I'm building an electric car. See postings elsewhere on this forum - it's a '71 Karmann Ghia w/ 144v 100ah thundersky pack. I chose to buy an Elcon PFC3000 battery charger.
Gregski's question about going over the rating of a power outlet reminded me of something which happened with the charger while we were setting it up. http://visforvoltage.org/forum/11200-25-amp-battery-charger-15-amp-outlet
The PFC3000 can handle 120 volt or 240 volt input and it's supposedly configured for 16A on either. 240v 16A is approx 3000 watts. At a 3kw charging rate the pack should take 3-4 hrs to recharge from a reasonably well-discharged state. Maybe. It also (with appropriate adapters) means being able to use the charging network that exists and the other charging network being built. Anyway ...
At my house the only outlets are (well, were) 120 volt outlets with 15A rated sockets. On the circuit breaker panel there are four circuits, 2 with a 120v 15A breaker, the other 2 with a 120v 20A breaker. I've since had an electrician add a 240v 20A circuit w/ a NEMA 6-20 socket right below the panel.
The charger came with a NEMA 6-20 plug on the end of the cord. They look enough like regular 120v plugs that I was confused, and some yahoogling showed the difference between NEMA 5-15, NEMA 5-20, NEMA 6-20, etc. NEMA 5-20 is 120v 20A, and NEMA 6-20 is 240v 20A. See: http://www.stayonline.com/reference-nema-straight-blade.aspx
I built a little adapter cord with 10 gauge wire and a NEMA 6-20 socket on one end, and a NEMA 5-15 plug on the other. With that the charger can be plugged into a normal extension cord to one of the normal power outlets on the house.
The first time running the charger it was set up with a pair of extension cords (one of which had 16 gauge wire) to a power outlet in the back of the garage. The circuit breaker kept tripping. Using a clamp-on meter we found the charger was pulling over 20A over the circuit, which of course is more current than the circuit breaker's rating.
We asked Elcon to explain ... because it wouldn't be very useful for the charger to take 120v but to insist on more than 20A. Of course to be useful the 120v side of the charger must be compatible with the 15A outlets at various places I might go to.
Elcon explained that the charger is configured for 2150 watts at 120v which translates to 120v 19A. In other words, they're trying to max out what can be used on a 120v circuit assuming it has a 20A breaker. BUT... because of the long/thin extension cord the voltage over the wire was diminished a bit and that caused the charger to require even more A's. That is.. for the charger to draw 2150watts at 120v is approx 18A, but at 110v it's approx 20A.
In other words - if you have a poor quality connection from charger to power outlet, not only will the cords get hot, it can cause the charger to draw even more A's than it would with a better quality connection.
Switched to a thicker extension cord (12ga wires rather than the 16ga wires on the other cord) and the charger now works on 120v. That is, so long as it's not plugged into the circuit that also includes the refrigerator.
I've since bought a) a 50 foot 10ga extension cord for 120v, b) modified a 12ga extension cord to have NEMA 6-20 sockets and plugs to create a 23 foot extension cord for 240v outlets.