Solar charging - what size/type inverter, etc?

[RobertC]

Your off-grid system would work well with a Level 1 EVSE to charge an electric vehicle during a sunny day.

I hope so. I've used it to power lower wattage chargers on smaller EV's (motorcycle for instance). The example I used is emergency usage that I have tested. In regular use I have a larger bank of mismatched used EV (no longer suitable capacity for mobile applications) AGM lead acid batteries. Any mainstream off grid solar designer would say it won't work. But I have 4 years of hard data showing that it does work and work well. Essentially my battery bank is free and will continue to be, as long as I do EV service and modifications. Some of them are orbitals that were manufactured in 2004!

The panels are 60 cell SolarWorld panels for a total of 2600 watts, The charge controllers are Morningstar 65 amp MPPT units (three paralleled). In day to day practice the panels are grid tied, but are also wired to divert the DC to the charge controllers if the grid is down. A small investment IMO to keep the food cold and our kesters warm or cool (depending on season) during a prolonged outage. Why only a 12 volt battery bank when 48V would be more efficient? It's much easier to use mismatched batteries if there are no series strings. Also a charged iMiEV battery could keep the critical loads going for up to 4 days through the DC to DC converter in the car (12 volt output). A Gasser can idle at about .6 gallons per hour cranking out 45 to 80 amps of charging power (again 12 volt output). So for the sake of flexibility of power sources 12 volts made the most sense to me.

Aerowhatt, that's awesome!

I had not considered before how well 12 volts works to tie in solar panels and electric vehicles.

I envision a home of the future with electric vehicle batteries and storage batteries integrated with solar panels tied to the electric grid that could:
1. Power the home during a power outage in conjunction with the homes solar panels.
2. Store the energy from solar panels at off-peak times and feed the grid at peak loading.

To date there have been solar panel battery energy storage applications (SolarCity and Tesla partnership), vehicle to home (V2H) applications (MiEV Power Box, Nissan Leaf and Nichicon), and vehicle to grid (V2G) applications (University of Delaware, and others). However, no project yet has tied all of these new technologies together with solar panels, a bi-directional home electric vehicle charger, a separate home storage battery, and a master control system.

Members of this forum have demonstrated that these technologies can work now. Several members have solar panels and electric vehicles, you have these and also battery storage, and member siai47 has shown how to charge a MiEV at home with a 12kW dc fast charger.

 

[PV1]

Check these out:

http://www.greencarreports.com/news/1073736_mitsubishi-miev-house-2012-geneva-motor-show

https://www.youtube.com/watch?v=RTNM61W9lVU
(skip ahead to 2:30 for the main bit)

Bonus:
A commercial!:
https://www.youtube.com/watch?v=-KsU0KFfbtg

 

[JoeS]

...In regular use I have a larger bank of mismatched used EV (no longer suitable capacity for mobile applications) AGM lead acid batteries... Why only a 12 volt battery bank when 48V would be more efficient? It's much easier to use mismatched batteries if there are no series strings. Also a charged iMiEV battery could keep the critical loads going for up to 4 days through the DC to DC converter in the car (12 volt output). A Gasser can idle at about .6 gallons per hour cranking out 45 to 80 amps of charging power (again 12 volt output). So for the sake of flexibility of power sources 12 volts made the most sense to me...

Very good reasoning! While crusing on a catamaran for seven years I also had excellent results with paralleling mismatched 12v batteries and, not only that, I had no problem with mixed AGM and FLA, as evidenced by monitoring the individual currents going in/out of each battery and limiting the charging Vmax to 14.4v at room ambient. Although I now have paralleled 48v strings of 4 12v AGM, 4 12v FLA, 16 LiFePO4, and 14 Li(NMC) because of my boat's 48v outboard needs, your 12v system makes a lot of sense, at the expense of perhaps more copper to handle the higher currents.

