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Electric bikes

 
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clv101
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Joined: 24 Nov 2005
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PostPosted: Wed May 01, 2019 9:17 pm    Post subject: Electric bikes Reply with quote

After meaning to build an electric bike for best part of a decade I've finally... gone out and bought one (well, not getting it until tomorrow). Electric bikes just seem like an absolute no-brainer but the UK lags woefully behind the rest of the world. Last year Germany sold just almost a million, one in four. The UK around 60,000.

They use hardly any energy, a 0.4kWh battery giving a realistic range of 30-80 miles depending on level of support, they flatten hills, calm head winds and lighten heavy loads.

I expect many people could replace many car journeys with an ebike and some households could replace a 2nd car with an ebike.

Our main use will be the 2 mile school commute, I've done it a few times with a regular bike but several steep hills really are a killer, its just not fun. I'm anticipating most school runs, with reasonable weather will be done with the bike this summer - saving a lot of annoying short car trips to the village.

What are other people's experience?
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PS_RalphW



Joined: 24 Nov 2005
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PostPosted: Wed May 01, 2019 9:31 pm    Post subject: Reply with quote

I rode an electric assist bike for about 3 years. 12 mile round trip to work, mostly flat. Worked great, but typically I wanted to be efficient as possible, so I pumped the tyres to hard, and the pot holes shattered part of the frame and several other bits of the bike (not the motor or electrics ) are worn out. 2 years ago I was diagnosed with cancer, and the treatment left me too ill to ride. Also my commute increased to 20 mile round trip. I have started riding it again one day a week when I work closer to home, the thing that really puts me off is the incessant noise, dust and danger of the 4 wheeled traffic on the roads I need to travel. Too many dangerous junctions.

Now I commute by electric car. So much more comfortable, quiet, and smooth.
Entirely relaxing even in heavy traffic, 4 times more efficient than an ICE car, and at least 40 times LESS efficient than my electric bike

I calculated the bike has a negative carbon footprint. It generates less co2 than the extra vegetarian food I need to cycle the same distance
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Snail



Joined: 14 Apr 2011
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PostPosted: Wed May 01, 2019 10:12 pm    Post subject: Reply with quote

The advantage with ebikes is they can go everywhere a normal bicycle can go: parks, canal paths, forests etc.

Cargo ebikes seem like a great idea too.

A small folding bike like Brompton is another alternative.

If I lived and worked in a town or city, id go with the ebike route. Cars are a hassle to buy, maintain, drive, and even to get rid off. Why aren't they more popular with young people and students(16-25 year olds for eg)?
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Snail



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PostPosted: Wed May 01, 2019 11:24 pm    Post subject: Reply with quote

I suppose they're bound to be a major theft risk.
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BritDownUnder



Joined: 21 Sep 2011
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Location: Hunter Valley, NSW, Australia

PostPosted: Thu May 02, 2019 12:23 am    Post subject: Reply with quote

I thought about buying an electric tricycle for personal use. However I was worried I would look a bit of a dick, which I often am. When many other people start doing it I will start doing it. If I get a job in the nearest city, which I am currently applying for then I might get a folding one to take on the train with me. i like the look of a Brompton e-bike. Are they still made in the UK? A lot of good stuff still is.
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Little John



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PostPosted: Thu May 02, 2019 12:52 am    Post subject: Reply with quote

I keep toying with the idea of building one with an inverter generator in tow on a mini trailer to keep the batteries topped up. In turn massively increasing its range.

Then I just think bollocks... get a petrol moped
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kenneal - lagger
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PostPosted: Thu May 02, 2019 1:13 pm    Post subject: Reply with quote

I bought an e-bike last year and use it for cycling into town, a couple of miles and now the warmer, dryer weather is here I'll use it for getting to parish council meetings and checking the cattle on the common. The route to town is across the common and then down a steep hill with a cycle track for about a third of its length and not heavily trafficked so noise and smell are not a problem until I'm in the town. With a hill up to the common on both sides the e bike makes the journey quite easy. One day on my way home up the hill I powered past a "pro" cyclist, with all the gears and the lycra, and left him puffing. That was using the maximum assist.

