large road legal electric go kart build. need help!

[Dauntless]

Well, why not go 12kw continuous, 30kw peak? Such have been my plans if I could ever jump in on this fantasy project:

http://www.electricmotorsport.com/karting/karting-bushed-motor-kits/me0909-drive-kit-with-motor-controller-throttle-contactor-wire-kit-and-fuse-block.html

Of course if I really had some money to spend, there's always AC. http://www.electricmotorsport.com/ev-parts/motors/ac-induction/ac-12-kit.html

Or now, how about liquid cooled? http://www.electricmotorsport.com/karting/karting-pmac-kits-liquid-cooled/pmac-12kw-30kw-liquid-cooled-motor-drive-system-48v-650a.html
For even MORE money, right? But I guess one would need to be sure their cooling would be adequate.

 

[galderdi]

Capacity of motors, batteries, and controllers are all about run time. If you plan on running them for prolonged periods of time stick strictly to their nominal rating. But batteries and motors can handle more than their nominal rating for short periods. The shorter the period the more you can squeeze out of them. But you will struggle to get a definitive/quantified answer bacause the person giving the answer could become liable if it turns out to be slightly inaccurate resulting in a major component failure.

But a couple of positives:
1.Make sure to make use of the cooling on your volt cells (like I have). This will reduce any risk of issues with them. I used garden plumbing, a small low volume pump and a heat exchanger from under the dash of a modern car.
2.Install heat monitoring on your motor and batteries. Set yourself limits for each (based on research for the relevant parts) and under no circumstances exceed those limits. Managing the heat is key to ensuring you don't destroy the components by asking too much of them. Or to put it another way, the higher the heat the more likely the components are to fail.
3.Don't make my mistake. Don't install your controller anywhere near your motor. The heat from the motor will radiate into the controller which is a bad thing.

 

[galderdi]

Oh by the way, I am a little confused about the batteries. 100ah at 48v would equate to 4.8kwh.
But I have 7kwh of volt cells at 144v (nominal). So something doesn't add up.
A 48v subset of Volt cells seems to equate to 1/3 of what I have. But if that were true it would only be 2.3kwh.
Unless of course you have 2/3 of what I have (96v) and are planning to run 1/3 in parrallel to the other 1/3 to halve the voltage.

Either way 2.3kwh or 4.8kwh is not much range. I would be lucky to get 25minutes from my 7kwh pack. Granted I am always at 100% acceleration which reduces range significantly. But I really hope you weren't planning on long journeys?

 

[falshami]

so i am stuck between two setups, i found a golden motor 5kw motor BLDC watercooled with an 20kw controller for 760$

or for 1200 dollars i can get a goldenmotor 10kw motor with a 10kw controller BLDC water cooled motor.


im between those two.


i saw the ME0909 motor which is a nice option but it seems to be brushed and only offer 4HP continuous. which i dont think would be enough.


I am purchasing a water cooler for the motor so i can drive it a bit harder. I am hoping to get a 45 to 60 mile range.

I will be mounting the controller way away from the motor per the advice given here. also what can i use to monitor temperature of motor and battery pack to shut things off? Is water cooling the battery an easy thing to do as well?

 

[falshami]

Oh by the way, I am a little confused about the batteries. 100ah at 48v would equate to 4.8kwh.
But I have 7kwh of volt cells at 144v (nominal). So something doesn't add up.
A 48v subset of Volt cells seems to equate to 1/3 of what I have. But if that were true it would only be 2.3kwh.
Unless of course you have 2/3 of what I have (96v) and are planning to run 1/3 in parrallel to the other 1/3 to halve the voltage.

Either way 2.3kwh or 4.8kwh is not much range. I would be lucky to get 25minutes from my 7kwh pack. Granted I am always at 100% acceleration which reduces range significantly. But I really hope you weren't planning on long journeys?

from my understanding you multiply volts by AH and divide by 1000? that gets me 4.8WH and yes i was hoping to get good range and make it a daily driver. the chevy volt has a 111kw motor in it. and the battery size is 18.4 KWH and gets an EV range of 25 to 50 miles and weighs 3500 pounds so im thinking a 45 to 60 mile range isnt hard to believe? should i add an extra 50 AH?

 

[galderdi]

If you have the space and budget the answer is always to add more batteries. So you are hoping for 45-60 miles? At what speed? The wind resistance of the designs you've shown will significantly decrease your range unless you are only planning on travelling at 25mph. The size of the motor doesn't make too much difference to range. How much you are asking it to do makes all the difference. Likewise the weight mostly impacts accelleration or tackling hills. Once you are at speed the weight doesn't make too much difference. But the wind resistance is a killer.

