Level 2 charger and rooftop solar

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coulomb is the expert about all things in chargers, but as i recall the OBC takes either 120 or 240 vac at 60 Hz (or 50 Hz in other countries) and rectifies that into DC; this DC goes thru a Power Factor Correction stage that forces the mains voltage and current draw to be in phase. From there it goes into an L-C boost stage. Then this boosted DC is chopped thru a pair of high frequency H-bridges to create a high frequency AC voltage that is sent into a pair of transformers to raise the voltage even higher as needed. This high frequency AC output is then rectified thru dual bridge rectifiers to make the DC at the Pack level. It is filtered in the Output stage and sent to the Pack.

The overhead for the control board is the same in either case as it is powered from the 12V system.

i don't have any input/output power numbers but i'm sure somebody has that data for L1 and L2 comparison.
 
We have solar on our roof with no battery backup. Our system is too small to provide enough power even at noon time to meet the needs of our L2 charger. We still generate more than enough electricity in a year to cover all of our needs including our electric car. Why is there a need to not use any power from the grid unless you are not connected to the grid? All I care about is generating enough electricity in total over a year to cover all of our needs. In fact, I see no benefit in having battery backup unless one is not connected to the grid or for cases of power failure from the gird.
 
bmw said:
We have solar on our roof with no battery backup. Our system is too small to provide enough power even at noon time to meet the needs of our L2 charger. We still generate more than enough electricity in a year to cover all of our needs including our electric car. Why is there a need to not use any power from the grid unless you are not connected to the grid? All I care about is generating enough electricity in total over a year to cover all of our needs. In fact, I see no benefit in having battery backup unless one is not connected to the grid or for cases of power failure from the gird.
Right now you're using the grid as your battery, assuming you are on net metering. This makes sense as long as your electric company doesn't charge you for the privilege. If you're not subject to frequent or prolonged power outages, there's no reason to need a battery backup or backup generator. As long as you can stay on net metering a backup generator is a cheaper option than battery backup. The only time you would need battery backup is if your electric company ends net metering and even then you should do a cost analysis to see if a battery backup makes sense.
 
@johnlocke - spot on. Another fellow SoCal user here so our situation is probably similar. Quite happy with the SDGE - TOU EV plan. Battery storage does not have the ROI for now even if the regulation allowed us to stop putting power back to grid. One alternative... If we had a viable V2H solution from LEAF to power our home we would invest in that (power panel changes needed with an ATS etc).
 
bmw said:
We have solar on our roof with no battery backup. Our system is too small to provide enough power even at noon time to meet the needs of our L2 charger. We still generate more than enough electricity in a year to cover all of our needs including our electric car.
What is your solar panel capacity (full load)?
I ask because we are heading into a (new) home with (new) solar panels installed, and I am considering a larger/newer EVSE that allows for power adjustment (like the ChargePoint) in order to leverage our solar output during the day (my typical charging routine is currently night with no solar). If I'm never going to be able to support L2 rates (even at the low-end of 16A), then I might as well stick with my (old) original (modified) Nissan L1/L2 charger...and install another outlet in my garage (like I currently have).
 
This will give you an idea of what's involved in DIY-ing a 240V off grid solution:

https://www.youtube.com/watch?v=mzZR6SWonrY

The need for two 120V supplies that are 180° out of phase, along with a bonded neutral, is what makes charging an EV using solar energy more complex.

It helps to be rich :)
 
OldManCan said:
@johnlocke - spot on. Another fellow SoCal user here so our situation is probably similar. Quite happy with the SDGE - TOU EV plan. Battery storage does not have the ROI for now even if the regulation allowed us to stop putting power back to grid. One alternative... If we had a viable V2H solution from LEAF to power our home we would invest in that (power panel changes needed with an ATS etc).
Just as a note of reference, I do have battery backup in place in addition to a backup generator. I'm in the Sunrise power corridor so SDG&E offered grant money to install battery backup. Cost will be Zero after I get the grant money back. The grant process is cumbersome and takes months to go through. Without the grant I wouldn't have done it and the grant process is intentionally cumbersome and requires that you pay for the system upfront and apply for the grant afterwards. Since I suspect that SDG&E will eventually charge me for transport costs both ways for power I store on the grid, I got the battery backup even though I don't really need it. In terms of power usage, I'm close to net zero but winter usage is high particularly in Dec-Jan.
 
Just to clarify--the main difference in efficiency charging the LEAF at L1, L2 at 12 amperes, and L2 at 30 amperes is the continuous power used by the car's systems such as the cooling pumps and computers. The onboard charger and DC-DC converter dissipate some heat which the liquid cooling system carries away. The heat generated in the onboard charger is only some of the loss during charging. Most of the losses are in the computers, coolant pumps, and fans (which run when the radiator gets warm enough). The computers and coolant pump(s) run continuously when the car is charging so they run longer when the input power is lower. This means that the best charging efficiency is at 6.6 kW L2 and the worst is L1, while 3.3 kW L2 is between these two extremes.

If you have unused solar capacity and want to charge the car, then efficiency may not matter to you so use L1 or whatever input current L2 your system can support. If you have plenty of capacity, but only 120V output from solar inverter(s), you could use a step-up transformer to feed an L2 EVSE. I have a 3 kVA transformer to use with my Honda generator that provides 120/240-volt, 3-wire output from the 30A, 120V receptacle to charge the car at 12A and 240V or to run test equipment which needs 240 volts (or both 120 and 240 at the same time).
 
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