Overvolting - as easy as it sounds?

[newguy]

I recently set up my first conversion. 36v Bafang (code 13) from BMS battery. It is working out great, plenty of toque but I'm now in search of a higher top speed. I use it on a 9 mile commute to work, with 0 traffic .

I'm surprised that my top speed is only around 17/18 mph, what are my options for getting a higher top speed? Overvolting appears to be the first option, but I dont want to buy another battery, can i use my existing battery in series with another?

Has anyone had a similar set up and modified for a better top speed?

Thanks,
Adrian

 

[Deleted member 4366]

First thing to try is the 3 speed switch connector, which can give a significant increase. You don't need a switch - just shove a bit of wire up the middle hole, and bridge it in turn one side and then the other. One way will make it slower and the other faster.

After that, 12S lipos for a 22% increase in speed and a bit more power, which requires no other mod.
A 48v battery will give a 33% increas, and it should work with no mods to your controller, although you might want to change the LVC resistor. which is pretty straight forward.

 

[Jeremy]

The above tip from d8veh also works with some Xiechang controllers (e-crazyman, infineon, but perhaps not Lyen).

By default all these controllers (both the Xiechang and the Wuxi Xichen Micro-Electronic Co ones) use the internal Speed 2 setting if there is no 3 speed switch fitted. If they've been programmed by the seller for less than 100% for Speed 2 (which seems to often be the case, certainly the e-crazyman versions are often shipped out like this) then simply fitting the link as d8veh says enables them to work at the 100% speed.

The Xiechang controllers can be fairly easily reprogrammed to get around this. I tend to usually programme all three speed settings for 100%, unless I intend to use a three speed switch. It's a pity we can't get hold of the programming protocol for the Wuxi Xichen Micro-Electronic Co controllers that BMS, GBK, Greentime etc sell, as it would then make these controllers far more versatile.

 

[newguy]

First thing to try is the 3 speed switch connector, which can give a significant increase. You don't need a switch - just shove a bit of wire up the middle hole, and bridge it in turn one side and then the other. One way will make it slower and the other faster.......

Could you explain this a little further? I suspect the motor isnt running at 100%, because it drops off and stops running at a certain speed. Are we talking about the 3 wires from the motor?

 

[newguy]

This is my controller, im only using the 3 wires to the motor and the 3 wires to the thumb throttle. Hope this helps.

Thanks.

 

[Old_Dave]

The KU90 controller comes in different variations, lol all with the same label, but afaik no 3 speed connector, I do have a spare 48v one


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[newguy]

So if this is isnt an option with the KU90 controller, would getting a new controller provide any significant gains? or would i be better investing in an additional battery to go from 36v to 48v?

 

[Old_Dave]

Just up the battery voltage... Not sure with d8veh's % comparing 12s lipo to 48v but he is normally right
But a 48v pack & charger will certainly be the simple option & just mod your existing controller for the correct Lvc, or get a 48v one at the same time as the battery if you don't fancy soldering.


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[wurly]

There should be another plug with three wires (three speed switch). One will be black, the others will be blue and green (i think). What Dave is suggesting is link a wire from the black(gnd) to the other colours. With the wheel off the ground you will hear the hub either going faster or slower. I have a KU93 controller and linking the wire make it go slower. So i believe mine is programmed for selecting a slower speed with the switch. I have never been able to get mine faster with any combination. Mines a code 10 on 48V so i wouldn't want it faster anyhow. Try Dave's method first, but i think you will be looking at getting a faster wind motor or higher voltage battery.
What battery do you have? maybe you can add cells?

 

[jackhandy]

I may be reading this wrong (wouldn't be the 1st time ) but I think newguy is hoping to add a 12 volt battery in series with his 36 volt one...

 

[newguy]

I have a 36v 20Ah battery 36V 20Ah LiFePO4 Electric Bicycle Battery Pack - BMSBATTERY (BMSbattery sent me this by accident, i ordered the 13Ah battery, but in this case im not complaining )

I was thinking I could add any 12v battery in series, and wire up a "boost" button, as only about 50% of the journey would really require it. Has anyone ever tried this?

I've checked the controller for the three speed switch, the only remaining 3 wire connector is used for the pedal sensor, i assume that isn't correct? Found the controller manual https://docs.google.com/viewer?a=v&q=cache:x__qNE4YfcsJ:www.pedelecforum.de/forum/attachment.php%3Fattachmentid%3D11437%26d%3D1304973214+&hl=en&gl=uk&pid=bl&srcid=ADGEESgAx03Xrp7KiY-S28Bm3O9z3GqqR21LsZLMe4MN-NZSIEJ1Td7owXlvFNDnl261QU-yz5_15-d4kS30rp9HbkUQHT3EyePXAp8PJWYi5X1osLuKNMN6uNKogm_cj0dZHadiKH1t&sig=AHIEtbRu19P39CMrkMtIIkHKQb04Z9lHrg

 

[wurly]

I was forgetting, we had a discussion here about the differences to the ku controllers including the link for changing between 36-48v.
http://www.pedelecs.co.uk/forum/electric-bicycles/13365-problem-ku123-controller.html

The boost button is a good idea but it would involve using a heavy relay to insert the extra battery inline with your original.

