# EV as solar Battery bank?



## Ziggythewiz (May 16, 2010)

Do you plan to leave the EV at home when it's sunny?

The simplest way to do what you want is just to use your EV's ACC batt with an inverter and run a cord to essentials and let the DC-DC keep the ACC batt full until the EV is drained.

Going through the house breaker would mean needing the mains feed cutoff, or using a grid tie w/ battery backup inverter to handle that part for you, and then you'd have to somehow feed your inverter(s) (typically 24 or 48V) with your pack voltage.


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## adeyo (Jun 6, 2012)

Yes, I intend to keep the car at home if power goes out. 

I already have the home wired with a grid disconnect and separate breakers for essentials. Plus, I have too many items to run an inverter. 

My Hope is to find a way to charge the EV battery directly (i will have an ac solar system due to the micro inverters) without damaging it due to possible voltage surges. 

Also, i want to be able to send my dc current back to my home from the EV batteries - possibly while even receiving a charge from the sun.


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## Ziggythewiz (May 16, 2010)

How much power will you need during an outtage? How big is/will the EV battery be?

If the solar setup doesn't use a large inverter, you have to have one to use the EV.


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## Ace_bridger (Nov 22, 2011)

I've heard that some people use a small petrol gen set for outages and, I think, they just plug it into one of the domestic sockets.

I'm not 100% sure that this is correct or even safe but ignoring those two things I wonder if you could do the same with the car and just run an inverter from the pack?

Or could you just disconnect the main supply to the house by removing the main fuse and bring the inverter feed from the car's pack in there, fused appropriately of course. You could then choose which domestic MCBs to have on or off dependent of what you deem essential...like lights, mircowave and Guitar Hero!


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## adeyo (Jun 6, 2012)

Ziggythewiz said:


> How much power will you need during an outtage? How big is/will the EV battery be?
> 
> If the solar setup doesn't use a large inverter, you have to have one to use the EV.


Without running the exact figures... I believe about 10 kw daily (my solar system can produce as much as 40kw/day). My EV pack... Haven't calculated but 20kw system? 20kw? Even with 50% dod I should be ok. 

Your right about the inverter. I guess I will need a large inverter to supply the kind of power I need. But if my vehicle charger takes a large amount of ac and converts it to dc, could it possibly do the reverse? I'm not well versed in this area.


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## adeyo (Jun 6, 2012)

Ace_bridger said:


> I've heard that some people use a small petrol gen set for outages and, I think, they just plug it into one of the domestic sockets.
> 
> I'm not 100% sure that this is correct or even safe but ignoring those two things I wonder if you could do the same with the car and just run an inverter from the pack?
> 
> Or could you just disconnect the main supply to the house by removing the main fuse and bring the inverter feed from the car's pack in there, fused appropriately of course. You could then choose which domestic MCBs to have on or off dependent of what you deem essential...like lights, mircowave and Guitar Hero!


Lol... Guitar hero comment. 

As for the generator, that is possible, although I already have a disconnect to the grid and my separate breakers wired up. I guess I will need a large inverter wired into the "essentials" breaker. 

Although, i feel as if my EV would already have this somehow? I mean, if I have an ac motor, shouldn't I already have a controller capable of taking my dc battery power and converting to ac? 

That means I just need to figure a way to move the controller connections from the ac motor to the home breaker right?


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## Ziggythewiz (May 16, 2010)

A charger is a one way device. There's no magical switch to make it work in reverse.

A car's inverter could push power back to the home, but it would have to be specially designed to do so and would probably cost 2-10x for the priviledge.

Unless you have weekly outtages, you're probably better off with a typical generator.


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## adeyo (Jun 6, 2012)

Makes sense... Only i would be looking at thousands and I also am exploring ways to go off grid. The money spent on a new generator might be more than a modified car inverter???


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## Ziggythewiz (May 16, 2010)

A generator costs a few hundred. You're looking at thousands to upgrade the solar to do something it doesn't want to do.

If you had a grid tie with battery backup this would be easy, but since you have microinverters you have to start from scratch.


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## Roy Von Rogers (Mar 21, 2009)

Most pfc chargers can handle dc input as long as in range of charger input voltage.

Thats one of the things about being tied to the grid, its called islanding, which means when there is no mains voltage, your done.

So in order to use your solar panels/EV you need to have a seperate house panel to use the dc supply in some manner, either dc directly or the use of inverter.

