Problems with Magic Pie: throttling, braking, cruise control.

[Artem]

Well, I forgot to experiment with the beeps, but anyway, during my unsuccessful attempts to program with USB cable I have definitely heard beeps. So it is not like sensorless mode problem, I think.

Yes, my wattmeter revived!
Today there were no rain and I took pre measures made of cellophane

Still can't find SAE plug, so I decided to solder wattmeter connection firmly. It helped a lot - fresh 54.4V battery didn't drop lower than 45,7V at 18.3A. I even started to hope, that there will be no usual cut-off, but, alas, it is still there. Also I noticed, that just before cut-off motor starts to "choke" a little - like my "regen" braking (that doesn't work as well) do on lower speeds.

Here are the stats from my ride (voltage without load):

4,565Ah   50,26V    18,76 km
7,871Ah   47,03V   30,26 km

By the end voltage under load was approx 44V, and I have feeling that overall power lowered, at least I didn't notice any current above 17A.

So, 850W is maximum that I saw from the 1KW pie in any condition: flat, elevation, downhill. Cold it be the case of those cut-offs?

[DirtyGinge]

750w was my typical output from the internal controller version of the Magic Pie

if I went on any long rides, as the internal heated up, I would feel heavy vibration under heavy load

my idea is that near the end of your ride, stop for 30 mins, have sandwich, beer etc, let controller and internal pie cool down ( even macs can be warm after several hours), then resume, try result....if same in first minute or two, then heat of the controller is not an issue

[Artem]

Well, the situation is not clear still, but anyway, with that bunch of problems it is obvious that controller is not in good condition too. So I decided to replace it until spring.

Since I never had any reply from GM, is there anybody on this forum, who can help me with buying/replacing it?

[SydneyCommuter]

I totally get the frustration. My internal pi hadintermittant fault. Cut out under load, wouldn't sart again after braking for about 3secs, wouldn't take the config changes from the pi200, regen braking wasn't much good etc.... Now I have a dual external to compare against and it's absolutely no comparison. Throttle responds immediately every time. Hasn't cut out on me once ever under all manner of stop, start, hills gutters you name it, even going slow on very steep hill with nit wit car trying to squeeze me into the gutter, just kept on purring. Regen works flawlessly at all speeds. So if that's not the experience your getting you got a dud faulty interal controller like me, my old one bought at about the same date as yours, my guess is there's something gone in the power CCt, blown fet or the like and fried something to do with the programmable EPROM. Just cutvyour losses and scrap it and start over with the external controller. I ether swap out the lot or check the post showing how to retire for xtnl.  Good luck!

[Artem]

Someone mentioned new e-mail to contact GM: wyh@goldenmotor.com
And suddenly it works

They have agreed to send me a replacement controller. So we'll see if it help

[Artem]

So, the good news are: the new controller has solved almost each and every issue mentioned here.

I tested it a bit, no problems with throttling, and I managed to see unbelievable 25A while going uphill (i assume nobody saw 30A cont and 50 peak here from base internal? ) Not to mention cruise controls, brakes etc. And I can change settings now.

But there is still a reason to worry about. 25A is good, but it drops voltage down to 40V from 54,6 fresh. That's not quite right, I believe? Seems like it will drop lower than cut-off limit after some kilometers.

So now I'll lay my hands on the battery, the controller issue seems to be closed.

Oh, wait. I found that speed characteristics are getting worse as well. Max speed is 38km/h even downhill. Maybe some settings to play with.

But for now I'm happy to have the cruise button back


 

[Bikemad]

I'm very pleased to hear your controller problem has now been sorted.

And a big "Well done!" to David at GM, whose customer service seems to be getting better every day.



Alan
 

[Artem]

And a big "Well done!" to David at GM

Absolutely!

[Artem]

Don't know, maybe I should start new thread, but I'll continue for now.

Well, I took a first serious ride after the controller replacement. And I got some really strange results

First of all I changed some settings via USB, set 48V, 100% rpm, low pedelec, etc.

At start feeling was like it really got little bit faster. At least I managed to ride some 45km/h downhill (with the first controller max was about 49). After maybe 24km it became obvious that power is getting down. No more wonderful 25A, maybe 16 as max. Throttle lights behave more correct - never got the whole way down.

