[cricketo]

Add a little isolation transformer to bring the voltage down say 100 times, then measure it using ADC.

 

[dougo6905]

Add a little isolation transformer to bring the voltage down say 100 times, then measure it using ADC.

Oh wow, really? Is that what everyone is doing? I feel like now instead of one simple part, I've got to build a whole circuit around just finding out if the input is 120 or 240V. I thought it would be simpler than that and stay all in the analog world as I don't have any digital components in my setup. Is there a reference circuit with chip selection and parts list? If using an ADC, is then the circuit running on 5V for TTL instead of 12V?

 

[catphish]

It seems that it would be more sensible to have a charger that can accept the full range of input voltage, however if this isn't possible, then you're going to need a way to get the voltage down to something you can measure. A 100:1 transformer, rectifier, and capacitor, would give you a low DC voltage you can measure and compare. A microcontroller is likely the simplest way to do the measurement.

 

[cricketo]

You can stay analog and use a Schmidt trigger or a similar circuit to distinguish between the voltage levels. Also I don't know what everyone else is doing.

 

[brian_]

I need to figure out if I have a 120Vac in or a 240Vac on the pin2 on the J1772 connector to enable my L1 charge circuit or my L2 charge circuit.

Why do you have two charge circuits? Assuming that we're talking about a normal North American style SAE J1772 "J plug" (IEC 62196 Type 1) the same two conductors are used regardless of voltage so no switching is required; the same terminal (labelled "N") is "AC Neutral" for 120 V Level 1 charging or "AC Line 2" for 208–240 V Level 2 charging. I assume that normal practice, as catphish suggested, is to use a single onboard charger which accepts the whole range (from somewhat less than 120 V to somewhat more than 240 V, usually 100 to 250 V) without a configuration change.

I'm not trying to be difficult or disregard the original question, but the best answer to "how do I detect voltage and switch charging circuits" may actually be "don't detect voltage and always use the same single charging circuit".

 

[remy_martian]

What exactly is your "L1 charge circuit" and your "L2 charge circuit?

 

[dougo6905]

Why do you have two charge circuits?

I hope I used the right terms, but these are the chargers inside the vehicle.
When I started my EV conversion project many years back I could not get a working charger that handled either voltage. I did not know exactly how others were doing it as I couldn't find much info. I got a 120Vac charger to start Level 1 charging, and now I got a separate 240Vac charger that doesn't work on 120Vac so that doesn't work if a Level 1 charger is plugged. I thought the easiest thing to do is detect the voltage at pin 2 of the J1772, I can automatically charge through one or the other until I build a combination charger. I don't know what is considered the defacto standard circuits these days. At the time everything seemed custom-built and no public information. Then I can work on the motor mounting plate and motor controller and then return back to fix the combo charger part. I'd like to drive my EV conversion sometime before I die so was looking for the fast way to progress.

 

[remy_martian]

Why not just have a separate 110V plug, behind a protective cover and where you can plug any extension cord into it (like an IEC cord entry on a PC), but put it behind a dustproof protective door/cover) on the car for the 110V charger and always have the J1772 plug as a Level 2 connected directly to the 240V charger?

 

[brian_]

Public Level 1 chargers are relatively uncommon, so having only Level 2 work through the J1772 plug seems like a reasonable compromise for now. The best long-term solution is likely a new charger to handle the whole AC voltage range, rather than a custom switching circuit.

 

[dougo6905]

Why not just have a separate 110V plug, behind a protective cover and where you can plug any extension cord into it (like an IEC cord entry on a PC), but put it behind a dustproof protective door/cover) on the car for the 110V charger and always have the J1772 plug as a Level 2 connected directly to the 240V charger?

The requirement is to be able to charge using both J1772 Level 1 Charger and Level 2 charger.

 

[remy_martian]

Correct. I met your requirement. Two plugs.

Why on earth do you want Level 1 J1772?

 

[dougo6905]

Public Level 1 chargers are relatively uncommon

I appreciate all the other comments, but I'm more interested in the technical question. Not all my friends have 240V accessible at their apartments and I don't want a connector that anyone can accidentally pull out. I think using my locking plug is a good idea. So I still need to solve my technical problem.

 

[remy_martian]

I appreciate all the other comments, but I'm more interested in the technical question. Not all my friends have 240V accessible at their apartments and I don't want a connector that anyone can accidentally pull out. I think using my locking plug is a good idea. So I still need to solve my technical problem.

You don't have the skills or the PE license to design/build stuff for the public to use. It's illegal.

This started out as your car, and now it's come out that you're building something for everybody who went to your wedding.

And none of you had the foresight to put a multivoltage charger in your cars? All are homebuilt copies of your dual charger abomination?

Hard to believe.

Yes, it can be done.

There's no reason to, though, because everybody owns an extension cord and apartments have 110V plugs in garages. Production EV's EVSE's run off 110VAC or 220VAC as do their onboard chargers.

 

[dougo6905]

I'm not trying to be difficult or disregard the original question, but the best answer to "how do I detect voltage and switch charging circuits" may actually be "don't detect voltage and always use the same single charging circuit".

I don't have a single charging circuit that can handle both. I was hoping not to have my life thrown into a new project, but can you point me to a project I can build myself that has schematics hopefully of a simple design, parts list, is relatively cheap, and is considered reliable. I'd like to be able to charge at 1.5KW (120V), 3KW (dual 120V), and 6KW (240V), and later I'd like to redesign the chargers to get 9KW. (240V + dual 120V).

 

[remy_martian]

Buy a new charger

 

[dougo6905]

You don't have the skills or the PE license to design/build stuff for the public to use. It's illegal.

This started out as your car, and now it's come out that you're building something for everybody who went to your wedding.

And none of you had the foresight to put a multivoltage charger in your cars? All are homebuilt copies of your dual charger abomination?

Hard to believe.

Yes, it can be done.

There's no reason to, though, because everybody owns an extension cord and apartments have 110V plugs in garages. Production EV's EVSE's run off 110VAC or 220VAC as do their onboard chargers.

Nope. My car that I'd like to charge at my friend places. Your answer is quite annoying and seem too misunderstand my need. Please don't respond. I did not find your response helpful.

 

[cricketo]

LOL! It's one of "those" threads again

 

[brian_]

The requirement is to be able to charge using both J1772 Level 1 Charger and Level 2 charger.

I appreciate all the other comments, but I'm more interested in the technical question. Not all my friends have 240V accessible at their apartments and I don't want a connector that anyone can accidentally pull out. I think using my locking plug is a good idea. So I still need to solve my technical problem.

Okay, but then my solution would be this one:

The best long-term solution is likely a new charger to handle the whole AC voltage range, rather than a custom switching circuit. One charger can fit all of your stated scenarios (voltage and power level).

If you want to build something that no one else has, just to prove that you can, there might be something along the lines of a voltage-sensing relay. Those are usually used in 12 V or 24 V DC systems, but they do exist for 240 VAC; here's an example (although it's only good for 15A... I only searched for two minutes):
Voltage Sensing Relay, 240V AC, 15A @ 240V, 5 Pins, Mounting: DIN Rail, SPDT

 

[remy_martian]

The 0.1 second dropout on that brownout PROTECTION relay is long enough to cook the charger...