Level 2 Charging My Tesla. I need more power, but which way do I go about it?

[TessieRed]

Hello All. I am in need of some advice with my solar system. I have an EG4 6K Off-Grid Split Phase inverter paired with 12 320W Canadian Solar Panels and a 5.1 KWh EG4 LL Battery. Max production I saw was about 3.6Kwh from my system.

The main purpose of this installation is to charge my Tesla Model S 75D. So far, I have been able to achieve a 7Kwh Charge at 5kwh per hour at 23A. (From 73 to 85% SOC on the Tesla)

My issue is after my battery is depleted, I don’t have enough solar to production alone to charge my Tesla. Once the home battery is recharged I can resume charging the Tesla. Even at night due to high idle consumption of the inverter, I cannot continuously charge off the stored energy of the battery (possibly at a lower amperage),

The question is, I am not sure whether to add more solar or more batteries? Another battery would allow me to store more energy and charge the Tesla without interruption for up to 10-12Kwh. I want continuous charging without interruption for a minimum of 20Kwh.

I can pull from the utility grid and charge my battery to continue charging, but I want to charge 100% off solar power.

From you experience what is the best solution? If I upgrade to 5Kwh of solar can one battery and solar bring me continuous power? Will another battery in combination with the current solar setup provide?

Your experience and advice would be greatly appreciated. Thank you in advance!

 

[JCSchwarb]

Hello All. I am in need of some advice with my solar system. I have an EG4 6K Off-Grid Split Phase inverter paired with 12 320W Canadian Solar Panels and a 5.1 KWh EG4 LL Battery. Max production I saw was about 3.6Kwh from my system.

The main purpose of this installation is to charge my Tesla Model S 75D. So far, I have been able to achieve a 7Kwh Charge at 5kwh per hour at 23A. (From 73 to 85% SOC on the Tesla)

My issue is after my battery is depleted, I don’t have enough solar to production alone to charge my Tesla. Once the home battery is recharged I can resume charging the Tesla. Even at night due to high idle consumption of the inverter, I cannot continuously charge off the stored energy of the battery (possibly at a lower amperage),

The question is, I am not sure whether to add more solar or more batteries? Another battery would allow me to store more energy and charge the Tesla without interruption for up to 10-12Kwh. I want continuous charging without interruption for a minimum of 20Kwh.

I can pull from the utility grid and charge my battery to continue charging, but I want to charge 100% off solar power.

From you experience what is the best solution? If I upgrade to 5Kwh of solar can one battery and solar bring me continuous power? Will another battery in combination with the current solar setup provide?

Your experience and advice would be greatly appreciated. Thank you in advance!

If your system is idle for days in between Tesla charges, you could add more battery capacity to rectify the deficit. This is likely an issue now due to less light levels than spring/summer. Adding more battery capacity will store energy when the sun is available guaranteeing a good Tesla charge. Based on your specs, you would need one more 5 kWh battery.

Best,
-Jay

 

[Riwall]

I recently built a similar ev charging system with two EG4 3kW inverters, two 100Ah EG4 batteries, and about 3kW of panels. Solar production has been pretty crappy over winter but I'm netting about 50% of my daily usage (about 25 miles) from solar. I have found the keys are to only have the inverter running while charging and try to match the charge rate to the solar production. I set my model Y to charge at 10A for 2.4kW. The battery bank is pretty much just there as a buffer to ride through passing clouds and such.

 

[timselectric]

More battery only helps if you have enough solar to charge it. So it depends on exactly what you're getting and how, currently.

 

[Hedges]

Switch back and forth between 240V and 120V charging based on battery SOC?

 

[740GLE]

What’s your daily consumption of the EV?

Are you able to charge while the sun is out?

Sounds like you should 4x storage and at least 2x the PV.

 

[MichaelK]

Maybe it's just me, but I'm against draining one battery to charge another. If it was my system, it would be set up to provide maximal charging in the daytime, and skip charging at night completely.

