Performances Magic Pie

[Denis]

Question      : is it possible that bad performances are caused by the missing of brakes with cut off and cruise control? Have someone tested Magic Pie without cruise control and brakes? Thanks for all your answers 

[Gapy]

Hello Denis,

I have connected just a twist throttle and on 36V I get around 31 km/h and on 48V I get around 42 km/h, so I think the problem is somewhere else...
Maybe it is just your battery-when I connected the fourth SLA battery wich is quite old, the preformance dropped after 100m-speed went from 42 to 30 km/h, but the battery still indicated 51V...

I really suggest that you try diffrent battery...

[jimabbott]

Hi Denis

You say your using a 36v 9A battery that is not lifepo4 please post a link to that battery for me to check out for you as if the continious or maximum ratings are low this could be causing a reduction in performance.

Jim

[Denis]

Thank you for all yours informations. I toke my battery from my other e-bike:

http://urbanmover.com/products/powerAssistedBikes/UM36SX.php

I don't have other informations about battery, but what I can say is that on the urbanmover bike, battery works well.

[jimabbott]

I'm sorry then as without the full specs for the battery I can't give an exact reply.

Jim

[muzza.au]

Denis,

You say that the urbanmover is 250w at 36v. That means it will draw a max current of 6.9a from your 9ah battery. Lets say its 9a as the battery is a 9ah battery. On another thread a MP user said they got a max current draw, using 48v admittedly, of 26a. Lets say its 20a for 36v, even that is more than twice what the battery may be able to handle and therefore it may not be up to the task to power the MP to full speed. Drawing more current from the battery than its rated at may cause the voltage to drop and then cause a lower top speed.

Muzza.au

[Denis]

Thank you all, but what kind of battery I must purchase to reach 33 Km/h. Is it possible to think about a battery lower than 5 kg? 

A battery with these specification could work?

lithium Ion/ LiFePO4 battery pack is as follows:
1. Battery voltage: 24V, 36V;
2. Battery capacity: 8Ah, 10Ah, 12Ah;
3. Weight: 3Kg~4Kg
4. Dimension: 80x150x250mm (OUT), 64x134x150mm (IN)
5. Cell Chemical: LiFePO4, LiMn2O4, NiCoMn
6. Continuous discharge current: 15A~30A

(From bmsbatterry)

[muzza.au]

G'day Denis,

If you want to reach and exceed 33km/h, then go with a 48v battery, but for a 36v battery having read the data sheet for the 36v MP I think it says the max current it draws is just under 25amps (I cant read chinese). Therefore you will need a battery that can supply that amount of current. For example Pingbattery has a 36v 15ah Lifepo4 battery that is rated at 15a but can supply 30a max. It is just over 5kg, see: http://www.pingbattery.com/servlet/the-9/36V-15AH-V2.5-LiFePO4/Detail
Whereas the 36v 12ah GM battery (I think it is LiMn204) says it does 35a max, is about 5.5kg and is almost $60 cheaper.

The above is probably the minimum ah rating, of coarse you can go higher and that will also give you greater range, but will also burn a bigger hole in your wallet.

You will have to do your research on what you need and what you can afford.

Muzza.au

[Denis]

muzza.au, thank you! extremly clear, my goal don't exceed 33Km/h (30km/h will be ok too), maybe i'll purchase gm 36v 12ah battery, i'll look around for other and cheaper solutions 

[Denis]

Another question: what is the range with a 48v 10ah using Magic Pie without pedelec? And if you help the motor?

[GM Brazil]

48v * 10Ah = 480Wh

If you use it at maximum power all the time, 45km/h with no wind or hills: something like 33km of range
If you go at 30km/h all the time, no wind of hills: 60 km

This calculation takes in account the power you need to keep that speed with a bike, considering the wind resistence caused by the speed alone, mechanical resistance from the bike, 5 starts from stop of a 140kg rider+bike and the efficiency of the pie that is considered constant 76,8%.

[Bikemad]

Another question: what is the range with a 48v 10ah using Magic Pie without pedelec? And if you help the motor?

Denis, there are many factors that will affect the range, these include:
Speed, overall weight, wind resistance, headwind/tailwind, tyre type, tyre pressures, road surface, hills, gear efficiency, amount of throttle used and amount of pedal assistance contributed etc.

at 48v I can get 40km/h average, on full throttle and I can get about 30km on full throttle

I don't know whether this was with or without pedalling, but the above 30km range was achieved using a 48V 12Ah pack in the Netherlands, which is not exactly famous for hills! So if you live in a hilly area, the range will obviously be greatly reduced.
To offset this, the more you assist the motor, (and the less throttle you use) the further you will go before the battery is fully discharged.

Hope this helps.

Alan
 

[GM Brazil]

Here is the spreadsheet I did for this calculation

[GM Brazil]

ps.: If anyone is curious I can explain the math/engineering behind the calculation

It is easy to change the formulas and add the % of the hill so you can know the power you need or even if you bike is able to climb that "steppy" hill you know with your weight.

To validate this spreadsheet I compared to some data from here and ES (data from CA or Wattup for example) and is showed very good approximation with the range and cruise power consuption!

[Denis]

Thank you for very clear explanation