E Dirtbike battery

Hi guys i'm building an electric dirtbike with a 2001 yz 250 frame, and the motor i'm using is a qs motor 138 3000w, i'm not sure which controller i'm going to use now, i was going to use the BAC4000 but I saw today they are super backordered.

My question is, i'm having trouble finding which battery I should use, I'm trying to make the bike similar to the Alta dirt bikes, it's mostly going to be offroad, jumping and such, I wanted a lithium ion battery pack but I can't find any that have high amps, I figure I need a peak of 350-400 or so. I was leaning towards a lipo pack but seeing they don't last as long i'm not a fan, any help would be greatly appreciated, what amps do people usually run on their qs motor 138?

If you have the skills to jump a full size dirt bike more than a couple feet and have ridden an alta you're probably going to be really disappointed with the qs 138. You would probably want a motor rated for at least 15kw continuous 40kw peak. But, of course, it all depends on budget. So first question is, how much will you spend on this project?

Did you try getting an eval kit straight from ASI? If you're considering buying from ERT, don't, the owner is habitually dishonest and inconsistent at best. The BAC4k is a great controller although the 8k would be more suitable for a full size dirtbike.

You can get as much power as you want without lipo you just need a proportionately bigger pack. Alta, zero, tesla....none of them use(d) lipo. You can make your own pack using canned cells, use salvaged EV cells from tesla, nissan, etc. There are a whole lot of options there. Where were you looking for batteries?

I was thinking of spending 2k or so for this project, it's my first electric project so i'm just trying to figure out how everything works going forward.

The QSmotor isn't set in stone just yet, I ordered it but it still hasn't shipped, what are some brands I should look into that give that power that I would need?
I tried getting a kit from ERT but didn't get response from the owner, but I saw he posted in a Sur ron facebook group yesterday saying the BAC4000s are on backorder from ASI, I was going to get a very good battery and controller so if anything my weakest point would be the motor and it wouldn't be that bad to switch out and upgrade.

I was looking on DHGate, Alibaba, Aliexpress, and then HobbyKing/Amazon for Lipo, I also checked out some sites people linked on here but they were to expensive.

Is there more controllers that are more electric performance based, like ERT

Thanks again for your help

If you want an ASI you would be well advised to buy direct. Learn from the mistakes of others.

https://www.youtube.com/watch?v=1BoWQ54NpU0

Alta used VTC6 18650s 80s6p(?) some more info in the vid

https://eu.nkon.nl/sony-us18650-vtc6.html

At 3.95 Euro per cell an alta sized battery (480 cells) will be expensive - 1896 euro before any connectors ,bms, case etc

QS as a company and their motors have a great rep, and they have many higher power models

but with higher performance in reality comes heavier weight, be sure you really need to go up.

I think you are right to focus your investment priority in the battery pack

but even without going LiPo you will trade lifespan for higher C-rates / lighter weight.

Going to higher voltage will increase top speed on the road, but where off-road torque is the priority 52V is apparently a good sweet spot, lets you put more cells in to build up Ah reduce the C-rate required for high amps.

For the controller I'd save your place now for the Nucular and just get a cheapie placeholder to tide you over while waiting for it.

I cancelled my Qs 138 motor order lol, I wanted to go with something more powerful.

Now I don't know if I want the Motenergy ME1115 its supposed to be rated for 12kw-30kw Or if I should go with the 10kw goldenmotor? I'm not really sure what i'm looking at when it comes to motors besides the weight, volts, and peaks tbh.

I found a way to get a BAC8000 for $800, might just go ahead and order it, as long as its a 72v motor it will be compatible right?
Any help is appreciated

ASI can be hard to find someone to program / tune for your motor.

Phaserunner based on one, much easier

or Votol?

Ideal is the motor + controller are pre-tuned, from the same seller.

QS is supposed tobe good for that, Sabvoton maybe, can then be tweaked.

Check out QS273 + SVMC72150

But weight!!

$2,000 electric for something you want to use like a $6,000 gasser, just isn't realistic. We all learn a lot with each successive build, and those who start so high we typically never hear from after the first build due to easily predictable disappointments that aren't fair strikes against electric, because electric really is so much better at everything but range, since a gallon of gas contains almost as much energy as a 650lb Nissan Leaf battery pack.

I'd suggest starting with a $2k in cost build of something far lighter than an MX moto that's still capable of some of the same thrills using downhill bicycle bike part combined with a solid electric drive system. What you learn in that build will make you far better capable of achieving your desired end result while giving you a real taste of the fun side of electrics.

Why downhill bike parts?