Roy


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## adeyo (Jun 6, 2012)

I currently have a disconnect already installed by the previous home owner... He had a propane generator and when power went out he would go off grid. 

I assume I could use my solar setup worth micro inverters and use the ac to go directly to my ev charger, and which should be able to accept variable voltages /amps, correct? (If i finagle a little) 

I think it is more tricky to go from EV battery bank to home circuit, no? 

I think it becomes more tricky to


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## Caps18 (Jun 8, 2008)

I will be installing a good sized inverter in my truck. But, the Enphase system I have goes down when the grid goes down right now. Luckily, I have only lost power for an hour in the 5 years I have been here.

It would be nice to have some way to charge the truck for sure, even if the grid is down. There are ways to do this, but it isn't straight forward.


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## Ziggythewiz (May 16, 2010)

Depends on your inverters, some require the grid to sync to or they won't turn on.

Charging the car depends on your charger, does it want 110V or 220? Can you adjust the amps or will it just fault if the power is insufficient?


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## Caps18 (Jun 8, 2008)

adeyo said:


> I currently have a disconnect already installed by the previous home owner... He had a propane generator and when power went out he would go off grid.
> 
> I assume I could use my solar setup worth micro inverters and use the ac to go directly to my ev charger, and which should be able to accept variable voltages /amps, correct? (If i finagle a little)
> 
> ...


With a good DC-DC converter and a 12V to 120V AC inverter, it might work.

You could always plug in your EV into your circuit breaker just like a gas generator backfeeds into it.

I was just going to run an extension wire through my house to my computer power strip, and possibly refrigerator.


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## jehan12413 (Feb 4, 2010)

Keep in mind that micro grid tie inverters have islanding protection so that they will not feed power back into the grid during power outages. I believe that is required by law to prevent injury to anyone working on the electric grid. What that means is that when the grid go's down you loose all your solar micro inverters. If you have a disconnect on your main breaker and then feed some power into your system from a generator or small stand alone inverter then all your micro grid tie inverters should come back on line and match phase with the power you are generating. What I do not know is weather the power generated from you solar array will damage your genarator/inverter.


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## adeyo (Jun 6, 2012)

Great to know. Thanks! I do have a disconnect (and will be required to have another (exterior) disconnect as well). 

Anyone know if a generator or inverter would be damaged by electricity from my solar array going directly to my home circuit? I guess my circuit would look something like this on a normal day... 

...... Solar array\
............................ > Home circuit
Grid Electricity /


Or like this on a power outage day, which is inefficient .... 

Solar array (ac) > inverter (now dc) > Battery bank > inverter (back to ac) >Home circuit essentials 

Or, possibly this on a power outage day (generator damage?)... 


Solar array \
.......................> Home circuit essentials 
..Generator /

When the generator kicks in and is of the grid, the micro inverters sense power has been restored and turn back on, thus supplementing the generator (possibly). 

Anyone know if this could work?


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## adeyo (Jun 6, 2012)

Also, i assume I might need a way to 'dump' electricity produced that isn't needed? I. E. If my solar panels produce it, I either need batteries to store it or a way to get rid of the extra, right?


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## Otmar (Dec 4, 2008)

adeyo said:


> Also, i assume I might need a way to 'dump' electricity produced that isn't needed? I. E. If my solar panels produce it, I either need batteries to store it or a way to get rid of the extra, right?


Yes, you need a dump load or some way to turn off your microinverters when the system is full. 

I do something similar with my 1970's Electrak set up with 180AH at 42V of lithium iron phosphate cells that run a 48V Magnum 4400W sine wave inverter. This converts power both for discharge and charge (the big heavy inverters do that, but not the light HF switchers). My Enphase microinverters only supply about half the available power from my 4kW system since they keep complaining and shutting down due to "unstable grid" when they try to link up with my Magnum which is providing the islanding function. The Magnum voltage varies more than they like. 

I manually switch off the main breaker and heater loads before I plug the tractor into the shop with a 14-50 suicide plug. I also have a separate 220V plug for the solar input which goes through a relay that shuts off when the cells are full or if the BMS detects a fault. 

Just to be clear, you don't do this to save money, you do it because it's fun and cool, but remember it's a fun toy. Generators are much cheaper. 

