To start: Electric motors- AC vs. DC
I’ll usually put this plainly- we can’t use an AC engine in a go-kart. Sure, it would be technically possible, and some electric cars use AC motors, yet those are with $10k control systems. The reason is that AC is opposite from AC. AC stands for ‘Alternating Current” and is what comes out of your wall socket. It’s used since it transmits prolonged distances improved along wires (from a energy plant to you) and doesn’t slay people utterly so badly. DC stands for ‘Direct Current’ and is what comes out of a battery. It’s plain electricity, and it’s what we wish to use for a go kart.
To get some-more technical, AC is called ‘alternating’ since a polarity (the + and -) reverses- in a AC in your house, it happens 60 times per second. An AC engine needs this. Now, it is probable to make AC out of DC. Most people have seen inverters, that we can block into we car’s cigarette lighter and afterwards block in a laptop, blender, whatever. Why not usually use one of those?
The answer is current, and power. For a good electric go-kart, your energy final are going to be around 1000 watts or more. 1000 watt inverters are available, yet they wouldn’t work- since not? Because of swell current. An electric engine is an ‘inductive’ load. Have we ever seen your kitchen lights low when a fridge or x-ray comes on? That’s since those are both preliminary loads, and preliminary loads need a TON of energy to start. Say some electric engine competence need 250 watts when a running- to start underneath bucket (like a go-kart does) it competence need 1000 or 1500 watts to start. Your 1000 watts kart engine starting underneath bucket competence need 5000 watts. Go cost a 5000 watter inverter. Yeah, we don’t wish to do that. You competence cruise that maybe we can make it work even yet some people contend it’s a bad idea- trust me, I’m one of those people who chases down bad ideas to see what will happen. Don’t even bother.
So to be clear, you can’t flattering use any AC engine in a kart unless we wish to go no serve than your longest prolongation cord. That means don’t worry with any engine noted AC or that comes out of a soaking machine, belt sander, or anything that plugs in to a wall. There are dual exceptions to this: treadmills and unequivocally shrill energy tools. Most treadmills use a 90v DC motor- a treadmill contains a rectifier that translates a AC to DC. Loud energy collection like angle grinders and turn saws use a engine called a ‘universal motors’ that can work on possibly AC or DC.
we wouldn’t use possibly a treadmill or concept engine either. Why not? They are done for 90 to 120 volts (in a US) and not unequivocally powerful. While a treadmill engine competence seem like it’s powerful, cruise that you’re going to have to lift around during slightest 7 batteries (of automobile battery size) to get adequate voltage and power. It’s a same as with a inverter- technically possible, yet as a DIY go-kart maker, it’s not what we want.
OK, that’s all bad news. What’s a good news? Well, there are copiousness of DC electric go transport motors out there ideal for go-karts. What should we demeanour for in a DC electric go transport motors?
1. Low voltage. The revoke a voltage, a fewer batteries we have to lift around. Also, if a rated voltage is lower, we can overvolt a motor, that gives we some-more power. Say we get a 24v motor- we could run it on 36v and get a lot some-more power. Could we run it on 48v… or 72v? Yes… yet for a unequivocally brief time. 48v is substantially a extent for a 24v engine (double is a order of float for a limit) Why? Well, putting that additional voltage in a electric go transport engine causes additional stream to flow, that is where your energy comes from. This is a problem since a some-more stream that flows, a hotter a engine gets- and when it gets too hot, it will bake up, explode, and leave we standed.
What happens is that a insulation in a electric go transport engine is rated for a certain lifetime (say 20 years) during a low temperature. If we double that temperature, that rating competence dump to say, 1 year. If we get it really, unequivocally hot, it competence grill in 10 seconds. Don’t overheat your motors.
You could do a 12v engine during 18v or 24v. You could do a 24v engine during 36 or 48v. You could do a 36v engine during 48v. we wouldn’t put some-more than 48v in a kart for dual reasons: weight (batteries are heavy, and 4 12v batteries is about as many as we wish to lift around) and safety. 48v is high voltage for DC. A chairman with dry fingers can hold both terminals of a 12v battery and (probably) not grill themselves. However, do it with 120v residence voltage, and you’ll get a nasty shock. That’s since it takes a certain volume of voltage to overcome your physique (especially your skin) resistance. Once there’s adequate voltage to overcome that resistance, you’re being electrocuted. It usually takes 0.025 of one amp to stop your heart, and any battery will do that easily. If you’re going to make an electric go kart, we need to teach yourself on electricity safety. we won’t write that book here, yet go review adult on it- and don’t put some-more than 48v in a kart unless you’ve had technician-level training. (Note: I’m not observant 48v is ‘safe’, yet conjunction are go-karts)
Okay, reserve harangue over.
Where can we find good motors for electric go karts?
DD Motor Systems, Inc!!
