Adding a little more 'magic'...

[martin]

Hi - my first post (feel I'm trespassing after lurking on the sidelines so long!) Thank you to everyone else has given me hours of interesting reading.

I've had my pie for 5 weeks, 350 miles and endless smiles - its like a drug, I keep wanting more! The only problem is, like any drug, you soon start wanting a stronger fix - My round trip of 24 miles was easily done with some careful wrist control (48v 12ah li ion), then my average speed slowly crept up until I needed to charge both ways, and now I'm considering upping my 'fix', so....

I would like to up to 72v 12ah, for two reasons, the first been doing the round trip on one charge again and also a few more mph! - I was wondering if you could help with a few Q's

Is there any maths I can use to work out my extra speed/distance (very approx.)
I'm guessing the internal controller is good to go?
Would I need a new/customised throttle?
Are the wires sufficient gage going into the Pie?
Anything else I need to consider?

Many thanks in advance to any help you can offer...

Ps. Anyone else from the UK enjoying cruising at 'ahem, 15mph officer, cough-cough'!
 

[Bikemad]

I would like to up to 72v 12ah,
I'm guessing the internal controller is good to go?
Would I need a new/customised throttle?

Hi andto the forum Martin.

Unfortunately the current Magic Pies are limited to 60V max.
I tried to run mine on a 16 cell LiPo pack (15 good cells and 1 which had simply died), but the 61.63V being supplied was too high, and the Pie simply refused to work!
So I wouldn't expect it to work with a 72V pack!

Your existing throttle should work fine with a higher voltage controller, but the LED battery gauge would need to have a suitable resistor fitted into the green power supply cable for the gauge to function properly.

Alan
 

[martin]

Thanks Alan - on a learning curve here!

So, I can add another 12v safely without any major remod... I guess my predictable questions are what do you think my gains would be in regard to speed and distance - a fifth more minus wind resistance/heat/etc?

Anyone tried this?

GM do not seem to do a 12v li ion, wonder who does?

[Bikemad]

Martin,

It's not quite that simple, as the 60V limit is the absolute maximum allowed.
Your 13s3p 48.1V pack will probably have a voltage of around 54.6V when fully charged, so a 16s3p 59.2V pack would be 67.2V, which is much too high for the Pie's 60V limit.

Unfortunately it looks like you're stuck with 48V unless you can upgrade to a Pie II controller when they eventually become available (assuming they will be sold separately).

Alan
 

[martin]

Alan, thanks again - looks as if I need to put a check on my speed urges for a bit! One last Q before you go and answer the (almost certainly) more sensible questions on this forum - are there any fruitful forum discussions here for a little more oomph?

Cheers for all your help... 

[PEDAL IN POWER OUT]

Hi Martin,
You can get rpm per volt data from the performance charts.
You wanted math right?
More volts = more rpm. Without a load if it turns 200 rpm at 20 volts it will turn 400 rpm at 40 volts.
It is too bad that the wind resistance will not let you double the actual road speed!
Doesn't "the man" discourage this type of behavior where you live?

[Leslie]

I also depends on your chemistry.  Lipos are higher at full charge per cell than lifepos and different than SLA.  So keep your eye out on that.

Looking at the Magic Controller, those STB140NF75 fets are rated at 75v and the 6 of them should be easy enough to replace with the 100v version rated .

Or buy 6 of these n channels. http://www.irf.com/product-info/datasheets/data/irfp4468pbf.pdf

The IRFP4468PbF has a resistance of 2 milliohm a current rating of 290 amps and max voltage of 100v. Switch caps to 100v and use an LM317t to bump the voltage down for the driver and logic regulators.

This would be an easier mod than most other controllers as the fets look easy access and the high current ability of the the original fets need only populate 6 of them, by the looks of it 3 for regen and three for motor drive.

Looking at the board you see the fets have 3 green blue and yellow sources connected to the battery side and drains connected to the motor for motor control and the regen has 3 fets sources connected to the motor side and the drains connected to the battery.

When you apply the brakes obviously the regen fets recieve PWM and the motor control signal hault. to sensor sync, and the pack source becomes the source of resistance..