I will add a caveat: I now use a circuit breaker in the positive leg of each individual battery or string. I did this after witnessing firsthand a battery explosion on a catamaran with a multiply-paralleled bank of FLAs. One cell in one battery had shorted and the remaining good batteries fed gobs of current into that shorted-cell battery to the point that the fluid in one of the good batteries boiled off and and an internal spark blew up the hydrogen in that good battery. Messy, but no fire.

In case anyone thinks paralleling mismatched batteries is a problem, here's a paper on the subject:
http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf

I don't know how many boats I encountered when cruising which replaced their perfectly good batteries in their paralleled banks when only one battery went bad, because the battery distributor told them you can't replace just one! :evil:

Sorry about drifting OT

 

[Aerowhatt]

Very good reasoning! While crusing on a catamaran for seven years I also had excellent results with paralleling mismatched 12v batteries and, not only that, I had no problem with mixed AGM and FLA, as evidenced by monitoring the individual currents going in/out of each battery and limiting the charging Vmax to 14.4v at room ambient. Although I now have paralleled 48v strings of 4 12v AGM, 4 12v FLA, 16 LiFePO4, and 14 Li(NMC) because of my boat's 48v outboard needs, your 12v system makes a lot of sense, at the expense of perhaps more copper to handle the higher currents.

I will add a caveat: I now use a circuit breaker in the positive leg of each individual battery or string. I did this after witnessing firsthand a battery explosion on a catamaran with a multiply-paralleled bank of FLAs. One cell in one battery had shorted and the remaining good batteries fed gobs of current into that shorted-cell battery to the point that the fluid in one of the good batteries boiled off and and an internal spark blew up the hydrogen in that good battery. Messy, but no fire.

In case anyone thinks paralleling mismatched batteries is a problem, here's a paper on the subject:
http://www.battcon.com/PapersFinal2002/McDowallPaper2002.pdf

I don't know how many boats I encountered when cruising which replaced their perfectly good batteries in their paralleled banks when only one battery went bad, because the battery distributor told them you can't replace just one! :evil:

Sorry about drifting OT

Sounds like we have come to many of the same conclusions. Actually a little innovative storage battery use experience doesn't feel off topic considering that they are more or less required to charge an iMiEV from solar "directly".

I figured on the shorted cell scenario even though it's an unlikely possibility. I have each battery wired to a positive and a negative busbar using #10 wire and each positive is fused within 2 inches of the battery positive post with a 15 or 20 amp fuse (Depending on condition and size of the used batteries). The fuses values, totaled up, add up to the fuse value required by the NEC + or - 10 %. The AHJ had a cow when he saw it but I explained it to him and then I overloaded the system with a clamp type amp gauge on the wires to the inverter. Within spec the fuses blew in a cascade. Once the first one goes the rest follow so fast that you perceive them going simultaneously. This saves a bunch of copper and lets me easily isolate each battery to test for stinkers once a year. The only high dollar heavy copper is from the busbars to the inverter.

Charging an iMiEV at the max of 12 amps at 120 volts is 1440 watts ac from the inverter about 1600 watts from the DC coming into the inverter. For my 12 volt storage that is a 135 amp load. The 2600 watts of solar panels could provide full L1 charging rate with some left over to charge the battery pack for 5 hours a day and tapering on each end. In a pinch, with the grid down, being able to charge the cars traction battery completely in two solar days and run critical loads at the same times. Now all I need is the car! Looks like that's going to be a bit of an uphill climb

Aerowhatt

 

[JoeS]

Back to inverters and grounding... came across this article where it's pointed out that portable EVSEs can actually be safer than hard-wired ones:

http://chargedevs.com/features/the-...director-thinks-the-standards-should-change/

 

[RobertC]

I will add a caveat: I now use a circuit breaker in the positive leg of each individual battery or string. I did this after witnessing firsthand a battery explosion on a catamaran with a multiply-paralleled bank of FLAs. One cell in one battery had shorted and the remaining good batteries fed gobs of current into that shorted-cell battery to the point that the fluid in one of the good batteries boiled off and and an internal spark blew up the hydrogen in that good battery. Messy, but no fire.

