Newbie Question: Regenerative Braking with Magic Pie

[SparkyNZ]

Hi Everyone. I had my first 5 minute play with my MagicPie conversion today. I realise there are installation manuals, but is there anything available which is truly a "user manual". Sure, I can move the throttle etc and my bike goes but I'd like to know more about what can be configured, how I should be riding the bike and using the motor etc. I've been told never to totally flatten the battery etc but whereabouts can I find an overall guide with this information?

Back to my main subject though: Is there anyway to increase the amount of braking that the motor provides? When I go to work I have some steep hills to go down and I go through brake blocks quite easily. I thought the regenerative braking may have helped me somewhat, but with the additional weight of the MagicPie motor and battery, I'm thinking this will become more of an issue now. So what is regenerative braking exactly? Is this just the natural resistance of the magnets in the motor, or can something be tweaked within the charging settings to increase the level of braking?

I have to say that I am very excited about taking the bike to work on Monday. Our hills are killers!

[Bikemad]

Hi Sparky andto the forum.

Unfortunately there isn't a dedicated user manual as these are pretty straightforward to use, but you will find a lot of useful information on this forum with a little bit of searching.

If you cannot find the required answers to your questions using the Search option, you can simply post your questions on the forum and hopefully someone will respond with a suitable answer.

You didn't mention which version of Magic Pie you have, but as long as it's an MPII, MPIII or MP4 (Vector controller), the regen amount can be adjusted using the correct USB cable and software to match the motor.

On the MPII and MPIII you can adjust the "Regen Brake" setting up to 116% maximum:



On the MP4 you can adjust the "Max EBS phase Current" setting up to 80A maximum:



Alan
 

[SparkyNZ]

Thank you Alan. I did indeed buy the USB cable for it but haven't had a chance to download the config software and experiment with it. I think its a MagicPie 3 that I have. What would the Regen %age be set to by default?

Tomorrow will be my bike's first maiden voyage so to speak, so I will get a good idea of what its like going down the hills prior to tweaking the regen braking %age. I made sure I put the charger in my bag just in case the charge drops low when I get to work. :-)

Cheers
Paul

[Bikemad]

Hi Paul,

You can download the required software from here, but you will need to know whether it's an MPIII or an MP4 as the programs (and the connection technique) is completely different for each of the two versions.

With the  MPIII you unplug the battery and disconnect the main harness plug (can be  either 8 or 10 pin) and plug the USB lead into the connector on the motor harness.The battery must remain disconnected until the USB lead has been removed. Take a look at Gary's video to see what to expect while programming the controller.

The MP4 is slightly different as you don't need to disconnect the main harness or battery because you need to turn on the battery power to allow the controller to connect to the software in order to program it with the USB lead which connects to a separate 5 pin connector on the motor harness. this is Gary's video for programming the MP4 vector controller.

Alan

P.S. The regen on my MPIII was set at 50% when I received it from the factory but I run it at 116%.
 

[SparkyNZ]

Hi Alan. Thanks again. I had a great ride to work this morning! The braking is actually more effective than I thought - a bit too effective to be honest so I think I'll have to turn it down as opposed to up. Was really good to feel it in action though. My cruise control didn't want to work though so I suspect that may be disabled. Having changed all the back gears on the bike I now feel the need for a bigger sprocket on the front - found myself pedalling very fast! :-)

[Bikemad]

My cruise control didn't want to work though so I suspect that may be disabled.

There is no way of disabling the cruise control apart from unplugging the switch so it is unlikely to be disabled.

It might be the switch contacts need a bit of use so try giving it several firm presses and see if it helps. If the road surface is bumpy you sometimes accidentally give it a double press instead of a single one which would turn it on and off straight away.

If it still refuses to work you might need to check that none of the pins have been bent over inside the connector.

When I go to work I have some steep hills to go down and I go through brake blocks quite easily.

I think the best things about regenerative braking is the huge reduction in wear on the mechanical brakes (and the wheel rim) which is why I have mine turned right up.


We just need to persuade GM to develop a variable regenerative braking system controlled by a Hall sensor in the brake lever instead of a switch.

Anyway, I bet you can't wait to go home again now.



Alan
 

[SparkyNZ]

I think the bug is with me, not the cruise control. It does work.. I think I'm either not holding the switch down long enough or I'm holding it too long. I found out that I need to have the throttle on to get it to work but sometimes I stop pedalling to test if its on and it hasn't kicked in so I need to try again. It will be something silly that I'm doing :-)

One lesson I have learned though is that a front motor system would have been a lot quicker and easier to install. Lessons learnt will be applied to partner and daughters bikes no doubt. I reckon I will get them bottle batteries to reduce rattling and front hub motors so their gears don't need modifying. Dropping from an 11 tooth rear cog to a 14 tooth cog has dropped the flat speed of my bike down significantly. I have found a 12 tooth rear screw on cassette that I can buy though so that will probably be my happy medium.

