will the Empulse work for me?

[badamsfx]

I have a 65 mile commute each way so I would definitely go with the 10.0 model. With a 100 mile range the answer would seem to be yes if I could plug in at work and recharge during the day for the return trip. However there are other factors. Sixty of those miles are on the freeway and I have three significant grades to climb. I'm going from Ventura, CA to Culver City, CA taking the 101 S to the 405 S so I climb the Conejo Grade, the Calabasas Grade, and the Sepulveda Pass. I'm guessing the 100 mile range estimate doesn't include all these factors so my question is how can I figure out if the bike will hack it before I buy one and find out that it won't? Another concern would be how quickly the battery pack degrades, especially if I'm riding it to near empty twice a day. One option would be to take the Pacific Coast Highway which skips the grades and has a lower speed limit (and great scenery) but it's also a much slower commute. I love the idea of commuting on an electric bike but I might need to do an extended test ride or rent one for a day to find out if it would really work for me.

[Richard230]

Those are tough questions, badamsfx. Based upon my experience, maximum range for electric vehicles, both cars and motorcycles, is typically given for a steady 25-35 mph on a level road with no headwind. At faster speeds and going up hills, your mileage will vary - as they say.

In order to answer your question for sure you will likely have to wait for real-world experience reports from actual owners, unless you get an answer from an actual Brammo Empulse developer. And my guess is that Brammo is still developing the final version of the Empulse and does not have any actual performance figures to publish right now, other than the ones in the specifications on their website.

Still, it won't cost you anything to submit your pre-order for an Empulse 10.0. That is what I have done. But in my case I need to travel 60 miles maximum, before a full recharge and can do so at expressway (instead of freeway) speeds. I am convinced that the 10.0 will meet my needs and I have already accumulated the cost of the Empulse in my savings account.

I currently have an electric motorcycle, a 72-volt (nominal), 50 Ah, 24 LiFePo4 battery pack (about 3.3 kWh) Electric Motorsport GPR-S, which is not very reliable (I am prepared to write a book about its problems) but during my 1500 miles of riding I have developed enough experience to give you a rule of thumb for power usage: Expect to use 1 amp hour for each mile ridden on level ground at 30 mph. Expect to use 2 amp hours traveling at 60 mph on level ground, or 45 mph going up a 6% grade hill.

[Brammofan]

The Motorcycle Industry Council is working on a range-measurement protocol for all two-wheeled electrics.  Not sure when they'll finalize and release it, but it should be early this year.  I think it's essential for everyone to be working on the same playing field -- comparing apples to apples.

I am actually working on a blog post about this very issue, so stay tuned.

[protomech]

My general suspicion is that the Empulse 10.0 would get about 70 miles of range at typical freeway speeds (65-75 mph, with short bursts above to pass). The Enertia 3.1 gets about 35 miles at ~35 mph (88 wh/mi), 30 miles at ~45 mph (103 wh/mi), 25 miles at ~55 mph (124 wh/mi). The Empulse may do slightly better at high speeds due to more usable capacity from a less stressed battery pack, or it may do slightly worse due to higher drag or more weight.

Brammo claims less distance per kwh on the Empulse vs the Enertia, presumably due to the likelihood that the Empulse would be used at higher speeds.

[Gavin]

Brammo claims less distance per kwh on the Empulse vs the Enertia, presumably due to the likelihood that the Empulse would be used at higher speeds.

added weight and wider tires will affect distance per kwh. Probably the difference between the Enertia and Empulse is accounted by that. Of course the Empulse might be slightly more aero at speed due to rider position...but then Empulse is wider, added air resistance...so maybe a push there.

I wonder if a small windshield will improve aero and range on the Enertia Plus?

Gavin

[BrammoBrian]

Brammo claims less distance per kwh on the Empulse vs the Enertia, presumably due to the likelihood that the Empulse would be used at higher speeds.

This is correct - we expect Empulse riders in general to be maintaining higher average speeds compared to the average Enertia rider. 

A couple of other factors to consider are rider weight and total elevation gain over the drive.  Would it be possible to use a Garmin-type GPS unit to record your commute to tell us total elevation gain and moving average speed? 

[badamsfx]

I was going to try to figure out the elevations on Google maps with some plugins (?) that calculate heights. I suppose a Garmin would be much easier. I don't own one but I'll see if I can find someone who will lend me one. I was going to measure from the bottom of each hill to the crest and then get the height change for that distance, correct? I assume that's how you calculate grade? It might be a few weeks before I can get to this so stay tuned.

Brian (also!)

[00049 (AKA SopFu)]

I might be speaking out of turn, but I think they are looking for the net elevation change for your entire trip.  Some of the extra energy used to get up the hills will be saved going down them...so the energy cost of the hills is from the in-efficiencies within the bike from transferring energy from the battery to the wheels which won't be recovered on the downward slope.

[HighlanderMWC]

I might be speaking out of turn, but I think they are looking for the net elevation change for your entire trip.  Some of the extra energy used to get up the hills will be saved going down them...so the energy cost of the hills is from the in-efficiencies within the bike from transferring energy from the battery to the wheels which won't be recovered on the downward slope.

You say they're looking for net and then give the arguments why net isn't good. I know for a fact (6k miles of actual experience) that any hills reduce range on an Enertia. Also, you don't save energy going down hills, you just don't use as much, never mind the braking losses.