A good rule of thumb that has worked well for me is identify what that charge rate should be, and double the amount of watts feeding that load. Let's say you want 20A at 240VAC. Then have ~9000W of panels to support that load.

 

[740GLE]

Having the car there during sun hours maybe too difficult.

 

[Supervstech]

Hello All. I am in need of some advice with my solar system. I have an EG4 6K Off-Grid Split Phase inverter paired with 12 320W Canadian Solar Panels and a 5.1 KWh EG4 LL Battery. Max production I saw was about 3.6Kwh from my system.

The main purpose of this installation is to charge my Tesla Model S 75D. So far, I have been able to achieve a 7Kwh Charge at 5kwh per hour at 23A. (From 73 to 85% SOC on the Tesla)

My issue is after my battery is depleted, I don’t have enough solar to production alone to charge my Tesla. Once the home battery is recharged I can resume charging the Tesla. Even at night due to high idle consumption of the inverter, I cannot continuously charge off the stored energy of the battery (possibly at a lower amperage),

The question is, I am not sure whether to add more solar or more batteries? Another battery would allow me to store more energy and charge the Tesla without interruption for up to 10-12Kwh. I want continuous charging without interruption for a minimum of 20Kwh.

I can pull from the utility grid and charge my battery to continue charging, but I want to charge 100% off solar power.

From you experience what is the best solution? If I upgrade to 5Kwh of solar can one battery and solar bring me continuous power? Will another battery in combination with the current solar setup provide?

Your experience and advice would be greatly appreciated. Thank you in advance!

Big difference between kWh and kW.

Batteries are rated in kWh

Solar panels are rated in kW

Solar arrays can produce kWh over time.

Inverters are rated in kW or kVA and daily production is tallied in kWh


So.
Is the most your panels have output 3.6kW? So, over the course of the day could be around 20kWh... if you have the storage or usage for the output.
Adding anothe 5.1kWh battery will give room to store the juice the panels output.
Adding 3 more will bring you up to 20.4kWh of storage to fully utilize the output of the panels.
Adding another 12 panels will let you output faster to fill the bank, and still have solar output during daylight hours.

 

[TessieRed]

I recently built a similar ev charging system with two EG4 3kW inverters, two 100Ah EG4 batteries, and about 3kW of panels. Solar production has been pretty crappy over winter but I'm netting about 50% of my daily usage (about 25 miles) from solar. I have found the keys are to only have the inverter running while charging and try to match the charge rate to the solar production. I set my model Y to charge at 10A for 2.4kW. The battery bank is pretty much just there as a buffer to ride through passing clouds and such.

Thank you for your response. I found the same.. if I keep my amps relatively low and pull 3kwh (Same as the solar). I get a consist slower charge through the day.

I will add more solar to charge at a faster rate if possible.

 

[TessieRed]

Having the car there during sun hours maybe too difficult.

I work from home so it’s definitely possible with my schedule. Batteries if not. Thank you very much for taking the time to respond to my question

 

[TessieRed]

Maybe it's just me, but I'm against draining one battery to charge another. If it was my system, it would be set up to provide maximal charging in the daytime, and skip charging at night completely.

A good rule of thumb that has worked well for me is identify what that charge rate should be, and double the amount of watts feeding that load. Let's say you want 20A at 240VAC. Then have ~9000W of panels to support that load.

I absolutely agree. Unfortunately my system was sized to my budget at the time. For now I will keep my charging amperage low until I can add solar and improve amperage for faster charging.

I will upgrade to 6K of solar in a few months and increase my charging speed to closer to 40A. Until then.. I guess I’m slow charging. The battery helps me compensate and charge a bit faster. 23A was the fastest consistent charge I was able to obtain, but the battery can only compensate for a bit over an hour.

 

[JCSchwarb]

I absolutely agree. Unfortunately my system was sized to my budget at the time. For now I will keep my charging amperage low until I can add solar and improve amperage for faster charging.