I figured on the shorted cell scenario even though it's an unlikely possibility. I have each battery wired to a positive and a negative busbar using #10 wire and each positive is fused within 2 inches of the battery positive post with a 15 or 20 amp fuse (Depending on condition and size of the used batteries). The fuses values, totaled up, add up to the fuse value required by the NEC + or - 10 %. The AHJ had a cow when he saw it but I explained it to him and then I overloaded the system with a clamp type amp gauge on the wires to the inverter. Within spec the fuses blew in a cascade. Once the first one goes the rest follow so fast that you perceive them going simultaneously. This saves a bunch of copper and lets me easily isolate each battery to test for stinkers once a year. The only high dollar heavy copper is from the busbars to the inverter.

Great stories!
The Tesla Model S 85kWh battery pack is composed of 7,104 individual cells in 96 groups of 74 cells in parallel. The nominal voltage of these cells is 3.7V. (Could we replace our LEV50's with these cells? That's another topic.)
As cells age or fail they become "mismatched," suggesting that you can parallel mismatched batteries.
Tesla "fuses" their individual battery cells in the pack with a thin wire that melts when there is an over current.
Here is a picture of the fusing from a Tesla Model S battery that was purchased by Tesla Motor Club Forum member wk057 for his off-grid solar project:

Of course you can't replace the melted thin wire like you can a cartridge fuse, and you can't reset it like a circuit breaker, but when the thin wire melts it removes the cell from circuit and prevents a catastrophic failure of the battery pack.

 

[ndm]

I have a solar powered cottage , it's run off of a 12 volt inverter fed by 2300 watts@30volts panels through a series of xantrex mppt controllers, I also have 2400ah @12 volts agm batteries, during a 2 week stay I brought the miev up as my run into town car (trailered up on my landscape trailer, since it was going up empty) I used the system when it was sunny only, I found plugging in when the panels were not producing was a large tap on the system(think of running a resistance heater on full) but when the sun was shining it makes more than the system needs and I dumped that into the car, consequently when winter hits I take all of my starting batteries and connect them to the aux load option on my charge controllers, keeps them from discharging and freezing, the point I'm trying to make is that if you would like to charge the car from solar it's best to do it low and slow when the sun is offline or do it faster when the sun is shining thus using the open circuit voltage of the panels and not wasting energy due to the lead acid sag , check out battery university and the effects of the sag from lead acid

 

[Aerowhatt]

That's one of the major strengths of the Tesla battery cell architecture. With 74 3.3ah cells paralleled together with the simple yet effective "fusing" if a (i'll call them sub cell fails it has only a small (1.35%) effect on the capacity or function of the entire battery. Trust me that those wire connections can easily handle anything a singe sub cell could put out. They are there to disconnect it if it develops an internal short only.

AC propulsion came up with this idea as near as I can tell. They called it "massively parallel battery architecture". The larger format cells (sub cells) used by the other EV's don't have this resilience. I don't know but the LEV50's are likely fabricated from 5 or fewer subcells. If one of those fails you loose 20% or more of your capacity for the whole pack.

Aerowhatt

 

[pbui19]

The panels are 60 cell SolarWorld panels for a total of 2600 watts, The charge controllers are Morningstar 65 amp MPPT units (three paralleled). In day to day practice the panels are grid tied, but are also wired to divert the DC to the charge controllers if the grid is down. A small investment IMO to keep the food cold and our kesters warm or cool (depending on season) during a prolonged outage.
Aerowhatt

Aerowhatt - I have plan to do a very similar configuration. Slightly OT, what grid-tie inverter are you using and how are the inverter & the charge controllers connected ? just paralleled in DC power ?

Thanks

 

[BenBrown]

PV1... Re: the videos... Wow... I lived in an eco cottage the first year out of college... The actual electric usage was under 2kwh per day. (based on billing/usage.) I could easily see an i-miev powering something like that and over time purchasing pv for both the home and transportation needs.

Unfortunately I think my current usage is several times more than that today, though a fraction of my neighbors... Still its incredible to realize I may be driving portable emergency electric back up.

Thanks for sharing the videos...