Here is a pic of the tractor running the shop power during the power outage last week:


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## dtbaker (Jan 5, 2008)

i've been picking around the edges of this myself... I'd love to be able to charge EV directly 'off grid' direct DC, then also be able to pump from car thru PV invertor to house at night or emergencies.

two issues become obvious rapidly..... there are no 'high voltage' charge controllers on the market i am aware of that could handle a typical EV pack in series at 120+vDC. most off-grid pv is set up for 24v or 48v battery banks.

then if you look at the feed back side.... the off-grid invertors expect low voltage, and the grid-tied invertors expect to see line voltage or shut down for safety. either way will require some real thought and design to be safe.

unless you've found something off the shelf I don't know about.....

the other thing I really don't get, and maybe somebody like Otmar can explain, is why you have to provide a dump for a PV system. Seems like if the PV output charge controller could be set accurately to whatever voltage you wanted your battery bank charged to, it would chug along at system capacity until voltage is reached and then just self limit with no amps flowing once battery bank hit 'end voltage'. wouldn't it?


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## Otmar (Dec 4, 2008)

dtbaker said:


> the other thing I really don't get, and maybe somebody like Otmar can explain, is why you have to provide a dump for a PV system. Seems like if the PV output charge controller could be set accurately to whatever voltage you wanted your battery bank charged to, it would chug along at system capacity until voltage is reached and then just self limit with no amps flowing once battery bank hit 'end voltage'. wouldn't it?


If you have a charge controller then you are fine. Any charge controller either dumps or shuts off the PV power. 
What I was referring to is a system like mine that utilizes many microinverters on the roof. Microinverters are mounted directly to each solar panel and the inverters are made to intertie to the AC grid up on the roof. The AC wiring goes to every panel on the roof, DC wiring is short and under the panel. Rewiring to get DC out of such a system would be very prohibitive so some of us have figured a way to fake the grid (islanding with another inverter) and in that way pull power off the AC output of the microinverters. Having done that, battery charge regulation is still needed since there is no charge controller in the system yet.


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## adeyo (Jun 6, 2012)

I decided today to eliminate the micro inverters from my system and go the dc route. Seems like or makes more sense based upon the great feedback here! I should be able to utilize many common parts from my ev for my solar array. (battery bank, bms system.. More??) Now if my power goes out for a few days, I can leave my ev parked and use it to store dc current from my PV array and power my home essentials from the EV battery. 

With the system being dc now, any tips on how I can best utilize my ev? 

Ex. (Normal day)... 
PV's to 'sunny island' to grid. (does this look correct?) 

Ex. (power outage)... 
PV's to 'sunny island' routed to battery bank (my ev) to house circuit 

Sunny island is an inverter / bms system in one... 
www.affordable-solar.com/store/archive-sma-inverters/sma-sunny-island-5048U-inverter 

Could I use this 'sunny island' as a grid tied charger/bms system on normal days to charge my ev??


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## Ziggythewiz (May 16, 2010)

That looks like an off-grid inverter. You want one designed for grid-tie w/battery backup.

I'd do a 48V and have 4 12V DC batts hooked up for when the car isn't connected, then get a charger that can take the 48V DC to charge your ev (have you decided a voltage for that?) or run any normal charger via the inverter. Then get a DC-DC converter that takes pack voltage and steps it down to 48 to run the inverter when the solar is insufficient.


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## adeyo (Jun 6, 2012)

I was told the inverter is actually designed to kick on if the grid goes down... But I thought it performed a function when the grid was on too? 

I am going with a 144 volt system for my ev. ...Basically, i want to be grid tied with ability to run when grid goes down... And i dont need to drive my ev on those days. On Days the grid is up, I'll drive my ev. I'm trying to share whatever (ev/PV system) in order to keep costs down.


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## Williewilliams (Jan 2, 2013)

adeyo said:


> Hi, I am currently purchasing a 10kw solar system for my home. It will have micro inverters and be a led bulb grid tied system. I am also trying to begin a ev project of my own. I would like to use my EV battery as a back up bank for my home needs (essentials) when the power goes out. I have two needs I guess:
> 1. Be able to charge my battery via my solar system (somehow dump the excess power)?
> 2. Be able to send power from my ev battery to my essentials breaker in my home.
> 
> ...


Have you purchased solar system? I am willing to have a solar system for my home.


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## shoup (Feb 10, 2009)

adeyo said:


> Sunny island is an inverter / bms system in one...
> www.affordable-solar.com/store/archive-sma-inverters/sma-sunny-island-5048U-inverter
> 
> Could I use this 'sunny island' as a grid tied charger/bms system on normal days to charge my ev??


