possible damage to the BMC 50A controller/motor/battery?

[mvly]

I just wanted to know if I damaged my BMC 50A controller/motor/battery setup.

Here is what happened:

Setup:
a) Modified BMC 50A controller
b) CA limited to 35A
c) 48V30Ah LiFePo4 w/ BMS
d) BMS rated at 60A continuous, don't know the burst current specs
e) whole bike + me ~ 200 pounds

situation:
I was going up a 15% hill and going at initial speed of 1-2mph and then I went full throttle without pedal assist and the bike just cut out.
I proceeded to let go of the throttle and turn it slowly up again and nothing happened, no power. I proceeded to remove the battery to "reset" the whole setup and everything was fine again. I touch the motor and other part and it was not hot at all. I tried to inspect for burnt smell or chard wires and nothing.

My question is if I damage any part of my setup during that stunt of mine? Is cutting out because of my BMS of the battery, the controller, the CA, or the motor.

Thanks,

 

[FMB42]

My initial questions would be:

1.Did you lose power to the entire system, including the CA, during this loss of power?

2.What are the factory recommended "peak" and "continuous" current/amp ratings of your battery?

Meanwhile, I'd start with:

Making sure that the battery is fully charged.

Double checking every electrical connection starting with the main battery connector/connection (also check for the proper adjustment and/or operation of e-brake switches, if equipped).

Making sure that you're not exceeding the maximum allowed current/amp draw rating of the battery (both the "peak" and "continuous" amp ratings).

 

[mvly]

1.Did you lose power to the entire system, including the CA, during this loss of power?
-Nope. The CA was still on. This has lead me to conclude that if there is a problem, it might be coming from controller/motor. I have ran my battery to empty before and the CA would shut down too. Moreover, the CA still showed 51V so I doubt the BMS was shut off.

2.What are the factory recommended "peak" and "continuous" current/amp ratings of your battery?
-The listed battery does not state. All it states the max current WITHOUT BMS is around 500A. But since there is a BMS, I figure it can't be more than what the BMS is rated at. Again all I see is max continuous for BMS is 60A listed on the battery I bought.

Everything seems to be fine. I still can use the e-brake function of the controller. I am still able to get the same power output as before. None of the wires looks chard.

Since the Controller is 50A and my BMS can handle continuous 60A, I don't I am over drawing my battery.

Any more help/response would be appreciated.

Thanks.

 

[FMB42]

Can you give us any further info on your battery (such as brand name, model #, etc)? This might help us find out more about just what the current ratings are, or might be.

I'd prefer to know "for sure" that the CA and BMS max current settings aren't actually more than what the battery is designed to output current wise.

 

[mvly]

I got the battery from ebay from conhismotor

here is the link to the item

http://cgi.ebay.com/48V-30AH-LiFePO4-Battery-wiith-BMS-Charger-Battery-Bag-/330535905924?pt=US_Batteries&hash=item4cf579aa84#ht_5708wt_905

looks like the max continuous is about 60A for the BMS.

 

[oatnet]

heat in a geared motor doesn't get to the sidecovers as fast as a direct drive motor.


Turn everything on and spin the wheel backwards. Do you feel resistance?

 

[mvly]

heat in a geared motor doesn't get to the sidecovers as fast as a direct drive motor.


Turn everything on and spin the wheel backwards. Do you feel resistance?

No resistance going backward assuming I don't twist the throttle. hahha. I might have over blown the situation. I was just concerned about the FETs in the controller. I just did a speed and range test today and everything looks fine as usual. It might be a tad weaker, but then again it might be just some wind.

Thanks for all the help!

 

[FMB42]

OK, so the maximum continuous discharge current rating for your battery is 30 amps. This, of course, is only 5 amps over what you have the CA set for (which, imo, should be "OK" as long as the CA is doing its job of limiting the amp draw to 35).

I'm not sure what the ambient temps are in your area, but I'd definitely monitor the heat build up in that hub motor (as "Oatnet" wisely suggests). Also keep in mind that geared hub motors tend to be happier with "measured" throttle increases as opposed to "sudden" wide open throttle applications (this is especially true on hills and while accelerating from "dead" stops).

 

[oatnet]

If it runs smoothly, then you are fine. At 35a, I assume you are running a V3. The cutout could have come from drawing too many amps, making your CA 'clip' the throttle, or the resultant voltage drop tripping your BMS or CA LVC settings.

