# Shifter Kart Conversion Questions and Ideas



## michaelmonaghan (Aug 1, 2014)

Hi everyone, this is my first time posting here, so bear with me. Before I start I guess it is important to know that this is not my first rodeo. I have built 2 electric bikes, raced RC electric cars professionally for 8 years (if that counts for anything) and built an electric motorcycle about a year ago. http://www.instructables.com/id/Electric-Motorcycle/ Anyways, I am interested in converting my 2008 CRG Kalifornia shifter kart into an electric vehicle. My motorcycle came out looking like it was something you can buy from Honda, but was built with a small ME-0909 motor and a 48V 22Ah SLA battery pack that only cost me $160 shipped (although I made the battery box to allow for various lithium batteries as well, but now I am looking to move on to something a little bigger. 
The 2-stroke engine I have in it now (PRD Fireball 125cc) produces around 26 to 28hp and does around 60mph on a short track, but does not take advantage of any type of clutch or shifting which means it is not always in the proper powerband. These engines weight something around 60lbs plus I have 28lbs extra on the kart to meets the 360lb minimum. 
Motenergy has a good variety of motors in the 15-23kW range that would work good for this application, but I am still not sure which one is right for me. Brushed controllers are less expensive, but require some maintenance. Are there any other advantages to brushes on these large motors? (i.e. torque efficiency rpm)
My main concern is batteries. I found some Headway LiFePO4 cells that were 15Ah, but they only have a max discharge of 10c which yields 150A. If I doubled them up I can get 300A which is closer to what I need but still seems to fall a little short. ElectricMotorsport also has some different LiFeMnPO4 batteries that are 20Ah or 40Ah with a 10c pulse rating. I would like to be able to do about a 15 minute or so track run and hopefully be able to charge between practices if possible (keep in mind weight is somewhat of an issue to maintain handling). If someone with more battery experience could help me out that would be great. I know some type like SLAs have a voltage sage under high loads but I don’t know too much about anything else. 
My final concern is that even if say I had a 23kW motor, wouldn’t it only produce as much power as the batteries can produce? (ex. A 30Ah 48V pack with a 10c discharge rate can only produce 300A x 48V=14.4kW) so even if the motor was capable 23kW, it would only be running at 14.4kW minus efficiency losses? 
I have access to a machine shop, 3D printer, welding equipment and 3D modeling software, but I need a bit more education on the electrical side. I look forward to hearing from some people and thanks in advance! J
-Michael


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## Karter2 (Nov 17, 2011)

For a race application, especially a kart where weight and space are critical, you would be mad not to fall back on your RC experience (electric ?) and use RC lipo. Its powerful (<100C ) light weight , compact , and relatively cheap.
I would not recommend it if you have not some prior experience, and understand the risks, but it really is the only viable solution for the performance you want to replicate.

You may find it useful to read this thread..
http://www.diyelectriccar.com/forums/showthread.php/silent-scream-build-thread-75205.html


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## michaelmonaghan (Aug 1, 2014)

Thanks for the link, there’s a lot of good information there! It looks like I am going to have to do a lot more reading before making any decisions. 
As for the batteries, I did consider RC lipo’s, but I’ve seen so many catch on fire. It’s sad when a little toy car bursts into flames, but it would be horrifying if you were in the car! As far as amp draw goes though, I cannot find any other battery that compares. Each rc lipo pack has its own balancing system, but is there a way to hook up a BMS to each of the existing balancers? 
I saw on that link that there is a 100 lap race too. That’s a lot farther than I was looking to go on a charge, but what type/ how much capacity are the batteries that they are running?


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## Hollie Maea (Dec 9, 2009)

How long are these races? A LiPo pack discharging at 60C will be empty in a minute. That's great for drag races, but if you need to go much more than that, you don't need the stratospheric power capabilities of RC LiPo. Might be better to get some safer high energy density cells that are more like 15-20C.


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## major (Apr 4, 2008)

michaelmonaghan said:


> I saw on that link that there is a 100 lap race too. That’s a lot farther than I was looking to go on a charge, but what type/ how much capacity are the batteries that they are running?


The 100 lap race was at the Indianapolis Motor Speedway  But not the 2.5 mile oval. It was a kart track set up in the infield RV parking lot and was about 1/4-1/3 mile long. Pretty nice and accommodated about 25 electric race karts for the main event.

Each kart was limited to 8640 Wh total energy storage for the race. Our team chose to split that and run 4.2 kWh on board and do a pit stop battery swap. Two crew members swapped batteries in 7 seconds. We pitted about lap 70 so ended up using about 6 or 6.5 kWh total. There were quite a few yellow laps which burned less Wh.