I am still confused about the battery capacity. Do you know how many cells you are getting?

I'm not trying to turn you off. I 'd just hate for you to be disappointed.

 

[galderdi]

You should figure on around 100watts of power per mile. That would equate to about 6kwh to achieve 60miles. But that is assuming a fair level of efficiency.
If you were to drive at 60mph with that wind resistance, or if you tackle some hills it could be 200watts per mile. Then you'd need 12kwh.
But at the end of the day range is fixable. If you want more range at a later date just add more cells.

 

[falshami]

OK so my average travel rate should be around d 45 mph. The 60 top speed is more of a precaution. I'd like to add a plexi glass windshield to help with aerodynamics although I won't exactly be wind tunneling it to see its aerodynamics.. So if my battery is 4.8 kWh I can expect roughly 48 miles of range at 100 watts per mile? I'm starting to think I should just add the third battery. I'm not sure of how many cells I'm getting but I can show you what I've purchased.its a Chevy volt 48v module. And each module is 2kwh or 47ah as listed on the ad. I'm basically hoping to get enough range to take this bad boy to work charge it up a bit then to class then work then home. Although I still haven't tackled how to charge it.... I'm considering throwing a 100w solar panel to maybe trickle charge it while I'm out and about as well?

 

[galderdi]

Great thinking. Regarding the solar charge idea, you'll still need to run it through a charger of some description. So you'll either need enough panels to power you're standard charger (whatever that ends up being). Or you will need a second charger that is small enough to be powered by a single panel.

By the way a simple way to roughly estimate the power required for any vehicle is basically: think of the power output required from a petrol motor to achieve the desired performance and divide by 3. So if you think a 45KW pertrol motor would power your kart to 60mph then 15kw should get similar results. But it is only a rough estimate. There are all sorts of other factors that make this a little inaccurate.

 

[falshami]

OK so the original engine is a 13 to 16 HP engine and its limited to 45 mph. A 5kw motor over ridden to say 10 killow watts is almost 14 HP. So this motor should drive me to 60 no problem ? Also yes I was thinking run 200 watts of solar on the roof as a roof if it fits. Which should be able to give me a trickle charge of roughly 4amps an hour I believe. I'll have to buy a smaller secondary charger. My primary will be a 48v 30a charger or else it will never fill up the battery in a timely manner. As a secondary I can run either an inverter from 12v to 120v and plug in a charger that roughly does 2 to 4 amps and that should trickle me for a while even while driving. Or maybe run 2 panels and run a DC controller that bumps 12v to 48v. Would that work?

 

[Dauntless]

Ooops, first link was supposed to be this. http://www.electricmotorsport.com/karting/karting-bushed-motor-kits/me1003-emc-rt200-drive-kit-with-motor-controller-throttle-contactor-wire-kit-and-fuse-block.html

 

[falshami]

lol oops , had i seen thise 5 minutes earlier, i just ordered a golden motor BLDC 5kw motor with water cooling so i will be running that around 10kw , from what i hear it can run cool at that temperature without a problem. now to grab me a chassis of sorts... and next i need to order a charger for all this stuff.

 

[falshami]

so work done tonight is as follows. i have gone ahead and purchased the 5kw golden motor from a forum member with a 20kw motor controller so i can send more amps if needed. also bought a water cooling kit with pump and resevoir as well as a fan cooled radiator. i have gone ahead and bought brake lights since ill need them to be street legal, i bought a fuse and terminal block for the 12v system ill be installing. will be looking for a rear view mirror as well as a horn kit. i have found potential rims to make the wheel size larger and use street tire to reduce my rolling resistance since off road tires are knobby and what not. im thinking of doing tires the size a Prius would use. so now i also have motor , controller and batteries on the way. tomorrow i will see if i can get a local to trade me for his go kart chassis. all i will have left is to wait for my stuff to come in order a CVT torque converter. this should help me get to the speeds i want. i found one for a 250cc go kart which should hold up well for me im still at a loss how i will attach this to the built in differential but i am working on it. i also have the license plate lights in LED to run them and i have headlights, i just need to get switches for them. and to top it all off i need to get a 360w 48v to 12v step down unit which i found for 34 dollars. so we are on our way. to top it off i will need to buy plexi glass to make a wind shield to finish making it street legal. any suggestions folks? i am still up in the air about a third 2kwh battery which would bring me to a total of 150AH instead of 100.

