Bafang Bake Off Pics 36V/350W Controller vs 48V/600W

zukster · May 8, 2009

Check out these pics. IMO, I think its safe to say that if you're going to try to run the
Bafang SWXH 26 Inch wheel model on the bigger Ecrazyman controller, you better use extreme caution.

Maybe on a smaller wheel, you'd fair better. Mine is a 26 Inch Wheel.

My original post on testing this is here http://endless-sphere.com/forums/viewtopic.php?f=2&t=10042

The unbaked motor was run with the 36V/350W Controller on 40V 12AH and 60V 18AH Canadian Tire 20V
Yardwork battery packs in Series. I ran it for a couple of weeks without problems until the hall sensors failed.

Then I switched to a new motor with the same battery packs and the 48V/600W Controller. The motor has
been overheated twice now - doing roughly the same driving (with and without a trailer for both).

So if your going to go with the bigger one, you better make sure your batteries are up-to-snuff and maybe
even get a Cycle Analyst CA with the battery-controller-shunt that allow you to limit current.

zukster · May 10, 2009

Bump. People should really read this one. Could save some grief.

docnjoj · May 10, 2009

Yep ! It looks fried! Where's Fechters' Guinea pig when we need it! I run my Bafang on 48 volts with a 20" wheel and other than trashing the nylon gears once I have had no difficulties.
otherDoc

gogo · May 10, 2009

There's not much of a path for the heat to escape. It seems the Bafang would benefit greatly from forced air cooling.

[EDIT] How many Yardwork batteries are in each of your packs? Do you have 4 batteries in your 40V 12AH pack and 9 batteries in your 60V 18AH pack?

zukster · May 10, 2009

yep - cooling would help. Some one suggested some kind of radial fan between the gears,
but I'm not sure what that is. And I guess you'd have to drill some holes for air flow too,
which would expose the internals of the motor to the elements more.

The gears were actually okay once I got it all apart.

Here's a picture of my recipe for Baked Bafang Pie. I don't think I can look at the
guinea Pig Spliff picture again.

voicecoils · May 11, 2009

Nice side by side comparison.

With the controllers you've been using, are you monitoring current while you ride? I'm interested to know how much current the controllers are actually delivering.

Depending on the terrain where you live, I'd suggest a setup that uses higher voltage and lower current. Doing so will enable the motor to provide an 'assist' over a wide range of cycling speeds and yet limit the heat build up of the motor.

Vents for air cooling or running the motor in oil are both interesting ideas, but I'm not convinced either is practical. With air cooling, the bafang case is cast aluminium and mine does not have any ribs, spiders, or reinforced sections in the casting of the case walls. I would not feel confident riding a bafang hub with air vents drilled into it. With the oil idea, I don't think the bafang is well sealed enough for the task. However, I'd like to see someone try either of these options and prove me wrong

My current view is that in any instance where you are either accelerating or riding up hill, a bafang bike needs to be quite actively pedaled to achieve reliable operation. For my situation this is fine as I'm happy to actively pedal which works nicely with the bafang's low weight and freewheeling ability.

Thanks for posting those photos.

johnrobholmes · May 11, 2009

Yes, with the small mass of the Bafang I make sure to either help it out or throttle back on a steep hill.

gogo · May 11, 2009

I have come to think of the Bafang as a low power/low top speed motor. I'd guess when you get past 20 MPH, the increased load from the wind combined with the Bafang's inability to dissipate heat quickly leads to thermal saturation. My forced air suggestion was with a mid-drive in mind.

More thermal testing is needed me thinks. Or at least the use of a temperature probe for higher power operation.

zukster · May 11, 2009

gogo said:
There's not much of a path for the heat to escape. It seems the Bafang would benefit greatly from forced air cooling.

[EDIT] How many Yardwork batteries are in each of your packs? Do you have 4 batteries in your 40V 12AH pack and 9 batteries in your 60V 18AH pack?

2 in the 40V pack. And 3 in the 60V pack. I now know thanks to dnmun that the batteries sagging
contributed to the heat. I'll be trying the smaller controller next to see if its nicer to the batteries.
I'm trying to keep the weight down.

Do you think a different pack, like a ping would be better?

zukster · May 11, 2009

voicecoils said:
Nice side by side comparison.

With the controllers you've been using, are you monitoring current while you ride? I'm interested to know how much current the controllers are actually delivering.

