# new build - research



## RIPPERTON (Jan 26, 2010)

Im also doing an Aprilia 125 for a friend. He has a 13kW Lynch 27 DC motor from a previous project. Biggest problem is gearing it for the best performance and speed. We figured for an 80kmh top speed we would need a double chain reduction for an overall reduction of 8:1 (I think).
13kW wont get you more than 80kmh with decent acceleration and if you gear it taller the motor will labour and overheat.
The double chain reduction is noisy and can wear the primary chain.
Ideally you could start with a hub motor mounted in the frame and then chain reduction to the rear wheel. Sounds like a hassle but the extra torque at low rpm means you only need one chain.
Keep thinking but your expectations of making both a zippy commuter bike and a fast track bike are shooting a bit high. Your will achieve the commuter bike part but not the track bike.


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## Sunking (Aug 10, 2009)

kingr said:


> Goals below.
> 
> Performance: Out perform the original ice engine
> Range: 70km's
> Budget: $6000


Never going to happen for $6000. You might get 90 Kmh going down hill at a slow acceleration rate. Way short of the 210 Kmh the spark engine can get. Better up your budget 10 times. Stop and think about it. You are going down from a 43 Kw 12,000 RPM with 29 ft pounds of torque gas engine, to a 11 Kw 7000 RPM motor.


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## Tomdb (Jan 28, 2013)

you will need a more powerful motor, have a look in the garage section at previous conversions or on http://elmoto.net/. 

What kind of batteries can you get in south africa? Because weight and size will be a big issue for your "small" bike.


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## kingr (Dec 5, 2014)

RIPPERTON said:


> Im also doing an Aprilia 125 for a friend. He has a 13kW Lynch 27 DC motor from a previous project. Biggest problem is gearing it for the best performance and speed. We figured for an 80kmh top speed we would need a double chain reduction for an overall reduction of 8:1 (I think).
> 13kW wont get you more than 80kmh with decent acceleration and if you gear it taller the motor will labour and overheat.
> The double chain reduction is noisy and can wear the primary chain.
> Ideally you could start with a hub motor mounted in the frame and then chain reduction to the rear wheel. Sounds like a hassle but the extra torque at low rpm means you only need one chain.
> Keep thinking but your expectations of making both a zippy commuter bike and a fast track bike are shooting a bit high. Your will achieve the commuter bike part but not the track bike.


Thank you for the technical feedback. I agree , I'm shooting for a stars on fairly low budget build. I will be more than happy with a commuter bike as this will be first ev project , so will stick with that goal. The Aprilia 125 has a great chassis , I will most likely go for the Aprilia over the NC30.

My experience with gearing is very little , last time I played around with sprockets was as a kid on my bmx. So lots to learn and research.


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## kingr (Dec 5, 2014)

Sunking said:


> Never going to happen for $6000. You might get 90 Kmh going down hill at a slow acceleration rate. Way short of the 210 Kmh the spark engine can get. Better up your budget 10 times. Stop and think about it. You are going down from a 43 Kw 12,000 RPM with 29 ft pounds of torque gas engine, to a 11 Kw 7000 RPM motor.


Your comparison is to the NC30 engine power , I acknowledge your point.

Do you think the Aprilia 125 would be a better donor ? the Aprilia makes 21kw/19nm stock. ME1003 pushes 11.5KW continuous, 23KW Peak for 1 minute @ 72Volts.


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## kingr (Dec 5, 2014)

Tomdb said:


> you will need a more powerful motor, have a look in the garage section at previous conversions or on http://elmoto.net/.
> 
> What kind of batteries can you get in south africa? Because weight and size will be a big issue for your "small" bike.


Hey man!

Will look in the garage. 

I can source these locally.
Sinopoly 3.2v 60ah lifpo4 cells.
Cell weight = 2kg
Cell Size = 18cm(height) x 11cm(width) x 6cm(depth)


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## Tomdb (Jan 28, 2013)

these cells have a very low energy density roughly 100wh/kg. Also rated max 5c discharge. How many do you thing you can fit into a rs125 frame?


