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Hadn't seen you here for a while, what's up? Would you be involved with Flux by any chance?
Hi Beagle.
Not involved with flux. Been pretty busy. Now we have pretty good experience with MOSFET based inverters in addition to IGBT. That is the reason for the poll on electric dirt riders. We are looking at producing MOSFET based inverters also. Looking to see what we can do traction wise. That is both a personal interest and also a potential product differentiator if we can get it right. So pretty busy...
It's weird seeing all the varied run times that people have posted, I'm sure nobody is making their stories up, but my friend who bought a varg let a top 10 250sx pro ride it at his private track, and he was able to do a 30 minute moto on 50% (unsure on power settings and effort used), on a firmer track.
The thing I hate the most about the electric mxbike community is that everybody is lying about the real performance of the bike. I built a custom electric Honda and I have overheating problem. But I go on diy ebike forum everybody says it is not possible etc. The specs of my bike are very close to those of the stark. I can get 80hp out of it too. But the overheating is the problem.
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He hasn't proved it yet.
For the record, I hope he does.
I was mostly just being a smart ass and throwing that out there to rib Phil for saying the Stark sucks cause it can't do Supermoto.
It is definitely a battery issue as it is a battery indicator light that appears and stark have also said it is battery related. I'm no electric wizard of any sort but I believe it is restricting current draw to stop the battery running hot, not because the battery is already running hot. There is 2 different warning lights that can appear on the stark phone, a battery one and a powertrain one I am only getting the battery one.
It sounds like you are someone who knows alot about this stuff so any feedback or advice you could give me would be much appreciated.
It's not a problem exclusive to electrics. Its a people problem, anything people are involved in will have inaccuracy's . Some people are doing it intentionally for whatever reason. Some people might be estimating and bad at it. Many people will talk like they have more speed and endurance than they really do.
It can go both ways too , with people lying about getting shorter range, having less power, etc.
I'm 300 pounds and I got 20 minutes of very easy trail riding on hard pack , on a power setting that was supposed to be similar to a 125 , I'll have to try and go back and see if I can see how much power I started with and what was left. I was not paying attention to the display at all but I noticed I could see it in video I took with a 360 camera.
I have a current generation RMZ450 that I am thinking of doing a conversion on. If it felt anything close to how the Varg felt , even at that lower setting I rode one at. I would probable ride it everyday.
I 100% agree, but its not just about the ev bike community, it's everything. Haters will always hate and lovers will always love. How hard is to just tell it as it is is. Everyone on this forum I believe has a common interest in the love of dirt bikes. I couldnt care less if it is 2 stroke, 4 stroke, 3 stroke or electric, if it is good bad or somewhere inbetween ill tell it as it is.
Not sure why anyone would think QMP is anything resembling sand. The closest would have been Haworth Park at Leyburn.
There are 12 temperature sensors inside the battery, six per side. It will limit on the hottest sensor. If one of them is problematic (reading a temperature significantly hotter than actual temperature) that will cause it to falsely limit. It will limit because it thinks the battery IS hot, not because it thinks the battery will BE hot.
The prototype bikes ran Molicel P42A. With those cells the weak point (thermal wise) was generally the battery. The batteries actually sold use Molicel P45B. With those cells the battery was generally no longer the thermal weak point. I say generally because it depends where in the RPM and torque range you are running the motor. If the motor is mainly where it is most efficient then it could actually be the battery (which is completely fine) overheating. However, this was generally not my experience and the motor was the weakest link in the thermal chain.
So what Stark is telling you could be right, but I have a suspicion there is a good chance there is a questionable temperature sensor in the battery. I don't know if the technician has a log of all 12 sensor to check if they are all within a reasonable range. You can ask if he does at what the difference between the minimum, maximum, and average values is.
During the very early days (before the bikes were shipping to customers) the display looked like this:
State of charge is 68 percent, the average of all 12 battery temperature sensors is 26.8C, the lowest is 24.3C, and highest 27.3C
You would expect no more than a 7 deg C deviation except if there is a good reason for it -- like the sun has been shining on one side of the battery.
If the technician confirms the deviation seems to be OK, then it is likely you are the exception to the rule.
When is starts to limit on battery temperature you can take off your glove and put your bare hand on the battery. It won't burn your hand, but if you want to move your hand away after 2 seconds or so because it starts to get uncomfortable, then it is thermal limiting on the battery.
A top 10 250 Rider? Who would that be?
I feel weird about blowing out people when they didn't post it themselves publicly, but I don't want to be like, "I have super secret insider knowledge and won't say". Just saying, a dude who held a 2 digit number and had a few top 10s rode it, and the owner (who I wouldn't consider a fanatic by any means) claims he only used 50% of the battery on a fast, worn in track.
