Practicality? Practicality!? We don’t need no stinkin’ practicality!

From: http://www.amazon.com/GE-Energy-WattStation-Wall-Mount/dp/B0069VTGPE/ref=sr_1_1?ie=UTF8&qid=1324238019&sr=8-1

OK, today I am going to put the cart before the horse a bit.  I did an interview with Jensen Beeler of Asphalt & Rubber the other day.  It was suppose to be a 5 minute review of the electric bike happenings over at the Long Beach IMS, and turned into a hour and a half long hen pecking-fest.  The problem is that you folks won’t be able to hear this interview for some time, and I am kind of responding to it now.  But I felt it is something I can no longer let sit on the back burner.  Besides telling me Santa Claus doesn’t exist, Jensen sees the normal range anxiety, power, and weight parity issues that us EV devotees feel are pretty much a non-issue these days and are certain won’t be very soon.  Then he mentioned the “charging problem”.  Charging problem!?  What charging problem?  You plug it in to wall and you are done, that’s it.  How hard is that?  Well, for some, like Jensen and I, who live in apartments it is a big problem.  This is going to take while folks, so you might want to go get something to drink, and eat.  Actually you might just want to order take out.

Ready?  OK.  There are 3 issues currently holding electric motorcycles back from parity with their ICE counterparts.  Weight, energy density, and the rates they can take and release energy.  Those translate into layman’s terms as weight, how far you can go on a charge, and how fast the batteries will let you accelerate and re-charge the vehicle.  Besides those issues there is also the factor of what people actually need, and what minor life style changes need to be made to incorporate even current EVs into their lives.  And finally, after those changes have been made, what short falls do we still have.

First up is the battery technology.  Right now, this very second battery technology is being driven not just by cell phones, laptops, and tablets, but also by EVs.  There is big pressure on the battery manufactures to make next super light, powerful, and long lasting battery for phones and what not, but they don’t have to deal with the severe drain and type of on/off abuse an EV, especially a racing EV, can place on the batteries.  It really is a whole other problem, but fortunately still roughly related.  Weight has, and will continue to lower at the same time energy density goes up.  You want proof?  Look at how much weight the MotoCzysz and Lightning dropped from 2010 to 2011, or just the MotoCzysz from 2009 to 2010.  In 2009 the E1PC was 590lbs with about 13kWh on board, 2010 525lbs with 12.5kWh, and in 2011 it may have not been much lighter (some where around the 500lbs mark from rumors) but it was to be carrying even more energy.  A completely unsubstantiated guess is upwards of 16kWh.  Power also went up from 66 hp and 120 ft-lb of torque, to 125 hp to 250 ft-lb, to in 2011 200hp and enough torque to make my old ’71 Chevy’s small block 350 take it’s own life in shame.  The Lightning has followed a very similar path since 2010 where it was a 600+lb intercontinental missile with 120hp EV-1 motor and a big pack.  In an interview at VIR (the last NA round in ’10) Lightning’s owner Richard Hatfield said they thought they could drop 80kg (176 lbs) and add 40, maybe 50 hp.  Well, I know the bike is under the 550lb mark, and I suspect closer to the 500lbs.  But they have over 200hp.  So they dropped about 100lbs but gained almost 100hp!  And as you heard in the interview, and I have repeated many times, they feel in 6 to 12 months they will have their hands on a new battery and their weight will drop down to the 400lbs mark, all the while they already have 240hp and by then they should have 250hp.  So if we look at last year, the trend is weight is harder to get than hp.  And really, isn’t 250 ponies enough?

2011 MotoCzysz E1pc at Miller

You’re right it’s never enough, what was I thinking.  So getting power from batteries is no longer a problem and weight is getting there.  So what about energy density?  Well the packs are carrying more power every year and either weighing the same or less.  I will not be surprised if we see 18 to 20 kWh packs next year that fit in the same space and weigh the same.  Predictions have been made of the 2012 IoM that it’s not a question of will MotoCzysz brake the 100mph barrier, but of everyone who does, by how much.  So that leaves charge times.  Well I’m seeing some improvement in that, but really the focus has been so much on getting the energy out of the battery, that the getting it back in part hasn’t improved too much.  The street legal production bikes you have right this second can only go about 30 to 40 miles on a charge but can re-charge in 4 hours on a 110 plug/  And this only if you have drained the whole pack, other wise the wait time is less.  The bigger 9 and 10kWh packs coming in 2012 from Brammo and Zero will take 9 to 10 hours to charge on 110,  they both will have charging options that can lower that time to anywhere from 2 to 5 hours.  Then there is another American company that has a battery technology that the Proterra buses use to recharge an 80kWh pack in 10 minutes!  Why aren’t these batteries already in motorcycles? I don’t know, but there must be a reason.  I suspect that their involvement with the military might have something to do with it.