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## Sunking (Aug 10, 2009)

kingr said:


> Your comparison is to the NC30 engine power , I acknowledge your point.
> 
> Do you think the Aprilia 125 would be a better donor ? the Aprilia makes 21kw/19nm stock. ME1003 pushes 11.5KW continuous, 23KW Peak for 1 minute @ 72Volts.


My point is acceleration and speed cost big bucks. Motor cycles even more so because drag coefficient of a motor cycle is 3 to 4 times greater than an automobile. A motor cycle with rider is on the order of 1 to 1.2 vs .2 to .4 of a car. That can be lowered with a Fairing to reduce drag. This chart shows the horse power vs speed to account for drag. Does not include weight and rolling resistance.


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## kingr (Dec 5, 2014)

Sunking said:


> My point is acceleration and speed cost big bucks. Motor cycles even more so because drag coefficient of a motor cycle is 3 to 4 times greater than an automobile. A motor cycle with rider is on the order of 1 to 1.2 vs .2 to .4 of a car. That can be lowered with a Fairing to reduce drag. This chart shows the horse power vs speed to account for drag. Does not include weight and rolling resistance.


My assumption was that the NM of the me1003 will provide good low rpm acceleration with a light motorcycle. 

From that chart I gather I will reach atleast 75mph when running at full power. If that's the case I will be happy with my setup.


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## kingr (Dec 5, 2014)

Tomdb said:


> these cells have a very low energy density roughly 100wh/kg. Also rated max 5c discharge. How many do you thing you can fit into a rs125 frame?


To be honest with you , I would like to put 72v inside the 125. I feel this will be a challenge considering the size of one cell. This will equate to 22 cells inside the frame , abit optimistic I think. I've been researching headway lifepo4 cells , these are much smaller and looks like a better match. I need to find out costs and how much SA will charge me for import duties. Nissan Leaf batteries might also be a option , need to research more. Would be great if I can source leaf batteries from a local junk yard , but this likelihood is small as there is only a handful of Leaf's on the road here by us. 

ELMoto is a great forum , I have spent lots of time on there the past few days.


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## Grinhill (Dec 9, 2014)

Hi there,
Let me know if you need to know any measurements from the Aprilia RS125, as I have one with the motor out of it in my garage at the moment!

I'm doing a conversion which will have a 4.5 kWh battery, hoping the final weight will be very close to stock.

Another battery worth investigating is some of the latest 18650 cells e.g, Samsung.

Here's my build thread for the Aprilia:
http://endless-sphere.com/forums/viewtopic.php?f=12&t=67256


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## kingr (Dec 5, 2014)

Grinhill said:


> Hi there,
> Let me know if you need to know any measurements from the Aprilia RS125, as I have one with the motor out of it in my garage at the moment!
> 
> I'm doing a conversion which will have a 4.5 kWh battery, hoping the final weight will be very close to stock.
> ...


Thanks for the tips , I will give you shout if I decide to go with the Aprilia.


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## Jayls5 (Apr 1, 2012)

Not sure where you're located, but Turnigy 4S 5000mAh packs are currently $22.98 before shipping. (wait on the screen for the promotional rate to come up) at HobbyKing.











That's 74 watt/hour with a weight of 1.31 pounds, 20C constant discharge, prewired power and balance leads. I built a ~79 lb 4.44 kWh pack out of them, and i'm using the ME1003 as well.

That's $1379 before shipping for your desired pack. You just have be careful with any LiCoO2 based lithium batteries, as they are more volatile than the LiFePO4 type. That's the trade-off for better power density. 

Don't go this route unless you know what you're doing.


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## kingr (Dec 5, 2014)

My experience with ev's and batteries are zero. This is my first attempt at building an ev. I will look into your suggestions , however I am abit intimidated.

I live in South Africa. Lifpo4 cells appears to be the least complicated to setup and easiest obtainable for me.


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## Jayls5 (Apr 1, 2012)

kingr said:


> My experience with ev's and batteries are zero. This is my first attempt at building an ev. I will look into your suggestions , however I am abit intimidated.
> 
> I live in South Africa. Lifpo4 cells appears to be the least complicated to setup and easiest obtainable for me.


