General Varg Beater

[Philip]

The Stark Varg is not out yet, but I think I have come up with an idea for a better bike. Who is it going to be who will make a Varg beater? Read on...

You know what the major limitation of an ICE bike is (besides the noise and the maintenance requirements)? It's its hardware. The weight and the cost of various powertrain things that make 125 - 250 - 350 - 450 - 500cc motocross or enduro bikes with small 2-gallon or large 5-gallon fuel tanks. You buy one of these cc displacements for your preferred riding, and then buy a bigger fuel tank if you want to ride all day, or put 1/2 a gallon into a small tank if you want to get a top-4 finish in a 5-minute LCQ.

You know what the major limitation of the Alta and the Varg is? Pretty much the same -- the heavy and expensive hardware -- the battery.

Except you can't buy a bigger tank. And charging the battery to just 33% won't make your bike any lighter.

The 60hp Varg is not any lighter and not much cheaper than the 80hp Varg. And the big and heavy 6 kWh battery is still probably not large enough for Tomac to win at Southwick or for Herlings to win at Lommel.

How would the Stark Varg's successor overcome this limitation?

 

[Philip]

A light bulb went off as I was at Glen Helen riding @DonCox"s DIY converted Yamaha and then loading it into my motovan. His bike is lighter than a 250cc 2-stroke! It has a smaller battery and a lower top power than my Alta, but it is also much lighter! It is a very fun bike and it fits Don and his riding needs much better than my Alta or the Varg would.

Why is it so? It's simple. Don is perfectly fine with just 3 or 4 kWh of batteries and 30-40 hp. He does not need more power, range, or the associated extra weight.

Why is this important? It's because pretty soon we will have a slew of motocross and enduro riders complaining that all the new available electric bikes are either too expensive, too heavy, or do not have enough range to ride in the woods, or that they run out of battery before their 30-minute or 60-minute race is over. There will be lots of unhappy people willing to spend the money on the right solution that fits their riding needs.

 

[Philip]

What's the solution?

I think it is pretty simple. We need a dirt bike with multiple hot-swappable liquid-cooled battery modules.

Install a 2 kWh module to win a 5-minute supercross LCQ. Or install 12 kWh of modules to ride in the woods all day long. Or install 6 kWh of modules and stop in the middle of a 1-hour enduro race and swap them for charged ones.

You can drain the coolant out of them and remove the coolant pump if you are going to run more than 6 kWh of batteries, or if you are going to ride in Mode 1.

The Varg's 6 kWh discharges at 10x C to produce 80 hp peak or 60 kWh continuous, and it doesn't even have liquid cooling. With liquid cooling you can discharge lithium batteries at 30x C, so you only need a small 2 kWh battery module. That makes the race bike about 50 lbs lighter!!!

Don't you think a guy on a 50 lbs lighter bike would be more likely to win a Supercross heat or an LCQ race?

 

[Number Six]

You've hit on the experience of many amateur woods riders that have moved from 300cc or mid size 4 stroke machines to 125 / 150 small bores, the lighter bikes require less effort to maneuver.
We've discussed similar weight limitations for off road riding for several years as it applies to our 250 & 300 2 stroke ICE bikes.
Modern chassis & suspension is mostly designed for the rigors of SX & MX , & both are far more robust ( read; heavier ) than what's needed by most amateur woods riders.
They're essentially overbuilt for 95% of users, users that would benefit greatly from a lighter bike, not one designed to huck a quad.

To your point, yes a modular battery configuration would in select situations solve what is perhaps the last negative aspect of an electric like the the Varg ; weight.
Although at a claimed 240 lbs, it's really not any heavier than a modern 2 stroke enduro bike with a couple gallons of gas on board & I'm told the electrics feel much lighter once in motion. ( looking forward to testing that premise sometime in 2023 ? )
Still, there would be real benefit in short races where one doesn't need any more than 10-12 minutes of run time, you'd have a significantly lighter bike to have to throw around.
I know little about batteries but I'd imagine they've come a long way in recent years with regard to power, capacity & weight & will continue to advance as e-vehicles become more mainstream.
In the near term though .. yeah, it'd be great to have options for battery size & weight based on the duration of a given event.
.

 

[Philip]

batteries but I'd imagine they've come a long way in recent years with regard to power, capacity & weight

There hasn't been any significant battery tech breakthrough since the Alta came out.

Someone on this forum has calculated that the 5.8 kWh battery capacity of the Alta powering an electric motor is equivalent to about 1/2 of a gallon of gas powering an ICE bike.

I think this is true. Let's check it... Google says that 0.5 of a gallon of gas contains 67,500 BTU of energy, which converts to 16.9 kWh. Multiply that by the ICE (in)efficiency of 25 - 30% and you will get 4.2 - 5 kWh at the rear wheel. The Alta/Varg has 6 kWh, multiplied by the EV efficiency of 85%, becomes 5.1 kWh. This is about the same as 1/2 a gallon of gas in an ICE bike.

