Noob advice S Bafang Overvolt

[cachexian]

Hi I'm new here (Another Aussie from Sydney) and would like some advice to see if I can overvolt my Ebike setup.

I have a Suzhou Bafang 8fun motor (SWXB I think)
http://www.szbaf.com/proshow.aspx?id=83
14amp, 36volt Ananda Controller (I think that it's this one)
http://www.ananda.com.cn/anandaenglish/product_list.asp?id=327
10Ah 36 volt Lipo battery.
Fully charged the batt reads at 41.7volts so I assume that it's a 10S. I tried to open the battery case to have a look but the cells were all glued in place with self-adhesive foam and I was worried that by forcing it I would damage some of the dodgy chinese soldering so I gave up and screwed it back together. I don't know the c rating of my existing battery pack.

I was hoping to overvolt to 12s or even to 13s. I don't want to be superhuman, just want an extra 5kph to get to 30-35kph

Do you think that the motor and controller will be able to take 50volts/12s or 55volts/13s? I realise that these are the peak not nominal voltages.

I opened the controller. There were three large capacitors? lying horizontally along one long side of the controller box rated at 100v and a smaller one standing vertically rated at 50v. The other diodes? and capacitors? don't have any printed ratings on them and it's a VERY long time since I knew how to decode the coloured bands.

I was hoping to build a "booster pack" that I could wire in series with the existing 10ah pack. So I understand from the forums that I should buy a Turnigy pack and somehow wire them together to create the correct capacity. So let's say I go with a 2s booster I'd get two 2s 5000maH packs and connect them in parallel to create a 7.4v(nominal) 10aH pack. With the 14amp controller I doubt that I will need to worry about the battery c rating. But does it matter that the original battery and booster battery have different c ratings and different voltages?

If I do bugger the controller, do I need to buy another one of the same brand or can I use a more powerful one such as those mentioned on this forum? Do they interconnect easily or is that another steep learning curve?

Cachexian

 

[renaud]

Hello,

I also have a Bafang 8Fun on a 26" wheel.

Since august 2010 I have done +-5000km with 7s 10Ah and 8s 8Ah. Since few months / 2500km I use a Lipo pack 6s+6s in serial to have a 12s 8000mAh with
an ecrazyman controller (36v / 350 watts).

With the original 24v control in 6s and 7s the top speed without pedaling is around 32km/h.

With the Hobby King 2 * 6s8000mAh in serial, the top speed is 50km/h and i cruise between 38/42 km/h without pedaling. I use the bike for job, 2*35km/day.

 

[kriskros]

i have used my bafang with a 36, 12amp Ping battery andan Infineon 36v, 25 amp[CA set for 20amps max] controller for about1600 miles..no problems... there are earlier reports of bafangs being used with up to 72 volts 20amps.. melted or stripped gears but did not damage windings

 

[cachexian]

Hi renaud,

Thanks for the info.

What is the peak amp output of your controller?

Thanks,
Cachexian.

 

[renaud]

With the 12S the peak is around 48v * 18A = +/-800W. The controller is rated 36v / 350W. When cruising at a conservative 40km/h on the flat the motor eat between 10W and 15W /km depending of the speed wind (the wind is awful in my trip, always in my noose on the morning).

When I use the 36v controller with my 8S batt, the throttle is smooth and comfortable, but when used with the 12S the thumb throttle is to much brutal, it is more on / off

So I have ordered a 48v 350W and waiting for it right now.

 

[cachexian]

At 36v, 15A I only use the throttle as on/off. Top speed unloaded is 30kph with me on it it will go at 25kph on the flat.

 

[cachexian]

So, it sounds as though the motor can take the extra volts. Whether the controller can remains to be seen. But I guess if it does kill the controller, I can always get another one. The Ecrazyman ones don't seem to be too expensive.

I think that I will order 2 3s 5ah Lipo packs. That way I can balance charge them as one 6s pack but can also bulk charge them with an adjustable power supply (eg Meanwell) as long as I adjust the voltage to be no more than 13.2v so as not to overcharge them. The 12v power supply can double as a power supply for the 6s battery charger eg this one http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=12105

If my main batt dies and the new 3s Lipo packs are still going, I can them incorporate them into a new pack with other 6s batteries.

Anyone see any problems with this cunning plan?

 

[renaud]

Well, I do not understand everything...

If you have a 36V batt, you can expect something like 36km/h with you on the bike. Otherless it sounds like a limitation on your controller or something wrong.

 

[cachexian]

Yes. My controller is the limiting factor. The Ecrazyman controller you have outputs 25A peak. Mine has 15A peak. That's the difference. I get max 30kph unloaded (wheel off ground) and 25kph on flat with me on the bike.

 

[kriskros]

to increase speed,increase the voltage..36 to 48....change wheel diameter...20" to 26".... change the motolr ... high torque to high speed.... amperage is torque,not speed... hill climbing, load weight.... if you are running a bafang at more than 10amps, changing one gear to steel is a good idea.. i did...running 12 amps i stripped one at about 300 miles... no problems since then