Arlo's Tuesday nights at a Drag race hi.

[Arlo1]

So this September I started volunteering to help some students from the 12-13 year old age, learn about electric vehicles and just basic mechanical skills.
I must start by saying I need no gratitude for this its just my way of giving back all the knowledge I get for free from all of you here on ES which I REALY appreciate!
I wasn't going to say anything but.... I need some help. I need to know things like save max voltages to work around with out getting killed etc. Remember these are grade ~6 students. Now I understand its a vague question because I think my electrical instructor said it takes .3 amps to stop the average heart.
I will up date this thread. As time goes by. With more questions and more builds.

[Arlo1]

So buid one gear reduction starter dirt bike!

[Arlo1]

Build two is a electric bar stool racer

[Arlo1]

And build three which we plan to put together over the next three years is a Chevy S10 extended cab that's been built to a mild drag truck! I will get pics soon but the pan with this one is KISS a brushed motor with as much power as we can build and simple and cheep. Just have to get it going then make it faster later. I might make a brushed controller from scratch to make this work too because money is an issue. But we have a Hyster forklift repair shop trying to get us a motor! Its just being sorted out now and as we find what we can get cheep we will work with it. The goal will be a truck to spin the tires and most of the time 1/8 mile races. So I will likely have enough lipo on a bike by the time comes to race it or we will get some donated! The owner Vern mentioned putting the motor in the rear coupled right to the 9 inch narrowed ford diff. I said well for 1/8 mile you wont need to shift gears and we could put lead batteries behind the axle for great wheel-stands!

[bobc]

Hi Arlo - I do a similar thing in UK & get a lot out of it ;^)
OK general rule for "safe low voltage" is 42V dc or less. This equates to AC at 28Vrms.
0.3A would kill a horse - a tenth of that would give you a nasty belt...
Folk who get a shock with lower voltages are usually doing something like interrupting the current through the inductance of a motor winding, the dI/dt in the inductance will cause a transient of very high voltage (several kV).
I just wikipedia'ed SELV & PELV & their numbers were quite different to mine.... much higher in Australia/NZ - I guess those guys have more resistance.....

[daveyjones97]

i know a noob has no place giving out advice but my understanding was its current as much as volts that kill people. since thats a no win trade off if you want any meaningful performance teach kids about the importance of keeping weight down and everything well adjusted and lubed so the watts you can get arent wasted. and maybe some sort of press switch in line with the battery on the left bar so if youre not riding or holding the switch there's no current. good work, teaching kids this stuff is what i'd do if i had any spare time, as it is i have young kids myself.

[Chalo]

i know a noob has no place giving out advice but my understanding was its current as much as volts that kill people. since thats a no win trade off if you want any meaningful performance teach kids about the importance of keeping weight down and everything well adjusted and lubed so the watts you can get arent wasted. and maybe some sort of press switch in line with the battery on the left bar so if youre not riding or holding the switch there's no current. good work, teaching kids this stuff is what i'd do if i had any spare time, as it is i have young kids myself.

Current won't push across a dry human body without plenty of volts behind it. Up to 36V systems are considered electrically safe, where the main risks are from thermal and chemical burns, etc., rather than life threatening electric shock.

Chalo

[fechter]

48v is generally recognized as the maximum 'safe to touch' voltage.
Yes, it's the current that kills, not the voltage, but resistance of your body determines that relationship. You can be killed by 12v if the skin is broken.

I've touched a 72v battery and could definitely feel it, but it's nothing like a 400v transmitter power supply

Spark/fire danger of dropping a tool or wire across the battery is something to beware of also.

[Doctorbass]

I agree with Fechter.. the max current voltage for ebike on the market is 48V..

when you get a shock with 48V it is generally low pain and just warn you that you still live

Something else i would recommand to them is not wearing jewelry like watch or other conductive material when playing with battery.. ( we must also care about severe burns!)... known as KFC

and have protective glasses.

generally with noob, the arc flash is happening at least one time during a built according to my experience.. so...

