Controller just stopped, but can be "rebooted"

I was climbing a particularly fiendish hill today and my controller just stopped. I'm thinking, damn, ruined my new bike! Its about 80 degrees out and I just climbed a 15-20% grade for about 2 minutes straight. 7 mph or so peddling hard. This is a 600w BMC v2 motor and a BMC 48v 30A controller. I checked the temps on the axle and the controller. The axle is about 120 degrees and the controller is about 150? I can put the back of my hand on both indefinitely, but on the controller it starts to hurt after a few seconds. Being a computer guy I can't think of what else to do, I unplug the battery and plug it back in, and it works. great. So I let it sit for a few minutes to cool off and then go back up the hill. I go uphill for a minute or so, then down for about 4 minutes, as I start pulling up the same hill, it happens again. I reboot, nothing is too hot, I try to go up and it dies again a few seconds later. I reboot and give it 3/4 throttle or so for another 2 miles with no problem, then WOT for another mile or so and it stops happening.

So, Does anyone have any experience with something like this? Am I blowing a fuse? On the flats, the bike seems capable of pulling 1100 watts indefinately, but I put it on a hill and the controller died on me. Do I need to setup a cooling fan? ambient temp too high? did I let the magic smoke out?

Thanks for any insight you guys might have, I'm still a total N00b on this...

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nutsandvolts said:

Which batteries are you using? It could be a BMS trip on max amps. That was happening to me on hills with 30A controller and 30A BMS until I paralleled two battery packs so neither get close to 30A. Or if it's not the BMS tripping then it must be a limiter in the controller, not likely a fuse, though maybe a thermal cutoff.

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Ahh.. Thank you. Yes, I am running 10ah Lifepo4. I don't know what the BMS cuts out at, but I know I saw the highest max amps I've ever seen on the CA, 43amps. normally I see in the the mid 30's but never pull more than 22-23 for more than a second or so. Maybe the shear incline of the hill is spiking the amps faster than the controller can limit them?

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the CA is standalone, so I don't believe I can override the controller. The controller is under warranty so I don't want open it up and modify the shunt. I'll ask the vendor if this is something they can do or if they'll still warranty it if I do it. I'm not even sure If i care, this is , quite literally, the steepest hill I can know of and I could just not ride it. I was having some serious trouble on the downhill just managing the brakes! Next bike(way next, currently building bike #2) will have to have regen. Thanks for all the info. this makes sense now and I'm much less worried. I'm just glad I didn't blow something up permanently.

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I stared at that diagram until now, I think I get it. the CA is inline on the battery, and sees amps. the ca also can pull the voltage down on the Hal signal when it sees those amps go too high, which causes the controller to let off on the throttle, even though you have the throttle maxed out? Am I getting this right?

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When a motor gets hot, and yours was near the safe upper limit for operation, ( maybe 160F inside it?) it will draw a lot more current. You have been having a controller cut out or a battery cut out. Either one, it stopped working because you were starting to pull exessive amps. Most likely it was the battery cutting out. I used to get both kinds with my brushed motors, but have never seen a controller cut off on my brushless controllers. I could feel it coming, because the motor would start to feel like I had voltage sag for the last mile before the cutout. With a good gearmotor, it may be harder to feel it coming.

Back last summer, I could feel a difference between the two, with the controller cutoff being a bit more abrupt than the battery shutdown which gave a millisecond slower shutdown as the controller caps drained out.

The cure is more battery, so you can supply more amps without cutouts, but be carefull you don't melt down a motor once the battery no longer lets you know it's time to stop. The ca features can help with that I'm sure, at least limiting the damage to the existing battery from pulling so much amps.

These motors can climb like crazy, but the designs still date back to sla batteries that run out before we ever got the motors all that hot. Now that we have lifepo4, etc, we can easily run a motor into the ground if we try. See Dr Bass's thread about the mountain and the 9c motor.

I'm finding with my motors, that once you get one hot climbing a hill, more riding on flats may be ok, but more hill climbing is not so ok. One great feature of gearmotors is that they don't produce heat going down a hill like a DD motor does.

i run a 10ah lifepo4 also. And i had the same problem. an easy way to tell if its your controller or battery cutting out for me was to look at the battery gauge on my throttle.(not sure if you have one). Mine would still show full power when the controller cut out and would show no voltage at all(no lights) when the lifepo4 BMS cuts out.

Definitely the controller then. the CA was still lit up and reading 51 volts. It's a really small controller. I'm going to look into some active cooling method for it, as it's always the hot part of the setup.

Hills that steep are still going to be hammering everything though. Is it gotta go that way, or going that way to test things?

completely optional. It's the most murderous slope I know of . 1/2 mile of 25% slope. I can barely walk up it. It wasn't too taxing on the motor though, from the sound of it. The bike works fine today. I'll just avoid that trail in the future. There is no way I'd ever go up it unassisted either.

UPDATE: controller appears to be hosed. I can't really start from a stop without it dying. over 11 mph I can go WOT, but below that it seems to pop. The vendor is sending out a replacement. I'll be gentler on this one. Looks like BMC controller are not meant for steep off road use. What is the most bulletproof controller one can buy?

Helpful topic.

I'm a total NOOB!

My setup: BMC 600W w/ BMC 48V controller - 48V15AH LiFePO4

I've got about 100 miles on this setup.

Bad news, I think my controller died. I was heading down the road when all of sudden I lost power, and the Cycle Analyst went dead. The controller was pretty warm, but not super duper hot. I had the controller mounted outside of the bag so it could be properly ventilated.

I was able to charge the battery, and the display on the Cycle Analyst showed the battery was charging properly (the Cycle Analyst shows 52 volts). When I disconnect the charger the Cycle Analyst shows nothing.

I have a electronic key system (the crystalyte trunk), when I try to turn on the power, the Analyst is still powered down, and the wheel has no power.

I've tried to connect the system up bypassing the Cycle Analyst, and still no juice. I've also plug everything in bypassing the key system.

Anything else I should check? If it is dead, how should I proceed?

I'd suggest putting a voltmeter on the phase wires(the three big ones going to the motor.) and seeing if you're getting power OUT of the controller, and checking to ensure there's power going IN it as well. Could be the throttle cable also. I'd say put a meter on everything coming out of and going into the controller. Also, where did you get it from, and is it under warranty?

Can you tell any more details of what you were doing when things went bad? hot weather, steep hill? doing a wheelie?

I suppose now would be a good time to get a meter.

Stupid question #77, with this voltage meter, I can stuff the probes directly into the Anderson power pols right?

You can while unplugged.
depending on the size of the probes and the sealant on the andersons, you can wedge them in the back and see voltage while riding as well.

Okay, I've got 53 coming out of the battery directly. With the controller connected to the battery I have nothing coming out of the motor plug. boo hiss. Rats!

I bought a new BMC controller - the same model and I'm rolling again! Woot!

Great to hear. I emailed my vendor (cycle9.com) and they shipped a new one that day. Great folks. I'm riding again too. Although I'm testing my 36 fatpacks and it's BORING at these speeds. 17mph is too slow.