What are the realities of our daily life?  Well, pretty much all of a majority us don’t travel more than 30 to 40 miles a day.  Here’s a secret to those who live less than 5 miles away from work.  A bicycle is faster.  No need for an electric or gas anything in rain or shine (or even snow).  One of the Brammo guys lives so close it’s faster for him to cycle to work than on one of the test mule Enertias.  But he, like myself, is an avid cyclist.  It used to be that one of the worst thing for a gas engine was to drive it 3 miles and then turn it off, because of the oil not getting up to temp and other various things.  I believe that is less of an issue now-a-days with modern medals, coatings, oil, etc..  But it doesn’t bother an electric motor much at all, if at all, to do that very thing.  So, you get up in the morning, unplug your electric motorcycle (all of a few seconds of your time) and ride to work.  If you are fortunate you can plug it in at work (a few more seconds).  Then you ride it home and plug it in (again just a few seconds of your time).  It charges over night and is full when you get up in the morning.  Because you “gas up” at home you avoid the lines at the gas station, the constant hunt for cheaper gas, fighting traffic to get to the gas, remembering to get gas, ect.  You save a lot of time and stress.

But you have to remember to plug it in every night, and you have to have a place to plug it into.  Easier said than done for some, and very easy for others.  Then, with no maintenance other than chain lube, chain, and tires, your costs after purchase are almost nil.  But what about the electricity costs?  Well, Maine has pretty high electric rates, not as high as some places in California, but about $.22/kWr.  The EPA says that a gallon of gas has the potential energy equivalent to 33.7kWh.  So a gallon of electricity in Maine is about the same as a gallon of gas.  But, the packs in the current bikes are only about 3kWh.  That’s less than 1/10th of a gallon of gas to go 25 to 50 miles.  You are looking at about 200 to 400 MPG for electric motorcycles depending on how heavy your wrist is, or how much you have to use the highway.  So those owner’s who complain about range, can actually afford to, literally.  For everyday life, there is little to no “charging problem” because your bike refuels while you are at home.  In my situation, it would be the perfect application 97% of the time.  Here in Clarksville, TN things are spread out a bit, and if I want to go across town on my bicycle, it is over 30 miles round trip.  I never have a reason to go over there, but if I did I would take very similar routes as I do on my bicycle.  I would pick the shortest, lower speed route, avoiding the highway, and having fun on the old tight back road-esque streets.  This would get me there just as fast while saving electrons.  What if you live in LA and drive the interstate all the time?  Well, I’ve ridden through LA on the interstate on my VFR.  As slow as you go on the interstates there, range shouldn’t as much of an issue. 😀  So for daily utilitarian use, there are no charging issues.  But if life was only that simple.

Ok, now for the meat of it.  What can’t electric motorcycles do yet to put themselves on parity with as motorcycles?  Well, with the current elmotos you can buy, if you want to run an errand one your way home from work, you may very well not have the range to do that, even if you can charge at work.  And, you cannot run on the interstate for a very long time, or at all if you live in NH or southern California and prefer not to get barreled over because of your meager top speed.  What if you get home and you have to leave again right away?  The new bikes coming out, specifically the Zero S and Brammo Empulse are claiming city driving ranges of 112 and 100+ respectively, with Zero saying 70mph commuting getting you 63 miles.  Back home in Maine that would get my father from his home in Plymouth, ME to Bangor, ME up the interstate and back no problem, but not much else for safety.  If he took a more direct back road route it would add some time, but would have left him with enough to run errands.  Now, where he worked he could have plugged into a wall socket at work on 110, and even on a half shift the bike would be almost fully charged.  On a full 8 hour shift it would have been nicely balanced and done charging.  Now he can run all the errands he wants.  He can stop by my Grandparent’s place in Kenduskeg, plug in there while visiting, and then take the back roads home with no problem.  Here in Clarksville, TN I could run around with impunity charging only at home.  This is because, if you didn’t notice, electric bikes get way better mileage at slower around town speeds than the constant wind fighting of the interstate.  The complete, and much more dramatic, opposite from gas bikes.  My wild guess is that I would get 80-100 miles on a full charge around here.  So, now you have an elmoto that is way less restrictive and with a cool work place and family it will more than suit your needs.