The final thing I’ll speak about with electric motors is their energy ratings. There are dual critical things we need to know- electric motors are rated for continous power, definition they can make that energy all day, all night, for years on end. Gas engines are rated on immediate power, that is how many than can furnish for a moment. Secondly, electric motors furnish limit torque (the force with that it spins a wheels) during 0 RPM. Have we ever ridden a two-stroke dirtbike? All a energy comes around 5000rpm, so we have to wait for a engine to get adult to speed, THEN we get power. Electric motors are a opposite- we get all your acceration during a unequivocally start, and it tapers off linearly as we speed up. This creates for unequivocally fun take-offs if your batteries, controller, and engine are adult to it.
What this means is that you have to cruise about electric energy ratings differently. A Harbor Freight 6.5HP gas engine competence be fun, yet a 6.5HP electric engine is scarcely 5000 watts (746W = 1HP) and will slice your face off and warp your batteries. Sweet. You can use many smaller HP rated electric engine than we would a gas motor, and have a same volume of fun.
So, how do we stifle an electric motor? You have 3 options: on/off control (likely to grill something), on-going on/off control with mixed batteries, and a controller. On/off control is where we usually have a vast switch (or some-more likely, a vast send or contactor) and we get full energy as shortly as your chuck a switch. we wouldn’t suggest this, as a swell energy materialisation that we discuss above means that you’re switching on a LARGE volume of stream all during once, and utterly frequently what this will do is indeed coupling a contacts of your switch in a hermetic position, that now means that you’re sitting on a kart that is during full stifle and won’t spin off. we know a chairman who attempted something like this on an electric motorcycle and has a scars to infer it. Unless it’s small engine and vast large switch, I’d equivocate this.
How about on-going on/off control? Simply, this means that we are switching on your batteries one during a time. Say you’re regulating a 24v motor, and overvolting it to 36v. You’ll have 3 12v batteries, many likely. What you’ll do is have 3 switches (relays). One will switch on a initial 12v battery. The second will switch on both a initial and second, giving we 24v. The final will switch all 3 batteries into a circuit, giving we full power. This is many reduction expected to kill you… as prolonged as we handle all adult right. we won’t pull adult a blueprint for you, yet there are some out there to demeanour up. I’ll advise we that if we usually pull one up, it’s easy to handle things adult such that we are dead-shorting a battery, that could coupling your contacts means a battery to raze if we are incompetent to mangle a circuit. Be careful. Be clever with this because your initial battery to be switched on is going to empty many faster than your final battery. You will need to assign your batteries away (not in series) and stop driving immediately when your opening with a initial battery [/i]only[/i] starts to decline. You will henceforth repairs your batteries if we over-discharge them.
Lastly, we can use a controller. This is a best option, and predictably a many expensive. Your best gamble is a golf transport controller. They are done for avocation like this and don’t need a special radio submit like a brushless controller does (just a potentiometer, that is a elementary electronic component). These can be had on ebay, and a code you’re expected to have fitness with is Curtis. Do your investigate on your controller and make certain it’s for a PMDC engine (Permanent Magnet, Direct Current) If it’s for a array motor, that’s OK (and array motors are OK to use) yet you’ll have to investigate a wiring blueprint delicately and review adult to offshoot all adult properly.
You can also find electric bike and scooter controllers, yet these are expected to be too small to use for a ‘fun’ kart unless you’re creation something for your eight-year-old that weighs 60lb.
Lastly, we can get engine controllers for fight robots from a same site we related to for a motors. These are a good option, yet costly again and need a handcrafted throttle, since they’re meant to interface with a radio. This would be a good choice if we found a inexpensive vast DC engine and don’t mind spending some $$$ to get to use it.
You competence not overvolt controllers. The max favoured rating is a max rating, and that’s it. A controller can be now broken if a voltage rating is exceeded, even some-more a moment. Manufacturers build in a small bit of space since a 24v battery bank will be some-more like 28v when it’s uninformed off of a charger, yet a rated voltage is all we can use.
The final thing I’ll speak about is batteries.
Unless you’re some-more modernized than someone who needs a info in this post, you’re going to use lead-acid batteries. This is a same record as a automobile battery. Don’t use automobile batteries, though, since they’re a wrong type. There are dual kind of batteries here- starting batteries and deep-discharge batteries. A automobile battery has to supply an huge volume of stream for about 3 seconds when we start a car, afterwards spends a rest of a life possibly being charged by a alternator, or provision a small volume of stream to keep your automobile radio presets in memory. Car batteries are built for this duty, and if we try to use them on a kart, you’ll have fun for about 10 minutes, afterwards a batteries will die- and not usually being discharged, they’ll be henceforth damaged. Don’t try this unless we wish to be unhappy or will be happy with a short-lived, costly project. If you’ve got a smoke-stack of automobile batteries we could use them for testing, yet that’s about it. Also, automobile batteries enclose glass sulfuric acid, that can brief out some-more simply than we think. If it gets on you, it will make we go blind, bake you, refinance your debt during 10%, pivotal your car, and punch we in a gut. Don’t disaster with acid.