If you have a 1.5-gallon tank then that's 12.6 - 15 kWh available to use during a 40-minute US Nationals moto. That is twice the energy that the Alta/Varg has inside their batteries!

I easily use up my Alta's battery in under 30 minutes at a race pace. And I am no Tomac.

Some racers have been known to use more than 1.5 ga in a Nationals moto. These are the guys who may need 18 kWh batteries to run at the same pace.

It is scary to think, but I doubt that my math is off by a factor of 3. Even if all the advanced traction control and regenerative braking added.

 

[DonCox]

To this point, I will include a YouTube that is in other discussions, and illustrates the concepts talked about above. This is Derek Timm's RM250 frame with the new motor many of us are using for it's light weight, and high power output. He has a 2.4KW swappable battery on this bike, that allowed him to run 15-20 minute Hare Scramble ( about 12 miles) under full power, swap a battery, and continue on. His bike weighs 210lbs. He has a mid sized controller that will give him up to 240Amps, There is, and I have the larger controller for more power, but it will limit my distance. But on my YZ with this motor and controller, and a 2.8KW battery, I could run the 12 mile Hare Scramble easily. But my battery right now is not swappable, but it will be in the near future. My YZ that Phillip talked about above, weighs 221lbs.

Here is a link to Derek's website where he has the battery and quick change systems for sale. Lithium-King.com
It is quit easy to build these conversions. I am starting one this weekend. It is a 2003 YZ250F, I receive the motor /controller tomorrow. It won't be using the quick change battery, but follow along with the build. Here are some pictures of where I am today. I will try to journalize this build. This is the bare frame, I just went thru the rear suspension and serviced that, now the build will start. More pictures to follow. This should not take very long, to get running. The battery will take a little time.

 

[Number Six]

Inspired.
Tempted to source a late model 125 chassis & build my own ...
Would it be a reasonable expectation to keep the weight under 225 & use a 6kw battery ?
Are you guys building your own batteries with purchased cells or are complete batteries in a 6kw range available ?
I need 25-30 mile range @ an A level race pace.

 

[rayivers]

I think it is pretty simple. We need a dirt bike with multiple hot-swappable liquid-cooled battery modules.

+1 ! This would also allow at least the possibility of a charger/temp controller, which would connect to both charging and cooling systems. If it were me I'd look at a Peltier setup, which would allow both cooling and warming for the cold-weather riders. I wonder what charge rate could be used at a maintained 60F/15C.

 

[enjoythesilenc]

There hasn't been any significant battery tech breakthrough since the Alta came out.

Someone on this forum has calculated that the 5.8 kWh battery capacity of the Alta powering an electric motor is equivalent to about 1/2 of a gallon of gas powering an ICE bike.

I think this is true. Let's check it... Google says that 0.5 of a gallon of gas contains 67,500 BTU of energy, which converts to 16.9 kWh. Multiply that by the ICE (in)efficiency of 25 - 30% and you will get 4.2 - 5 kWh at the rear wheel. The Alta/Varg has 6 kWh, multiplied by the EV efficiency of 85%, becomes 5.1 kWh. This is about the same as 1/2 a gallon of gas in an ICE bike.

If you have a 1.5-gallon tank then that's 12.6 - 15 kWh available to use during a 40-minute US Nationals moto. That is twice the energy that the Alta/Varg has inside their batteries!

I easily use up my Alta's battery in under 30 minutes at a race pace. And I am no Tomac.

Some racers have been known to use more than 1.5 ga in a Nationals moto. These are the guys who may need 18 kWh batteries to run at the same pace.

It is scary to think, but I doubt that my math is off by a factor of 3. Even if all the advanced traction control and regenerative braking added.

I guess everybody gets queasy when math is bandied about. I did the same calculations except giving a gas motor 15% efficiency. I ended up with the Stark needing 9kWh to meet the claim "range equal to a 450 sx bike"

When you ride your gas bike at the same ferocity, does it go about 45 minutes per tank?

 

[Dain_SSE]

I guess everybody gets queasy when math is bandied about. I did the same calculations except giving a gas motor 15% efficiency. I ended up with the Stark needing 9kWh to meet the claim "range equal to a 450 sx bike"

When you ride your gas bike at the same ferocity, does it go about 45 minutes per tank?

I just finished a day of filming with MXA where they ride my SSE YZ450A, and I discuss a little what is my opinion on necessary capacity. 10kwh in a 65lb pack is what I think it will take at the highest level of racing. A couple iterations out (+115wh/cell) we will see the 4680 cell get damn close to this - so for certain races it might be able to compete!

 

[Philip]

I did the same calculations except giving a gas motor 15% efficiency.

That's fair. A 15% efficiency is probably a better estimate for a dirt bike engine.

So, maybe it is closer to 1 gallon of gas = a 6 kWh battery.

