Step Up Transformer Could Really Change Things

Step Up Transformer Could Really Change Things

I am shocked at the 2 miles/hour charging I get off a 110V outlet, and it makes my planning for overnight trips problematic, as overnight charging at private homes on 110 V is inadequate.

I have been toying with the idea of using a step up transformer, and it seems promising to me. Any engineers out there have thoughts on this? I have looked online at step up transformers, many of which aren't so expensive. If I used one to supply 230-240 V from a 110 V set of outlets when traveling or at work, do you think it would speed up the charging process? Would it be safe for the car?

It looks like you can buy compact models for 5-6 kW fairly cheaply. The car has a 10 KW onboard charger, so it would not exceed the car's capability. It this idea is feasible, it would really change things. The only problem I see is that finding two 110V outlets which are 180 degrees out of phase might take a little hunting with an extension cord, but it would be well worth it to get more amps into the car.

Any thoughts? Do I have a feasible idea here?

Flaninacupboard | February 11, 2013

I can't remember it's name, but there is a commercial product available which plugs into two 110 outlets and outputs 230 (it has LED indicators to let you know you've found sockets with the right phase).

GoTeslaChicago | February 11, 2013

No free lunch. You can't double the volts without halving the amps, before losses.

2 outlet idea could work, then you get twice as much i.e. 4-5 miles/hour charging.

July10Models | February 11, 2013

If you have two 110V AC circuits already 180 out of phase, you don't need a step up transformer to create 220 circuit. You just need a pig tail that will accept the phase lead from each 110 outlet and terminating into a 220 outlet. The wiring and the circuit breakers on the 110 circuit will still be limiting factors. For example if your 110 circuit is capable of 12A then you use another similar 110 circuit but 180 out to create a 220 circuit, the resulting circuit will be limited to 12A, by the neutral conductor rating, but at 220V effectively doubling your charge rate and nowehere near the 40A max on a 240 circuit.

Grant910 | February 11, 2013

flaninacupboard: Yes that is what I am talking about

Gotesla and July10: Thanks. So it probably isn't worth bothering with for just 4 miles per hour of charge. Like you said, no free lunch.

shop | February 11, 2013

And you'd have to make sure both 110V AC outlets where in fact out of phase, which is a 50-50 proposition - it all depends where on the breaker panel they are plugged into. Not to mention you'd have to use extension cords, which is a no-no unless you happen to have really, really beefy ones. Anyways, really a non-starter.

In California, some suburban homes have their washer/dryer either in the garage or very close to it, so finding a close by dryer plug is the best bet.

It'll be interesting to see what I come up with as I'm taking a three day trip to Palm Desert area from San Diego in early March, and I'll need to recharge while there. I am hoping to find either a hotel with adequate recharging capability, or an RV plug where the car will be parked during the day (horse riding show park). I think I'll be parking in the RV parking section at the show...

surfside | February 11, 2013

@shop, you can always get some charge while shopping (or grabbind lunch) at the mall where the SD tesla store is located...

jat | February 11, 2013

The product you want is Quick220, but as July10Models says basically the problem is you can only draw 12A@120V out of a standard outlet.

shop | February 11, 2013

@surfside - unless the Tesla store has a supercharger, it probably wouldn't be worth it.

MarvK | February 11, 2013

The charger that comes with the Model S can charge up to 40 amps @ 240 V = 9600 watts drawn from your C supply. By far the best way to feed your charger is to install a 50 amp double pole circuit breaker in your distribution panel and run hefty wiring to a 14-50 outlet. Then you can charge even the 85 KWH pack overnight. This is a slam dunk for most electricians.

Darmok | February 11, 2013

Try this thread over on TMC for excellent answers to FAQs on electrical matters: