A to B magazine carried out the very first English-language review of the Kalkhoff Agattu back in 2008 and they were mightily impressed. Four years later we sent a 2012 Kalkhoff Agattu Impulse to David Henshaw, editor and Chief Test Pilot at A to B magazine. "unprecedented range, extensive equipment, fast charging, and excellent fuel economy" were some of his findings. Here's an abridged version, the full review was published in A to B 89, which you can get through the excellent A to B website (link below)
We first tested the Kalkhoff Agattu back in January 2008, and concluded that the electric bike had ‘come of age'. It had a solid German frame equipped with all the usual accessories - lights, rack, mudguards and so on - that you might expect to find on a quality European roadster, and it was equipped with the Panasonic crank drive.
Like all the best classic machines, it did most things pretty well, and could thus be advertised as being all things to all men, and of course women, who make up a high proportion of purchasers. Soon there were all sorts of variants, from the sporty to the dumpy and practical. When we got fed up with Chinese bikes failing left, right and centre we bought a Kalkhoff Pro Connect ourselves. It tows trailer-loads of post, carries Alexander to Middle School Orchestra on the rack, nips out to granny's house and back on a charge (36 miles) and generally acts as the family runabout.When we replace the venerable Lafree, it will probably be with a Kalkhoff. Others have copied this winning formula, but in Britain at least, they are not widely known.
Genesis of the Impulse
Why fiddle with a trusted and well-established formula? The now rather elderly Panasonic had some odd quirks. A particular issue in Europe (irrelevant in the UK) was the inability of the crank-drive to work with back-pedal brakes, which are popular on the Continent, but almost unknown here. Then there was the sensor issue.
Because the Panasonic motor only responds to pedal torque, and has no way of sensing whether the bike is actually moving, if you rest your foot on the pedal at traffic lights, the motor will struggle to turn, throwing away oodles of precious energy. At the other end of the spectrum, the motor can't tell when the bike has reached the legal 15mph limit, so maximum speed is usually controlled by the crafty technique of gearing the motor to run out of steam at the right speed. This works well enough, but it means that the motor and your legs (they're always geared together) are whirling around a bit fast at this speed, so pedalling faster downhill is difficult. Owners, of course, often get round this by re- gearing the bike, giving a slightly illegal top speed, and more relaxed cruising.
The answer to these twin grumbles was to make the motor more intelligent, principally by sensing wheel speed. With three commercial systems available (Panasonic, Daum and Bosch) we were surprised to hear that Kalkhoff/Derby had produced their own, but according to industry sources they hadn't, because beneath the skin, the Impulse is designed around the excellent Daum motor. How does it fare?
The Impulse in Action
We're not going to say much about the attributes of the bicycle, because the exciting news here is in the new power unit. Suffice to say, the Agattu is well equipped, although not quite as well equipped as the original Agattu we tested back in 2008 (it lacks a skirt guard and frame lock [though the lock is fitted to the Agattu HS, Agattu XXL and Agattu C11 Premium, and easily fitted to the Agattu C8 - plus all Impulse bikes come with the B&M Flatsafe rear light that brightens when braking - Tim, 50cycles]). On the positive side, at 24.9kg, it's almost a kilogram lighter, despite coming with a battery of double the capacity. On the road, the gears, brakes and suspension (boingy forks at the front and slightly less boingy seat post at the back) do just what you would like them to do.
The real good news is that ginormous battery, with a claimed capacity of 558Wh or 540Wh (it has one figure on the back and another on the front). Either way, it's a battery with a whacking great capacity, but it's physically quite small and weighs only 2.9kg. That's an energy density of 180 watts per kilogram, a figure that breaks new ground against all the Chinese tat, the original Panasonic battery (104 watts/kilogram) and even Kalkhoff's own Panasonic upgrade (146 watts/kilogram). It's a spectacular advance.
Dynamically, in town at least, the motor feels somewhere between the sensible Panasonic and sportier Bosch. In typical modern fashion, there are four power levels:‘Standby' (a useful fuel-saver when the going is temporarily easy),‘Eco' (dead wimpy), ‘Sport' (adequate for gentle pottering) and ‘Power' (feels raunchy, but see below).
On the Power setting, the Agattu completed our ten-mile ‘commuter' ride in 33.5 minutes at an average of 15.9mph, putting it up with the zippier legal bikes, such as the Raleigh, Gazelle Innergy and Emotion. It's a full 3.5 minutes faster than the original Agattu and 30 seconds faster than the sporty Pro Connect, yet it sips fuel at 11.3Wh/mile, which compares well with both the older bikes. So on this flattish course, it's fast, fun and frugal.
On our hilly test route, the first light started flashing at nine miles and went out at 20.6, the second was flashing at 31.4 miles and out at 42.5, and the final light was flashing at 50.7 miles and out at 56.4 miles. Just for the record, the bike was ridden on the default Sport setting (rather a misnomer), with Power reserved for steeper hills, and Eco or Standby where these lower settings would have no useful effect on speed. In other words, it was ridden quite hard.
Average speed usually drops as a long run progresses, but in this case, almost uniquely, the speed rose from 13.1mph to 14.4mph, before falling marginally to 14.1mph.This is partly because the longest (but not necessarily steepest) hills come in the first ten miles of our course, and because the Impulse maintains a nice even speed whatever the battery condition.