I can do three or four journeys into town before a recharge is required. The loss of charge over the winter storage was minimal. All said and done, a good buy. I'm thinking of a trailer for it as well that a couple of small children could fit in although I don't do much shopping but it might encourage the family to use it.
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PS_RalphW



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PostPosted: Thu May 02, 2019 2:38 pm    Post subject: Reply with quote

BritDownUnder wrote:
I thought about buying an electric tricycle for personal use. However I was worried I would look a bit of a dick, which I often am. When many other people start doing it I will start doing it. If I get a job in the nearest city, which I am currently applying for then I might get a folding one to take on the train with me. i like the look of a Brompton e-bike. Are they still made in the UK? A lot of good stuff still is.


My wife had an electric tricycle. Horrid thing. You have three wheel tracks so you hit 3 potholes for every one on a bike, and on a bike you can usually steer round them. Also, you cannot lean into corners so it feels horribly unstable.

Brompton only recently started making e-bikes, previously they were a modification by another company. They are good but expensive.
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adam2
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PostPosted: Fri May 03, 2019 9:56 am    Post subject: Reply with quote

Electric bicycles have many advantages as already noted, the only slight caveat of which one should be aware is that modern designs tend to use lithium batteries.
Such batteries can only be safely charged with the supplied charger, they can NOT be charged directly from a PV module, nor directly from a 12 volt or 24 volt off grid home.

If you wish to charge the battery from renewables you will normally need an inverter with a sine wave output that mimics the mains supply.

Alternatively you may be able to obtain a charger with a 12 volt or 24 DC input, intended for charging the electric cycle in a motor vehicle.
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Little John



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PostPosted: Fri May 03, 2019 7:49 pm    Post subject: Reply with quote

adam2 wrote:
Electric bicycles have many advantages as already noted, the only slight caveat of which one should be aware is that modern designs tend to use lithium batteries.
Such batteries can only be safely charged with the supplied charger, they can NOT be charged directly from a PV module, nor directly from a 12 volt or 24 volt off grid home.

If you wish to charge the battery from renewables you will normally need an inverter with a sine wave output that mimics the mains supply.

Alternatively you may be able to obtain a charger with a 12 volt or 24 DC input, intended for charging the electric cycle in a motor vehicle.
So, could one charge an e-bike's lithium battery directly from an inverter generator?
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adam2
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PostPosted: Fri May 03, 2019 8:20 pm    Post subject: Reply with quote

Using the same charger that you would use to charge the bike from the mains, then yes you could use an inverter generator.
The output from an inverter generator is a reasonable approximation to the mains and is therefore fine.
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clv101
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PostPosted: Sat May 04, 2019 12:44 am    Post subject: Reply with quote

My bike 'charger' claims to put out 36V DC (2A), guess any complex charging electronics is built into the battery. The charger looks to be just a regular transforms like a laptop power supply.
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adam2
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PostPosted: Sat May 04, 2019 9:41 am    Post subject: Reply with quote

clv101 wrote:
My bike 'charger' claims to put out 36V DC (2A), guess any complex charging electronics is built into the battery. The charger looks to be just a regular transforms like a laptop power supply.


I would not count on this !
Ratings on battery chargers are often inaccurate and refer to the nominal voltage of the battery for which they are intended, and NOT to the actual output voltage.
Note that battery chargers intended for car batteries are commonly marked "12 volts" which is the nominal voltage of the battery and NOT the actual output voltage. The actual output should be about 13.8 volts for float charging and about 14.5 volts for faster charging.

Lithium batteries are potentially dangerous if not charged correctly, and are also expensive. I would strongly advise against charging with anything other than the supplied charger. This should be powered from the mains, or from a reasonable substitute such as a good quality inverter or generator.

I SUSPECT that a charger intended for a 36 volt lithium battery has an output of about 45 volts, current limited to about 2 amps.
Lithium battery cells do not tolerate even a very slight over charge, there will therefore probably also be circuitry built into the battery that monitors EACH CELL during charging.
As each cell reaches full charge it is electronically bypassed to prevent over charging but allow the other cells to continue charging.
The battery charger must therefore continue to supply a constant current from perhaps 45 volts initially, down to about 6 volts when only the last cell is still charging.
When the voltage drops to say 3 volts, that indicates that every cell is now charged and has been bypassed, the 3 volts being the voltage drop in the connections, the charger should then shut of and signal "battery full"

This however is my supposition and it would be MOST UNWISE to count on this supposition being correct.
It might well be possible IN THEORY to charge such a battery direct from a couple of PV modules with a voltage of at least 45 volts and a short circuit current not exceeding 2 amps.
I would however STRONGLY ADVISE against so doing, the circuitry might differ from my supposition. A fire or explosion might result.
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