 

[falshami]

SO good news is i have the batteries coming in soon, as well as the 5kw and 20kw motor controller coming in. I finally have begun the purchase of the go kart. so in the next week or so i should have almost everything i need. i still need to pick wire gauge for the battery and controller its 250 amps ill be running so im guessing 0 gauge? also i need to find a 48v charger for lithium batteries. any ideas or recommendations? I am also going to add between 1-3 hundred watts worth of solar so it can trickle charge while im away at the shops. that should equate to roughly 6 amps per hour meaning i should get an extra 6 miles of charge i gain per hour while it simply sits there which is awesome i think. i will be next working on how to attach the motor to the stock tranny or putting in a torque converter but even then hooking that up to the differential or gear box is something else.

 

[falshami]

So a new question arises as well. would a torque converter be beneficial to this build to allow us multiple ratios to achieve higher speeds? we could remove its engagement weights so it still starts off from zero if that helps

 

[galderdi]

In the ev world torque is cheap

 

[falshami]

true that, I am waiting on my motor to come in so we can purchase the proper torque converter CVT. my next question is charging, what kind of charger can i buy and how do i set up a BMS system?

 

[galderdi]

BMS is a very personal choice. Just do a heap of searching and choose what ever meets your requirements. If you want the bare basics you could but a series of BMS circuits of Ebay (or similar) but then you won't have monitoring etc built in. The alternative is a complete / integrated system which is way more expensive. I went with an ZEVA integrated BMS that talks to my controller and charger. My decision was kinda driven by my decision to buy the Zeva controller, what was mainly becuase they have local support.

I have been charging 6 cells at a time with a hobby charger. This is super slow but has been a very economical stop gap.

I have now opted for a charger from Thunderstruck motors. They have been quite supportive in configuring the charger to suit my components / requirements. I have only just received it and still need to wire it all up.

Be careful with any second hand charger purchases as most chargers are difficult to re-configure from one battery pack to the next.

 

[falshami]

I am currently looking at this charger for 300 buck. also im doing alot of research on BMS systems i am still hwoever confused, i was looking at some ebay set ups but they seem foregin to me still, im willing to spend a few more bucks for a better system.


im looking at this charger now, any suggestions? http://www.ebay.com/itm/48V-Volt-35A-Amp-2kW-2000-Watts-Lithium-Battery-Charger-USA-STOCK-NEW-/182310765925?hash=item2a72918565:g:VCEAAOSwZJBX~U08


Update! today i took ownership of the buggy and ran it with the gas engine for a comparison. the gas engine is adorably sad. it moves and gets up to 35 or so but its terribly cute. my electric motor should really get me going. i have almost all the electrical parts in . the buggy will be stripped and re painted then LEDs will be installed to conserve power, it has 180w of halogen lights now, we should be able to ddrop that to about 72 watts , or at least under 100 but much brighter than original and i dont have to use them all at once all the time.

next issue coming up is as follows, having trouble finding a torque converter to fit my motor, it seems that my motor shaft is 7/8 and most torque converters are one inch or 3/4s... so what so i go from here. un sure but im working on it.

 

[galderdi]

Be very careful buying any second hand charger. Chargers need to be configured for your specific battery pack (Chemistry, voltage, number of cells). Buying a second hand charger will force you to have it re-configured. Often this can only be done by the factory. Don't just assume you can get it going. Be very sure before you commit to the purchase.

 

[falshami]

you are very right, from my understanding this should work with my battery as is , no? what do you recommend?

 

[falshami]

Here is the first shot of the buggy tell me what you all think!

http://imgur.com/WMmboKg

I got the batteries today and they are super dense and smaller than I thought. I will eventually fit 4 on there instead of two. Maybe even 6 they are so small!

 

[galderdi]

Looks cool. I'd love to see a pic of your batteries so I can compare against mine. I might then be able to give a better response regarding chargers.

 

[falshami]

here is the battery http://hybridautocenter.com/HAC4/index.php?option=com_hikashop&ctrl=product&task=show&cid=79&name=2kw-h-lithium-battery-pack-chevrolet-volt-45v-45ah-12-cells&Itemid=605

 

[falshami]

Im also curious as to, can i add a charge controller for some solar panels so that while driving and parked its trickle charging the battery, i did the rough math and saw that 300 watts of solar on the will improve my range by 6 miles every hour which is wonderful in my opinion. is this possible?