Had a Nema 14-50 installed at work but only getting 23 mph charge on my model 3. Had one installed at my parents house in 2018 and get 30 mph charge. What could be causing this low rate of charge? Only difference I can think of is the electrician (different one from before) used 8 awg wire for this one. This one is also a very short run compared to the install at my parents place. Here's a picture of the screen below:
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Getting a low rate of charge
- Thread starter emadz89
- Start date
You are charging at 197 volts which is a 17 percent voltage drop if your service supply was 240V. 10% drop if it is 220, which it may be.
That will cause 17% less power than if you charged at 240v.
That will cause 17% less power than if you charged at 240v.
Yes, voltage difference explains this clearly, because the charging speed scales with power, which is the volts times amps, so lower on either one will make a slower charging rate. Now about those voltage differences:
I'm really sure it's not dropping from 240V down to 197V. The car would have already activated its safety measure and lowered the amps if it had dropped that severely.
And 220V is not a thing in North America.
You said this was at work. Commercial and industrial buildings usually don't have 240V. They get 3 phase electricity inside the buildings, and with the way that is connected, you can get 120V and 208V. I've seen several places where that 208V drops some from some long wiring runs or marginally thin wire and shows as just about 200 or a little less, so that's not unexpected.
I'm really sure it's not dropping from 240V down to 197V. The car would have already activated its safety measure and lowered the amps if it had dropped that severely.
And 220V is not a thing in North America.
You said this was at work. Commercial and industrial buildings usually don't have 240V. They get 3 phase electricity inside the buildings, and with the way that is connected, you can get 120V and 208V. I've seen several places where that 208V drops some from some long wiring runs or marginally thin wire and shows as just about 200 or a little less, so that's not unexpected.
Do you know if that's really the full run length, though? In a commercial building like that, maybe that last 15 feet is from a subpanel that is already a pretty long way from their main service entrance panel. It could already have drop down near 200V before it gets to that last 15 feet.
Here are some pictures attached of the set up. The silver conduit you see there is the wiring for the 14-50 outlet coming from the smaller breaker.
ucmndd
Well-Known Member
You’re charging at a lower rate due to the 208v commercial service, and the fact that the 208v nominal service is only delivering 197 volts to your car. That’s about a 5% loss, which is on the edge but generally fine.
When you’re charging at home you’re getting 32 amps at ~240 volts, which is (32 x 240) 7.68 kw of power.
At work you’re getting 32 amps at 197 volts, which is (32 x 197) 6.30 kw of power - about 18% less.
When you’re charging at home you’re getting 32 amps at ~240 volts, which is (32 x 240) 7.68 kw of power.
At work you’re getting 32 amps at 197 volts, which is (32 x 197) 6.30 kw of power - about 18% less.