Bradbury Mountain State Park, ME

But is it on parity with gas bikes?  No.  Are there bikes out there that are?  Yes . . . and no.  Let’s examine how you ride.  I am more of a sportbike rider, but as a VFR rider I do more than different types of riding I think, say, the average GSX-R rider does.  I have ridden up and down both coasts, and across the country, commuted, and had fun on the back roads and canyons on both sides of the country.  Exactly what the VFR is for.  I see the average GSX-R or Ducati 748/848/998/1098/etc. (really it’s pretty ridiculous how long the list is. Ducati, pick a size) rider as someone who may commute, but is going to tear up the twisties on the weekend, and if they can afford it do a track day or 2.  For their every day commuting the 2012 bikes will be fine, but for weekend blasting?  Well how far do sportbikes go?  I decided to split the difference and check the internet for mileage of a ’10 GSX-R750 and ’09 VFR800f.  They both get about 40 mpg with a nod going to the GSX-R, but the VFR holds an extra 1.3 gallons of gas, so you are looking about 160 to 180 miles out of a GSX-R750 and 200 to 225 out of the VFR800f.  The current Mission R and Lightning are both rumored to go about 150 to miles on a full charge.  And we are only looking at 14kWh+ sized packs (or about less than a half of a gallon of gas) on bikes that are much heavier than the production 2012 bikes coming out.  Electric production bikes are actually as light if not lighter than their gas fueled cousins, but the racing ones are most certainly not, at least not for another year or 2.  Back to the Mission and Lightning. The thing I noticed about my ’91 VFR750 after I got a full exhaust and jet kit, was that it never seemed to matter how hard I rang the throttle I got 41 mpg.  Electric bikes are just the opposite.  So how much juice do we need to be on par?  Well, if you take the 750’s 4.5 gallon tank and and multiply it by 33.7 kWh/gallon you get 151.65kWh of power on tap.  However, as engines are only about 30% efficient (and that is being kind) which means only 30% of the 151kWh comes out of the engine.  Everything else goes up in smoke, pun intended, and only 45.5 kWh of energy flows out of the motor and into the transmission.  Now, most electric motors are over 90% efficient, which means less than 10% of the energy put into the motor is lost to heat and electrical resistance.  So divide 45.5kWh by .9 and you get 50.55kWh (1.5 gallons of gas).  That is, by this math, how much energy you need on board for parity of a gas powered GSX-R750.  And all that is at the motor and not including the transmission, controller or fuel injection, and drive train.