 

[DonCox]

Inspired.
Tempted to source a late model 125 chassis & build my own ...
Would it be a reasonable expectation to keep the weight under 225 & use a 6kw battery ?
Are you guys building your own batteries with purchased cells or are complete batteries in a 6kw range available ?
I need 25-30 mile range @ an A level race pace.

We built a 2017 KTM 150SX into an electric with the QS motor. It has a 4.8KW battery. It is 245lbs. It has twice the battery that the RM250 had in the Hare Scramble above. The RM did the 12 mile lap and had about a half a lap left in it on the 2.4KW battery ( approximation, since it was still running with good power at the end of the first lap). So the KTM with 4.8KW should be able to do 25-30 miles. I don't know if his riding is what you consider "A level" riding. The owner of the KTM did get 40miles of single track out of the battery, to near empty. If you come out west let us know and you can take one of ours for a distance run.

 

[Oded]

I use my Alta for Enduro / trail / rocks only. I finish the rides with about 40-50% battery left (2-3 hours rides).
I wish I did not have to carry this "unusable weight" with me.

Slow technical rides (even the hardest Enduro) are quite easy on the battery. We rarely exceed 30 kmh.

 

[Number Six]

We built a 2017 KTM 150SX into an electric with the QS motor. It has a 4.8KW battery. It is 245lbs. It has twice the battery that the RM250 had in the Hare Scramble above. The RM did the 12 mile lap and had about a half a lap left in it on the 2.4KW battery ( approximation, since it was still running with good power at the end of the first lap). So the KTM with 4.8KW should be able to do 25-30 miles. I don't know if his riding is what you consider "A level" riding. The owner of the KTM did get 40miles of single track out of the battery, to near empty. If you come out west let us know and you can take one of ours for a distance run.

Thank you Sir,
A 2017 KTM SX 125 is a light chassis, so apparently the battery / motor combination is pretty heavy once one gets beyond 2.5kw or thereabouts ?
The RM guy is easily an 'A' level rider & the course was fast, our terrain is more technical, about an 11-12mph average on a 24 mile loop, more old school enduro than hare scrambles.

Hence the thought of building something similar as your Yamaha or the RM, the problem for me is our distances & the battery needed ( 4.8 or above it would appear ) which apparently puts the overall weight into the 240+ category.
The Varg is already 242lbs but .. I don't have to build it, it has numerous mapping parameters, is 6kw, & has the very best in suspension & brakes.
It sounds as if the adage ; 'there's no free lunch' particularly applies to electric dirt bike builds where weight vs capacity is concerned.
And thank you for the gracious offer to try one, very kind of you.
.

 

[chrisflysit]

I am absolutely loving my CRF250R conversion. It has the QS138 v3 motor and 20s10p Molicel p42a 21700 (3.1 KWH) and a BAC8000 controller running at 800 Phase amps. It weighs 232 lbs (including Fasst Flexx bars, double thick skid plate and aluminum hand guards) and does about 18 miles of single track. I am 20% faster on this bike than my KTM 200 xcw and my 300 tpi bike. The Honda pulls incredibly hard out of the turns. It's running a 428 chain with 12/63 sprockets. The bike is also great for hard rocky technical stuff. It weighs the same as 200 xcw with a full tank of gas but feels much lighter and playful. Rider fatigue is significantly lower on the electric bike. It has no cooling but nothing gets hot, even on 100 degree days.

 

[Number Six]

I am absolutely loving my CRF250R conversion. It has the QS138 v3 motor and 20s10p Molicel p42a 21700 (3.1 KWH) and a BAC8000 controller running at 800 Phase amps. It weighs 232 lbs (including Fasst Flexx bars, double thick skid plate and aluminum hand guards) and does about 18 miles of single track. I am 20% faster on this bike than my KTM 200 xcw and my 300 tpi bike. The Honda pulls incredibly hard out of the turns. It's running a 428 chain with 12/63 sprockets. The bike is also great for hard rocky technical stuff. It weighs the same as 200 xcw with a full tank of gas but feels much lighter and playful. Rider fatigue is significantly lower on the electric bike. It has no cooling but nothing gets hot, even on 100 degree days.

A 20% difference is monumental !
I have a well developed 250xcw but it does feel like a lot of machine sometimes when the going is slow, uneven & technical.
Are these electric bikes THAT much easier to manuver over rough terrain than an ICE bike ?
My impatience regarding delivery is growing ..
.

 

[Philip]

Are these electric bikes THAT much easier to maneuver over rough terrain than an ICE bike ?

Yes. Trail riding and hill/rock climbing on an electric vs. ICE motorcycle is like Zen meditation vs. cross-fit.

 

[Redwolf]

Riding rocky uneven technical and steep terrain on an electric bike is so much easier than ICE, it's like cheating

 

[bluefxstc]

it's like cheating

NO, it's being smarter.

 

[Redwolf]

Cheating, being smarter... It's all about your perspective. The ICE guys will call it cheating.