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  #1  
Old 01-21-2015, 04:49 PM
Drain_Bamage Drain_Bamage is offline
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Thumbs up Planning EV Commuter Motorcycle conversion!

Greetings!

I'm new here (as you can tell by my post count) but I've been reading for a while and I'd like to tackle something new to me, an EV conversion project! I'm blessed by the fact that I have a 9 mile commute each day (4.5 one way) so when the weather is nice, a car for a daily driver does not make a lot of sense. You can do a lot of wear and tear to an internal combustion engine doing a lot of "short hop" commuting where the car never gets to warm up, so I've been looking into alternatives. Of course, a motorcycle immediately sprung to mind but then you run into the same problem of warmup. This is where the EV idea sprang from. Our office also has 120VAC 20A outlets in the parking lot for golf carts that we no longer use, so I can get a solid 8hrs of charge in each day, provided I go with onboard charging. The outlets are in a "open" area of our parking lot but the facility is not exposed to the "public" so vandalism/theft should not be an issue.

Being quite familiar with internet forums, I took the advice from the sticky in this section and have started my "intro thread"

Your skill level with auto mechanics and fabrication
  • Quite skilled in auto mechanics, somewhat of a neophyte fabricator. I've been playing with cars and wrenching on thing for many years. I can run a soldering iron, build a wiring harness from scratch (Thanks Dr. Lucas) and I know how to use a set of dial calipers correctly. I can handle pretty much any automotive task thrown my way provided it does not require specialty tools and I have clear enough instructions. The family comes to me when they need their brakes and oil changes looked after I have no problem swapping and engine or doing a set of chassis bushings in a couple of weekends. I'm no welder but I have friends with the tools and experience. I believe in using the right tool for the job and I prefer to learn from other peoples mistakes and do it right the first time.

The range you are hoping to get (how many miles/charge)
  • Technically 10 miles would be a minimum, but I see no reason not to shoot for 20~30 miles per charge.

What level of performance you are hoping to get
  • Most of my commute is in town/country roads so 25/35mph would be an average. Maybe 45mph top speed but only for short bursts.

How much money you are willing to put into your project
  • I'd like to keep the budget around $2000~$3000 all in.

What parts you've already considered, if any.
My plan, in the broadest strokes, looks something like this:
- 200-400cc bike frame (availability & insurance cost dependant)
- 48vDC
- Motenergy ME-1004 or ME-0708 motor
- Alltrax AXE 4844/4845
- Magura Twist Grip Throttle
- DC/DC converter (headlights, blinkers, etc)
- Onboard charging

I've been going back and forth between PB (Optima AGM) and something like CALB LiFePO4 for batteries. Here are my thoughts and the numbers I've found so far:

Pricing out a set 4 of 55Ah AGM bats as used in the above linked article (4S) puts me at like $3.65/Ah @ 12v, so $14.60/Ah @ 48v, so we are talking a shade over $800 in batteries. Pricing LiFePO4 from someone like evsource.com requires 15 cells (15S) to get my 48v (3.2v nominal) and 60Ah comes out to $1.37/Ah @ 3.2v, so $20.55/AH @ 48v. That's $1230 total in LiFePO4.

For PB/AGM, it looks there there are no shortage of $50-150 chargers available for bulk charging at 48v. As for the LiFePO4, things get a bit ...complicated. I'm familiar with the volatility of LiPo from playing with multirotors and while I understand that LiFePO4 is supposed to be better, it still seems to require a managed BMS and a lot of additional hardware to the tune of 3-5x the $ cost of charge equipment for PB/AGM. Everything I've been able to find tells me that its fidgety, heavy, and not exactly "onboard charge friendly" for something like a motorcycle. That alone seems to kill LiFePO4 for this particular project.

As for weights, AGM comes to 174lbs and LiFePO4 tips the scales at 66lbs. That's 38% of the weight and 153.75% increase in cost. Seeing as I'm on a "$" budget and not a "#" budget, I'm thinking AGM might be the way to go, simply due to ease of implementation.