I think you would be better getting eight identical cells,bms and charger from BMSBattery to make a 48V battery. It would be the cheapest way of increasing the speed. My other code 10 BPM runs at 23-24mph on 36Volts which means getting another hub if you didn't want to alter your battery. You could swap the internals and sell the code 13.
No options appear easy.

Is your battery made up of these type cells?
http://www.bmsbattery.com/lifepo4-cell/314-lifepo4-7070260-polymer-cell.html

 

[Jeremy]

The KU controller is really a Wuxi Xichen Micro-Electronic Co (goodness knows why the sellers give them different names). This does have the three speed switch connections internally, even if they aren't brought out of the case.

Generally, if the 3 speed switch wires aren't brought out of the case then the controller will be programmed by the seller so that Speed 2 is 100%, so it will most probably already be running at the maximum speed it can.

 

[Deleted member 4366]

A bit of a bummer not having the three speed switch connected. 17/18mph sounds a little slow for a code 13. I would have expected more like 19mph. It's not worth gambling on a new controller, for the small difference it might make, but if you get the chance to borrow one, it might be worth checking any difference in the no-load speed.

Your best option now is a 48v battery, which will be expensive, although you could sell on your 20aH 36v one for a fair bit if it isn't too old. I wouldn't bother trying to add a 12v battery. It might work, but it'll be untidy and complicated.

Which motor do you have - front or rear? 350 or 500w?

 

[rpurchon]

you could try a controler from e crazyman,ask for programming cable and 3 speed switch.
these can be programmed to output 120%.
richard

 

[newguy]

@wurly yeah I think the battery is made up of those cells, its shrink rapped, so i cant be sure. I have 36v 20Ah only need a 9 mile radius, i wonder if i could reconfigure the cells to get 48v? could anyone hazard a guess at the current configuration?
I assume these cells aren't load balanced either.

My code 13 should run at 235rpm, code 8 runs at 393rpm, which seems a substantial improvement, about 40%, the 18mph would maybe go to 25mph . Unless I'm missing something important.

@d8veh the battery isn't too old, about 2months now. Buying a new battery would be very expensive, I think i would go down the route of making my own from zippys or similar to save money. That area seems very complicated still.

Its a 350w front fork hub motor, its attached to chrome forks with torque arms. My last cast aluminium forks snapped, doh!

Thanks for all the help guys

 

[Deleted member 4366]

@wurly yeah I think the battery is made up of those cells, its shrink rapped, so i cant be sure. I have 36v 20Ah only need a 9 mile radius, i wonder if i could reconfigure the cells to get 48v? could anyone hazard a guess at the current configuration?
I assume these cells aren't load balanced either.

My code 13 should run at 235rpm, code 8 runs at 393rpm, which seems a substantial improvement, about 40%, the 18mph would maybe go to 25mph . Unless I'm missing something important.

@d8veh the battery isn't too old, about 2months now. Buying a new battery would be very expensive, I think i would go down the route of making my own from zippys or similar to save money. That area seems very complicated still.

Its a 350w front fork hub motor, its attached to chrome forks with torque arms. My last cast aluminium forks snapped, doh!

Thanks for all the help guys

Here's what's inside. It depends whether you've got th long thin one or short fat one (2 versions). This is the short fat one:

 

[newguy]

Think mine is the short and fat version, looks more complicated than I thought in there, I guess reconfiguring isn't an option. Its either a new battery or higher RPM hub motor???? I'll compare prices

thanks

 

[Jeremy]

you could try a controler from e crazyman,ask for programming cable and 3 speed switch.
these can be programmed to output 120%.
richard

Worth noting that "120%" is not 120% speed! This is a confusing translation error on the pseudo-English
software interface. What changing from 100% to anything up to the mythical 120% does is change the point at which speed control switches from pulse width modulation of the motor voltage to what's called block commutation (which gives 100% battery voltage to the motor). I can explain this further, but don't want to wind up the anti-technical members...........

In essence, it can be quite iffy to set notional speeds of greater than 100% with some motors, as the no-load current will rise quite markedly for little or no increase in performance. This just makes the motor run hot and increases the risk of the controller getting hot too, so needs to be used with extreme caution.

For example, on one of my motors anything over 105% causes the no load current to increase by a factor of 4, with a distinct change in the noise the motor makes at full speed. The motor doesn't actually run any faster when you measure it, either.

 

[NRG]

Sod the non technical members, post to your hearts content Jeremy...if its too technical those that don't understand or care can skip the post...I've read a bit about it on ES but to save sifting through reams of posts please could you explain here, thanks!