With a 26-inch bottom gear, it's not surprising that a standing start on a 1:6 hill is easy, but you do have to get a tiny bit of forward motion under your belt before the motor cuts in (that's the traffic light power saver in action), so you'll want bottom gear. Once underway, the bike feels as though it's going to accelerate up into 5th, but as usual the power droops and you end up climbing at near walking pace.
Interestingly, Kalkhoff claims a range of 60 miles for this 540Wh battery (there's a smaller 396Wh battery, but it's only fitted to the Kalkhoff Sahel Compact bike).The company also quotes test results of 75 to 113 miles, but these figures are for a German boffin riding very carefully on a completely flat course at a comfortable 10 - 15 Centigrade, in Sport and Eco respectively. You will not achieve this on your way to work.
Other manufacturers suggest ranges of 80 or even 100 miles, but their bikes typically do 20 to 30 miles in our ‘real world' conditions, so a bike that really does achieve 56 hilly miles is most impressive. It's easily the best mileage figure we've seen, beating the original Nano-Brompton by 81/2 miles, and the long-range version of the Dawes S-Drive by 71/2 miles. These long-standing records are for slower bikes, and in the case of the Dawes, one carrying enough fuel to launch a space shuttle. Obviously if you live somewhere flat and potter gently about on Eco (or of course Standby), range will be considerably higher than 60 miles. On the other hand, if you tow a trailer in the Lake District it will be much worse.
Energy consumption varied from 11.3Wh/mile riding fast on the shorter commuter route, to 10.6Wh/mile on the longer, hillier range-finding ride. By way of comparison, the much slower Panasonic-powered Agattu recorded 11.8-10.3Wh on exactly the same routes. The lighter, sportier Pro Connect and clever Daum (sharing the same motor, of course) did a little better, but the Agattu Impulse is still one of the most economical bikes we've tried. And the only one with a range anywhere near 50 miles.
Charging
At 100 - 125 watts, charging is around twice as fast as the Panasonic system, which worked well enough with the original smaller batteries, but is now looking a bit slow. With the Panasonic you had to take the battery off the bike to charge it on a dock, but Kalkhoff has listened to the grumbles about this (the dock is big and cumbersome, and if you lost the key, you were stuck) and provided a dual system on the Impulse.The gloss black Apple-style charger can now be plugged straight into the battery, or into the equally snazzy dock that accepts the battery. So if you're out and about, you carry the charger, leaving the dock as a style icon in the sitting room.
Charging takes exactly six hours, and we calculated the capacity to be 522Wh, which is close enough.We had a brand new battery, so it's conceivable that capacity would hit 540Wh after a bit of running in. How about running out? Obviously, with the batteries costing £549, you want a few years out of it. Derby has continued the two-year guarantee pioneered by Panasonic, and suggests a useable life of 1,100 charges, so after five or six years of hard use, capacity will have fallen to still useable 324Wh, giving another few years of pottering. We won't know the truth until 2018, but for now our running costs assume failure at the two-year guarantee point, so that 21.5p figure could be much lower.
Accessories
For £1,895 you can still get a ‘Limited Edition' Agattu (effectively a 2011 model) with the Panasonic motor and 468Wh Derby battery, plus all the extras you'd expect on a quality German roadster: Axa Sprint LED headlight, Shimano hub dynamo, rack, pump, and so on, but no frame lock or skirt guard. Our 2012 bike is very similar, but it comes with the new power unit and bigger battery, plus Busch & Muller LYT Eco LED lights (not the best, but adequate) for £2,095. Whether you feel it's worth paying an extra £200 depends how important you consider a 60-mile range. For some people, the option of riding continuously for at least four hours up hill and down dale will be a terrific bonus.
For wealthier customers, another £100 buys the Agattu Impulse C8 HS, with Magura hydraulic brakes and a Busch & Muller Lumotech IQ headlight, or for a wallet thumping £2,695 you can have the C11 version, with all the above plus push button ‘crawler gear' for walking the bike up footpaths, a nifty illuminated dashboard with all the usual trip functions, plus a power meter (very useful), cost and ‘CO2 saved' calculators (less so), and much else. It's the first time we've recommended an everyday electric bike in the £2,000+ zone.
Conclusion
Yes, we have a few niggles. The LED headlight is not as bright as some, and you need a bit of a technique to climb steep hills, but these are minor issues against the very considerable plus points: unprecedented range, extensive equipment, fast charging, and excellent fuel economy. Our only proviso - unless Kalkhoff recalibrates the power assistance - is try before you buy if you live somewhere really hilly. Then there's the cost, but if the last few years are anything to go by, Kalkhoffs keep their value very well indeed. That doesn't make two grand any easier to swallow, but it certainly helps.
Specification
Kalkhoff Agattu C8 Impulse £2,095 . Weight Bike 22kg Battery 2.9kg Total 24.9kg (55lbs) Battery Li-ion . Capacity 522 Wh . Replacement Cost £549 . Max Range 56.4 miles Full Charge 6hrs . Power Consumption 10.6-11.3Wh/mile . Running Costs 21.5p/mile
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