Slow speeds with heavy load (such as a steep hill) are the best way to fry a hub motor; especially a geared one which cannot shed heat like a direct-drive. At those speed, motor side amps go WAY up, which the motor's resistance converts to heat. Your geared motor will melt the windings long before the sidecovers are even warm, the only way to effectively monitor temps are to install a temp sensor inside of the motor.

Take hills at speed and WOT, pedal as needed, and if you bog down under 10mph or so, don't do it for long...

-JD

 

[alsmith]

How have you mounted your battery? 48V 30Ah has to be some size and weight! I notice my 36V 20Ah one which is rack mounted, and am looking at better ways when I go to 48V next year- weight meant I was only considering up to 20Ah as even this will be bigger and heavier. At the moment it looks like a split pack with half on each side in a pannier- if I can find suitable panniers that will take the weight.

 

[oatnet]

How have you mounted your battery? 48V 30Ah has to be some size and weight! I notice my 36V 20Ah one which is rack mounted, and am looking at better ways when I go to 48V next year- weight meant I was only considering up to 20Ah as even this will be bigger and heavier. At the moment it looks like a split pack with half on each side in a pannier- if I can find suitable panniers that will take the weight.

Ah the ever-popular where-to-put-the weight issue. I won't run front hub motors, I consider them a hazard, so I only run rear motors. If you put the battery back there too, then the front wheel is underload. I lifted an underloaded front wheel in a turn on just such a setup, went down, messed up 2 ribs, and would be dead if I hadn't had my helmet. The worst example I have of this in my stable is my xtracycle, which has a front wheel so underload that turning the handlebars is more of a suggestion than a directive. So the next most popular option is to put in the triangle, which is great from a balance perspective, but in your knee area and is NOT stealthy. My current solution is to put the pack under the handlebars, which puts the mass between your hands, and makes the whole bike feel light. If you look at this picture, draw a line between the motor an battery, and see it goes right through the frame... That balances the motor weight against the battery weight, and feels really tight. YMMV

-JD

 

[mvly]

OK, so the maximum continuous discharge current rating for your battery is 30 amps. This, of course, is only 5 amps over what you have the CA set for (which, imo, should be "OK" as long as the CA is doing its job of limiting the amp draw to 35).

I'm not sure what the ambient temps are in your area, but I'd definitely monitor the heat build up in that hub motor (as "Oatnet" wisely suggests). Also keep in mind that geared hub motors tend to be happier with "measured" throttle increases as opposed to "sudden" wide open throttle applications (this is especially true on hills and while accelerating from "dead" stops).

Yeah I figured 35A is not too much to ask from my 30Ah battery, even if they are LiFePo4. Again it's rated at max of 60A anyways. Ambient temperature was cool (~20C) during the cutoff. I will be more careful this time around to not full throttle from rest.

If it runs smoothly, then you are fine. At 35a, I assume you are running a V3. The cutout could have come from drawing too many amps, making your CA 'clip' the throttle, or the resultant voltage drop tripping your BMS or CA LVC settings.

Slow speeds with heavy load (such as a steep hill) are the best way to fry a hub motor; especially a geared one which cannot shed heat like a direct-drive. At those speed, motor side amps go WAY up, which the motor's resistance converts to heat. Your geared motor will melt the windings long before the sidecovers are even warm, the only way to effectively monitor temps are to install a temp sensor inside of the motor.

Take hills at speed and WOT, pedal as needed, and if you bog down under 10mph or so, don't do it for long...

-JD

Yes the motor is BMC V3 1000W. I usually never let the speed dip under 10mph I usually change gear and pedal by then. Thanks for the recommendation though

How have you mounted your battery? 48V 30Ah has to be some size and weight! I notice my 36V 20Ah one which is rack mounted, and am looking at better ways when I go to 48V next year- weight meant I was only considering up to 20Ah as even this will be bigger and heavier. At the moment it looks like a split pack with half on each side in a pannier- if I can find suitable panniers that will take the weight.

I have 2 batteries. If you take a look at my bike review, you can see how I mounted the batteries.
http://www.endless-sphere.com/forums/viewtopic.php?f=4&t=29194
One is a 36V20Ah battery that I keep in the center of the bike just for weight distribution. I rarely use it since it is weak and only gets me around 28-29mph on flats. It is more of a backup battery. The 48V30Ah battery is located on the rear placed in the topeak MTX DXP bag. It barely fits in the that bag though. I still have the side panniers for extra storage like charger and such.
36V20Ah ~= 15lbs
48V30Ah ~= 30lbs
both are LiFePo4.
Without the center battery mount, I would not be comfortable to place the 48V30Ah battery in the rear, but since I do have some weight on the center, it balance the bike out pretty well.