But something is off here, and it’s my massive over assumption of the gas motor’s efficiency.  I am going to go into the world of assumptions a bit to prove a point, that really can’t be proven because no one wants to give away their numbers.  Let’s take the 2012 Zero S.  Zero claims 63 miles at 70mph commuting range.  Because electric motors don’t use any juice when you close the throttle is one reason the mileage is so great.  For argument’s sake we’ll use the 70 mph range where the motor is constantly fighting the wind at quite a high rate of speed, as equivalent to canyon carving, where the average speed would be slower but ham fisted out of corner accelerations would be common place.  So 63 miles out of 9kWh gets you .15kWh/mile from the battery to the rear wheel.  Say you get 160 miles out of a GSX-R750 on a canyon ride following the Zero.  That would give you .95kWh/mile coming out if the rear wheel.  So the Zero would need 3/19ths (.15/.95) the amount of energy to go as far as fast, or a 23.9kWh pack.  That’s half the amount I originally calculated.  But this argument is based on a whole lot of assumptions.  But lets look at some data I was able to scrap together from the race at Laguna Seca.  For this exercise we are going to compare the Mission R to Ted Rich’s R6 (thank you Ted).  Let’s just say (this is my most ludicrous assumption yet) that Mission used all 14.4kWh to do the 17.9 mile race back in July.  Which they didn’t, but for now that’s the assumption.  That means they would have used .8kWh/mile.  Ted Rich’s R6 uses all of it’s 4.5 gallons for the AMA Daytona Sport Bike race, and was doing about the same lap time, only they were suppose to do 23 laps, or 51.5 miles.  It is the same sized tank as the GSX-R750 I used as an example earlier, so I can re-use the 151.65kWh figure from earlier.  Do the math and the DSB class R6 is using 2.95kWh/mile during the race.  So that gives us a ratio of 16/59, much closer than the Zero/GSX-R street comparison.  Some more math and I get that the Mission would need 41.13kWh to run and finish the DSB race at Daytona.  Still much lower and evidential that gas powered motorcycles only wish they were 30% efficient.  But, lets say I recalculate for a more realistic (but probably still high) 12kWh used by the Mission during the race and I get it only needing a 34.46kWh pack.  The other thing we haven’t looked at as we look into the future is weight.  Minimum weight in DSB is 355lbs, and the Mission R weighs in at 545lbs.  At the same lap times, as weight comes down range will be extended, requiring less energy to be carried than we would need to need now to have parity.  I think people sometimes miss that part.

Now, we get into charging, and what we really need to charge.  So now it is (lets say) 2016 and we have a 500lb bike with a 35kWr pack that will go just as far if not further as a GSX-R750 on the street, and is probably faster.  We have a better bike, but we go for a tear through the canyons and 2 hours later the guys want to keep going.  Well there are 2 choices: 1) recharge it, or 2) have a battery pack twice the size.  If you could convince the guys to break for lunch for an hour, could you get it recharged?  Yes.  What you need is a 35kW charging station.  Commercial property can I believe, but mostly industrial properties have access to 480v and over 100amps.  Sticking with the even 100apms gives us 48kW (480*100).  A 35kW station would only need 73 amps at 480 volts to do the job.  10 minute chargers are out there and possible, but I don’t think they are practical as of now.  Basically a 210kW charging station is needed to charge this fictional bike in 10 minutes.  Now, after the ride when you got home you would have a much less expensive than now ($1500) home charger hooked up to you 240 line that you already have access too.  It’s what your dryer runs on and may be available for up to 40 amps, but I’ll assume 30A for now.  That gives you a 7.2kW (240v*30A) charging station in your home, and would recharge your fictional bike in just under 5 hours.  40A would make that 9.6kW and drop the charge time to a little over 3 and half hours.  Now these are estimated charge times and doesn’t include any balancing time that the batteries might need.  But it gives you an idea of what is possible.  A bike with strict parity of a modern gas bike would not need anything fancy in the way of chargers as long as you didn’t exceed the range in one day.  Then you need a high powered charger to make things convenient.  But lets face it, after 180 to 200 miles in the saddle, who doesn’t need an hour break and some lunch?

On my trip across the country where I followed Route 66 as best as I could, I averaged about 500 miles a day.  If there were 480v 100A (or 48kW) powered charging stations I could get to, then I would ride for 3 hours, rest for one, ride for 3 hours, rest for one, ride for 2 and plug in at the camp site and be ready for the next day.  If, I was really lucky, and the I could use all of it, a 480V 200A station, or 96kW, would halve my recharge time.  Either way, that’s a full days riding, and not really an unreasonable schedule.  Don’t get me wrong, I’ve gone from Virgina Beach, VA to Dixmont, ME in 19 hours, and usually I ride 180 miles, fill up, ride 180, and then an hour break.  So I would have been on the road for a full 23 to 24 hours on an electric with proper charging stations available.  But what about battery technology.  Starting a year or 2 ago there have been University’s claiming that they have will be able to increase the density of Li-ion batteries 5 fold in the next 5 years.  There are so many now, and the stakes are so high, that one has to make it.  So imagine the Mission with a 72kWh pack that is the same size and weight it is now.  At even a .2kWh/mile energy consumption rate you are looking at 360 miles of range highway driving.  However, your 7.2kW home charger would need 10 hours to charge it from empty, and even the 9.6kW charger would need 7.5 hours.  So that is a pain, but what it means is that you still want to pull every 3 hours and charge for an hour to top the pack back off, and then you have a lot of extra extra range encase you need it.  If Mission is right, and you can drive 150 miles around town that would mean your city range would go up to over 700 miles to a charge.  Now, the batteries I mentioned earlier that can take 80kWh in 10 minutes.  They exist and have been used in the city buses in everyday for a year.  But that charging stations draw a lot of power.  If those could be implemented through out the country then you could drive 350-700 miles, plug in and in 10 minutes be on your way.  But that is a lot of power, and would have to be a special, and not small, station.  Practical for a bus line, but not for a gas station type of thing I don’t believe.  Not to mention how big a connector would you need, and just how beefy would your BMS/on board charger would have to be.  Maybe in five years there will be a solution?