[Richard230]

My GPR-S has a sepex motor and provides a level of regenerative power when the brakes are applied. The power produced can go as high as 30 amps. But even so, the power put back into the batteries is only about 3% and I go up and down a lot of hills. It is kind of a cool feature to have, but it won't extend your range much.

[00049 (AKA SopFu)]

You say they're looking for net and then give the arguments why net isn't good. I know for a fact (6k miles of actual experience) that any hills reduce range on an Enertia. Also, you don't save energy going down hills, you just don't use as much, never mind the braking losses.

I do not know the specifics on Brammo bikes, but let's assume the bike is around ~80% efficient turning the energy from the battery into forward motion.  So, using 100% throttle at 40kw from the motor would actually require ~50kw from the battery.  Assuming the bike can go down the hill at 0% throttle, and for arguments sake we would have required 20% throttle if the ground was level (which for our motor is 8kw of forward energy, or 10kw from the battery) it would have only "lost" a total of 8kw of work while going up and down the hill rather than traveling on level land.  The loss is only due to the inefficiency of the motorcycle.  However, going up even a short slope requires 50kw of energy the for the entire ascent.  Obviously the impact is much more apparent when using extremes, but any net difference in beginning and ending altitude will still be more significant when not switching between WOT and closed throttle than the number of hills.  So yes, hills do make a difference, but depending on the actual efficiency of the bike, probably not as much as the net change in elevation.

Now, compare a Brammo to a traditional ICE motorcycle which is less than 5% efficient at turning gasoline into forward motion, and consider how much of an improvement the Brammo is.

[HighlanderMWC]

It's nice in theory, but my practical experience says that there are significant losses not being accounted for in that theory. Obviously any braking on the downslope would represent a pure loss and battery discharge rates also impact capacity.

[protomech]

You say they're looking for net and then give the arguments why net isn't good. I know for a fact (6k miles of actual experience) that any hills reduce range on an Enertia. Also, you don't save energy going down hills, you just don't use as much, never mind the braking losses.

I do not know the specifics on Brammo bikes, but let's assume the bike is around ~80% efficient turning the energy from the battery into forward motion.  So, using 100% throttle at 40kw from the motor would actually require ~50kw from the battery.  Assuming the bike can go down the hill at 0% throttle, and for arguments sake we would have required 20% throttle if the ground was level (which for our motor is 8kw of forward energy, or 10kw from the battery) it would have only "lost" a total of 8kw of work while going up and down the hill rather than traveling on level land.  The loss is only due to the inefficiency of the motorcycle.  However, going up even a short slope requires 50kw of energy the for the entire ascent.  Obviously the impact is much more apparent when using extremes, but any net difference in beginning and ending altitude will still be more significant when not switching between WOT and closed throttle than the number of hills.  So yes, hills do make a difference, but depending on the actual efficiency of the bike, probably not as much as the net change in elevation.

Now, compare a Brammo to a traditional ICE motorcycle which is less than 5% efficient at turning gasoline into forward motion, and consider how much of an improvement the Brammo is.

Depending on the grade and speed, you may still need to apply power to maintain a constant speed going downhill.

Neglecting aerodynamic drag and rolling resistance, the power you need to overcome gravity (ascending) is equal to sin(angle of grade) * gravitational force * velocity. Roads are almost always designed to be less than a 12% grade, or about a 7° angle.

Ascending a 7° slope at 60 mph with 550 lbs loaded weight requires about 8 kw. Add perhaps 5-8 kw more for drag and rolling resistance, and the Enertia 3.1 will lose some speed in the process of ascending. But it's nowhere near 40kw of power.

wolframalpha link

Also note that batteries typically have lower effective capacities at higher relative current draws. A 2C draw can pretty easily deplete a battery in 15-20 minutes, which might mean a worst-case of 10-15 miles of uphill ascent on an Enertia.

[HighlanderMWC]

Also note that batteries typically have lower effective capacities at higher relative current draws. A 2C draw can pretty easily deplete a battery in 15-20 minutes, which might mean a worst-case of 10-15 miles of uphill ascent on an Enertia.

Would a 1C draw on a stock Enertia be 3.1kW? Would this also mean that higher capacity bikes like the Empulse models would be more tolerant of the extra draw (although hills + freeway speed is likely a tall order).

I don't think an Enertia will handle 10-15 miles of uphill at 60mph. Maybe it would if flat -- some of the riders here might be able to chime in on actual 60mph range experience but I think I recall seeing 6kW draw going 60mph on relatively flat (I don't normally do flat or 60mph).

[protomech]

Would a 1C draw on a stock Enertia be 3.1kW? Would this also mean that higher capacity bikes like the Empulse models would be more tolerant of the extra draw (although hills + freeway speed is likely a tall order).

Yes, that's right. I expect the Empulses should be much more capable of holding pace or even accelerating going uphill - as much due to the larger battery as due to the more powerful motor. I imagine the Enertia Plus will also be able to handle uphill grades more easily, though that will have to wait for testing to be revealed.

I don't think an Enertia will handle 10-15 miles of uphill at 60mph. Maybe it would if flat -- some of the riders here might be able to chime in on actual 60mph range experience but I think I recall seeing 6kW draw going 60mph on relatively flat (I don't normally do flat or 60mph).

Right. I suspect on (very) steep grades the Enertia 3.1 would drop to a steady 30 mph (hence 10-15 miles in 15-20 minutes).

The major part of the ascent to Pike's Peak has an average grade of 11%, for what it's worth. Much steeper than many are likely to tackle with an Enertia 3.1.