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Old 09-05-2015, 11:05 PM   #1 (permalink)
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Running costs electric vehicle (battery replacement)

Often the cost of replacing expensive batteries is not considered in the running costs of an electric vehicle I want to know:

What is the life expectancy of batteries?
How much do batteries cost?
How many batteries do I need for each litre of petrol?

Once I have an answer for these I'll know if electric powered vehicle is an economical alternative to petrol.

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Old 09-06-2015, 06:11 AM   #2 (permalink)
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This has been discussed before quite often, you can get more than you want to know by searching this site.
Not to be pedantic, we just want to avoid repeating ourselves over and over again.

In a nutshell, yes battery replacement is quite costly - though it varies per make.
The life expectancy is mainly reduced by heat. Park your EV in the shade on hot days.
Next comes running it down to zero or overcharging it. Most battery types degrade slowest when used around the 50% state of charge.
Time also kills batteries, don't expect your Lithium Ion pack to last more than 10 years even if well kept (though that helps).
And of course usage does eventually reduce the battery capacity.

The plus side it that most EVs need very little maintenance; the brakes get hardly used, there is no cooling system, intake filter, exhaust (cats!), oil, spark plugs, clutch, gearbox etc. to tend or replace. Just fill the window washer liquid and go.

The minus is battery life, tire wear (EV's are usually slightly heavier than comparable gas cars), short range and long charging time.

It is really hard to give a 1 on 1 comparison of EV's and gas cars consumption wise. As an EV will do start-stop city traffic in mild weather very efficiently, and highway runs in winter less so. In a gas car the heater operates more or less free, in an EV it eats into the power and thus range.

That said, you can do about 100 miles with a Leaf; you'd do 4 to 5 miles for every kWh used. In a comparable gas car (I had a Nissan Almera which was more or less the same size) you'd do 9 miles per liter (35 mpg). I did, when I really tried hard enough.
Somy rough estimate would be 2 kWh for every liter used.
Then you'd lose some in charger losses etc. so say 2.5 kWh.
Over here that is still just 1/3 of the cost of a liter of gas.

And there you have it. The fuel cost of an EV is so much lower than a gas car that that alone more or less makes up for the battery replacement cost, if it ever comes to that.
The gain comes from not having to do all the maintenance and replacements a gas car needs.

Bin the calculator now. The EV has another plus; it is more fun to drive.
It is almost silent and very smooth. It gives you much more control with much less effort than a gas car would. Acceleration is instantaneous; you really feel the right pedal controls the power, directly and well measured.
You really need to do a test drive to appreciate this fully. It is much like driving a CVT hybrid, but without the noise and more powerful.

So, yes an EV is an economical alternative. And a fun one. And probably an impractical one, but that depends on your needs.
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It always takes longer than you expect, even when you take into account Hofstadter's Law.

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Old 09-06-2015, 11:26 PM   #3 (permalink)
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Sorry I asked as I have had difficulty finding information sorting through ebike 500 watt and other applications that are not quite what I am looking for.

If I want 10kw of power (my current 125cc motorcycle's power) and I use 4.5 litres of fuel to travel 160km (35km per litre). I would need at least 4.5 x 2.5kw 11.4kw of power in my batteries to make the example 160km trip.

If a Panasonic 18650 is 3.7 volts and 3.4 amp

3.7 volt x 3.4 amp x 1 = 12.58 watt hour.

I need 30 Panasonic 18650 batteries.

3.7 volt x 3.4 amp x 30

= 111 volt x 102 amp = 11,322 watt hour

Is this correct?

What percentage more power should I have to prevent full discharge?

At a weight of 46 grams each the total 30 batteries will weigh 1.380kg which is lighter than my current lead acid motorcycle battery.

If I buy 30 Panasonic NCR18650B batteries for AUD $12.42 each it'll cost AUD $372.60.

Only counting the cost of petrol at current available price I need to get 7303km from the 30 batteries before replacing them.

If they have 1000 power cycles that means I should get something like 160*1000 = 16000 km.

Providing these calculations are correct the electric vehicle is more economical.

Last edited by Spaghetti Man; 09-07-2015 at 12:19 AM..
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Old 09-07-2015, 12:04 AM   #4 (permalink)
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Quote:
Originally Posted by Spaghetti Man View Post
... What percentage more power should I have to prevent full discharge?...
The deeper you discharge the fewer cycles you'll get. I designed my ebike to never have to discharge more than about 50% of charge. So, doing what I did, you would double your planned capacity... 60 batteries and 2.6 kg.
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Old 09-07-2015, 02:43 AM   #5 (permalink)
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Quote:
Originally Posted by Spaghetti Man View Post
If I want 10kw of power (my current 125cc motorcycle's power) and I use 4.5 litres of fuel to travel 160km (35km per litre). I would need at least 4.5 x 2.5kw 11.4kw of power in my batteries to make the example 160km trip.
10 kw is over 13 HP. Do you need that continuously (for cruising at 100 kph) or for short bursts of acceleration?

I think the forklift motors that have been used in budget conversions put out that sort of power to move small cars (at maybe 50 kph).