The incredibly "dumbed down" version of safe lithium battery operation:
Don't exceed voltage ranges of the battery. (Of course, same goes with going beyond its current rating)

If you are not familiar with high voltage safety, do not go further until you become highly knowledgeable about proper procedure to keep yourself from getting electrocuted.

Think of a lithium battery cell as having a "range" of useful voltage to work with. Charge too high or discharge too low, and you get problems. Some people use "BMS" (battery management) circuits to monitor each battery to help keep them in line. Batteries aren't all going to be exactly the same capacity or internal resistance, so this means that they will charge and discharge unevenly when a load is applied to them. The effects of this are mostly seen on the high end of charging and the low end of discharging. The BMS circuit will (using one of many ways) take power away from overcharged batteries, disconnect over discharged batteries, and/or redirect things where they need to go. Basically, you can get the REAL rated capacity from your battery reliably with that BMS circuit.

That being said, a BMS is expensive. In many cases, you can afford to get the bigger battery by forgoing the BMS and simply run it in a smaller tolerance of "acceptable voltage" to keep things safe. Instead of doing a 100% charge to 20% capacity discharge with a BMS, you might be satisfied with a reliable 85% charge to 30% capacity discharge with a larger battery and no BMS. 

You'll hear all sorts of people talk a about "top" and "bottom" balancing to keep their batteries in line. This is because voltage readout alone doesn't tell you the whole picture. I said earlier that the capacity can be different between cells. Just because a AAA battery and a D cell might have the same 1.5v, doesn't mean they'll last the same amount of time when you hook it up to a motor. We are dealing with a string of these lithium batteries in series. For practical purposes, you can consider the current draw on each battery in that string to be about equal when applied to a load, so your capacity is going to be limited to your weakest battery. That's going to be the one to reach the lowest acceptable discharge level first; even if your other batteries have some capacity left, you can't really use it without taking that battery out of the chain. To make things easier, people often do one of those balancing methods so they know that their batteries have been filled to similar _capacity_. This means they can more reliably look at their "kWh" power consumption dial and total voltage and (reliably) believe that no one battery in thee pack is near a critical range while the others aren't. Long story short, people have different preferred methods of monitoring and making sure that the "basic rule" for lithium voltage range isn't exceeded.

For the sake of this discussion, I'm going to assume your battery pack is just going to be individual (large batteries) in series, not a combination of more in parallel. The point to take home with all of this is: It's the individual cell voltages that matter, not the total. If one battery dies down to 1 volt while the rest are well charged, your total voltage readout will still be in the normal range. Just find a reliable way to monitor/treat each battery, and you'll be good. I recommend you stick with a safer chemistry like LiFePO4.


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## kingr (Dec 5, 2014)

wow Jay , that was a mouthful of knowledgeable info!

Thanks for being so clear and explaining everything in detail. I will use a BMS for my setup and have been advised this is the best route to insure longevity of my cells. I've heard 'bottom balancing' popup very often on EV forums.

I have read the safety precautions tips and will use all best practice safety tips when building my EV. Thanks for the headsup.

FIY. I just got back from a local Nissan dealership here in South Africa(Melrose Nissan Johannesburg). Was told by the dealership they are still awaiting prices from the factory for the Leaf batteries. Was also told they will not be selling individual cells and they estimate the full pack will cost about $10 000. The dealership also has x3 land-based chargers for the leaf onsite.


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## kingr (Dec 5, 2014)

Grinhill said:


> Hi there,
> Let me know if you need to know any measurements from the Aprilia RS125, as I have one with the motor out of it in my garage at the moment!
> 
> I'm doing a conversion which will have a 4.5 kWh battery, hoping the final weight will be very close to stock.
> ...


I've just found a local supplier that can sell me these for $7 a piece. What type of bms can one use with these cells ?


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## kingr (Dec 5, 2014)

kingr said:


> I've just found a local supplier that can sell me these for $7 a piece. What type of bms can one use with these cells ?


Found this BMS on BesTech website. Looks like it will do the job. No prices though.


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## Tomdb (Jan 28, 2013)

I would not recommend going for 18650 cells for your first build.

Constructing packs will be a *MOUNTAIN *of work, to get it right.

Example of what Jehu is/was doing https://www.youtube.com/watch?v=_9aEWZvWNbc


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