Anyway, that's where I'm sitting in this particular case. I'd love to hear some input from folks who have built EV motorcycles or recommendations for other resources. I've poked around a bit on elmoto and endless sphere but I figured this looked like a pretty good places to start. Thanks all for documenting and sharing your ideas!

Edit: I took another look today at my 9 mile commute on Google Maps and discovered that by adding 1/2 mile to my route I can completely avoid the 1 mile section of highway and the need for speeds above 45mph. I'm feeling a bit more confident about 48v now, so needs can be adjusted accordingly.

Last edited by Drain_Bamage; 01-22-2015 at 11:34 PM.
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  #2  
Old 01-21-2015, 05:27 PM
Brute Force Brute Force is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Two things to consider on the batteries:

1. You will not get 55AH from your lead acid batteries. Read up on Peukert (sp?) effect. They will have 30AH (or less) capacity in an EV application.

2. Cost of ownership. The lead acids are cheaper up front, but because the lithiums have a longer lifetime (both calendar and cycle) they are cheaper per mile driven.
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Old 01-21-2015, 05:47 PM
Drain_Bamage Drain_Bamage is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Quote:
Originally Posted by Brute Force View Post
Two things to consider on the batteries:

1. You will not get 55AH from your lead acid batteries. Read up on Peukert (sp?) effect. They will have 30AH (or less) capacity in an EV application.
Thank you for the heads up! A quick google search gave me something to start with.
Quote:
Originally Posted by The Wikipedia: Peukert's law
Peukert's law, presented by the German scientist W. Peukert in 1897, expresses the capacity of a battery in terms of the rate at which it is discharged. As the rate increases, the battery's available capacity decreases.

Manufacturers rate the capacity of a battery with reference to a discharge time. For example, a battery might be rated at 100 A·h when discharged at a rate that will fully discharge the battery in 20 hours. In this example, the discharge current would be 5 amperes. If the battery is discharged in a shorter time, with a higher current, the delivered capacity is less. Peukert's law describes a power relationship between the discharge current (normalized to some base rated current) and delivered capacity (normalized to the rated capacity) over some specified range of discharge currents.
Very interesting, this is not something I had run into previously. Are the lithium based batteries not subject to this type of effect? If that is the case, I might be able to get away with 40Ah LiFePO4 cells thus saving more dollars and weight. I'll do some more reading for certain.

Quote:
Originally Posted by Brute Force View Post
2. Cost of ownership. The lead acids are cheaper up front, but because the lithiums have a longer lifetime (both calendar and cycle) they are cheaper per mile driven.
I could see that, but with my particular application I'm having trouble wrapping my brain around finding a BMS/charge solution that is small enough, light enough and rugged enough for onboard use that won't destroy my budget and vehicle performance. I'm all up for more places to look and things to read if you have any specific recommendations about LiFePO4 charging stratagems and equipment.

As I said, I'm still in the planning phases so all information is welcome. Thanks again!
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  #4  
Old 01-21-2015, 06:15 PM
Brute Force Brute Force is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

The Peukert effect is negligible in lithium chemistry batteries. And they are usually rated at C instead of C/20 as lead acids are. So you typically get 60 AH from a 60 AH lithium cell.

There is a great debate on BMS systems. Some swear by them, some at them. I think they're a necessary evil. But if you're careful, you can get by just fine without one.

Oh, and buy your batteries when your ready to install them. You don't want them to go bad before you get to your first test drive!
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  #5  
Old 01-21-2015, 06:29 PM
Drain_Bamage Drain_Bamage is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Quote:
Originally Posted by Brute Force View Post
You will not get 55AH from your lead acid batteries. <snip> They will have 30AH (or less) capacity in an EV application.
Interesting... as I'm basing my build on the linked article where the author was seeing 20-30 miles of range on his 4x 55Ah AGMs, perhaps the 40Ah might actually be enough for my application. Using the cost of the 40Ah instead of the 60Ah LiFePO4 puts me within $25 of the AGM cost. Weight is also down to 46.2lbs for the entire LiFePO4 battery pack whereas a single Optima YellowTop D34-78 weights 43.5lbs C vs C/20 is not something I noticed. That really changes things as well!