By contrast, we wish to be means to float your transport for, say, 30-60 mins sketch a assuage volume of stream a whole time. For this, we need a deep-discharge battery. The usually automobile batteries that are good for this are Optima Yellowtop or Bluetop batteries, or similar. They don’t have glass poison inside and are done for low discharge. These are good batteries to use if we can means them. You can find other lead-acid batteries called AGM, or Absorbed Glass Mat. These are like hermetic lead poison (see below) solely they electrolyte (acid) is engrossed adult in fiberglass mats inside a battery, creation them startle resistant. AGMs are typically high peculiarity and high cost.
Also, we can use a hermetic lead poison battery (SLA). These are great, and substantially what I’d use. You’ll be tempted to buy a small ones- they come in tiny, affordable sizes that are finish crap for kart use. You wish a vast ones. At minimum, 12Ah for a small scooter-motor kart ridden by your 8 year old, and 18-30Ah or some-more for bigger karts. More battery is improved 99% of a time. Until we get to a indicate that your kart has so many battery that it weighs a same as a brontosaurus, some-more batteries are going to help.
Why? Because of current, again. Karts need a lot of current. Small batteries put out a small volume of stream happily, or a vast volume of current, and afterwards die immediately. If we don’t wish to be singular in opening and murdering your batteries dead, use vast batteries. The same approach that overdischarging your batteries by regulating them totally prosaic will kill them dead, overdischarging by seeking for too many stream during once will fast kill them.
On tip of that, seeking for lots of stream will revoke how prolonged we can ride- since of something called a Peukert effect, sketch a lot of energy from a battery effectively reduces how prolonged it will last. An SLA battery is generally rated during a 20-hour liberate rate. So it competence have 18Ah of extract in it… yet usually if we ask for it solemnly over 20 hours. If we ask for all of a extract in 30 minutes, we competence usually unequivocally get 10Ah out of it. (I pulled that array out of spare air). It’s a flattering poignant effect, though.
Okay, what are Ah? Ah stands for Amp-hours. If a battery is rated during 18Ah, it can put out one amp for 18 hours, or if we omit a Peukert outcome we usually explained, 18 amps for one hour. Or 9 amps for 2 hours. Get it? You competence also see batteries rated by ‘RC’ or Reserve Capacity. This is how many mins a batteries will final during 25A liberate (that is, if your alternator gives out and we need your headlights and engine control unit). You can modify RC to Ah with elementary math- if you’re embarking on an electric kart build, reckoning that one out should be something we can do.
What about CCA and CA? These are not ratings of how prolonged a battery will last, or ratings that we will see on batteries that we wish to use in a kart. Note above where we talked about starting batteries vs. low liberate batteries. CCA stands for ‘Cold Cranking Amps’ and is a magnitude of how many stream a battery can put put for usually an present when it’s cold. (CA is a same thing, yet not as cold- cold impact batteries) Generally, usually starting batteries are rated for CCA or CA. There are some dual-use batteries that competence be rated for CCA and still be deep-discharge, yet these are some-more costly and we can do improved with a properly-sized deep-discharge battery. Big wheelchair batteries are super for many karts.
How do we assign your batteries? I’d suggest removing several normal 12v automobile battery chargers and charging any battery that way, or regulating one and doing any battery after a last. (That takes forever) If we can find one or means one, a golf transport battery horse that matches your voltage is a best thing.
Some simple things to turn it out:
Wiring something in together means + to +, – to -. You’ll get a same voltage, yet some-more stream and capacity.
Wiring something in array meant + to -, and afterwards we take your energy off of a other + and -. You get some-more voltage (it adds) yet no additional stream or capacity.
Current magnitude how many electricity is flowing, like a rate of H2O by a pipe. Current is totalled in amps.
Voltage measures how many electrical ‘force’ there is, like a vigour of H2O in a pipe. Voltage is totalled in volts.
Power is a multiple of a two, and is like measuring both- how many H2O is issuing by a siren and with how many force. Power is totalled in watts, and volts times amps equals watts. You can also go backwards- a 500 watt engine during 24v will need 500W divided by 24V = 20.8A theoretically but in use will need more, due to potency losses. 70% is a satisfactory guess for engine efficiency, so unequivocally it’d be around 20.8 divided 70% (0.70) = 29.7A.
Okay, that’s a good starting indicate for what we need to know for electric energy systems on karts.
So we wish to make a fun electric go-kart? Inclined to do overkill? Here’s your recipe, pre-overkilled:
Get an electric golf transport motor, it will substantially be 36v rated and lots of power. Get a 48v-rated golf transport controller and 4 Optima Yellowtop batteries. Strap this all to a support of your elite format and go have fun.
Want to make a fun small electric kart for your child that’s outgrown his powerwheels? (Or are we skinny?) Get one of those 900W scooter motors and run it during 36V instead of 24V, and use a 18Ah SLAs that are common for wheelchairs.
There we go. Go for it and make some cold electric karts. Post pics.
Article source: http://ddmotorsystems.com/