I would like to have a system that would charge my Electric vehicle and only have it do that, not grid tied or any battery, is that possible. In an ideal situation I don't want to convert it to ac, I want to skip that step. I believe this will be common some day and I would like to do it soon. We can sort out excess power storage at a later time, like the second car or third car or heating water. My goal is to be efficient, and simple! And I don't know what I don't know, so lets see what we can come up with. Thanks for your input!
Stand alone system for charging an EV
- Thread starter TRW
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Ampster
Renewable Energy Hobbyist
It sounds like you want to use just DC. What EV do you have and does it have a DC charging port?
Generally you will need a charger that communicates with the vehicle computer. The supply will determine the maximum power and the vehicle needs to reduce power as the battery approaches full. I believe the minimum could be close to 10 kW so you are looking at 20 to 25 amps and 400 to 500 volts minimum to feed the vehicle. That is a lot of solar to go direct. Not sure if the hardware to communicate maximum power direct from a solar array has been developed. A cloud for instance would shut down the charging.
In the US it will be CCS or CHAdeMO connector as they are a bit more open source compared to Tesla Supercharger. Give those two a search.
Here is a home unit at $4,000 with a AC plug. Maybe they will talk about going straight to DC as a power source.
https://www.evseadapters.com/products/portable-chademo-ccs-combo-dc-quick-charger/
May need to poke around on some EV forums get some additional thoughts.
Here is some explanation on how the system works:
http://tesla.o.auroraobjects.eu/Design_Guide_Combined_Charging_System_V3_1_1.pdf
In the US it will be CCS or CHAdeMO connector as they are a bit more open source compared to Tesla Supercharger. Give those two a search.
Here is a home unit at $4,000 with a AC plug. Maybe they will talk about going straight to DC as a power source.
https://www.evseadapters.com/products/portable-chademo-ccs-combo-dc-quick-charger/
May need to poke around on some EV forums get some additional thoughts.
Here is some explanation on how the system works:
http://tesla.o.auroraobjects.eu/Design_Guide_Combined_Charging_System_V3_1_1.pdf
Thanks for the info. Here are a few thoughts on my goal. First, most rectifiers produce heat, that consumes energy, so skipping that step makes sense to me. With the price of PV panels, when a person has excess room, and so many EVs in the future, seems we can and should work to make them simple and efficient. I have already leaned that we are not close to being able to do this in a satisfactory manor, but will predict someone is going to concentrate on making this happen.
Yes, it would seem logical and desirable to charge EV's directly from PV's especially since they are both DC hence avoiding the inefficiency of going to AC and back. While I share your view that this would be nice to have I wouldn't expect it to be available any time soon for the following reasons:
- historically all current EV chargers have been primarily developed to serve grid plug-in chargers for the various power standards around the world as this is the most popular charging method
- there are at least 3 main charging standards competing for market share by the car makers
- as pointed out above, for technical and safety reasons specialized communication is required between the charger and the vehicle
I know you are after dc-dc , however teslas 5.15 (110V) 6.15 (240v) mobile connector coupled with a suitable sized dc/ac inverter would get you charging today from off-grid.
https://www.tesla.com/sites/default...bile_connector_owners_manual_32_amp_en_US.pdf
The 15% inverter loss is known and may be comparable to any dc/dc conversion device.
All EVs would have similar and changing battery specs wont present a major problem.
edited irrelevant afterthought: Look at all the traffic leaving home between 7&9am and returning home between 5 &7 pm. The logical conclusion is most EV's should be charging between 7am and 7pm when the sun is shining and power is cheapest and when they are away from home. So expect to see low amperage charges at every workplace and shopping centre carpark.....you get charged via the microchip in the plugs....nothing for the power but $$'s for the road tax!
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Thanks for the input and info. I am excited about the potential, especially when they come up with a use for the excess power like heating water or space heat. Many years ago, hooking up to the grid was difficult, and while that is not a problem anymore, I see the day coming when we will not hook for a few reasons. For me it is expensive, (cheap for what we get). But some of us like the independence, and when we can charge the car, we can also charge the batteries more efficiently.
Some great points and info. Your comments on day charging is very accurate. But I for one, have a schedule that this would work for, and I can think of lots of people who work evenings and nights, and are retired, so there is still a large number of uses. I also envision the day when people will charge their back up battery pack, that interchanges with the main one. Yes I know that concept is not here yet, because of expense and weight of the battery.
I have had my Tesla for a couple of years. For the first six months I home charged via a 110v extension cord, which was fine, but not as efficient as 220v. So eventually I installed a 220v Tesla home charging station. FYI, Tesla only does DC charging at their big Supercharger stations.
I have also been able to charge at campgrounds, at 220v, using a 14-50 NEMA adapter.