Again, onboard BMS/charge solution is still a question and I appreciate the insight. It appears as though there is a bit of a "holy war" about such things

I also just noticed something else about the LiFePO4; the maximum discharge rating of 2C. That does not seem like much. Cells in series will provide higher voltage, but capacity (and I assume C?) needs to come from a parallel configuration, yes? Cell specifications are here: http://www.evsource.com/datasheets/B...able%20(1).pdf

I'm not phenomenally good with calculating this stuff out, and most of the EV calculators I've seen are for bicycles or cars rather than motorcycles. I'll have to see if I can come up with some ballpark numbers to work with.

Last edited by Drain_Bamage; 01-21-2015 at 06:32 PM.
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Old 01-21-2015, 06:45 PM
Duncan Duncan is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Hi Drain
The 2C is continuous - so for 40Ah you can draw 80amps continuous
80 amps x 48v = 3.8Kw = 5Hp
More than enough to maintain speed
The "burst" rating is probably 10C - 400amps for 15 seconds
More than enough for acceleration

Charger
I'm sure you can find a simple 48v charger
The secret is don't be greedy at the top end - if you only try to charge to 90% you will have a lot more room for error

DC-DC
I just use a small lithium ion battery and charge it at the same time as my main pack
Not as good as a DC-DC but a whole lot cheaper and easier

You can get a decent charger for home and just use 90% one at work
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Old 01-22-2015, 02:22 AM
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Yabert Yabert is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Quote:
Originally Posted by Drain_Bamage View Post
perhaps the 40Ah might actually be enough for my application.
Hi Drain

I suggest you to don't be too cheap on battery to begin.
15 cells 40Ah is only 2 Kwh of storage energy and 48v nominal isn't best to reach your 50 mph goal. A little more voltage will give you higher top speed.
I can suggest you to go with 16 lifepo4 cells 60Ah or better 14 Nissan Leaf cells for a nominal voltage of 52.5v and 60Ah for 3,1 Kwh of storage energy.
http://hybridautocenter.com/HAC4/ind...0ah&Itemid=605

With only 14 cells, it will be easier to manually manage all the cells (suggest you learn bottom balancing), more energy imply that will be easier to stay away from full discharge-fully charge cells and, finally, the higher voltage will give you higher top speed.


If budget is the most important thing over top speed and range, I suggest you this 12 cells 45Ah chevy Volt battery: http://hybridautocenter.com/HAC4/ind...lls&Itemid=605

Good luck!
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Old 01-22-2015, 11:13 PM
Drain_Bamage Drain_Bamage is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Quote:
Originally Posted by Duncan View Post
Hi Drain
Hiyas!
Quote:
Originally Posted by Duncan View Post
The 2C is continuous - so for 40Ah you can draw 80amps continuous
80 amps x 48v = 3.8Kw = 5Hp
More than enough to maintain speed
The "burst" rating is probably 10C - 400amps for 15 seconds
More than enough for acceleration
Thanks for the maths, as I said its not my strong suit. But I'm trying!

Quote:
Originally Posted by Duncan View Post
Charger
I'm sure you can find a simple 48v charger
The secret is don't be greedy at the top end - if you only try to charge to 90% you will have a lot more room for error
I had thought that you ABSOLUTELY had to have a balance system for anything Li based, it sounds like maybe I can get away with a bulk charger with the voltage cutoff set at 90% rated voltage? I admit, I need to spend some more time in the battery section and do some reading.

Quote:
Originally Posted by Duncan View Post
DC-DC
I just use a small lithium ion battery and charge it at the same time as my main pack
Not as good as a DC-DC but a whole lot cheaper and easier

You can get a decent charger for home and just use 90% one at work
There are some incredibly el-cheapo DC-DC converters on ebay. I'm thinking a combination of converter and small 12v battery might not be a bad idea, but I don't want to make things too complex.