The Sunny Island is not a grid-tied inverter. 

I have been toying with the idea of using my EV as the battery backup since I installed my 5.5kw solar system last year. My biggest issue is working with the anti-islanding protection on the Sunny Boy grid tie inverter. To do battery back-up the right way I would need to purchase another inverter i.e. SunnyIsland to kick on when the grid goes down. I believe the SunnyBoy sends out high power elecrical pulses to the grid as part of the anti-islanding protection. The artificial grid created by another power source (generator, sine wave inverter/battery, etc.) cannot absorb these pulses so the SunnyIsland shuts down until the grid comes back up.

With the SunnyIsland I was going to wire the batteries in the car into 48V packs to work with the solar inverter/charger for backup. When there is not a power outage the backup would just be 4x 12V batteries. 

As Otmar mentioned you don't do solar battery backup to save money. There are much cheaper options especially with how stable most of the grid is in the US.


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## prensel (Feb 21, 2010)

All grid tied solar inverters have anti-island protection.
What you can do is to fake the grid from your batteries when the grid goes down.
The solar inverters will keep working as long as you absorb the power they produce. When you cant absorb any power just change the faked grid frequency a few Hz and the solar inverter will stop working.

Take a look at the Victron Phoenix Multi AC inverters they will do the trick.
We have used them many times for this purpose.


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## spdas (Nov 28, 2009)

I don;t know beans about grid-tied system. But I have been off-grid, running my home and small factory on solar only for 4+ years now. (100 panels, 9 outback charge controllers and 8 or so large electric forklift batteries.
Panels are cheap now (.75 a watt), so why not dedicate 12 panels for off grid use, unless somehow grid-tied will work. I charge my 46 180ah calbs 1/2 pack at a time (80volts). Yes outback only says 60v on their specs but they do 80v @60 amps. Charging 1/2 pack at a time has had no problems and throttle down to .1 amps and nail the voltage to 80v each 1/2 pack. Anyway works for me. And I have a second system using 16 TS 400ah storage batteries through a Outback charge controller that runs all my more sensitive electronics. (ie no fridge, or pool pump or welding machines on this system)


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## shoup (Feb 10, 2009)

prensel said:


> All grid tied solar inverters have anti-island protection.
> What you can do is to fake the grid from your batteries when the grid goes down.
> The solar inverters will keep working as long as you absorb the power they produce. When you cant absorb any power just change the faked grid frequency a few Hz and the solar inverter will stop working.
> 
> ...


Have you used the Victron Phoenix inverter/charger with the SunnyBoy grid tie inverter? The Vitron Phoenix is still more than I would like to spend on something that may or may not work. Not all anti-islanding technology works the same.


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## Caps18 (Jun 8, 2008)

I wish Enphase or some other grid-tie company would come up with a way that would let you turn off the main breaker in your house, and then turn on the solar panels with a 12V starter battery and an inverter of sorts.

Yes, this device would have to monitor the battery bank to ensure it wasn't getting too full, but turning off the inverter should be easy.

It has been a long time since I have lost power, but now that I have solar panels, it will be kind of sad if a big disaster happens and I couldn't use them to get power.


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## Ziggythewiz (May 16, 2010)

I haven't looked into it for a while but when I did it seemed there were standard options for grid-tie w/ battery backup that would run just fine when the grid was down.


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## Caps18 (Jun 8, 2008)

I researched one option for a big inverter with battery system, but it cost 3 times as much as the microinverters I got. It isn't to say that technology hasn't changed, or I haven't heard of some product that does what I am looking for.

Although to be honest, it wouldn't be a very good business to be in... The grid is too reliable now, and if the power did go out for days or weeks at a time, there would be other problems.

Now being able to drive someplace close by to charge your EV up, and then have a big enough AC inverter be able to run some things in your house would be something to look into. At least some fans, laptop, and lights.


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## tenthousandclowns (Jun 21, 2012)

Previous poster mentioned that most PFC chargers would run on DC.

I have delta-q quiq chargers for my car. would these run on DC? If so, why wouldn't I get a dc grid tie solar system with a big old anderson disconnect, and when the power goes down I take the dc ouput from the panels and unplug it from the grid and plug it into the car. Then I could get a Blue Flash inverter and have 2kw of ac to use. I would make sure the solar array voltage was between 85 and 265v, as specified by delta-q. A 2 kw solar system could power 2 of the quiqs.