Hope that helps.


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## major (Apr 4, 2008)

That's weird  I couldn't use the quote feature in the above post and now I can't edit it. Oh well. Just noticed I forgot to mention the battery type. We used EnerDel; the energy cells. The race and practice/qualifying sessions were such that we couldn't really discharge fully in less than about 15 to 20 minutes, so average 3 to 4C. They'd get warm but had no problem with it.


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## michaelmonaghan (Aug 1, 2014)

Where can I find a link to Enerdel batteries? I am curious on the weight and voltage you used. And were you guys using the AC-15 setup? The races are 16 laps on a 3/4 mile long course for the TAG class karts (an average practice run is 8-12 laps). I would like to find some races near my area for electric, but for now I would like to just run with some buddies without the $150+ per hour of maintenance of a 2-stroke. I know the upfront cost is higher for electric, but something about creating a custom designed power plant is a little more gratifying. 
Also, with the motor/controller setup you guys are using, what is your average amp draw? I Calculated 450A from what I just read but I may have done the math wrong.


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## major (Apr 4, 2008)

http://www.diyelectriccar.com/forums/showthread.php/fs-enerdel-modules-480-86245.html 

Had a 14 kW limit by rule and 45V nominal. ~100Ah. Likely about 300A peak.

edit: additional info:

The kart would run 3 EnerDel modules in parallel, each 2P12S, 33Ah, 44.4V nominal. Yes, the AC-15 stock (pretty much). I don't recall kart weight.

Note: After that race, we retuned without the kW limit and nearly doubled the power. Batteries held up. Also considered rewiring to 90V. Maybe someday. To take full advantage with that would need to gear properly which means adding a jackshaft or adding a real gear set.


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## Karter2 (Nov 17, 2011)

Hollie Maea said:


> How long are these races? A LiPo pack discharging at 60C will be empty in a minute. That's great for drag races, but if you need to go much more than that, you don't need the stratospheric power capabilities of RC LiPo. Might be better to get some safer high energy density cells that are more like 15-20C.


No, he won't need anything like 60C, but he will need a power dense cell to keep the weight down, and minimise voltage sag
On a kart, weight is a killer if you want to be competitive, and there is no way an electric kart can get down near the tag minimum weight limit carrying enough battery to finish a race.
There are many possible cell options, but until you decide what motor/power you plan to use, it's impossible to get specific.
I suspect your best bet for lightest pack weight would be a few hundred High discharge 18650's,....but that becomes a complex pack to assemble and would cost much more than an RC LiPo based pack 
All other options will cost more , or weigh more than RC systems.
If you want to have fun and be "Tag competitive" something like 20kW would probably work.


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## michaelmonaghan (Aug 1, 2014)

From what I have researched, the AC-15 does look like the best choice for reliability and regen, though it does look a bit bulky and about double the price of a permanent magnet kit. Do you know the power/torque output it was producing on those batteries? 
At a 300A current that's 20 minutes of run time (if it was drawing 300A 100% of the time) which sounds perfect. How much does each one of those 33Ah packs weigh?


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## major (Apr 4, 2008)

michaelmonaghan said:


> From what I have researched, the AC-15 does look like the best choice for reliability and regen, though it does look a bit bulky and about double the price of a permanent magnet kit. Do you know the power/torque output it was producing on those batteries?
> At a 300A current that's 20 minutes of run time (if it was drawing 300A 100% of the time) which sounds perfect. How much does each one of those 33Ah packs weigh?


Click on the attachment here: http://www.diyelectriccar.com/forums/showpost.php?p=371096&postcount=27 15kg each. We used 3 of these on the kart. 

Regarding the motor, HPEVS has very good documentation on their website (performance curves).


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## michaelmonaghan (Aug 1, 2014)

I do like the price of these batteries there are about half the price of the headway cells, but I'm curious how much it would cost to ship to southern California though. What is the dimension of each pack? I think this would work well in my motorcycle as well! Also, what charger are you using and how long does it take to charge ~100ah of these batteries?


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## major (Apr 4, 2008)

michaelmonaghan said:


> I do like the price of these batteries there are about half the price of the headway cells, but I'm curious how much it would cost to ship to southern California though. What is the dimension of each pack? I think this would work well in my motorcycle as well! Also, what charger are you using and how long does it take to charge ~100ah of these batteries?


All the dims and specs are in that thread. A quick tape measure = 7 x 8 x 10.5 inches. I use a DeltaQ at 17A. And I have tried numerous times to ship and have not been able to do so. As the thread says: Shipping is buyer's responsibility.

My price is good and I have a few left but do not expect to get any more at that cost.


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