Doc

[Evoforce]

It's the amperage that can be a killer. Good job working with the kids. Was a scoutmaster for several years myself. Good luck at keeping track of all those fingers! I was a kid in 4H helping to rebuild farm tractors and really enjoyed it. I'm sure these kids will have a blast.

[Arlo1]

Thanks guys. I was thinking to aim with a 48 volt limit. I can also put the contractor in the middle of the pack so then when power is disconnected there is only 1/2 the battery left in series. Eg a 48 volt system then you open the contact to disable the truck and there is only 2 24 volt batteries left to deal with. Of course we will be teaching all the safety things we can and so far I ask were is your glasses about 10-15 times a night lol. These guys are already excited! I showed them video of a couple cool things like the 70,000 watt kart from you tube and the camaro in the low tens! I also showed them how to calculate how much HP the tea kettle uses then from there used an amp clap and a volt meter to show them how many watts it takes the started bike to do a burn out! we started with a dead battery and it pushed 300 watts then we used a good battery and the wattage went up over 3000 (3kw starter) so it worked out good because it filled the shop with tire smoke!
It really is a lot of fun and I leave there relaxed! We just build things with no dead line! And I get to help build and test way more things at once then I could on my own!

[amberwolf]

Wherever you break the circuit, you do still end up with the full potential across the actual break.

[Arlo1]

Wherever you break the circuit, you do still end up with the full potential across the actual break.

Oh yeh good point.

[Gordo]

I am sure the last thing anyone needs is an electrocuted child on their hands. I made most of the mistakes one can make with electricity and seen many others do the same. I've burned a metal watchband off my wrist, seen a friend loose a finger from shorting a SS ring and had a workmate laid low for weeks, from 600V DC. One RF burn hole in the finger to the bone was all it took to "never do that again." From 50V AC in my mouth, to 110VAC while holding a carbon rod in each hand, to 220VAC, I'm still here. In my entire life in the trade, I personally only know one fellow who has been killed by electricity and he was winching a nylon line, in the rain, across a canyon, when lightening struck the line. Education of the danger is a good thing, as is caution when working with electricity, but don't ruin the experience with scare tactics. In my view, the number of dead bodies, just doesn't support the theory.

[Fishmasterdan]

Been an electrician for 22 years. I have been shocked and seen 100s of people shocked 480v on down. Its never fun but I have never seen fatal shock. I have been shocked literally a thousand times. It clears the arteries

[amberwolf]

I dunno what it clears besides memories, but it definitely lets you know it happened when you get up there in voltage.

I forget now what voltage the welders were, but they were some kind of "generator powered" stick welders (when you plugged them into the four-pronged huge wall outlet (that I think was 220VAC but might've been more; the plugs were bigger than my hand in highschool, whatever they were) a motor inside could be heard to start up, and a whine start a moment after that, as if a motor was spinning a generator). Anyway, I was on a metal bench putting my gloves and flipdown mask on, with puddles from the previous night's flood all over the FFA/highschool shop floor, to the walls and up to the bottoms of the welders, and the benches. Somebody set their stick electrode down on my bench, and my legs convulsed and threw me into the shop wall hard enough to dent the corrugated sheet metal (it was like a barn style building). I didn't actually remember any of it, or about 3 weeks before or after, and was told what happened (probably more than once). I dunno if it was the electricity or the impact that damaged my memory....


I can't count the number of times I've been lightly zapped by things I was sure I'd discharged (CRTs and caps in disassembled electronics under repair, etc), plus a few times I was working on AC wiring with idiot partners that turned breakers back on while I was still working on stuff. Now that I have lots of big batteries, I've been zapped a few times on those, but only on the ones at 72V and up so far. Below that, I haven't felt anything beyond a slight tingle even with sweaty hands or arms.


Still, I've been very careful to avoid electric shock, so I haven't been zapped nearly as many times as I would probably have been if I were careless, and I'm sure that I'd've been hurt a lot more otherwise.

