: 16 Amp Charger Vs. 40 Amp Charger?



honoreitiscom
12-04-2010, 01:05 AM
OK you Electrical Engineers, please explain for us lay people.

The SPX Voltec charger (https://www.homecharging.spx.com/volt/Display.aspx?id=13&menu=6)is 240V 16 amp, while the EV Charge America (http://www.ev-chargeamerica.com/products_ev2104.html) charger is 240V and 40 amp.

Other than the fact that it draws more power and thus will need at least a 40 amp breaker, what will the difference be in terms of charging the car? Will the 40 amp charger charge it faster than the 16 amp charger?

Marty
12-04-2010, 01:19 AM
OK you Electrical Engineers, please explain for us lay people.

The SPX Voltec charger is 240V 16 amp, while the EV Charge America (http://www.ev-chargeamerica.com/products_ev2104.html) charger is 240V and 40 amp.

Other than the fact that it draws more power and thus will need at least a 40 amp breaker, what will the difference be in terms of charging the car? Will the 40 amp charger charge it faster than the 16 amp charger?

Not if you're charging a 2011 Volt or Leaf.

The EVSE, commonly called a charger but really a charger interface, communicates with the vehicle by means of a low-voltage pilot signal. Among other things, the EVSE notifies the vehicle of its maximum amperage rate.

The charger itself, which is in the car, uses this signal to set its charging rate to no greater than that which the EVSE signifies as its limit.

The EV Charge America charger is designed to be protected by a 40-amp breaker but signals the vehicle that it is capable of delivering 32 amperes. The Voltec is designed to be protected by a 20-amp breaker but signals the vehicle that it is capable of delivering 16 amperes.

The national electric code states that the maximum allowable load is 80% of the breaker rating, hence the difference.

So, the EV Charge America may have larger wire and a higher rated relay to allow it to deliver 32 amperes.

However, the actual chargers in both the Volt and the Leaf are only capable of consuming 16 amperes so for these vehicles any EVSE capable of 16 amperes or more will charge at the same rate.

If the Tesla were to adapt the J1772 standard, it would charge twice as fast with the EV Charge America unit. Future models of the Volt and Leaf may also be so capable.

So, even if you're installing a Voltec 16-amp charger, it makes sense to run wire capable of 40 amperes so that in the future you can replace it easily with higher-rated EVSE. Note that even with larger supply wiring, the Voltec or any 16-amp charger should still be protected with a 20-amp breaker.

ChrisC
12-04-2010, 01:47 AM
Marty is precisely right. The Leaf and Volt onboard equipment can only allow charging up to 3.3kW, which is covered by a 16 Amps charger at 240 Volts. If you get a 40A-capable charger you are future-proofing for when you might have a car that wants to draw more than 3.3kW. Honestly though, as Marty also said, right now you are better off getting a 16 Amp charger but running 40-Amp-capable wiring. Then in a couple years when EVSE prices come way down (and features go way up) you can upgrade the EVSE and the breaker but not need to run new wiring. The wiring run consumes a lot of labor.

Quibble: the national electric code states that the maximum allowable continuous load is 80% of the breaker rating.

(I'm an electrical engineer)

brewster
12-04-2010, 02:51 AM
As Australia has domestic supply of 240V I would assume we won't be able to 'opportunity charge' if thats the appropriate term. Such as when I travel to my daughters home 400km away, I wouldn't be able to plug into their normal powerpoint, I would need a hard wired charger there?

I wonder if they will have a mobile charging unit with the car similar to the 110V used in the USA?
Is Europe 110V or 240V for their version of the Volt?

Any info on this?

I realize the VOLT is not supposed to be coming to OZ until 2012.

Really looking forward to seeing one and I am envious of you all receiving your VOLTs :)

Marty
12-04-2010, 03:47 AM
As Australia has domestic supply of 240V I would assume we won't be able to 'opportunity charge' if thats the appropriate term. Such as when I travel to my daughters home 400km away, I wouldn't be able to plug into their normal powerpoint, I would need a hard wired charger there?

I wonder if they will have a mobile charging unit with the car similar to the 110V used in the USA?
Is Europe 110V or 240V for their version of the Volt?



Europe is 240 volts.

My feeling is that you indeed will be able to "opportunity-charge" and will be at an advantage to those of us in North America.

It is more difficult to upgrade the amperage of a wiring device than the voltage. To allow more amperage, contacts and conductors need to be made larger. To upgrade voltage it is only necessary that the insulation be capable of withstanding the higher voltage. Most portable cordage has insulation rated at 600 volts regardless of the mains voltage in use.

Because the J1772 standard is already set up for 240 volts, the portable EVSE is easy to adapt. Simply attach the appropriate mains plug and ensure that the logic control electronics won't be damaged by the higher voltage. Note that most modern electronics comes equipped with switching power supplies capable of operating from 100 to 240 volts at 50 or 60 hertz. This is true of everything from computers to electric shavers to cellphone chargers.

It is rumored that the portable EVSE supplied with the Volt is designed for 100-240 volts input, in which case all that would be needed would be to change the mains plug to an Australian or European standard. When the Volt is introduced in Australia it will almost certainly come equipped with a portable EVSE unit capable of 240 volt operation.

The great news for you is that because the charge time is based on watt-hours, the 240 volt mains means that your opportunity charge will be roughly twice as fast as here in the USA. At 12 amps, you will fully charge in about 5 hours. If 12-amp circuits aren't the norm, even at 8 amps you'll fully charge in 7 1/2 hours.

