Author Topic: Charging EV with solar  (Read 121 times)

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Offline lighthunter

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Charging EV with solar
« on: May 04, 2019, 09:28:03 am »
I now have plenty of extra solar generating capacity and would like to use some of the extra to fuel the car. To do this with my current system I would need to 
      A:) Use large battery and leave the car home when the sun shines.
      B:) Use two smaller removable battery packs and switch daily.
      C:) grid tie all my solar and do net metering with utility.

So far i have kept utility  and solar generated power separate and it would be great to keep it that way. Having a day job and solar ev charging arent so compatible though. Is anyone else doing net metering?  Im guessing its not so bad, i just like the independence of the off grid system. It would kinda make sense for EV charging though.
Suggestions welcome :)
LH

Offline WooferHound

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Re: Charging EV with solar
« Reply #1 on: May 04, 2019, 02:22:23 pm »
What Voltage and Current do you need to charge that thing ?
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Offline lighthunter

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Re: Charging EV with solar
« Reply #2 on: May 04, 2019, 09:57:32 pm »
It requires 262.5v @ anything up to 20 amps. 75 series LFP cells.
9.6kwh for 35-40 mile range. On a sunny day we get at least 40kwh and only use about 15kwh. Its not a huge return on investment but if you can "why not". I love how quiet electric is to drive. I also snagged a 3phase pmg from a hybrid. Its capable of about 25hp, i wanna strip the gas engine and associated pieces out of a small car and convert it. It wont be quick off the stop but it should be enough to get normal road speeds.
LH

Offline WooferHound

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Re: Charging EV with solar
« Reply #3 on: May 05, 2019, 07:15:22 am »
My Goodness, I didn't know those cars used such a high voltage.

Since I mainly use a bicycle I recommend to leave the car at home on sunny days and take the bike. But I live in-town and rarely need to travel more than 3 miles one way, about 20 minutes. The rain, heat and cold can be inconvenient. Been riding for more than a year now, the positive benefits of health and weight should also be mentioned.

Having 2 batteries sounds appealing, but expensive and possibly difficult and time consuming to change. Combining 2 batteries with occasionally leaving the car on sunny days sounds like the ultimate in reliability. 

Grid Tie isn't real for me, or cheating. I want to use the same electrons that I made, a closed system.
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Offline Solarnewbee

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Re: Charging EV with solar
« Reply #4 on: May 06, 2019, 10:51:43 pm »
LH you helped answer a lot of my questions about my lfp’s and consequently later on found out one charge controller was not programmed correctly and the banks were not filling up fully. Now the ac can run all night and still charge the mini ev’s in the morning.

When you say 75 series, do you mean 75ah? How many cells?

For me I stay off grid, no grid tie, but I have an inexpensive ats on standby when the inverter gives up. Typhoon / rainy season we run off grid one day and charge up on grid one day with whatever light we can get and grid power alternating day to day. Our biggest power bill since kick off day in January this year has been $8.

As far as grid tie goes, I’m kinda Leary if it. I think it’s one of the reasons some gti’s Smoke fets. I sort of think I know what you mean by net metering. Your idea of switching out batteries in the ev sounds novel if the weight is not prohibitive. Maybe if you have carts that accommodate sliding out the batteries as a pack without killing yourself. Best of luck to ya!

Pic of my ats switch on the left. I know, green wire, ya get what ya can find in the Philippines. Got this this off of eBay. It’s motorized and switches mighty fast for the money.
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Offline lighthunter

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Re: Charging EV with solar
« Reply #5 on: May 07, 2019, 10:04:55 pm »
Hi guys!  Thanks for your ideas and comments! I have been busy with planting sweet corn among other things. I love spring but it doesnt last long  :)

"My Goodness, I didn't know those cars used such a high voltage."

Yeah, neither did I  :o the oem pack is NiMh 28 7.2v modules for 201v nominal. Then it goes to a boost converter, the software controls the boost in a varying amount depending on load up to 500v to an inverter that passes the power to a 50kw 3 ph perm magnet motor that can spin several thousand rpm. The battery doesnt supply all the dc power though, over half comes from a 30kw generator spun by the gas engine. Heres a photo of the battery voltages in blocks of two. One screenshot is during braking, (neg current) and another during accel (pos current)
LH

Offline lighthunter

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Re: Charging EV with solar
« Reply #6 on: May 07, 2019, 10:34:51 pm »
LFP can easily do a better job than these nimh batteries though but im not planning on replacing the oem pack, im just gonna use the LFP bank to give a steady supply of current into the 200v buss which will cause the ecu to use more electric assist than gas. You can use all electric but top speed is only 41 mph due to the max rpm of the pmg.

"When you say 75 series, do you mean 75ah? How many cells?"

I mean qty (75)  3.2v 40AH cells. This way i can use a simple bank of FETs with pwm to feed a steady current into the 200v buss. The higher voltage eliminates the need for a boost conversion to charge.

I agree with you guys regarding  not partnering with utility. Its just that it would be nice to bank power into grid and get it back at a time when you need it. No battery could match that if the trade was one for one. Yet i know the utility wont trade one for one anymore. Much of the US has passed state legislation allowing utilities to charge whatever they feel is (reasonable) for grid usage. I also couldnt agree more S/N about the fets and grid ties. Pushing all your power into grid means keeping a grid tie inverter working to do all that which equals failure at some point and high replacement cost. On the other hand the LFP charging can be done efficiently by simply choosing the correct number of panels and direct connecting to LFP string with bms monitor and HV cutoff of course.



LH