Any thoughts?


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## tenthousandclowns (Jun 21, 2012)

Still looking into this solar power business. Still am curious if anyone has any experience running DC into a delta-q quiq or similar charger. Anyone?

Luke


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## adeyo (Jun 6, 2012)

tenthousandclowns said:


> Previous poster mentioned that most PFC chargers would run on DC.
> 
> I have delta-q quiq chargers for my car. would these run on DC? If so, why wouldn't I get a dc grid tie solar system with a big old anderson disconnect, and when the power goes down I take the dc ouput from the panels and unplug it from the grid and plug it into the car. Then I could get a Blue Flash inverter and have 2kw of ac to use. I would make sure the solar array voltage was between 85 and 265v, as specified by delta-q. A 2 kw solar system could power 2 of the quiqs.
> 
> Any thoughts?


Would love to see someone comment on this quote. 

Also, what is a blue flash inverter? Could I run it on my Nissan leaf?


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## adeyo (Jun 6, 2012)

Also, I edited the original post. Any thoughts now that I have chosen a DC to inverter setup and settled in on a Nissan leaf?


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## PStechPaul (May 1, 2012)

I would think these would run just as well (if not better) on DC, but the usable and safe voltage range would probably be 120-375 VDC which is the peak voltage for 85-265 VAC. But the PFC input circuit may change that, and might need to be bypassed to work properly on DC. Here is the website for the chargers that I found, for reference:
http://delta-q.com/product/quiq-charger?/products/quiq.shtml


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## major (Apr 4, 2008)

tenthousandclowns said:


> Still looking into this solar power business. Still am curious if anyone has any experience running DC into a delta-q quiq or similar charger. Anyone?


Sorry clowns, adeyo,

I hadn't seen the question until now. We use the QuiQ DeltaQ chargers for our eKarts and had inquired of DeltaQ company and were told that they would operate from a DC source without modification. We never did try though.

major


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## Zak650 (Sep 20, 2008)

Hi,

I've been running 600 watt exeltech inverters off my pack for about a year now. I've bottom balanced the pack and split it so I can draw off 1/2 of the pack to each inverter. Recharging each half seperately with a 48v NG1. I had the utility company set my account to time of use metering. The living room, computers, light loads, and even the refrigerator can all be run off the inverters. By recharging the pack in the lowest rate time only and minimizing any draw during peak hours, I've cut my electric bill to about 1/3 of what it was previously. 

Time of use electric rates:
Low $.10-.11/kwh	
Med $.17-.18/kwh	
High $.28-.29/kwh

Time of use rate structure:
Monday: 
Low: midnight to 5pm, 9pm to midnight	
Med: 7pm-9pm
High: 5pm-7pm

Tues-Fri:
Low: midnight to 10am, 9pm to midnight 
Med: 10am-1pm, 7pm-9pm 
High: 1pm-7pm	

Weekends:
Low: midnight to 5pm, 8pm to midnight 
Med: 5pm-8pm 

It's really not that difficult to setup and adjust your electrical life to it.

Zak


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## adeyo (Jun 6, 2012)

Pretty cool Zak!
thanks for the insight. I will keep that in mind as I take the next few steps.


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## adeyo (Jun 6, 2012)

major said:


> Sorry clowns, adeyo,
> 
> I hadn't seen the question until now. We use the QuiQ DeltaQ chargers for our eKarts and had inquired of DeltaQ company and were told that they would operate from a DC source without modification. We never did try though.
> 
> major


thanks major. I'll have to follow up and ask them some more specific questions. I could not find a number on their website, do you imagine a product like that can accept a variable DC input as long as that input stays above xxx volts, could it charge a battery at a constant xxx volts?


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## Roy Von Rogers (Mar 21, 2009)

Zak650 said:


> Hi,
> 
> I've been running 600 watt exeltech inverters off my pack for about a year now. I've bottom balanced the pack and split it so I can draw off 1/2 of the pack to each inverter. Recharging each half seperately with a 48v NG1. I had the utility company set my account to time of use metering. The living room, computers, light loads, and even the refrigerator can all be run off the inverters. By recharging the pack in the lowest rate time only and minimizing any draw during peak hours, I've cut my electric bill to about 1/3 of what it was previously.
> 
> ...