[Bikemad]

The cruise control function simply holds the throttle setting in the controller, so you need to hold the throttle where you want it before you press the cruise button.

Front wheel kits might be easier to install but they are not so good as far as traction is concerned, especially with the more powerful motors, and they are a complete waste of time for pulling wheelies!

With front wheel drive you also need to make sure that you have very strong forks (ideally steel) and fit suitable torque arms to help withstand the axle torque.

You should be able to find an 11 tooth screw on freewheel in 7, 8, 9 and even 10 speed, just do an ebay search for "DNP Epoch freewheel 11" and see what you can find, but take a good look at the shipping charges before you commit to buy!!.

Alan
 

[SparkyNZ]

Thanks Alan. I could have went back to a 7-speed gearing but after changing it back from 9-speed to 6-speed I think I'll just leave it as-is. I managed to get another 6-speed freewheel with one tooth less.. so that will make a slight difference.. once I adjust it so it doesn't throw off the chain that is ;-)

I am a bit confused about the regen braking though. When exactly does the battery charge? If I'm freewheeling downhill without touching the brakes - I assume my battery will be charging, yes? So.. if I touch my brake handles and the regen braking kicks in - what exactly happens - does this result in power use that would otherwise be used to charge the battery, or does is actually result in the battery being charged more? Perhaps charging takes place in both scenarios but at different rates?

I've been away for a week and a bit so only just got back to the ebike this morning.

[Bikemad]

The motor will produce a small amount of charge if you are freewheeling faster than the motor's maximum speed, but the battery will receive a lot more charge when you activate the brake switch (regen) at higher speeds.

Below 8-10mph activating the brake switch will only produce an electromagnetic dynamic braking effect (as against regenerative braking) and it does not actually charge the battery.

Alan
 

[Brendon1128]

Im still a little confused on how the regen setting for the new vector program works. When it says "max ebs phase current", is this how many amp-hours that could be delivered back into the battery? If so, man wouldnt 80 amps, heck even 20 amps really damage your battery? I have a fast charger for my li-ion pack and it only charges at 4 amp-hours!

[Bikemad]

The "EBS" refers to Electromagnetic Braking System rather than "regenerative braking" and the "Max EBS phase Current" refers to the maximum peak current allowed through the phase windings during braking, which is typically a lot higher than the continuous steady current measured at the battery leads.

At slower speeds, high generated current can only be achieved by lowering the generated voltage (which will be much lower than the battery voltage) therefore without using some form of inverter to raise the voltage, no regenerative current will actually find its way to the battery. At slower speeds, all of the generated energy is basically being converted into heat within the windings as the current is used to provide the electromagnetic braking force.

At higher speeds the generated voltage will also be higher, and when it is greater than the actual battery voltage the surplus generated energy can then be used to charge the battery.

If you have your max EBS phase current set to 80 Amps, you will get a large amount of braking assistance from the motor, but you will not get 80 Amps of charging current.

I haven't measured the regen current on the MP4, but I would only expect it to be around 10-15 Amps max @ 30mph with a 48V battery. This should not cause any problems as the cells in the 48V 10Ah batteries have a 20 Amp maximum (2C) charge rating.

If anyone is using a Cycle Analyst with the MP4 it would be interesting to know what the actual peak regenerative charging current is, and at what maximum speed.

Alan
 

[Brendon1128]

Oh ok. Just curious too, would setting the max EBS higher affect the reliability of the motor? Would it cause the windings to heat up hotter and do damage? Right now, I have it set at 20. I know it maxes at 80, but I'm a little hesitant about damaging the motor.

[Bikemad]

If there was any chance of the motor being damaged by the higher current setting then GM would have reduced the maximum setting options available within the program software. I have all of my vector controllers set at 80 Amps to give maximum braking force as I don't like rubbing away the alloy rims with the brake blocks.

The heat generated during braking will usually be dissipated quickly enough to prevent the windings from getting too hot.
Unless you were braking continually down a very long steep hill for several minutes, I don't suppose you'd even notice much difference in the temperature of the motor casings as the a the air moving past the hub assembly at speed will cool it quite effectively.

There's no need to worry about damaging the motor, the MPIII and MP4 have proven themselves to be very robust indeed. 

Alan
 

[GM Canada]

I also have to endorse the 7 and 8 speed DNP 11 tooth freewheels. I have sold them for a few years now and have them on all my personal ebikes. Being able to keep up with the pedals at full speed is a great thing.

Gary