GoldenMotor.com Forum
General Category => Magic Pie & Smart Pie Discussions => Topic started by: Ron Burgundy on July 05, 2020, 02:02:03 AM
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Hello, I have a new Smart Pie Ext rear hub kit and set my brake regen to max. It is amazing when slowing down but I am hoping that I am not prematurely wearing something out. Any recommendations about using brake regen on MAX with this kit?
Thanks, Ron
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You should not be wearing anything out as the braking is performed magnetically instead of using friction.
The only thing that may cause problems it high speed braking that can produce high current/voltage which can sometimes exceed the charging limits of the battery's BMS.
Try not to exceed 35~40 mph on steep hills (in a downhill direction ;)) if you have 26" wheels, or 27~30mph if you have 20" wheels.
Alan
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Funny Guy!
Is the charging current not significantly higher with the regen settings to max? I have 700 c wheels on both bikes, if I exceed the charging limits of the BMS, obviously because I would not know I was, what would happen?
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If the BMS charging current or charging voltage is exceeded the BMS will quickly disconnect the battery from the controller until the voltage/current is below the maximum voltage/current settings of the BMS.
although this protects the battery from being overcharged, the sudden disconnection of the controller under high load is suspected to have damaged a few vector (internal) controllers.
I don't suppose that you will go fast enough to cause the BMS to cut out, unless you go extremely fast down a long, steep hill with a fully charged battery. ;)
Alan
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I did recently go down a really steep hill for about 90 seconds doing about 60kph, but I tried not to brake steadily. I applied the brakes on and off as much as possible to prevent a problem. Just to verify, there is no charging taking place unless I apply the brakes... correct?
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There will be a very small amount of residual generated power but the battery should easily absorb it.
54kmp/h is ~434rpm for a 26" wheel, and at this speed, the motor will be trying to produce a higher voltage than the battery voltage, and this may cause it to automatically perform like a generator.
I once spun up a Magic Pie by spinning the pedals very fast by hand with the bike suspended from the ground and no battery connected.
The voltage on the Pie's battery connector went right up to ~77V, but it instantly pulled the voltage back down to ~60V the moment I applied the brake on the other wheel to activate the regen.
If the battery had been connected, I'm sure the voltage would not have risen this high, as the battery would have absorbed any current produced if the motor voltage tried to exceed the battery voltage.
I don't think you need to worry about overcharging the battery when you are not braking. ;)
Alan
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Thanks