Depending on the terrain where you live, I'd suggest a setup that uses higher voltage and lower current. Doing so will enable the motor to provide an 'assist' over a wide range of cycling speeds and yet limit the heat build up of the motor.

Vents for air cooling or running the motor in oil are both interesting ideas, but I'm not convinced either is practical. With air cooling, the bafang case is cast aluminium and mine does not have any ribs, spiders, or reinforced sections in the casting of the case walls. I would not feel confident riding a bafang hub with air vents drilled into it. With the oil idea, I don't think the bafang is well sealed enough for the task. However, I'd like to see someone try either of these options and prove me wrong

My current view is that in any instance where you are either accelerating or riding up hill, a bafang bike needs to be quite actively pedaled to achieve reliable operation. For my situation this is fine as I'm happy to actively pedal which works nicely with the bafang's low weight and freewheeling ability.

Thanks for posting those photos.

I was trying to avoid a cumbersome CA setup, so I have not monitored the current. I'll be using
some fuses in the future which will give some indication of current when they blow.

I'm fairly hopefully that the little controller and the 3 battery 60V pack will work well. Maybe even the
40V pack, but I have to keep an eye on the batteries for sagging. Will let everyone know.

I can tell just riding that the bigger controller delivers quite a bit more current.

However, with the little controller, 60V was a huge speed improvement.

Maybe we should start a "Baked Bafang Recipes" thread for pics, or is there already one out there?

gogo · May 11, 2009

zukster said:
gogo said:

There's not much of a path for the heat to escape. It seems the Bafang would benefit greatly from forced air cooling.

[EDIT] How many Yardwork batteries are in each of your packs? Do you have 4 batteries in your 40V 12AH pack and 9 batteries in your 60V 18AH pack?

Click to expand...

2 in the 40V pack. And 3 in the 60V pack. I now know thanks to dnmun that the batteries sagging
contributed to the heat. I'll be trying the smaller controller next to see if its nicer to the batteries.
I'm trying to keep the weight down.

Do you think a different pack, like a ping would be better?

Ya, you might be getting some voltage sag. When you put batteries in series, you only get to add the voltage and not the AH. So you have 40V 6AH and 60V 6AH.

If each battery's LVC is 15V, at least one will start cutting out at somewhere around 45V of saggage on the 60V pack. After one battery's LVC circuit trips, the most you will have available is 40V. So if the 48V controller's LVC is set for 41V, you could be tripping it after one battery's LVC goes first.

You can fix the voltage sag by adding parallel batteries (6 batteries for 60V 12AH, 9 batteries for 60V 18AH... etc.), but that may only add to your motor heating issue. You may want to try either partial throttle or reverting back to the smaller controller.

At speeds above 20 MPH, wind resistance will cause increased current draw and that equates to many watts and much motor heating. If you keep the top speed down, the 60V pack can help acceleration without heating the motor excessively. But my guess would be that the load at top speed (60V) combined with full throttle hill climbing puts too many watts and heat into the motor.

zukster · May 11, 2009

gogo said:
Ya, you might be getting some voltage sag. When you put batteries in series, you only get to add the voltage and not the AH. So you have 40V 6AH and 60V 6AH.

If each battery's LVC is 15V, at least one will start cutting out at somewhere around 45V of saggage on the 60V pack. After one battery's LVC circuit trips, the most you will have available is 40V. So if the 48V controller's LVC is set for 41V, you could be tripping it after one battery's LVC goes first.

You can fix the voltage sag by adding parallel batteries (6 batteries for 60V 12AH, 9 batteries for 60V 18AH... etc.), but that may only add to your motor heating issue. You may want to try either partial throttle or reverting back to the smaller controller.

At speeds above 20 MPH, wind resistance will cause increased current draw and that equates to many watts and much motor heating. If you keep the top speed down, the 60V pack can help acceleration without heating the motor excessively. But my guess would be that the load at top speed (60V) combined with full throttle hill climbing puts too many watts and heat into the motor.

Boy - I have a few posts to correct regarding not adding the AH for batteries in series then!

Just to note, Keywin setup my 48Volter to not LVC until around 30V. But anyway, I'm convinced
that voltage sag largely contributed to the bake fest. I both cases, when I hit the little test
button on the batteries, they were low.

I'm still trying to go light so what I really want is a 60V pack that packs about 10AH that
will not sag as bad. But 9 Yardworks batteries is not going to cut it :shock:

Little controller tests are next. Stay tuned!

Bafang Bake Off Pics 36V/350W Controller vs 48V/600W

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