[Arlo1]

Yeh safety is being taught as number 1 so they will be taught proper handling and how to make sure there is a main power cut and how to test with a meter etc. Anysugestions on gloves? I have to do some digging but I think the brushed motors we are looking to use in the truck will be lowish voltage. Im hoping we can run them at ~50v.

[Arlo1]

Another sugestion list I could use from you guys is cheep things we can build.... Like where do we look for cheep motors, controllers, batteries etc.?

[amberwolf]

If you don't mind small brushed stuff...powerchairs and electric wheelchairs. Can get them used for next to nothing if you have repair places around that could be convinced of the worthiness of your project.

Some of them are quite powerful and easily overvolted, with built-in nice mounting plates and such.

[Arlo1]

The next thing I want to do is make a list of the 10 biggest misconceptions about electric vehicles and have the data to prove them wrong.
#1 You are just moving the pollution to another location well I'm sorry but Ev's are typically ~ what percent efficiency 70%? gas powered cars are around what? 15%?
so first off you go further on a charge using less energy add some numbers and calculations.... THEN show what most people don't think about how much electricity goes into a litre of gas.... I worked in the oil fields and they use electricity to run the pump jack that pulls the oil from the ground, then they use electricity to move the oil to the tanks then they use electricity to refine the oil into gas and other products and along the way they burn off the bad gas they don't want not using it to produce anything just burn it! Then after they have gas made they haul it to a gas station with a diesel truck then the gas station is powered by electricity.

#2 Range
#3 Battery replacement
#4 Batteries are bad for the environment
#5 Cost of electricity will just go up. But this is where we say you can use wind, solar, hydro and other power to power your car so it doesn't go up!!!
#6 Lithium and rare earth deposits are not sufficient you only need to dig the lithium once you are not consuming it like gas so we don't need to look at lithium mining numbers in comparison to gas or oil because you are using the lithium like a gas tank and the study should actually compare the lithium mining numbers to what they mine for building gas tanks!!!
#7 They are slow
#8 Expensive... Because Ev's are simple with less moving parts they can be compared to electronics and the price of electronics is almost always coming down!
#9 Charging over night in your garage is an inconvenience.... Depending on the batteries but some can be charged in as little as 1/8th hour 8c (might be some faster can be edited) and a charger that stores some energy would be able to charge the car faster, Wireless charging is alrady being developed see Nissan, and honestly you go home most the time anyway... Going to a gas station is actually out of your way and more of an inconvenience!
#10 If it is so easy why have the big manufacturers not already done it... GM did then they took them away and crushed them... Zero bike is doing it right now, so is Tesla,
there is a good chance you wont see the manufactures who already make gasoline powered cars make much of an effort to produce electric cars because they see how much money they will loose! The no longer sell all the parts for services and well lets face it if you were an oil company would you not give the guys producing things to use your product some kickbacks!!!!

This all needs work and editing and more data to back it up, but I want to have a Set of boards in the back when we go to events and display this to all the people who come to see the kids and what we have built!

[Arlo1]

Here is a good link showing some safety gloves. http://www.sandyblogs.com/techconnect/2 ... stems.html

Some important safety practices:

•Remove or cover belt buckle
•Wear safety glasses
•Wear rubber-soled shoes
•It is recommended to wear class 0 isolation gloves (leather outside, rubber inside), which are rated up to 1000V (Fig. 5)
•Know where the components are located in the hybrid system and follow all precautions

[Gordo]

Another sugestion list I could use from you guys is cheep things we can build.... Like where do we look for cheep motors, controllers, batteries etc.?

So I don't forget, there is a golfcart motor and to rear axles in my back yard you can have.

[Arlo1]

Another sugestion list I could use from you guys is cheep things we can build.... Like where do we look for cheep motors, controllers, batteries etc.?

So I don't forget, there is a golfcart motor and to rear axles in my back yard you can have.

Awesome. We need that.

[Arlo1]

So gordo give me this motor today I am not sure the shape yet but I will look at it soon. I was wondering if any of you have a idea what its like??? Reversible?

[Gordo]

It is definitely reversible. We drove that cart around before scrapping it.