Cheapest/fastest EVSE for existing 240v garage socket?

[Jaypi]

You could also get nrg for a monthly payment & no one time fees.

http://www.nrgevgo.com/los-angeles-basin/

Is this generally considered good value? What about if I have solar panels on the roof and generate part of my own electricity power?

You pay them monthly for the charger and installation they do for you. electricity you still have to pay on your own.

 

[ThreeEyes]

it probably is not the same plug as your dryer.

My Siemens EVSE has a 3 prong plug. I think this is pretty standard for plugged EVSE.

I considered the juicebox, but it wasn't eligible for my rebate because it isn't UL certified (or wasn't at the time, if it is now)

Could you tell me more about rebates on EVSEs? Would I get a rebate on a UL device?

 

[Schnort]

Mine was offered by my electric provider, so I doubt it's of value to you.

 

[ThreeEyes]

Thanks! I have a 14-50. So I can just plug in the JB and go?

To be safe, you should set the JuiceBox's maximum charging current to be 32 amps, the maximum continuous current that's safe on a 40 amp circuit. But even if you don't do this, your i3 won't request more than 30 amps. However, when your buddy with a Tesla Model S, Toyota RAV4EV, or Mercedes B Class ED visits and asks for a charge, the JuiceBox would happily allow 40 amps continuous which would heat up your circuit wiring a bit and eventually trip the circuit breakers.

Long story but our electrician discovered we only have a 30A circuit, and there's no option to update it because we share it (never simultaneously) with our clothes dryer.

We now have a neat garage installation with 2 14-50 sockets side by side, one for the dryer, one for the JuiceBox 40 Pro which I just installed.
(We got the 40 Pro because we wanted the app to set schedules, limits, etc. It's a pretty neat app and worked first time – rare!)

Our EV rate with our provider (11¢) kicks in at 10pm and ends at 8am. We never dry clothes after 11pm. So we've set the JuiceBox to only work after 12am/midnight to be super safe = cheapest rate and no clash with dryer.

Summary: We are only ever using one 30A device on a 30A circuit.

Question 1: Is the general 'common sense' consensus that it is safe to leave the JuiceBox at 30A on a 30A circuit? (Actually 29A just for good measure.) Or do we really have to drop it to 25A?

Question 2: Rough calculation, what would the full charge time be on a 25A setting? I make it approximately:
25A = 4 hours
-vs-
30A = 3.5 hours

Does that sound about right? So we're losing 30 minutes by going with the "circuit must be 120% of the charging amperage" rule? Not the end of the world for overnight charging.

 

[i3Alan]

Question 1: Is the general 'common sense' consensus that it is safe to leave the JuiceBox at 30A on a 30A circuit? (Actually 29A just for good measure.) Or do we really have to drop it to 25A?

When using high currents for short periods (minutes or seconds), it is fine to use the full rating of the circuit, which is determined by the "weakest" link in the circuit, be that the circuit breaker, the wiring, the outlet, or the current consuming device. However, for longer continuous current draws, the maximum current should be no more than 80% of the full rating. 24A is the max recommended (safe) current draw for a 30A circuit.

 

[ThreeEyes]

As I learned when the breaker tripped after an hour at 30A on a 30A

I make the safe calculation 25A, based on the previously mentioned regulation here that the circuit must be 120% higher than the draw.

Using 80% isn't a straight swap calculation as it equals 24A not 25A. I've had no problems at 25A. Can someone confirm which it is: 80% of the circuit (24A) or 120% of the draw (25A)?

 

[I33t]

alohart, do you know what the standby power draw is?

I have an answer regarding standby power:

Standby current draw is extremely minimal - about .05A nominal.
All you're doing is running an Arduino EEPROM and the WiFi module ecache...

So at 240v, standby is around 12w. I can live with that

Ordered JB Pro40, it's on the way.

 

[alohart]

Using 80% isn't a straight swap calculation as it equals 24A not 25A. I've had no problems at 25A. Can someone confirm which it is: 80% of the circuit (24A) or 120% of the draw (25A)?

The rule is that continuous current should not exceed 80% of the circuit's capacity. The mathematical equivalent is that the circuit's capacity should be 125% of the continuous current. 1/0.80 = 1.25 or 1/1.25 = 0.80. So 24 amps is the maximum continuous current that would be considered safe on a 30 amp circuit.

 

[alohart]

alohart, do you know what the standby power draw is?

I apologize, l33t, for the late reply; I've been on vacation with limited Internet access.

I have an answer regarding standby power:

Standby current draw is extremely minimal - about .05A nominal.
All you're doing is running an Arduino EEPROM and the WiFi module ecache...

So at 240v, standby is around 12w. I can live with that

I can't. I don't allow 10-12 watts standby power for any device in our apartment, so I'm not going to allow our EVSE to sit there doing nothing for 97% of the time (we don't drive much) while consuming standby power. Most of Hawaii's 30¢/kWh electricity is generated by imported petroleum and even coal (!), so I try to minimize our waste of electricity. Living in an apartment, I unfortunately have no ability to install PV panels. Our electricity company is worried about losing business to private PV installations, so they make connecting to their grid very difficult even if I could persuade our apartment association to install PV panels.

I asked EMotorWerks about the standby power before I ordered my basic JuiceBox kit last November. The answer was ~10 watts, but that was without a WiFi transceiver, so 12 watts for the Pro 40 seems correct.

 

[I33t]

If 10 or 12 watts is a problem, just install a switch and turn it off when not in use, or throw the breaker.

I agree with your sentiment. Thankfully we have a decent PV installation that negates our power usage and costs. We've just replaced our failing wastewater plant and the savings are about 300w continuous. I think we can afford 12w!

 

[Blue20]

If 10 or 12 watts is a problem, just install a switch and turn it off when not in use, or throw the breaker.
...

If you decided to use the breaker, make sure it is switch-duty rated. Not all breakers can take ongoing flipping on and off.

 

[alohart]

If 10 or 12 watts is a problem, just install a switch and turn it off when not in use, or throw the breaker.

A proper on-off switch was included when my charging circuit was installed. I switch off the power to my JB when it's not in use with this switch rather than a circuit breaker. This is possible because my charging circuit is only 20 amps.

 

[jadnashuanh]

FWIW, you can find double-pole switches of pretty much any capacity should you want a local on/off switch for the EVSE.

 

[I33t]

Thanks for the advice. The JuiceBox (pro 40) is now installed with an isolation switch, and it works really well! Still have to get wireless sorted, no coverage in the garage yet.

The local price for a 32A EVSE here is quite high, at least twice what I paid for the JB. Even then, the JB has more functionality.