Ben Nelson's Electro-Metro Build thread

[bennelson]

I was wondering if I would be able to setup the large charger that came with the forklift to run off the electricity in my detached garage.

Need at least 240 volts to run that charger, but do I have that?

I hit the internet looking for answers.
Seems that the power running INTO a breaker box is typically 240v. It is 3 wires, two hot ones, and a neutral. Then that is broken into two legs, one down each of the two columns of breakers in the box.

To get 240 volts, you use a "double-breaker". It connects to both of the hot wires and gives you the full 240 volts.

I wasn't sure if the power in my garage was a "real" breaker box, or if it was just a glorified outlet.

I took the cover off the breaker box. Sure enough, on the left is two wires, thick red and black ones, going into a "master" breaker.

I think all I need to do is add big double-breaker and run the wires from that to a big power connector like an electric stove uses. Then plug the charger into that (after setting it to run on 240v - it is 480v right now)

The breaker box is setup for 100 amps, and the charger is a 65 amp continuous, so I think I should be ok on power there.

Any electricians or engineers here to confirm or correct my thoughts on this?

[MetroMPG]

The charger is probably 65 amps @ at 36 V DC. So its 220v AC current rating will be much lower than that.

Aside from that I can't help you at the moment, 'cause I don't know much about household AC. But if you don't get an answer by tomorrow, let me know and I'll ask Ivan. He's an industrial electrician.

[bennelson]

Originally Posted by MetroMPG

The charger is probably 65 amps @ at 36 V DC. So its 220v AC current rating will be much lower than that.

Right, I overlooked that. Now how does one convert AC amps to DC amps? I suppose there is also a certain efficiency loss inherent to the transformer to account for as well.

I should eventually figure this out so I can put the right size circiut breaker in the end.

I guess the other bad thing about 240 is that I can't use my Killawatt to see how much power was used. It was great being able to see the total power use of the electric motorcycle by plugging the charger into the Killawatt.

I suppose I can still do that will a lower amp 120V on-board charger. That would at least get me in the ballpark for measuring power use.

[WaxyChicken]

Alternatively, you can make two (120?) v plugs for the car's 240v charger input.
a measure on one of the 120v currents *2 will likely get you very close to how much juice the charger pulls. Just a thought.

[bennelson]

I may also be able to beg borrow or steal one of those big clamp-on electricians' amp meters. That should work.

[TomEV]

As long as you use two breakers next to each other (like the two on the left) you will get 220/240VAC. They should come with a 'tie' to make both breakers work at the same time as the one in the picture. On a breaker box such as the one in the picture, every other slot alternates - using the left 110 feed, and then the right. If you use breakers from the opposite side of the box, you could end up with two wires from the same leg (which wouldn't produce 220/240)

The bonus about your breaker box is that it is wired correctly as a subpanel. Sometimes people will buy a box and not remove the bond between the ground and neutral (required on a main panel, but not permitted on a sub).

If you look on the charger data plate, it will probably say how many amps it uses under full load - Probably around 12-15 amps @ 220vac

[trebuchet03]

Originally Posted by bennelson

Right, I overlooked that. Now how does one convert AC amps to DC amps? I suppose there is also a certain efficiency loss inherent to the transformer to account for as well.

It's been a few years since I learned this gunk... But I don't recall there being a different method to calculate amperage in DC versus AC....

So 65A * 36V=2340W
and 2340W/220V= 10.64A

But yes, there's efficiency to consider (curse ye, consideration of efficiency). At 80% efficient - 12.768A and 50% efficient is 15.96A. It's probably stamped on the charger someone (as others have mentioned ). If it's that low, be sure to no block it - that's a lot of freaking heat it'll be dumping

[bennelson]

I was able to find some more amp info on the charger itself.

It is 26 amps max at 240volts.
Output is 95 peak amps at 36 volts.

That means it uses 6240 watts in to make 3420 watts out!

Doesn't sound very efficient

What happens to the other 2800 watts? If it is all converted to heat, that's a big electric heater! Ok if I am working in the garage in the winter, but a lot of wasted electricity otherwise!

The vents on the back of the charger were covered with duct tape. I am assuming that was to keep dirt and dust out, NOT to help keep it warm!

It looks like a new 240V, 50 amp circuit breaker is about $30. I can find electric stove power connectors at the local thrift store for cheap.

[Ryland]

Make sure that you know what you are doing when you are doing wiring, it would be well worth picking up a few books from the libary, I would also be warry if buying thrift store outlets... I don't like to burn garages down.
It might be worth having a real life consultant help you out if you are at all unsure about what you are doing, everyone in the construction trades are exprinceing a slight slow down, so altho they are still going to want to be paid we are only talking about half an hour or so of work, and most people acept cash.

[bennelson]

I fixed the yellow strobe light from the forklift.

The xenon flash tube was burned out. It's the exact same one they carry at Radio Shack, so getting a new one was no problem.

I soldered it in and put it all back together. Now I have a yellow flasher that will run on any 12-80 volts DC power supply.

Maybe I can put it in the back of the electric car to warn people how slow I am going.