Drag Motorcycle

[dominik h]

I testet a 200A JK-B2A-24S to "death" with an electronic load.
3x400A for 30 seconds , 3x450A for 20Seconds was no problem 3x500A für 10 seconds was also ok.
Then I tested it with 500A for 20seconds. After 15 seconds it turned completly off without any visible defect components. All the Fets and the shunts are still ok.
I think it was a software based 2nd level short circuit protection, which turned of the BMS completly.
I now use the version with integrated heating controller with 400A settings and it is doing fine since 8000km and nearly two years.

 

[A-DamW]

Is a "cheap" 28S BMS an actual thing?

You could use 2 JBD model SP14S004 14s, cost about $10 ea., about the size of a credit card. bluetooth builtin.

Wire the output to some small intermediary relays to the contactor.

 

[Tonymunn]

I don't know much more about it than what I wrote. Your ignition key would be in series with a switch that is closed by the BMS when discharge is allowed, and that would close a precharge contactor in series with a resistance connected to the motor controller, and then after 1-2 seconds, the precharge contactor circuit would open the main contactor (which would probably have a fuse in series). Apparently you can get contactors with a built-in adjustable timer as a side function, but I'm sure you could also implement the delay in different ways (could even do it manually with a three position key switch, but then don't forget to wait 1-2 seconds on position 2).

As far as I understand it (which is not very far, admittedly), it has several advantages:
- the BMS is not under load, which should increase its lifespan and remove some failure points
- the BMS doesn't get hot
- if the BMS gets fried, the contactor will in most cases close, but if the main load flows through the BMS, it might still conduct when damaged
- you can in theory upgrade the battery without having to replace the BMS (for example if you get cells with a better C rate)
- and of course, the main reason why it would make sense in your case: you are not limited to the amp rating of the BMS

I'm sure people who have actually done it and understand something of the matter like @harrisonpatm can give better information.

I have looked at ANT BMS, and it seems the "small" 28S BMS are only like $50 cheaper than the large ones at the moment, so you probably wouldn't save much, if anything at all.

I currently have a 420A continuous ANT BMS on the way. Thanks to A.I. I understand how to control a high current contactor using a BMS. This will definitely be my go to for future builds. Thank you all. That is why I'm here.

 

[Tonymunn]

You could use 2 JBD model SP14S004 14s, cost about $10 ea., about the size of a credit card. bluetooth builtin.

Wire the output to some small intermediary relays to the contactor.

Thank you. I will research how to integrate 2 - 14S BMS' onto a 28S battery while integrating contactor control.

 

[Tonymunn]

On the table again for swing arm fitting. Long and low.

 

[Tonymunn]

Welded in the swingarm mount today.

 

[forcefed86]

You can generally run 40-50kw on those "5k QS motors" for 10 sec bursts. I do on the QS165s (both the 5kw version and the 10kw).

Thats s ton of frame and battery weight. For a drag build you want it to be as light weight as possible generally. Might look into LIPO cells. They are by far the most energy dense for their size. My 128v pack is only 15AH and will dump 330a (max line that 96680 can do) easily in a 28s3P (12 5ah 7s packs.) configuration. The pack is just under 25lbs. 200+lb battery seems crazy on a drag bikle to me. My bike is about 110lbs w battery for refrence.

I typically just us a $30 balancer and skip the BMS. Use the software to limit current. That 96680 will do 28s no problem I ran mine at that for years. I will say FD hard limits phase amps at low RPM. So they make for pretty poor all out drag setups. Still fun to play with but you want a modified FD or upper end Moxin or Kelly if you really want lots of launch Phase amps down low.

 

[Tonymunn]

You can generally run 40-50kw on those "5k QS motors" for 10 sec bursts. I do on the QS165s (both the 5kw version and the 10kw).

Thats s ton of frame and battery weight. For a drag build you want it to be as light weight as possible generally. Might look into LIPO cells. They are by far the most energy dense for their size. My 128v pack is only 15AH and will dump 330a (max line that 96680 can do) easily in a 28s3P (12 5ah 7s packs.) configuration. The pack is just under 25lbs. 200+lb battery seems crazy on a drag bikle to me. My bike is about 110lbs w battery for refrence.

I typically just us a $30 balancer and skip the BMS. Use the software to limit current. That 96680 will do 28s no problem I ran mine at that for years. I will say FD hard limits phase amps at low RPM. So they make for pretty poor all out drag setups. Still fun to play with but you want a modified FD or upper end Moxin or Kelly if you really want lots of launch Phase amps down low.

Good to hear about the peak capability of the QS motor. You have a good point about battery and frame weight. The frame is pretty light weight being all aluminum. The power density of the battery is not the best but, the peak amp capability is incredible. 1,200 amps at 28S is scary. I just call it a drag bike because of the way it looks right now. I am happy about how robust the battery enclosure is. I will not fear the bike falling and damaging the pack. It is my first attempt at doing a real quality build. I've built other projects but not to the level I could be totally proud of. With my current build, I've left plenty of room to upgrade batteries motor and controller. I'm also proud of the build so far. Thank you for chiming in. I appreciate your input.

 

[forcefed86]

That frame and all look top notch. Don’t get me wrong, that’s beautiful work! 140kw is def. nothing to sneeze at! I think it will sag pretty heavy on ya at 1200amps though. At 200A, I saw about 15v of sag on my 20s1p SPIM08 pack (only 8ah). Great little pack though. It took a beating regularly and never had an issue.

Was only mentioning you could get by with a 87% lighter bat to max that controller and motor if drag racing was the goal. That controller only takes 330 line amps. You’re gonna fight traction more than anything with that skinny tire. Hubs are def the power kings, but its a constant battle trying to get any of it to the ground. That setup looks like its screaming for a 26x10” slick and 2 giant mid mounts to me.

Best of luck with it!

 

[Tonymunn]

I mounted the remote handlebars. Steering link rod tomorrow.

 

[senlin]

I mounted the remote handlebars. Steering link rod tomorrow.

That is such a good design for a lightweight aluminium drag frame, lots of room for battery. I'd just bypass the BMS on the output and use it for charge only and balancing cells. Really looking forward to your progress.

 

[Tonymunn]

That is such a good design for a lightweight aluminium drag frame, lots of room for battery. I'd just bypass the BMS on the output and use it for charge only and balancing cells. Really looking forward to your progress.

I'll post an update really soon. Thank you.