That's real interesting Zak, could you show how many cells and how you set it up, voltage of each pack etc. I'm thinking about doing the same and would be interested in how you did it, and how you switch it, if the battery power goes too low for any reason.

Roy


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## Ziggythewiz (May 16, 2010)

I had considered doing something similar especially with one of the local providers offering 'free' nights. Unfortunately their definition of free is probably more like $0.10/kWh while my regular rate is ~$0.07


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## major (Apr 4, 2008)

adeyo said:


> thanks major. I'll have to follow up and ask them some more specific questions. I could not find a number on their website, do you imagine a product like that can accept a variable DC input as long as that input stays above xxx volts, could it charge a battery at a constant xxx volts?


Yes. I think so. It should regulate the proper charge algorithm even as the input varies.


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## tenthousandclowns (Jun 21, 2012)

To answer adeyo's question:

A blue flash inverter is a higher voltage inverter that can take your battery voltage directly if it isn't too high.. your nissan leaf is too high... I've never used one. Probably will get one once I get the solar on the house going...

http://www.kta-ev.com/category_s/1932.htm

I think this is a very important thread and one that foretells the end of electric companies...


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## raoulduke (Nov 26, 2013)

Hi all I'm new here I've searched and it looks like this is the best thread for me to ask my question:

Similar to how was sort-of discussed earlier in this thread, I want to plain-and-simply charge a battery bank with solar, then hook that battery bank to my EV (will use the Leaf as example EV) and transfer the charged batteries' electricity to the car battery bank - can it be done? And if (very hopefully) yes, what equipment would be needed? (besides panels and external battery bank)

PS - I've done a little bit of research, and have found similar questions, and they all seem to be 'dismissed' without providing an actual answer, but instead all diverge to the same conclusion (something to this effect): 'Don't bother!! Just use the solar panels to tie into grid and use grid power to charge your car!!' Yes, I realize that option_ makes the most sense_, but be that as it may, let's assume that's not an option - only option is connect charged solar-powered battery bank directly to EV (somehow?) and transfer E from battery bank to car battery bank - how do we do it? (please!) Thanks in advance!


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## dtbaker (Jan 5, 2008)

raoulduke said:


> Hi all I'm new here I've searched and it looks like this is the best thread for me to ask my question:
> 
> Similar to how was sort-of discussed earlier in this thread, I want to plain-and-simply charge a battery bank with solar, then hook that battery bank to my EV (will use the Leaf as example EV) and transfer the charged batteries' electricity to the car battery bank - can it be done? And if (very hopefully) yes, what equipment would be needed? (besides panels and external battery bank)
> 
> PS - I've done a little bit of research, and have found similar questions, and they all seem to be 'dismissed' without providing an actual answer, but instead all diverge to the same conclusion (something to this effect): 'Don't bother!! Just use the solar panels to tie into grid and use grid power to charge your car!!' Yes, I realize that option_ makes the most sense_, but be that as it may, let's assume that's not an option - only option is connect charged solar-powered battery bank directly to EV (somehow?) and transfer E from battery bank to car battery bank - how do we do it? (please!) Thanks in advance!



the major challenges are that off-grid PV-battery systems are not available at high enough voltages to have the PV system bank at a voltage higher than your EV. So you have to either find/build high voltage DC charge controllers to charge the high-voltage PV bank, or use dc-dc transformer to step up the voltage, and then still need a high voltage charge controller to charge from the PV bank to your EV.

then.... you have to figure out how to start/stop charges SAFELY and accurately to as not to ruin batteries.....


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## raoulduke (Nov 26, 2013)

Thanks soo much, Dan! *Exactly* the info I'm looking for!  Thanks again.


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## dtbaker (Jan 5, 2008)

raoulduke said:


> Thanks soo much, Dan! *Exactly* the info I'm looking for!  Thanks again.



you are certainly welcome.... I am still pondering and puttering along these lines myself.  