 

[Aerowhatt]

Aerowhatt - I have plan to do a very similar configuration. Slightly OT, what grid-tie inverter are you using and how are the inverter & the charge controllers connected ? just paralleled in DC power ?

Thanks

I went with micro inverters for the grid tied end of things. Enphase inverters, I liked several things about that approach. Most importantly is avoiding high voltage DC wired into your home. Especially from a source like solar panels which won't trip a circuit breaker but will support a very hot arc at high voltages.

The charge controllers are paralleled on the output side to the same battery bank. But on the input side each is fed by part of the array giving each charge controller it's own (sub) array to feed from. Each of the charge controllers gets power from three panels. Again, in the interest of safety and efficiency I paralleled each of the three panels rather than series wiring them. Heavier wire but a lower arc voltage and also the charge controllers are more efficient taking 30ish volts down to 12 volts battery storage than they are at reducing 100 volts to 12 volts. That leaves one panel odd man out. It's always connected to both a grid tie micro inverter and a smaller charge controller. That keeps the battery bank topped up and conditioned on a continuous basis.

The only drawback is the lack of complete automation. But a similar sized conventional grid tie with battery back up would have cost five or six times as much and would not be able to use used EV batteries for the storage bank. Also I kind of like that it has to be switched to backup by a person. Because in a house fire situation the first thing fire fighters do is turn off utilities. Which with automated systems turn on the backup AC putting first responders at risk. The NEC is beginning to address this, but right now very few products are to up to speed and another additional $1,000 or $2,000 equipment is required to resolve the issue. My lower tech way keeps the highest open circuit DC down around 42volts which would be very hard pressed to hurt anyone. When the AC main goes off, or the meter is pulled no backup AC comes on automatically. So the house is safe to work on for first responders.

Feel free to PM me for questions or details,
Aerowhatt

 

[pbui19]

what's your email Aerowatt, i couldn't find you on "Find members"
Thanks, Paul

 

[Aerowhatt]

what's your email Aerowatt, i couldn't find you on "Find members"
Thanks, Paul

Paul I sent you a Private message with my email address.

Aerowhatt

 

[SirCaptainAhab]

I DID IT!! MISSION ACCOMPLISHED!

I finally have created and am using, literally as I type this message, my all new "Portable Solar Powered Electric Vehicle Charging System"!! I finally got the whole system put together and working!!

1. I first had to send my EVSE charge cord to CA to get the upgrade. I can now adjust the amperage down to a 6 amp draw, instead of the standard 12 amps. This allows me to charge the car at a rate of 630-650 watts.
Cost, $320

2. Then, I upgraded to the Xantrex Pure Sine Wave 2000 ProWatt Inverter.
Cost, $350

3. Then, I got the Rynogy Charge Control and T5 Meter
Cost, $240

4. I replaced the batteries I had been using with 4 VMAX Tank AGM (Absorbed Glass Mat) sealed batteries, 155 AH each. I got these on www.bargainshore.com
Cost, $1,140

4. I had to get a 52" luggage rack. The first one I got, was 48"; not wide enough even for the i-miev!
Cost, $40

5. I now have a 215 Watt Moser Baer panel installed on the roof, secured to a luggage rack that I had to strap down to the hood. (I didn't trust the metal grips that lock onto the edge of the car to hold my solar "kite" while driving. The panel is secured to the rack with hinges and wing nuts for easy angling and securing while driving.
Cost, $125.

6. To increase the voltage, I added a smaller 100 watt panel I had laying around at home that I have wired in series to the 215 watt panel to increase the voltage. It easily just fits in the back seat.
Cost, $100

7. I use a Kill-O-Watt meter that I leave plugged into the Inverter, that tells me how much power I'm feeding to the car from the battery bank.
Cost, $20

8. Lastly, I have a 4 digit voltmeter wired to the battery bank to let me know how much charge I have.
Cost, $5

Total Cost: $2,340

As I've mentioned before, I live almost 33 miles from work. I use more than 50% of the charge to get here. This will allow me to charge the car enough to get back home, and then some left over. For every 1kw I add back to the car, I'm adding an additional 3.5-4 miles of driving range. So far, I've added 3.0 kW and increased my driving range by 11 miles. Today, I suspect I will have even more when I get ready to leave work here in an hour.