So, in 240-volt countries the opportunity charge portable EVSE will be better in terms of charge rate than in North America by a factor of two if the amperage is the same. My suspicion is that if the portable EVSE allows a 12-amp rate they'll probably change the default to 8 amps and allow the user to go to 12 if the circuit is so rated.

CAB members, how about telling us what the nameplate on the supplied portable EVSE reads in terms of input voltage?

brewster
12-04-2010, 07:36 AM
The great news for you is that because the charge time is based on watt-hours, the 240 volt mains means that your opportunity charge will be roughly twice as fast as here in the USA. At 12 amps, you will fully charge in about 5 hours. If 12-amp circuits aren't the norm, even at 8 amps you'll fully charge in 7 1/2 hours.

Just for interest sake, the normal circuits are 10 amps (which would be at my daughters). However at my place I would put in a higher amp capable cable, for future-proofing I guess, would be the way to go.

I am getting ahead of myself aren't I. :)
Its just when reading through this and other VOLT forums the excitement builds in anticipation. I've always only ever owned 'GM Holden' cars (40+ years) and I intend for that association to continue.

Congratulations to the USA for the game-changing VOLT. Here's hoping IT will be my next GM Holden car :)

honoreitiscom
12-04-2010, 09:52 AM
right now you are better off getting a 16 Amp charger but running 40-Amp-capable wiring.

...except that the 16 amp charger is not really available and I want to buy it now to get the tax credit that expires 12/31, so I'm going with the 40 amp.

Another question: Although it is rated at 40 amps, if I know the charger built inside the Volt is really only going to let it draw 16 amps, why wouldn't I want to wire it for 40 amps, but protect it with a 20 amp breaker? Then in the future if I ever have a car that pulls 32 amps through that charger, I'd swap out the 20 amp breaker for a 40 amp breaker. Good idea or bad idea?

Wow this is an amazing forum. All these really detailed, informed answers just a few hours after I posted the question. You guys are great. Thank you.

VoltGuy
12-04-2010, 11:05 AM
CAB members, how about telling us what the nameplate on the supplied portable EVSE reads in terms of input voltage?

I am not a CAB member but I do have a Voltec Charging Station. The ETL label on the unit says 240volt 15amp 60hz 3600watts.

Jerry

Marty
12-04-2010, 01:10 PM
I am not a CAB member but I do have a Voltec Charging Station. The ETL label on the unit says 240volt 15amp 60hz 3600watts.

Jerry
Good to know, but I was looking for the data on the portable charger supplied with the vehicle.

By the way, did you get your Voltec from SPX? I'm having a very difficult time getting them to commit to any kind of delivery.

VoltGuy
12-04-2010, 06:01 PM
Marty

I did get my Voltec charger through SPX. It took working really hard on my Volt Advsior to make that happen.

Jerry

Marty
12-05-2010, 04:47 AM
Another question: Although it is rated at 40 amps, if I know the charger built inside the Volt is really only going to let it draw 16 amps, why wouldn't I want to wire it for 40 amps, but protect it with a 20 amp breaker? Then in the future if I ever have a car that pulls 32 amps through that charger, I'd swap out the 20 amp breaker for a 40 amp breaker. Good idea or bad idea?


Bad idea in my opinion. If your charger is specified to require a 40-amp breaker, then that's what I would use. Otherwise, the EVSE (I'm trying to break myself of the habit of calling it a "charger") would signal that it's capable of 32 amps but the breaker would trip at 20.

As more EVs come to market, you might have a visitor with an EV containing a higher-rate charger who wants to "fill up" and this would result in tripping of the breaker with no easy fix other than swapping it out then or reprogramming the charger on the spot.

There's no safety gain in the 20-amp breaker and unless you configure the EVSE to a maximum of 16 (assuming that you can do so), you would be in a position where a legitimate combination of 32-amp pilot signal and a 32-amp capable car would needlessly trip the 20-amp breaker.

The 40-amp breaker with 40-amp rated wire (usually #8, perhaps #6 for longer runs) and a 40-amp rated charger is a safe combination. The Volt won't care, it is designed to the standard and will automatically current-limit at 16 amps regardless.

For what it's worth the SPX people claim that they're getting in a shipment of 140 Voltec units this week and should be able to ship.

honoreitiscom
12-05-2010, 11:02 AM
There's no safety gain in the 20-amp breaker... The 40-amp breaker with 40-amp rated wire (usually #8, perhaps #6 for longer runs) and a 40-amp rated charger is a safe combination.

Thanks for the advice Marty! That makes sense, since I would be wiring for 40 amps, there is no safety reason to trip the breaker over 20 amps, so a 40 amp breaker is best. In other words, the breaker needs to match the max load that the wiring can carry, which in this case will be 40 amps.

Marty
12-05-2010, 02:04 PM
Thanks for the advice Marty! That makes sense, since I would be wiring for 40 amps, there is no safety reason to trip the breaker over 20 amps, so a 40 amp breaker is best. In other words, the breaker needs to match the max load that the wiring can carry, which in this case will be 40 amps.

Correct in your case with 40-amp EVSE.

But, be careful with thinking of just the wiring. A 20-amp EVSE may built with a contactor and cord set that is only capable of safely carrying 20 amperes, in which case a 40-amp breaker would be overfusing it and could result in overheating or fire within the EVSE or its cord set.

Think of the EVSE as a "wiring device". You shouldn't use a 20-amp wiring device on a 40-amp circuit.

Under normal circumstances the pilot signal and electronics would prevent a car from pulling more than 16 amps from a 20-amp charger. But circuit breakers are designed to handle abnormal circumstances.

To sum up:

20-amp EVSE = 20-amp breaker, 20-amp or greater wiring.
40-amp EVSE = 40-amp breaker, 40-amp or greater wiring.