I do appreciate the feed back!
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  #9  
Old 01-22-2015, 11:29 PM
Drain_Bamage Drain_Bamage is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

Quote:
Originally Posted by Yabert View Post
Hi Drain
Hi!
Quote:
Originally Posted by Yabert View Post
I suggest you to don't be too cheap on battery to begin.
15 cells 40Ah is only 2 Kwh of storage energy and 48v nominal isn't best to reach your 50 mph goal. A little more voltage will give you higher top speed.
I can suggest you to go with 16 lifepo4 cells 60Ah or better 14 Nissan Leaf cells for a nominal voltage of 52.5v and 60Ah for 3,1 Kwh of storage energy.
http://hybridautocenter.com/HAC4/ind...0ah&Itemid=605
I like the idea of the Leaf cells, but they are confusing as hell as I'm used to looking at 3.2v nominal and everyone lists the Leaf ones at 3.6v~3.8v. It took me longer than I care to admit to realize that

You are right, that 8 module unit you linked (3.5kW/h Battery Pack 60.8V /60Ah) meets my requirements in spades, but may be a bit much. It's also listed at $995 + shipping for 78lbs. I'd have to step up to a 72v compatible controller as the Alltrax AXE series 48v will only accept up to 60v before "overvoltage shutdown" kicks in, according to the specs. The motor would need to be able to handle higher voltage as well and both upgrades are additional expense. I'd need to read up on how these AXE controllers handle such a large stepdown (60v -> 48v) and how that effects their efficiency and longevity.

That same vendor also sells a 6 module (2.7kW/h Battery Block 45.6V /60Ah) that looks like it would also be a good fit. It's listed at $775 + shipping for 62lbs so that still puts me at less than the cost of the AGM stuff I listed earlier. The 45.6v puts me closer to my original spec'd 48v and I can probably use the 48v controller and motor as well. I'll probably shoot an email to the folks at Alltrax and see what they have to say.

Quote:
Originally Posted by Yabert View Post
With only 14 cells, it will be easier to manually manage all the cells (suggest you learn bottom balancing), more energy imply that will be easier to stay away from full discharge-fully charge cells and, finally, the higher voltage will give you higher top speed.
14 Leaf (prismatic/pouch?) cells in series (53.2v/30Ah) or 14 LiFePO4 in series (44.8v/30~60Ah)? Sorry, I get confused easily, still trying to wrap my brain around this stuff. I've seen bottom balancing mentioned in a few places and it looks like the way to go. I'm not sure how that is accomplished with the Leaf 2S2P "modules" (other than assuming they are paired and thus balanced?) but again, I need to read some more.

Quote:
Originally Posted by Yabert View Post
If budget is the most important thing over top speed and range, I suggest you this 12 cells 45Ah chevy Volt battery: http://hybridautocenter.com/HAC4/ind...lls&Itemid=605
Haha! That certainly is cheap! I like that the listed "continuous current 200A, short time 350A" is right around what I expect to see. I wish they had some notes about the weight as it appears to be unlisted.

Quote:
Originally Posted by Yabert View Post
Good luck!
Thanks, I'm going to need it!
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  #10  
Old 01-23-2015, 05:55 AM
arklan arklan is offline
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Default Re: Planning EV Commuter Motorcycle conversion!

couple of things i noted when reading this...

yabert is right that with such a small number of cells you could very easily get away with no bms and just monitor them yourself.
bottom balance and charge to 80-90% and i dont think youd ever have a problem

theres 3 kinds of lithium battery afaik, you got the prismatic type, pouch type and the lipo type u see in rc helicopters
the lifepo4 ones like calb are the safest and u could pretty safely charge a set of 4 with a normal car battery charger aslong as u only went to like 80-90%, theyr pretty bullet proof
the pouch cells from the leaf and volt etc are the pouch type which are halfway between pretty safe and catching on fire.
in a motorbike where people in cars look u directly in the eye while pulling out in front of u, i wouldnt have anything other than prismatic in one.

the motenergy motors on a "power to weight" ratio are heavy
heavier than other offerings from kostov or netgain etc, just something iv noticed

those cheapo dc converters off ebay are designed for stationary use in a machine in a factory or something not the vibration and crap that youd accumulate from riding a bike
that said, for the price i dont think it makes any difference

for testing purposes youd get away with 4 second hand car batteries, should cost u like 20 bucks each

someone tell me if im wrong
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