I ended up not having to use the yellow plug in that was suggested for tricking the ground fault.

And...guess what my employer just made officially available this week here on campus? 10 electric car charging stations! I already pay for parking, as an employee. If I want to park in the EV charging parking space, I'll have to pay an additional 75 cents/hr. It's good to know that its there and available, finally after waiting 3+ years, but I think I will work on recouping some of my project costs for now.

I'm adding some pics so you can see what my set up looks like. It's of my car in my parking space just outside my building.

Thanks for everyone's suggestions and advice as I began working on this.

Cheers!

Captain
SE Ohio
https://www.facebook.com/brian.mccoy.1840/media_set?set=a.1002141193169973.1073741826.100001223046280&type=3

 

[Phximiev]

How about a pic?

 

[SirCaptainAhab]

Im not sure how to add the pics here. So I created an album of pics on my fb page. The url is at the bottom of my msg.

 

[PV1]

Not bad. What does all that lead acid do to the ride?

OT - South Park Mitsubishi? Did that come with the car, or did you buy it there?

 

[JoeS]

Congratulations for getting your very own power station up and running, although that's awfully heavy and awfully expensive. Fun project for you! A few comments, if I may...

a) Presumably you will keep the bank fully charged at home using a conventional smart charger so when you get to work you can simply turn on the inverter and run it while the solar panel trickles a bit into the AGM bank. Does your conventional charger have temperature-compensated AGM setting to preclude charging over 14.4vdc at room ambient?

b) That's a very fancy charge controller for only one panel (which puts out 8A max), but at least you have expansion capability for the future. Ensure that you disable any Equalization charging phase and be sure the charging voltage is programmed for AGM. If it has a temperature probe, be sure to use it.

c) I fail to understand why you want to add the second panel in series, especially since the smaller panel may restrict the current flow through it? The single 215W panel has a MPP of 28.8v and the MPPT controller will probably keep it around that. Maybe I'm missing something here as I've never put mismatched panels in series (but have in parallel). What is the operating voltage of the smaller 100W panel, as maybe you could parallel the other panel for the desired power output increase? Interesting experiment to try doing it both ways to see which is best.

d) Do you have a low voltage cutoff to prevent the inverter from draining that AGM battery bank? Remember, for maximum life, FLA and AGM don't like to be regularly discharged much below 70% SoC.

e) Four 155Ah batteries contain a total of around 7.4kWh at a nominal 12v. Figure that gives you 2.5kWh usable, or a little under 4 hours of charging the car at 6A at 120vac if you want to keep the AGMs for a while. That will give you a little under three bars or about 12 miles?

f) In four hours you may get 0.5kWh back in from your solar panel, adding maybe a couple of miles.

g) As soon as you get home, be sure to immediately plug the charger back in to recharge the AGM bank; i.e., don't let the AGMs sit discharged.

Gosh, that's quite an expensive and complicated way of ensuring range peace of mind for your daily commute by adding 10-15 miles. Anyway, congratulations for biting the bullet and doing it!

 

[pbui19]

Captain SE Ohio,

I couldn't get to your fb page to see the photos ? so you are carrying the extra weight back & forth ? with the panel on top ?

would a pseudo sine-wave work instead of a pure sine-wave converter ?

I was thinking of doing something similar to your setup, except with pickup truck or an old car, configured with panel & batteries & converter & an AC plug, leave it parked on my work at a sunny spot and just plugged in for a few hours a day.

that's awesome what you've done !

 

[BradfordUK]

Hello im contemplating buying a used imiev and hoping my existing solar pv installation will work or help towards charging the car without any modifications, my panels were provided and installed free by Ashadegreener in the Uk and ive got a 4kw on grid system, im assuming when i get a home charger some how this will get connected and i will get some or all of the power they generate without any issues.. ??