 I continued to work out battery - I was wandering how long will it last, remembering my 48 km long rides. Closer to 42 km something really strange become obvious - amperage almost vanishes. I got some hilarious 2 Amps. No hill climbing with those conditions, of course. Meanwhile lights shown stable red without even a flicker (with the old controller by that time usually all lights got off under load). Well, it seemed that motor could honestly ride all 48km, but it was of no use - when I took the bike home it hardly could carry its own weight up the rails beside my stairs (with 0.6A).

45km, including 3-5km of some ill hobbling.

And overall voltage didn't drop lower than 42V.

First thing home I disassembled battery and measured triplets (yes, I finally realize that it is LiMn rather than LiFePo as it is stated on a label . To my surprise, all of them had approx 3.35+- 0.04V. So battery looks like normal.

So, what was it, anyway?

[Bikemad]

Artem, now that your motor is drawing more power from your battery pack, it will obviously consume the available battery power much quicker.

If you use more power, the majority of the extra power is used to overcome the additional drag from the increased speed, therefore your range will also be reduced.

If a pack could deliver 100% of its stated capacity, a 12Ah pack @ 17 Amps would last more than 42 minutes, but the same 12Ah pack @ 25 Amps would last less than 29 minutes. The duration is reduced by 32% because the pack is now supplying 47% more energy under maximum load!

More power will result in faster acceleration and higher speed, but a large proportion of the extra power will actually be wasted by the extra aerodynamic drag at the higher speed. Check out this site for more specific details.

This would probably account for the power starting to reduce much sooner than it did before, but I can't explain why the battery light used to go out completely under load, whereas now they do not.

The fact that your cells were all discharged to 3.35V ±0.04V is a pretty good indication that your motor has actually consumed around 98% of your pack's total capacity:



If your battery management system has been designed to gradually reduce the current when the voltage approached the pre-set minimum voltage (instead of simply cutting it off completely) this could account for the extremely low current readings that you observed during the final part of your trip when your battery was almost completely exhausted.

Alan
 

[Artem]

Understood that. But I have standard GM 48V battery in aluminum case, so, the standard BMS (GM misguide me again, I'd rather expect that I've bought LiFePo). I can expect some power degradation while battery discharges, but should it be so dramatic?

I can conclude from what I saw, that the battery internal resistance is 0.500-0.650 Ohms. Is it normal at all for this battery?

[Bikemad]

As I've never used one, I can't really comment on how noticeable the typical power degradation is with the GM LiMn battery packs during use, perhaps other users on this forum would be kind enough to comment on their experience.

Regarding your estimated internal resistance, the individual LiMn cells are reported to have an internal resistance at shipping of 23±1 milliohms By AC 1 kHz which (if my calculations are correct) is approx 0.008 Ohm for each group of three paralleled cells. Multiply this by thirteen (for the thirteen cell groups connected in series) and we get 0.104 Ohm.
As the cells are no longer new, presumably their resistance will have increased as a result of both use and age, which would make this value a fair bit higher.
If we also take into consideration the build up of resistance from the internal wiring, the MOSFETs and shunts on the BMS itself, and not forgetting the resistance across switch contacts, battery power connectors and even the shunt within your ammeter itself.

With all thing being considered, it's possible that your suspected 0.5-0.65 Ohm could actually be normal. 

Alan
 

[Artem]

Thank you very much, you clarify many things for me again Will wait if somebody o current owners will respond.

[Mat]

Hi,
I am having a similar problem, 2 months ago when I received the Magic Pie 3 48v.
It was working perfectly, then 2 weeks ago sometimes it didn't start on its own, I had to pedal for a few meters then the engine would start.

Yesterday he engine didn't start again, I pedalled for 200m and still nothing happened I only hear a small noise from the engine meaning it is alive but it doesn't want to turn. I only hear the noise if I pedal but it doesn't bring power. I tried in freeweel mode and even by turning the wheel by hand it is to weak to start. (battery fully charged, throttle showing green light, and same problem if I unplug the brakes and cruise control button)

Can anyone help me?
Thanks in advance

[MAGICPIE3FOCUSPOWER]

Maybe hall sensors problem..