On my first reply here I got a little carried away and seemed to be pointing you away from lipo.

Lipo is actually probably the best option if you want to go with a small pack and get decent power. I like Turnigy Graphene. You could make a 18S config (good max voltage for asi) out of their 6S 8Ah packs easily.

john61ct said:

ASI can be hard to find someone to program / tune for your motor.

Click to expand...

No it's not. He can do it himself. There is a big misconception that ASI are hard to program. In general (for larger motors like OP wants) that's not true and programming is straightforward. It's nothing like a Sevcon. The most complicated part of the whole process is usually doable by autotune. People here will help you figure it out and there is documentation.

But in case the OP missed this first two times around, DO NOT BUY FROM ALAN AT ERT.

Yes had Alan reprogram my P.V. controller and it stopped working. Start over.
Go down to Zero and get a test drive.

flat tire said:

...But in case the OP missed this first two times around, DO NOT BUY FROM ALAN AT ERT.

Click to expand...

https://endless-sphere.com/forums/viewtopic.php?f=46&t=102675

flat tire said:

You could make a 18S config (good max voltage for asi)

Click to expand...

Is there a problem with say 20S, too close to component ratings?

Or are you saying because top speed is not an issue with this use case and torque at lower rpm will be better with a slightly lower voltage?


> There is a big misconception that ASI are hard to program. In general (for larger motors like OP wants) that's not true and programming is straightforward

OK thanks, many people whose opinion I respect have said otherwise, and I didn't even know autotune was an option.

So you're saying these issues only exist with smaller motors, say under 3000W units? If so, why is that?

Isn't there an extra cost for the hw/sw needed for programming?

Or is that just Sevcon?

flat tire said:

I like Turnigy Graphene. You could make a 18S config (good max voltage for asi) out of their 6S 8Ah packs easily.

Click to expand...

Do you mean the lower C-rate Professional or the pricey Panthers?

How about the 12Ah ones?

Or two 18S strings at say 8Ah and 4Ah for flexibility?

john61ct said:

Is there a problem with say 20S, too close to component ratings?

Click to expand...

No 20S is fine. 18S is just convenient since 6S bricks are common and give you an easy build. You can also do 21S but it is on the ragged edge and the controller may blow. You may need to set a wider tolerance (separate option) for the max voltage since the controller may not let you program 84v max (or 88, or whatever) directly it will cap in high 70s.

ASI does autotune for hard things motor inductance, resistance, and hall sequence. You just need to input relatively easy things like motor pole pairs, your battery's parameters, power limit, throttle voltage, whether you have regen or not and some other misc parameters that are easily determined.

ASI has trouble with high kv low inductance motors especially if they have a freewheel (not direct drive). Like RC motors. If you motor is relatively big like the OP is talking about the autotune should work well.

john61ct said:

Do you mean the lower C-rate Professional or the pricey Panthers?

How about the 12Ah ones?

Or two 18S strings at say 8Ah and 4Ah for flexibility?

Click to expand...

If Turnigy Graphene is still a good brand pick whatever C-rate matches your planned discharge and whichever cells are easily available and least expensive. I don't know anything about Pro vs Panther.

Yeah I was not going to buy from Alan at ERT, I found a place that has BAC8000s in stock.

Just trying to figure out what motor I should run now since i cancelled my qs motor 138 order, i'm pretty sure I still want a mid drive motor to give the bike a more balanced feel, just can't seem to find a good one for a decent price.

Lipo is my option if all else fails, I still have a lot of learning to do with batteries, so if I had a 72v motor and the lipo packs are 22.2v do I go over 72v?

So for example to get 72v I would use 3 12.0ah 6S15C turnigy graphene 22.2v packs only gives me 66.6v? And I would run them in series to get the right volts and then each additional pack in parallel is an additional 12ah correct?

If anyone has any good mid size motor ideas let me know!

20S could be 4x 5S packs or v/v, gets you to 72Vnominal, 84Vcharging.

21S limit for ASI might be too stressful for best longevity, but charging to 85V only would help with that, and extend battery life, especially if you bulked up Ah for both higher range and to reduce C-rate.

check if 7S is a thing, if not then 7x 3S would work

If we're talking hobby grade lipos that we presume will have varied longevity and you aren't into hacking bricks apart to replace bad cells, it might not be a terrible idea to go 4s to keep replacement pack costs down when cells do fail. Interconnects be damned. (Though they do add up)

I've been doing some research and I think i'm going to go with Lipo, do people mostly use the smaller packs and if they need more AH they just parallel them together? I see they make like 20ah packs lol, but still no idea about the motor

HK12K said:

If we're talking hobby grade lipos that we presume will have varied longevity and you aren't into hacking bricks apart to replace bad cells, it might not be a terrible idea to go 4s to keep replacement pack costs down when cells do fail. Interconnects be damned. (Though they do add up)

Click to expand...