Please correct me if I am wrong anywhere.  I learn jack otherwise.

I know the irfp4468 fet is a a little robust but would they swap out in a Magic controller with no issues?

[martin]

317537 - Crikey, I'm a little intimidated and a little excited about trying this - haven't held a soldiering iron for 20 years! Anything else I need to know before I have a go?

...and 'PEDAL IN POWER OUT' - "the man" is always a problem, but until he catches me enough times to get on first name basis.....

[Leslie]

317537 - Crikey, I'm a little intimidated and a little excited about trying this - haven't held a soldiering iron for 20 years! Anything else I need to know before I have a go?

...and 'PEDAL IN POWER OUT' - "the man" is always a problem, but until he catches me enough times to get on first name basis.....

Note I put my choice of FET in question form so maybe wait for feedback.

Yeah sure there is a few things to know.

1: Is don't blame me if it goes wrong.
2:  Get some more advise.  Ive only seen a picture of this controller.
3: Jump in on this discussion and do tell what you want to do and run it past this lot. http://endless-sphere.com/forums/viewtopic.php?p=168835#p168835

They may have a better cheaper suggestion, or at least already tried something similar.

4: Dont quote me on the above.  If it was my magic controller I would put a little more homework into what to do.

Biasing might have to be changed if you want to run it higher.  Who knows.

Good luck and let me know how what every you decide to do goes.

Cheers.

[Leslie]

At a closer look those IRFP4468PbF.  They are a different package so heat sinking may be different.

Otherwise they should just drop into the old fets spot.

All the main parameters seem in order.  Type of channel, gate max and threshold voltages and current. And the recovery times seem to be smaller.  Better on-resistance.

Fets are a complex little device.  You have so many breeds and flavours these days.

I'll do some more homework tomorrow.  Its late.

[martin]

Hi Mr 317537

you seem to know your stuff, - I'm only touching on the subject at the moment to see what I can do!

Its a good option, replacing the fets - that link you kindly posted with discussions of beefing up the foil traces, how does that sit with your knowledge? (I'm a humble maker of websites and anything made of actual substance is new to me!).

I'd appreciate your thoughts...

Cheers

[GM Canada]

Maybe I'm missing something, but can't you just add another 48v12ah battery in paralell like I did to double my distance?

Gary

[Leslie]

Ps. Anyone else from the UK enjoying cruising at 'ahem, 15mph officer, cough-cough'!
 

Maybe we both missed something.

15mph on a 48v pack is a little, should I say a bit limited.

You may be stuck on the 15mph speed for a while until we can figure out how to get into the software of the controller.

When you up the speed in the software you should get around and about 26mph on a 48v pack.  Would this be an improvement?


Some Pie speeds are limited in this way to be legal all over the world.

Double packs will certainly get you further and your current battery might be worse for wear too..  It seems to lost a bit of capacity over five weeks.

But for a 72v mod you should replace both input capacitors Fets with 100v and make sure the regulator doesnt get fried.


But will Martin get any more speed or distance from a 72v mod?  If he series his battery with one that wont go the distance with a software limit on the speed.

Id say not much speed or distance is going to present itself in a large way.

How fast does martin want to go?  Like 48v unlimited and 20ah pack should be enough of a fix.

[Bikemad]

Ps. Anyone else from the UK enjoying cruising at 'ahem, 15mph officer, cough-cough'!
 

Maybe we both missed something.

15mph on a 48v pack is a little, should I say a bit limited.

You may be stuck on the 15mph speed for a while until we can figure out how to get into the software of the controller change the European law regarding the acceptable maximum speed of an eBike.

When you up the speed in the software don't abide by the law you should get around and about 26mph on a 48v pack. 

Leslie, you did miss something, the actual speed is hiding behind the implied 15mph top speed!

Alan
 

[Leslie]

Logically.
 
I have found that at 60v my hbs36v really sucks the batteries dry when I try to take advantage of the speed hit.  And at 60v the bike seems to use power  more efficient if I rode it as fast as a 36v or 48v bike.  Closer to the hubs intend wattage rating.

If you do over volt your motor, if you want the extra distance hit over speed, one needs to slow the hub down back to an acceptable efficient wattage rating.