Drag Motorcycle

[Tonymunn]

Well, I'm finally doing it. I'm building a ground up custom electric drag bike. The batteries were my starting point. I'm using SPIM08,, 8Ah cells from Battery Hookup. The configuration is 28S 6P. The cells are capable of 200A discharge. Six in parallel is 1200A. At 102V, and 1200A it should be pretty potent. I currently have an 300A ANT BMS, peak to 500A, I think? I have a 5KW, 4T, QS260 V4 with a 16" rim and a 140/70-16 Michelin City Grip tire. The front end is a Kawasaki Ninja 250 also with a Michelin City Grip tire. The controller is the FarDriver ND96680. More to come.

 

[dominik h]

To begin with the ND96680 is ok, but for a drag bike you need more phase current.
Phase current is tourque and starting tourque is what you need to be fast.

 

[Tonymunn]

To begin with the ND96680 is ok, but for a drag bike you need more phase current.
Phase current is tourque and starting tourque is what you need to be fast.

Thank you. I realize that phase current is key for torque. The ND96680 is a starting point. I will not even be able to run my battery at full charge. The ND has a HV limit of 115Vdc. A fully charged 28S battery has a voltage of 117.6. Everything is being over built to handle future current. Even the QS160 may likely be replaced. My buddies at Keith's Kreations Inc. here in Albuquerque are incredible craftsmen that care about doing it right.

 

[thebes]

The nd96s should be fine at 28s, I know they say the limit is 115v but the mosfets are 150v and you can set the limit in the app to a max of ~121 (it might be slightly lower for new versions of the app/controller).

 

[SlowCo]

Great project, I'll follow your build with interest. Good luck and enjoy the process.

 

[Tonymunn]

The battery is 36" long X 14" wide X 9" tall. It has thermostat controlled fans for cooling.
Battery:

• Ant BMS 300A
• 300A circuit breaker
• 300A fast blow fuse
• 500A contactor with a pre-charge resistor

The frame:

• Water jetted 1/4"aluminum sheet.
• Bent with the brake
• TIG welded by a welding artist.

 

[gromike]

Looking good, but curious. How much does the battery weigh?

 

[Tonymunn]

Looking good, but curious. How much does the battery weigh?

I'll weight it tomorrow at the shop.

 

[dominik h]

The battery is 36" long X 14" wide X 9" tall. It has thermostat controlled fans for cooling.

For drag use only you probably won´t need a cooling fan, but I would think about pre heating the battery for less resistance.

I´m missing my battery heating system these days seeing 15V sag @400A instead of 5V in warmer days.

 

[Tonymunn]

For drag use only you probably won´t need a cooling fan, but I would think about pre heating the battery for less resistance.

I´m missing my battery heating system these days seeing 15V sag @400A instead of 5V in warmer days.

I'm in Albuquerque, NM. It's usually very warm during racing time. It was 61 degrees today. It was in the 60's yesterday.

 

[AdR]

300 amp BMS on a 1200 amp battery????
5Kw motor for a drag bike????
102V X 1200A=122Kw battery power.
the numbers don't seem to add up

 

[Tonymunn]

300 amp BMS on a 1200 amp battery????
5Kw motor for a drag bike????
102V X 1200A=122Kw battery power.
the numbers don't seem to add up

Yes. You ever heard of a work in progress. You do realize, I can install a higher current BMS and buy a hub motor rated for more than 5KW. I can also use the ND96680 controller for another project and get a bigger controller. Here " Building A Ludicrous 14s2p SPIM08hp battery ", These are the batteries I'm using. They are in a 28S-6P configuration grab a calculator and check the math see if it adds up. I also have a 72V 63.5Ah battery pack on a 1.5KW hub motor scooter that exceeds 65mph. Just because the batteries can do 1200 amps doesn't mean I have to use all it's 122kw capability.

 

[Tonymunn]

Frame is coming along just fine. 1/4" aluminum. The Ebay swingarm from an '86-'87 Honda XL600R is arriving tomorrow. It has the 200mm dropout width I need for my QS motor. I forgot to weigh the battery today. I'll do it tomorrow. I'm guessing the weight will be about 120lbs. without the CB/contactor/fuse/Terminal block assembly

 

[Tonymunn]

I'll weight it tomorrow at the shop.

The batteries weigh 205lbs. A little more than I expected.

 

[Tonymunn]

A little more welding today. Checking out the battery fitment in the frame.

 

[Tonymunn]

More welding. Worked on the battery pack enclosures today.

 

[Tonymunn]

While adding a 300A 28S ANT in place of my 120A BMS today and pinched a sense wire and !*PIFF*!!!!. I'm ordering a new BMS right now. They are almost impossible to find lately. It's coming from China so who knows when I'll get it. Pretty bummed but I'll definitely be a lot more careful next time.

 

[CRF265]

Cool build, fabrication looks very impressive. What are your power and et goals?

When wiring my ANT bms I did not plug in my sense wires into the bms until all the wiring was completed to avoid any such issue.

 

[Tonymunn]

While adding a 300A 28S ANT in place of my 120A BMS today and pinched a sense wire and !*PIFF*!!!!. I'm ordering a new BMS right now. They are almost impossible to find lately. It's coming from China so who knows when I'll get it. Pretty bummed but I'll definitely be a lot more careful next time.

 

[Tonymunn]

Aligning the rear wheel to the swing arm. I don't know how to figure out what spring rate and shock length I will need. I'm sure A.I. can tell me once I give it the specs.

 

[Tonymunn]

Cool build, fabrication looks very impressive. What are your power and et goals?

When wiring my ANT bms I did not plug in my sense wires into the bms until all the wiring was completed to avoid any such issue.

I was done wiring. Pinched a wire while putting on the battery cover. I really haven't set any power or E.T. goals yet. This is just a baseline build. I will be upgrading from the ND96680 and the 5kw QS260 hub motor once learn a bit more. The battery and frame are being built for future upgrades.

 

[adsc]

Regarding the BMS and the amp ratings, couldn't you just make the BMS control a contactor instead of running the whole battery power through the BMS? Basically wire the motor controller directly to the battery through a normally open contactor, and use the BMS (and the ignition key) to control this contactor (and a precharge circuit, if you don't want to weld the contactor shut on the first activation).

I'm not sure if it's the case, but it seems to me it would be easier to source the parts for such a setup, and it would allow you to use a cheap BMS, so probably the costs would also be lower.

 

[harrisonpatm]

Regarding the BMS and the amp ratings, couldn't you just make the BMS control a contactor instead of running the whole battery power through the BMS? Basically wire the motor controller directly to the battery through a normally open contactor, and use the BMS (and the ignition key) to control this contactor (and a precharge circuit, if you don't want to weld the contactor shut on the first activation).

I'm not sure if it's the case, but it seems to me it would be easier to source the parts for such a setup, and it would allow you to use a cheap BMS, so probably the costs would also be lower.

This is a common method, you'll see in my signature that my builds have used it. It's really a matter of preference.

 

[Tonymunn]

adsc, I would love to learn more about how to do this method of controlling a high current contactor with a BMS. It does appear to be a more affordable option. Is a "cheap" 28S BMS an actual thing? I haven't received my 420A continuous ANT BMS from China yet. I have a 500A contactor and the pre-charge resistor.

 

[adsc]

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.