So now, with COVID, my work is all from home, and the car gets very little use. I have been toying with the idea of a solar/inverter/battery trickle charger setup, with the idea of trickle charging the car with maybe 3Kwh/day. I have learned a lot by lurking here, and watching Will’s channel, and I feel like I might actually pursue this. I am sure that 220v would charge the car more efficiently that 110v, but I am not sure if it is worth the trouble. I would be happy to hear any comments or suggestions from you more experienced folks, before I go any further.
Thanks for a great forum….
curiouscarbon
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Hi, I too am wanting to trickle solar charge. My gut and brain both suggest 110V if that’s what your house is like.
Reasons:
1) You say low speed charging, and ~3000 Watt hours per day total.
2) 220V charging could deliver this in a very short amount of time (3000W -> 1 hour)
3) 110V charging could deliver it in a short time still, (1000W -> 3 hour)
3kWh/day is 125W for 24 hour. Assuming lowest charge speed of 500W from 110V, that’s only 6 hours to deliver those 3 kWh.
Assuming you park at this system overnight, 110V seems like a great option.
Eager to hear more thoughts on this topic.
I am planning on using a Victron Multiplus 24/3000 (110/120VAC input/output) in combination with at least one 8S pack of 100Ah Frey/Fortune LiFePO4 cells to realize this sort of experiment.. Victron Bluesolar MPPT for solar input..
8S 100Ah Frey pack can deliver 5120 W continuously (2C discharge).
1000-1500W discharge will be 0.2-0.3C discharge.
I believe minimum charging protocol is 6 amps 120v or 720 watts. Need an adjustable EVSE or vehicle control to go this low. The trouble is the overhead to run the computer, circulate coolant etc is 200 to 300 watts while charging. At the low end, the % getting to the battery is dropping quickly and reducing efficiency. For best efficiency it is better to charge faster.
Yep. It’s a question of whether or not the efficiency is worth it. I have charged the Tesla with my Delta 1300, just to see if I could, but I wouldn't want to do it on the regular.
Right now, I am leaning towards a 120v milk crate or hand truck system, as it would allow me to use it in the house during blackouts, as well as trickle charging the car.
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curiouscarbon
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5A minimum observed
5A can be set manually in vehicle interface.
as you mention, only a fraction goes to the battery. (confirmed by verifying CAN bus messages indicating power delivered to battery). it’s absolutely not 100% delivered.
Yes!!! Observing the CAN bus will confirm this.
This is why I desire to charge at max current inverter and batteries can support. 220V dedicated inverter preferable! But that’s an added expense on top of 120V inverter. One day.. dream of victron phoenix 5000VA 220V….
It’s simple to exceed a single 120V AC plug power capacity just by HVAC system being active.
The difference between power delivered to the HV battery is always minus the coolant and auxiliary systems power draw.
TL;DR it can be most power delivered efficient to buffer the entire day of solar power and then deliver it at a fast rate. if the battery and inverter support it.
meetyg
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I like the idea, but you must use some kind of buffer between the panels and the EV, or else you risk burning out the relays on the HV battery.
Basically, these relays are activated by the 12v system, either when you turn the car ON, or when charging is activated, connecting the HV battery to the car (inverter, motor, etc...).
If solar panels are used to charge an EV (either AC or DC), they will cause charging to stop and resume many times as there are clouds, shading, etc... This will cause the relays to connect/disconnect each time, causing premature wear.
I don't see how you can implement this without either with a grid-tied system (maybe the simplest way) or a good amount of batteries.
Basically, these relays are activated by the 12v system, either when you turn the car ON, or when charging is activated, connecting the HV battery to the car (inverter, motor, etc...).
If solar panels are used to charge an EV (either AC or DC), they will cause charging to stop and resume many times as there are clouds, shading, etc... This will cause the relays to connect/disconnect each time, causing premature wear.
I don't see how you can implement this without either with a grid-tied system (maybe the simplest way) or a good amount of batteries.
Typically in EVs, DC is only for fast charging. Now, you can buy a 25kW DC fast charger and install for your home but it is costly and still requires an AC feed. So for a stand-alone system you’ll still batteries and a large inverter.
https://www.evchargesolutions.com/Bosch-DCFC-el-52240-p/el-52240.htm
https://www.evchargesolutions.com/Bosch-DCFC-el-52240-p/el-52240.htm
There is also this that utilises grid & solar
SMA grid/solar EV charger
Probably still pricey but the rest of the article may be interesting.
Yes, I always assumed that the PV system would charge a battery, that would then power the inverter. I have enjoyed reading the discussion so far. Maybe I will try a 120v system first, as it seems less costly, and could be repurposed for home power. I could always upgrade to 220 later, I suppose.
curiouscarbon
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11,000 watt / 240 volt ~ 45.8 Ampere
it can be adjusted all the way down to at least 5 Ampere on the model 3 i tested. which at 240V translates to about 1,200 watts (~(5*240)watts)
it can be adjusted all the way down to at least 5 Ampere on the model 3 i tested. which at 240V translates to about 1,200 watts (~(5*240)watts)
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