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Discussion Starter #1
Been wanting to split my 40A circuit for a while. I have two 40A 240V circuits in the garage but one is for the garage heater. I use it for my second Volt most of the year but in the winter I have to choose between L1 and L2. No more.

Decided to create a portable sub-panel. Started off with only going to have two double pole 20 A breakers, one for each Volt. That would have cost me about $80. But I decided to add a single pole 20 A 120V connection in case I wanted to use it in the garage when not charging the two Volts.

Below are the parts. Found a nice plastic sub-panel reasonably priced at Home Depot. It is a good start for the project. Here are the parts, prices and links. Also pictures.


1 TPL412CP 125 AMPS MainLug Indoor PowerMark Gold - $16.77 (HD)
1 GE 1 Pole 20 AMP THQP 120 - $3.94 (HD) only need for 120V setup
2 GE 2 Pole 20 AMP THQP 220 – $8.98 ea. (HD)
1 TGL2P Ground Kit - $4.88 (HD) only need for 120V setup
4 Wire 14-50 Oven Cord 6 ft - $18.99 (Amazon)
1 20 AMP Straight Blade Connector 120 V – $17.97 (HD) only need for 120V setup
3 ft. 10/3 SJOOW cord - ~$1.80 ft (HD)
2 ft. 12/3 SJOOW cord - ~$1.50 ft (HD) only need for 120V setup
PG19 Cable Connectors - $8.99 (pkg 10) (Amazon)
PG29 Cable Connectors - $4.99 (pkg 2) (Amazon)
2 NEMA L6-30 30 AMP 250V connector - $3.00 Ea. (ebay)

Total $110 with 20 AMP 120 V
Total $80 W/O 20 AMP 120V
 

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Clever idea. Do you intend to operate the L2 and garage heater at the same time? If yes, what are the max operating amps combined?


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I'm not an electrician, but my brother-in-law is and I've learned just about enough from him to thinks that you might really want to show that to a certified electrician before you start using it. At bare minimum, I think I'd have an independent ground wire set up for it just to be sure.

Seriously, not trying to be a jerk, I just don't want you or a family member to get injured.
 

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Why not plug in the two volts, start them, open the windows, and use them as garage heaters? I've stopped using my space heaters in the garage while working on stuff because the volt does a much better job of heating.
 

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Why not plug in the two volts, start them, open the windows, and use them as garage heaters? I've stopped using my space heaters in the garage while working on stuff because the volt does a much better job of heating.
Now that's a clever idea. Built in garage heater.


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Now that's a clever idea. Built in garage heater.


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AC works too in the summer time but it really eats through battery charge even with the car plugged into L2. I think because the AC is on, the batteries get warm, so the radiator emits heat as the cabin releases cold, the car is kind of working against itself. In either case, heating or cooling, make sure you are there and watching the battery levels as you don't want the ICE to turn on and fill your garage with exhaust.
 

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Discussion Starter #7 (Edited)
Clever idea. Do you intend to operate the L2 and garage heater at the same time? If yes, what are the max operating amps combined?


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I have two dedicated separate 40 AMP circuits. The heater will run at the same time off of one of the 40 AMP circuits. The two Volts will charge off of the other 40 AMP circuit, via this portable sub-panel.

Each Volt will draw a maximum of 14 AMPs for a total of 28 AMPS. This will be far less than the total 40 AMPs of the main panel. And each one now will have its own 20 AMP breaker in the sub-panel.

The heater draws about 32 AMPS but will be on its own 40 AMP circuit.

I did this because I ran out of room to add another breaker in the main box and because I can take it with me if I ever need too. It also lets me keep my 14-50 receptacle in the garage.
 

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Okay, the L2's are sharing the same Main panel circuit. I am surprised the the amp draw is only 14 each. All of the L2 EVSE's I've seen are 28-32 output requiring 40 amp circuits each. What am I missing?


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Okay, the L2's are sharing the same Main panel circuit. I am surprised the the amp draw is only 14 each. All of the L2 EVSE's I've seen are 28-32 output requiring 40 amp circuits each. What am I missing?
If he converted his stock EVSE to L2, they'd be limited to 12 amps output each.
 

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AC works too in the summer time but it really eats through battery charge even with the car plugged into L2. I think because the AC is on, the batteries get warm, so the radiator emits heat as the cabin releases cold, the car is kind of working against itself. In either case, heating or cooling, make sure you are there and watching the battery levels as you don't want the ICE to turn on and fill your garage with exhaust.
I would recommend against trying to cool a garage this way. The heat emitted from under the hood will outweigh the benefit of the "cool" coming from the vents. The net effect is that the garage gets hotter. This would be like trying to air condition the kitchen by leaving the refrigerator door open (does not work).
 

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Discussion Starter #11
Okay, the L2's are sharing the same Main panel circuit. I am surprised the the amp draw is only 14 each. All of the L2 EVSE's I've seen are 28-32 output requiring 40 amp circuits each. What am I missing?


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The L2 EVSE's you are referencing (and I have two that are capable of that, Siemens, Chargepoint) simply mean that is their maximum. The Gen 1 Volt will never draw more than 14 amps regardless of the type of L2 EVSE you use. The Gen 2 will never draw more than 16 amps (but I don't have a Gen 2).
 

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Okay, the L2's are sharing the same Main panel circuit. I am surprised the the amp draw is only 14 each. All of the L2 EVSE's I've seen are 28-32 output requiring 40 amp circuits each. What am I missing?
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I think what you are missing is that the Volt will only draw 14-16 amps
 

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I was misinterpreting the basics of OHM's Law.

I = P/E or

( 3.3kw / 240v = 13.75 Amps)


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How are you getting the Neutral line for 120 VAC circuit?
His original circuit uses a 4 prong plug (Gr,H,H,N) the extra prong would be a neutral tied to the neutral buss bar in the sub-panel. 1. 20a breaker with return back to the neutral buss.




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I was misinterpreting the basics of OHM's Law.

I = P/E or

( 3.3kw / 240v = 13.75 Amps)


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I was confusing manufacture and Code requirement safety buffers with actual performance.


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Discussion Starter #17 (Edited)
His original circuit uses a 4 prong plug (Gr,H,H,N) the extra prong would be a neutral tied to the neutral buss bar in the sub-panel. 1. 20a breaker with return back to the neutral buss.




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yes. I have a 4 wires coming from the main so I can add a 120V connector. In the sub-panel, all green go the the ground. I have a separate neutral bar for the neutral on the 120V. It is important to have a ground bar and a separate neutral bar in the sub-panel. Ultimately they come together in the main panel but should be kept separate in the sub-panel.

If you have only 3 wires coming from the main box then you cannot do the 120V connection. Only the 240V split can be done.
 

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Discussion Starter #18
Installed it in the garage and got everything hooked up. It is working just fine include my 20A 120V receptacle. Both Volts are charging tonight of the one circuit. (not sure why the post is turning pics on their side)
 

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I saw on Clipper Creek's web site that they now make a unit to split single 40A supply over two cars. When one car is charing, it gets all the power. When a second car plugs in, they share with each car at a reduced rate. When one of the two is done, the remaining car goes to full tilt. Seems like a good solution, though it was pricey.

Personally, we charge one car on 120V and one on 240V -- we can swap if/when needed.
 

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Fixed photos

Very cool presentation.








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