the bike lacks power: The BMS is rigged to only allow 15amps. I knew something was weird. This battery has a tiny BMS. I'm not sure if I like it or not. It really lacks power, but at the same time, its protecting the battery from my abuse. I'm putting in an order for a 14ah LiMn battery. It has a 30amp BMS. I'm really not satisfied with the bike's performance yet. I'm going to hook-up a watt meter to get some exact measurements and report back. Hopefully it will help others understand how to build a better bike.

Here's the BMS:



I don't understand the purpose of selling a strong 500+ watt hub motor that only goes 16mph. That can easily be achieved by a mini motor. The next motor I buy will be a Code 10 or 11. This Code 14 is too slow. This hub would be great at 72v! But for now, I need to figure out a bike to sell!!!!

So, here's my updated set-up:
1) More powerful battery!!! 14ah 48v LiMn
2) 9fet or 12 fet controller (22 amps???)
3) Code 10 or 11 Bafang BPM 48v 500w

Does that sound better?

Thanks,
Eric

 

[d8veh]

The 9FET controllers give 22 amps and the 12 FET ones 30 amps. The 12 FET one's the best for the 500w Motor. Which controller are you presently using?

Your BMS is rated at 15 amps continuous, but will allow 30 amps max. It'll probably cut off if it gets hot running at 30 amps for too long. The battery isn't limiting the speed in any way.

Another possibility is that you're not getting full throttle. if you could get a friend to lift the motor-wheel off the ground and give full throttle. While it's running like that, short out the red and white throttle wires. If you see/hear the motor speed up, then you should get more power with a different throttle. The shorting out is best done with a 1K resistor for a bit of extra protection. You can buy one from any electronics shop for about 10 cents. You can short out by tucking the ends of the legs in the back of the connector.

 

[Beagle123]

Hi dev:

As usual, you're right again. It wasn't the battery. I hooked-up a watt meter, and tested two different batteries:

Battery1: 15s 10ah lifepo4 @ 49v
Battery2: 16s 10ah lifep04 @52v

I tried giving it a light load by slowly accelerating up a 4% hill:

According to the watt meter here is the maximum output for the light load:

Battery1: 17amps (850watts) with 4v of sag
Battery2: 18amps (900 watts) with 4v of sag

Then I tried going full throttle uphill from a standing start:

Battery2: 28amps (1300w) with 6.5v of sag

So obviously the batteries are fine. I don't know what a good "sag" number is, but it seems reasonable to me. I need to swap to a smaller controller now!!

But what I don't understand is how the user, casainho got such great results with the exact same set-up. Watch this video:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=35323&start=75#p587217

See how powerful it is? He's using a Faster code 11 motor, A KU123 controller and a 10ah battery. So his set-up is exactly the same as mine except he should be getting more RPMs and less torque. And his looks MUCH more powerful than mine.

Is it possible I have a bogus motor? The motor was sold to me as a Code 14 BPM, but it doesn't look like the other BPMs:



Its not the shiny chrome with the 8fun logo. Has anyone seen a BPM that looks like this? I don't trust BMSBattery.

Another possibility is that I'm running it sensorless now because BMSBattery doesn't take the time to provide the proper connectors. I'm fixing it now.

I'm going to set-up a battery/controller/motor testing facility in my garage. I will keep you posted of my results.

 

[chvidgov.bc.ca]

I think the KU123 controller is too big for your 10Ahr battery. I regularly see spikes to 1300 watts on 16S LifPo4 which is well over 25 amps. I think It could emit 30 amps on occasion. I doubt your battery is 3C rating.
I get a max of 22 mph on my Code 10 BAFANG BPM with 16S Ping, and KU123. They are nice controllers though. Your motor "looks" the same as mine, except I know mine is a Code 10 - I can't remember why. I think it said somewhere. on the box or something, or on the sticker on the motor. My 9C on the same controller and battery kicks the BPM's butt on the high end, but the BPM is a very good climber - be careful with your torque solution.

 

[Beagle123]

Thanks chvidgov.bc.ca:

I think the KU123 controller is too big for your 10Ahr battery. I regularly see spikes to 1300 watts on 16S LifPo4 which is well over 25 amps.

I'm learning to trust the labels on these controllers. I agree this is a problem. I've since switched to a 17.5 amp controller:

http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2012-7Q-P96D.9KNYX

Do you think 17.5 amps is too much for a typical lifepo4 10ah? 1.75C? It still seems high huh? Keep in mind that it hits the 17.5 amp peak very easily. If I do any reasonable acceleration or hill-climbing hits the maximum, 17.5 amps easily.

I ran a test on the hill in front of my house, its a great testing hill because its a long 4% grade. The bike went up this hill using 10.5 all the way up. That's about 500w. Does that seem good?

I'll get a test on flat land, and post it here.

I think I'm starting to understand why the bike feels sluggish. I think when I start accelerating, the bike is going very slowly and the motor's efficiency is terrible. The controller is putting out max amps, but its all just being wasted. When the bike slowly accelerates to about 5mph, it seems to gain a lot of power as the motor's efficiency goes up. Between about 5 and 14mph, the bike feels fairly strong, but then it starts hitting its maximum speed where it lacks power to go faster. In a way, it feels less powerful because its a slow torquey motor.

When the bike is going 0-4mph, its really a disaster. Its just wastes all the energy in the battery, and you get nothing in return. I'm planning on designing a bike where pedaling will provide most of the energy when traveling below 4mph. I think this is the achilles heel of the electric bike.

 

[d8veh]

Your motor's a BPM2, which is the new type. The voltage sag that you're getting is a lot. Mine sags about 2v under load. Speed is dependent on voltage, so yot lose a proportional amount of speed, i.e. about 10%. A smaller controller won't make any difference to the power/speed you're gettin, but it'll give the battery an easier time.

The motor is inefficient at low speed, as you've already figured out, but the highest torque comes in that range. Themotor's also a generator, and it generates a voltage in proportional to its speed. The generated voltage is opposite to the battery voltage, so as the speed goes up, the effective voltage goes down until you reach the maximum speed, where the two voltages cancel each other out, which is why you can't go any faster.That's why a higher voltage battery will let you go faster. The current from the battery also goes down with speed because of the falling effective voltage.

I think that you'd be better off getting a new battery, rather than a controller. You need one that can deliver 25 to 30 amps continuous, which means a Headway battery or lipos. A code 14 BPM should do 17 to 18mph with your battery (allowing for sag). You'll gain about 1 mph with a decent battery, and acceleration/power will be much better. It would be nice if you could check the no-load speed with a cycle computer. It should be about 21 mph.

 

[-dg]

Your motor's a BPM2, which is the new type

Any opinion on the merits of the BPM2 vs the original BPM? They seem pretty similar spec wise, and I'm assuming the design change had more to do with production processes then anything else, but is there any advantage or disadvantage to the new or old BPM? The only thing I can see is that one needs the special tool to take apart the BPM2 instead of just a screwdriver. Anything else?

 

[d8veh]

I've never had a BPM2, so I can't give you anything of substance. The CST is much neater inside than the BPM, so I guess that you might find something similar in the BPM2. They probably addressed the water ingress issues. The CST was very well sealed.. The special tool is a bit of a bummer!. When they first came out, there were one or two reports of the free-wheel thread breaking off, but I've not heard of any more since then.