The problem is that the existing off-grid PV solutions were almost all designed not to exceed 48volts, mostly for safety of the operator so they would have a hard time electrocuting themselves.... Obviously, we need a battery bank ABOVE our pack voltage to charge with.

grid-tied PV systems generally have high enough voltage DC from panels piped into the main invertor... 200-300 volts DC is not uncommon. But, then you are back to AC power downstream of the main invertor. Theoretically, a grid-tied main invertor would be a good place to plug your EV in place of the PV panels if you wanted to run your house from the car pack at night.... BUT you'd first have to disconnect your house from the grid (so your car wouldn't try to power the neighborhood!) , and grid-tied invertors are designed to shut down if they don't see AC power on the output side.... to prevent energizing the grid when the regular power is out, so you don't kill linesmen, or blow up your system trying to power the neighborhood. So..... you'd have to isolate your house, turn off all big loads, THEN run a separate small invertor to energize the house AC to fake out the main invertor, then connect the main invertor, then bring house loads back on line.

nobody I am aware of has 'packaged' this.

thats just the second half.... how to power the house with your car. The first half being direct dc-dc charging of the car. If you had a high voltage (grid tied) PV system, you could theoretically disconnect the input to the main invertor and dump the juice into your car, if the system voltage is higher than the car. BUT, there are no commercially available high-voltage charge controllers handling high voltage, high amp dc-dc charging I am aware of.... turning 200volts and 20amps on and off is something you have to be pretty careful with. Getting an accurate charge into the battery pack, and stopping gracefully, is not easy to do....


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## major (Apr 4, 2008)

raoulduke said:


> Hi all I'm new here I've searched and it looks like this is the best thread for me to ask my question:
> 
> Similar to how was sort-of discussed earlier in this thread, I want to plain-and-simply charge a battery bank with solar, then hook that battery bank to my EV (will use the Leaf as example EV) and transfer the charged batteries' electricity to the car battery bank - can it be done? And if (very hopefully) yes, what equipment would be needed? (besides panels and external battery bank)
> 
> PS - I've done a little bit of research, and have found similar questions, and they all seem to be 'dismissed' without providing an actual answer, but instead all diverge to the same conclusion (something to this effect): 'Don't bother!! Just use the solar panels to tie into grid and use grid power to charge your car!!' Yes, I realize that option_ makes the most sense_, but be that as it may, let's assume that's not an option - only option is connect charged solar-powered battery bank directly to EV (somehow?) and transfer E from battery bank to car battery bank - how do we do it? (please!) Thanks in advance!


I don't really understand your problem. Yes, it can be done. You need the proper equipment as in the chargers and charge controllers. I don't think there are any OTS (off the shelf) systems you can just order and install. A competent solar PV installer may be able to design such a system for you. Maybe check with Manzanita Micro. I think Lightning is using their chargers for the race bikes from the portable PV array.

Another option is to concede to the AC link even if it is not grid tied. Then you can use standard EV chargers. You would also have 60Hz power available for other equipments in your garage/home. The AC link is likely a less expensive option than DC only. Transformers are a lot cheaper than DC/DC converters.

A favorite approach of mine which is seldom taken seriously is the modular battery. Have a universal battery which you can charge from any of a number of sources including PV. Have a sufficient number of those batteries. Have the EV designed to accept those batteries in such a way as they are easily removable. Have other equipments designed to operate on the same batteries. Have enough batteries charged so you can load the EV and then put the extracted batteries on charge while you're out driving around. As the batteries age and see a decrease in energy density, dedicate those to stationary jobs where the "range" isn't an issue.

There are people using EVs with homes which are off-grid. But I think they had to be creative and find their own solutions. I knew a guy who totaled his Tesla Roadster and intended to use that battery for his off-grid home.

You mention the Leaf. Those come with the L3 charge port, don't they? That is a DC input isn't it? 

I know a guy with a Leaf. He has a good size solar array in his yard. His inverter is mounted on the wall of his garage next to his EVSE for the Leaf. Yeah, it is grid tied, but what's wrong with that? His PV production per month exceeds his charger use, so he's driving on the sun, isn't he?


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## raoulduke (Nov 26, 2013)

Wow to say you guys are a wealth of knowledge is definitely an understatement! Great stuff! Thanks again for info and potential resources!!  I'll post reply with more details about what I have in mind in coming weeks.


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## adeyo (Jun 6, 2012)

Good luck Raoulduke! I look forward to seeing what you come up with. I now have a nissan leaf to go along with a 10 kw solar array (not micro inverters like I originally thought). I plan on simply charging while grid tied. It might be possible to charge when grid goes down using a small inverter generator to produce the required Sine wave to fool the system into thinking its grid tied. Wish I knew the best way to use that power from my nissan leaf to power my home essentials panel. (well pump, hot water heater, a few lights etc etc)


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## tenthousandclowns (Jun 21, 2012)

In regards to the question about using off-grid solar to charge an EV: The simplest way (not the cheapest or best), is to get an off-grid system with battery-backup, and get an inverter that is rated for more than the level one 120vac charging of your EV... There are basically off-the-shelf options for this.