I will upgrade to 6K of solar in a few months and increase my charging speed to closer to 40A. Until then.. I guess I’m slow charging. The battery helps me compensate and charge a bit faster. 23A was the fastest consistent charge I was able to obtain, but the battery can only compensate for a bit over an hour.

My recommendation to add a battery and capture over several days was recommended as least expensive and intrusive to your time and pocketbook. Adding that many more panels seems way more complex than adding a battery. I get the argument to charge direct from the sun, but may not be feasible in your rainy season and adds a lot of costs in panel sprawl.

 

[Hedges]

Thing is, PV panels are cheaper and simpler than batteries.
If you can install oversize array and your inverter supports zero/limited export (depending on net metering situation), that will allow loads and EV charging while preventing import from grid over wider range of sun condition.
Multiple orientations, too. That gives a flatter power curve over the day.
I think hardware for complete GT PV system is 1/2 the cost of cheapest batteries alone. Overpaneling with used panels even more cost effective.

 

[JCSchwarb]

My recommendation to add a battery and capture over several days was recommended as least expensive and intrusive to your time and pocketbook. Adding that many more panels seems way more complex than adding a battery.

Thing is, PV panels are cheaper and simpler than batteries.
If you can install oversize array and your inverter supports zero/limited export (depending on net metering situation), that will allow loads and EV charging while preventing import from grid over wider range of sun condition.
Multiple orientations, too. That gives a flatter power curve over the day.
I think hardware for complete GT PV system is 1/2 the cost of cheapest batteries alone. Overpaneling with used panels even more cost effective.

One needs to look at the entire concept of operations. Adding a battery would be way less intrusive and quick and easy. Having additional panel sprawl is not necessarily desirable, nor as easy to maintain. Further, if one has many gray days, more panels will not accomplish sufficient charging.

I have eight strings powering 20 kW and one of my strings has gone out already. So now I need to go troubleshoot that.

 

[740GLE]

If there are many gray days, a large battery battery will never get charged.

Also he already has 50-100kwhr of storage, it just has 4 wheels and is unplugged from the system really easily.

IMO it all comes back to daily consumption of the EV.

If 30kwhr/day is needed, adding more fixed batteries doesn’t generate more power.

I do agree that adding more storage maybe the easiest and can never hurt anything, but IMO more PV is needed especially if the EV is plugged in during peak solar hours.

 

[JCSchwarb]

If there are many gray days, a large battery battery will never get charged.

Also he already has 50-100kwhr of storage, it just has 4 wheels and is unplugged from the system really easily.

IMO it all comes back to daily consumption of the EV.

If 30kwhr/day is needed, adding more fixed batteries doesn’t generate more power.

I do agree that adding more storage maybe the easiest and can never hurt anything, but IMO more PV is needed especially if the EV is plugged in during peak solar hours.

the one spec that stood out is his desire to charge continuously. To me this points to more battery capacity. I would do a trade space to determine payoff using grid in the winter time vs adding a lot more infrastructure.

 

[740GLE]

Continuously, you mean from say 10am until 5pm when the sun is shining? The “work from home” think was what sold me on more PV will really solve his problem.

 

[400bird]

I'm confused as to why there is so much discussion on this. Work from home means you can charge while the sun is out, right?

If your running out of energy, more battery doesn't create more energy. It can store energy from elsewhere (solar)

I don't see how more battery storage will help.

I think you should work to (automatically) adjust (car) charge current to match PV production to better directly utilize PV and not pointlessly cycle the EG4 battery. One battery should provide plenty of buffer to stabilize the time between PV changes and the car actively adjusting current.

 

[Hedges]

Ideally, you have variable charge rate, and implement zero export by varying charge current into Tesla. I guess that takes Level 3? CHADEMO?

But a simple way to go would be smaller battery system and a relay switching charge cord between 120V and 240V depending on SoC (of fixed battery). That varies charge rate between Level 1 and Level 2. Fixed battery buffers production. That should work off-grid; if grid-connected, need fixed battery to implement zero export. Which is a common function for AC coupled batteries.