http://view.s4.exacttarget.com/?j=fefb137174670c&m=fe9c15707365007a75&ls=fe241570776d0d7b7c1370&l=ff5c1d7877&s=fe5c17767562057c7c1d&jb=ffcf14&ju=febf137273650c75&r=0

Ok, so electrics will make great commuters and already do.  And will make great canyon carvers if the battery tech comes good and 480v charging stations are available, but maybe not so much for touring.  What about track day bikes?  Little to no maintenance, but what about charge times there?  Well, how much juice do you need?  Say the typical session is 20 minutes, and then 20 minutes off, and then a last 20 minute session, and you get 30 miles each session, that’s 90 miles.  Now, the eCRP 1.4 has a 9kWh pack and is pretty quick.  If the batteries could hack it, a 48kW (480v*100A) charger could recharge the pack in under 12 minutes.  The eCRP bike is only about 70hp, so for a 140hp electric superbike that uses .8kWh/mile of energy you would need more than 72kWh on board.  Or you need a pack with  just over 24kWh that can be recharged in 10 minutes.  You would need at least a 144kW charger.  That is too far beyond the realm of realistic expectations right now to expect tracks to install those kinds of monsters.  So this brings us to the quick change pack.  We have seen some examples of these in the racing world, but never seen them put to use.  It would most certainly not be cheap, but would be easily changed in a matter of minutes (if that), and it’s very not likely the wear out quickly.  If someone was just doing track days, I’m sure the batteries would last as long as the bike if not longer.  And, if you ever wreck the bike, you’ll might make some real good coin back selling the remaining packs off.  I think you will see quick change packs be very prevalent in future racing.  Right now the riders and teams cannot take advantage of all of the time they get (at least at some tracks) because they do their 8 or 9 laps and they are in to recharge the pack.  If they had multiple quick change packs they would have more track time.  If there was ever to be an Electric Gold Wing type thing, the Tesla model of quick change packs at the local dealer would work for that crowd I think.  I don’t see it working for any other group other than maybe the sport tourer folks. So that is also an option, and only as expensive as the batteries which will get cheaper just like every damn game system that has ever come out.  The “10 minute charge” technology would be a help.  If an electric superbike was carrying 72kW than the Gold Wing would want to be around 110kWh on board (the same ratio of a GSR-X750’s 4.5 gallon tank, to a “Wing’s” 6.6 gallon tank) then it should take less than 15 minutes to recharge. Now, with a bike that size I think you cold fit a small 200hp/300ft-lb electric motor in there and save a ton of weight and space even with batteries this fictional future “Wing” would weigh less.  It seems like there might be room for an on board charger/BMS that could handle the load.  Hmmm, maybe not.  A quick change at the Brammo store probably you best bet.  110kWh, at .3 Wh/mile would give you a 367 mile range.  How many Gold wing owners would like a 200hp wing with a 370 mile or better range, even if it weighted the same?  So, bigger packs will give as much if not double the range that we have now, and it will still be reasonable to charge them at night at home.  But o be completely convenient we need at least 480v charging stations.  Massive 200kW+ stations would mean 10 to 15 minute charge times for people covering big distances like touring trips and such.  Those types of stations exist but would not be an easy or practical intimidate solution, more so restricted by the possible size and weight of the on board charger needed.  Touring folks might be batter off with a quick change battery system.  We’ll have to see, but either way these things are do-able and a heck of a lot easier to do and available sooner than fuel cell technology seems to be.