When I rode the same bike, it was a tight, deep, rutted track, getting play rode by the owner all day in between letting everybody spin laps on it, plugging it in to 110v while we took breaks, and it never had a problem. I didn't pay attention to battery life while I was riding it, but I used 2 maps, 60 hp and higher regen, and 48hp with low regen.
Thanks heaps for your reply. I'm guessing there's no way I can see on the phone what temperature the sensors are at?
When it does limit itself the battery definitely feels very hot, like there's no way you can hold your bare hand on it very long.
I'm not sure you can answer this question but I'll try anyway. When riding in the sand would I be better off using a scoop tyre to lesson wheel spin which may cause more heat or would the extra traction create more load that would create more heat?
Also if I'm constantly running the battery to point where it is derating will this significantly effect the lifespan of the battery?
This is a very interesting thread!
Would changing the final drive gear ratio help? Add a tooth or two to the rear sprocket?
Maybe I missed it, but is there a certain percentage every time that the light goes on and it de-rate’s the battery?
I ask because for me I rode mine tonight, started with 26% and took it to 7% battery and it still wasn’t having any issues. But I did a mix of hard enduro and slower moto for 45 minutes, a mix of mud, rock, many logs and hard pack with jumps on small moto track.
On my home built ecrf, outside temperature and traction are 2 contributing factors to controller over temp and ability to recharge battery caused by heat. On occasion, traction helps with run time because of less wide open throttle in turns. Outside temps are extremely critical on my application.
You weigh ~210lbs, you are riding deep sand, Stark recently went to a 47 tooth rear sprocket from 48.
Can you modify the chain guide to accept a larger rear sprocket?
@fs, if I am off base please correct me.
Pit Row
The Stark's maximum rear wheel torque is 938Nm, if you are riding at 20mph that's 32hp, even if power is set to 80hp.
The 60hp limit doesn't start until speed reaches 31mph, the 80hp limit doesn't start until speed reaches 49mph.
From what I can see it's not the chain guide that is the problem its when a larger sprocket is fitted the wheel comes too far forward and some tyres can rub on the swingarm. The problem is the stark doesn't have a very large axle adjustment range so finding a gear ratio and chain length that will work might be the hard part.
If a larger rear sprocket is something that will help the battery im more than willing to buy a few different sprockets and a chain to see what might work.
There is no specific battery percentage that the light comes on at and it de-rates, it is all dependent on the battery temperature. At 60hp I can get it to come on with still 60% battery left, at 56hp I got it down to around 35% left. Yesterday at 52hp I got it down to 20% before it came on.
I don't believe with the type of riding you describe you will have any issues at all.
Just to clarify, you said you started at 26% and went down to 7% and rode for 45mins. So are you saying you got 45mins of riding on 19% battery?
There’s plenty of people competing at the highest level of hard enduro on 4 strokes, Johnny Walker is on a 4 stroke now. Billy Bolt won the world super enduro championship on a 4 stroke this year, a few years ago people were saying it was a 2 stroke only event as well.
The beauty of dirt bikes is that the bike means fuck all, the rider makes the difference.
Makes sense, I am set at 50hp anyway.
huh, I guess I am just stumped. I’ve never had the issues happen to me you are talking about.
Yep got 45 min of riding on 19% battery. But what I was doing, it’s nothing like deep sand full on moto riding like you are.
I’ll try to remember to grab my Stark phone to get a screenshot of the ride. But until then here is a screenshot of my watch data. I think it follows prettt closely to what I describe above. You can see the obvious part where moto happened with the elevated heart rate and speed, again slower moto though and the rest was hard enduro which just isn’t hard on the battery.
And I don't think you ever will have any issues with the riding you describe.
I'm still shocked with you saying you got 45 minutes ride time and only used 19% battery. I used 10% battery in 10 mins just play riding around my sheds and thats on hard gravel dirt. I believe you it's just shocking the drastic differences people get.
How much do you weigh if you don't mind me asking?
If you are using full throttle at your max speed of 27.2mph, that's 44.4hp, full throttle at average speed of 5.8mph is 9.3hp, even when power is set to 80hp!
I think you should mention regen settings as well, going from 90% to 20% regen has probably much more effect on your battery temperature than decreasing power by 4-8 hp 😉
Yeah sorry should have mentioned that. Although I actually think the lower hp has more of an effect then the lower regen.
Thanks for all the details of your struggles with your Varg. And your awesome profile pic 😎
Just for clarity, to help other Varg owners, could you please sum up what worked best for you on your private sand track so far, you've found settings to get at least one full run without temperature warning, right?
Hp, regen, ride time, battery left, was it 52 hp, 20% regen for 20-30 min ride and 10% battery left?
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