Quote:
If a Panasonic 18650 is 3.7 volts and 3.4 amp

3.7 volt x 3.4 amp x 1 = 12.58 watt hour.
12.58 w-h per battery is right if 3.7 is your average voltage during discharge.

Quote:
I need 30 Panasonic 18650 batteries.

3.7 volt x 3.4 amp x 30

= 111 volt x 102 amp = 11,322 watt hour
111 volts is 30 cells in series at 3.7V each. Good for calculating your capacity. At 4.2, your charger would be putting out 126V to get to 100% charge for the 30 cells in series. At 0% charge, your batteries would be 2.75V - 2.50V, for a pack voltage of 82.5V - 75V.

10 KW (your desired output) / 111V is 90 amps. The panasonic batteries can do 2C output, or 2X rated capacity. So about 6.8A for each cell. To get 90 amps, you need 13 cells in parallel.

That's 13 batteries wired in a parallel set, and 30 sets of batteries wired in series to get 111V. 390 batteries.

That's part of why you need to know if you need 10 KW continuous, or just for a few seconds to accelerate up to cruising speed, when your power consumption goes down.

Quote:
30 batteries

Is this correct?
I don't think so

Quote:
At a weight of 46 grams each the total 30 batteries will weigh 1.380kg which is lighter than my current lead acid motorcycle battery.
30 * 12.68 w-h is 380 w-h. That may work for electric assist on a pedal bike.

I think you need 13 times that if you want 10 kw.

You also need to know how long you drive at 10 kw. 160 km is a fair distance, so maybe 2 hours? (average of 80 kph including stops and acceleration). If you use 10,000 watts all the time, times 2 hours of driving, that's 20 kw-h.

20 kw-h is the size of a Nissan LEAF battery pack, so it's likely too big. But if you DO need 20 kw-h, at 12.68 w-h per battery, that means you need 1577 batteries(!!)

A quick search gives this (2009) article/blog at DIYelectriccar

Step 1: How to plan a DIY Electric Motorcycle - DIY Electric Car Forums

Perhaps some reading will help you get a handle on what power you need for cruising, depending on your chosen conversion.

There are motorcycle projects at ecomodder, but I'm not familiar with them

Looking forward to reading about your project!

Last edited by thingstodo; 09-07-2015 at 02:50 AM.. Reason: Correct errors :(
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Old 09-07-2015, 03:55 AM   #6 (permalink)
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One nice motorbike project here is Bennelson Vectrix to Leaf cell conversion:
http://ecomodder.com/forum/showthrea...fit-31595.html
18 Leaf cells fit the Vectrix frame perfectly!

Still, that Vectrix has just 9 kWh.

I'm building a portable plugin kit for my car, based on LiFePO4 cells. It has just 1.4 kWh and weighs over 15 kg including boxes, cables and BMS. (still highly portable, as the pack is split in 3!)
A pack with 10 times its capacity would be too heavy for a motorcycle.

Electric bikes are perfect for a relatively short commute. Charged every day, not using the entire range, you can keep doing that for years and gain back the investment.
Making a long range EV is hard and costly, and unless you do use that range on a near daily base you probably won't make up for the cost.

I won't say it cannot be done. The Stella solar racing car has a 15 kWh battery pack that weighs just 63 kg. Light enough for a fun midrange electric motor bike. But probably not a cheap one...
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It always takes longer than you expect, even when you take into account Hofstadter's Law.

When I drive a car I'm a driver. When I'm sitting on my couch I'm a biker.
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Old 09-07-2015, 09:02 PM   #7 (permalink)
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10kw is the power of my 125cc motorcycle and I would not want any less for on road use. I'm at full throttle/max power with tuck to maintaining high way speed of 110km. Vehicle weight is 124kg and I weigh 97kg so 221km combined weight.

The longest trip I make on my motorcycle is 160km 2-3 times per year.
Every day travel is below 30km at or below 70km per hour in city conditions.

I'll do a bit of reading.
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Old 09-07-2015, 11:28 PM   #8 (permalink)
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Quote:
Originally Posted by Spaghetti Man View Post
If a Panasonic 18650 is 3.7 volts and 3.4 amp

3.7 volt x 3.4 amp x 1 = 12.58 watt hour.

I need 30 Panasonic 18650 batteries.

3.7 volt x 3.4 amp x 30

= 111 volt x 102 amp = 11,322 watt hour

Is this correct?

Providing these calculations are correct the electric vehicle is more economical.

Not correct. 3.7V x 3.4 Amp-hours 12.58 Watt hours

However if seriesed up to make 111 Volts the amp=hours stay the same, then you have 111 volts x 3.4 Amp-hours= 377.4 Watt hours.

If parallelled, the voltage level stays the same then 3.7Volts x 102 Amp-hours= 377.4 Watt-hours.
JJ
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Old 09-07-2015, 11:34 PM   #9 (permalink)
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Do you have any streamlining on the bike? That will extend your range if done properly.
JJ
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Old 09-08-2015, 12:32 AM   #10 (permalink)
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Quote:
Originally Posted by jjackstone View Post
Do you have any streamlining on the bike? That will extend your range if done properly.
JJ
It would actually be for a new vehicle resembling a velomobile. I think electric will fit better in a velomobile than petrol engine, hence me asking about electric power.

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