So, as we have seen, production electric motorcycles are already fun and practical, if a bit restricting.  But as early as a few months from now that will change and doing something like running errands or even a short canyon, or twisty back roads ride, is not out of the question.  The current racing machines are capable of so much more than their production brethren.  It is simply a matter of waiting for the technology to trickle down and for production to start on machines like those.  But the future holds the answers on not when, but how soon these bikes will have parity with the gas bikes.  It’s not the everyday sport rider that will miss out, but it may well be the touring guys who will just have to slow down a bit.  I have generalized a lot in this post, but mostly because I don’t have access to the hard numbers that factories do.  However, when you compare gas motorcycles to electric motorcycles you don’t need exact numbers because the gap in efficiency is so large you can’t miss it.  Does your brain hurt yet? 😀

8 thoughts on “Practicality? Practicality!? We don’t need no stinkin’ practicality!

  1. Hey, two things to consider.

    First, Zero’s ZF9 is 9.0 kwh maximum, but 7.9 kwh nominal. The distinction between the two is max capacity is pack amp-hours times maximum voltage just coming off charge, where nominal capacity is more like pack amp-hours times an “average” voltage. (voltage drops slightly as the pack depletes, meaning you have to draw more current at lower voltage for the same power as the pack nears empty)

    Zero claims “maximum capacity” is more commonly used in the EV motorcycle realm, but at least in Brammo’s case the Enertia is rated at a nominal 3.1 kwh capacity. Valence rates their Ucharge 12UXP battery packs at 12.8v nominal, 40 ah. 6 * 12.8 * 40 = 3072 wh.

    Second, Zero’s “highway commute” range is 50% distance city UDDS schedule, 50% 70 mph highway (or 55 mph for X / XU). Given 114 miles UDDS and 63 miles combined, 70 mph range is 43.5 miles. You can call this 180 wh/mi @ 7.9 kwh nominal capacity or 207 wh/mi @ 9.0 kwh maximum capacity.

    1. For those who don’t know, protomech is waaaaay better at this number crunching thing that I am, and has been doing it a while.

      Sir, I don’t know why I didn’t think to send this thing to you first. So, do you think my assumption of of .2kWh(or 200Wh) per mile for an electric superbike rolling down the highway is a fairly OK assumption, or tilting in favor of electrics too much? It’s amazing the difference in fuel consumption between city driving and highway driving for electrics.

  2. 200 wh/mi is a good average figure. In practice your energy usage can be much higher or lower depending on how fast you ride and how aerodynamic your bike + your posture is.

    90-100 mph is probably 250-300 wh/mi.
    70 mph is 180 wh/mi for the ’12 Zero S.
    50 mph is probably 120 wh/mi.

    I think Laguna Seca had a warm-up lap, eight laps starting from a stop, then a cooldown lap. Say 250 wh/mile for warm-up and cool-down, 1.1 kwh for 4.5 miles. Let’s say Mission ran pretty close to the edge, 5% pack remaining after the cooldown lap. That leaves 12.6 kwh for the 8 race laps, 17.9 miles. Race pace is right around 700 wh/mile.

    Rapp’s qualifying lap was still two seconds faster than his fastest race lap. I suspect he limited his maximum speed on the straights to limit power consumption – so there certainly is room remaining for more speed as battery packs improve or for shorter races.

  3. Here are Zero’s figures:

    180 wh/mi, ’12 Zero S ZF9 steady 70 mph (43 miles in 7.9 kwh)
    120 wh/mi, ’12 Zero XU steady 55 mph (21 miles in 2.6 kwh)
    69 wh/mi, ’12 Zero S ZF9 EPA UDDS (city) (114 miles in 7.9 kwh)
    62 wh/mi, ’12 Zero XU EPA UDDS (city) (42 miles in 2.6 kwh)

    ZF9 S is 340 lbs, XU is 220 lbs.

    1. The 63 mile highway commute range for the ZF9 is 50% UDDS miles, 50% steady 70 mph miles.

      Zero computes the “highway commute” range by the following formula:

      highway commute = 1 / ( 0.5 / 43 + 0.5 / 114 )

      Zero is correct in that commuting traffic is never 100% freeway (and often the freeway suffers from congestion), but I wish they would simply specify the steady 70 mph range instead of an implicit specification.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s