Yeah I wouldn't be into hacking a brick apart for that, do they go bad often?

john61ct said:

check if 7S is a thing, if not then 7x 3S would work

Click to expand...

I actually found Turnigy Heavy Duty 5000mAh 7S 60C Lipo Pack w/XT90 for $86 a pack. Discharge: 60C / 120C (Burst)

ProtoFTW said:

I've been doing some research and I think i'm going to go with Lipo, do people mostly use the smaller packs and if they need more AH they just parallel them together? I see they make like 20ah packs lol, but still no idea about the motor

Click to expand...

Pretty much the size of it. I think most tend to lean 10ah and up when selecting cells, often opting for the 16ah if not the 20ah versions. It goes quickly though at these power levels, so the more the merrier imo.

HK12K said:

If we're talking hobby grade lipos that we presume will have varied longevity and you aren't into hacking bricks apart to replace bad cells, it might not be a terrible idea to go 4s to keep replacement pack costs down when cells do fail. Interconnects be damned. (Though they do add up)

Click to expand...

Yeah I wouldn't be into hacking a brick apart for that, do they go bad often?

Click to expand...

It happens, and the harder you run them the more likely it is. Not a foregone conclusion necessarily but on a long enough timeline it probably shouldn't be too unexpected.

john61ct said:

check if 7S is a thing, if not then 7x 3S would work

Click to expand...

I actually found Turnigy Heavy Duty 5000mAh 7S 60C Lipo Pack w/XT90 for $86 a pack. Discharge: 60C / 120C (Burst)

Click to expand...

I won't speak for john, but 5ah is too low in capacity to be worth looking at imo. At the kind of power levels you're talking about a 20ah pack will be flat in no time if you're ripping on it. I don't believe the higher c rate is necessarily worth paying for in this application unless you were planning on a very small format pack overall afaik. Of course a lot of it will ultimately come down to motor and controller requirements, but there isn't much on 2 wheels that 30 or 40ah of even 12c lipo can't get moving.

All that being said, before you place an order, spend some time researching recycled ev cells like that found in the leaf, volt, etc. If you can fit them they'll supposedly perform far better than hobby lipo, and for far longer. Far from plug and play however. Worth the effort though, from what I understand.

ProtoFTW said:

I actually found Turnigy Heavy Duty 5000mAh 7S 60C Lipo Pack w/XT90 for $86 a pack. Discharge: 60C / 120C (Burst)

Click to expand...

So, one thruple gets you to the magic 21S maximum rpm plus (probably?) most efficient torque at low speed cranking up a steep hill.

At 5Ah, of course only enough for a brief time trial at minimum weight. Or more likely too weak (vendor C-ratings being way "optimistic") to keep holding the amps output at what you'd want.

So buy say three or four of those thruples and parallel those strings until you get the range / ride time you need (total 15-20Ah) at the power you want (from lowering the C-rate)

Maybe end up with one (larger?) pack hard-wired in, and a (smaller or equal) pack as auxiliary, for when the extra is needed more than lower weight.

Note that (I am led to believe*)

All of the balance leads from the (21/42/63/84) cells can be paralleled into one set of 8 balance leads, plus one pair of power leads

thus allowing one 7S BMS to monitor & protect everything even while in use in series. Maybe balancing too but see below. . .

But for **charging** using a single 7S balancing hobby charger, you'd need to isolate / disconnect the power-lead serial connections and reconfigure all in parallel.

This would obviate the need for an 84V adjustable charger, and could buy a BMS without the redundant (and likely inferior) balancing functionality, aka "protective only" BMS.

And of better quality since just a single 7S is needed.

Multiple 7S chargers could be used for faster charging, but can only leave the serial interconnects in place if you make certain all of them are fully isolated from the source side and thus from each other.

Using hobby chargers lets you also easily regularly benchmark standardized resistance and SoH% capacity tests, key to tracking how soon packs will need to be retired to stud (phone charging, portable powerpaks etc)

______
* I tried to explain the concept most recently here https://endless-sphere.com/forums/viewtopic.php?p=1514687#p1514687 If you try to grok it, there's a (crude) drawing farther down.

Skip eMark's posts and those dealing with the OP, my subtopic is really a thread derail and he was very confusing/confused there, so went the thread most of the time.

I feel I never got explicit confirmation from the gurus @'ed, and have not actually tested the idea.