What I am trying to do is not get the second stationary battery bank and the extra switching between AC and DC.

I have a Midnite Solar classic lite 250ks charge controller that can charge up to 150v, which works for my lower-voltage EV. That will carefully charge the EV batteries directly from the solar. I will post more info when I get it hooked up.


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## dtbaker (Jan 5, 2008)

tenthousandclowns said:


> What I am trying to do is not get the second stationary battery bank and the extra switching between AC and DC.
> 
> I have a Midnite Solar classic lite 250ks charge controller that can charge up to 150v, which works for my lower-voltage EV.



very interesting..... do you have a link/source to read more about this charge controller? cost? can you set the 'hold' voltage or charge curve?


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## tenthousandclowns (Jun 21, 2012)

The manual is at:
http://www.midnitesolar.com/pdfs/classicManual.pdf

Keep in mind the KS suffix is the only one that can do the high voltage batteries...
They are about $600, I got mine on Ebay for $425... The "lite" version is harder to program.. I have not yet been able to get it to talk to my computer, which is necessary for programming it to charge an unusual battery.. I might buy the front module with buttons which allows it to be programmed directly.

It seems like the charge specifications are very customizable, but I haven't gotten that far yet..


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## dtbaker (Jan 5, 2008)

looks promising for battery sets less than 150v nominal..... keep us posted!


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## tenthousandclowns (Jun 21, 2012)

This is what I am planning on as of now..


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## tenthousandclowns (Jun 21, 2012)

Not going so well.

The Blue Flash inverter put out a very weak 80vac or so and had a connection that needed to be jiggled to function so I returned that.

I am considering a small 24v pack in the car, or a more robust 12v pack, with a bigger dc/dc. these would be to run a standard 12 or 24v input inverter.

On the input side, I ordered the programmable panel for the charge controller, but now the firmware needs to be updated... arrrg. Also I hear that the KS series has ben discontinued, so they only sell ones that charge lower voltages now.


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## joeblack5 (Apr 21, 2009)

This is not hard as long as you integrate all systems.
We have a 8 KW solar array with 2x outback grid tie battery backup inverters GVFX3648. We use our 48 volt electric forklift as battery backup. This is all of the shelf and hardly more expensive then then "normal" grid tie systems without battery backup option.
The higher cost is in the battery. But if you use an existing set up like a forklift or EV then you have an extremely high value for money
If you choose your EV battery at multiples of 48 volt and wire your EV such that you can parallel your 96 VDC or 144 VDC system in 48 volt sets then you can or charge directly from your charge controllers and or run your inverters directly from your EV.

Battery backup grid tie inverters have a somewhat lower efficiency then direct high voltage grid tie. This is not counting the charge / maintain losses in your battery bank.

Our system runs at about 85%, a direct grid tie would be closer to 92% .

Later j


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## dtbaker (Jan 5, 2008)

joeblack5 said:


> If you choose your EV battery at multiples of 48 volt and wire your EV such that you can parallel your 96 VDC or 144 VDC system in 48 volt sets then you can or charge directly from your charge controllers and or run your inverters directly from your EV.



that's part of the problem... available off-grid or hybrid inverter/chargers from companies like Outback, Xantrex, etc operate at 48 volts at most. So, you have to charge in 48v chunks, presenting balancing issues. Additionally, most of the hybrid/off-grid charger/inverters are set up for either flooded lead, or AGM charge curves.... SOME allow 'custom', which might be suitable for lithium, but I dunno if the end of charge voltage control is accurate enough to trust with LiFePO4.

The grid tied PV systems generally have DC coming in at 300vDC.... which would be great if we could find a reliable DC-DC charge controller that could handle that DIRECTLY to charge at full pack voltage without two inversions from DC to AC, and then back to DC....


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## joeblack5 (Apr 21, 2009)

I agree that would be nice and clean solution. I do not know about the accuracy of the charge controllers but since they have a thermistor for voltage corrections I would think that they are able to handle accurate shutoff voltages.

For our application the real problem is how to get the energy out for the cars battery and back into the house. From a code perspective 48 vdc is the maximum battery voltage allowed, for whatever that is worth. I am happy that i can still touch the terminals of my forklift and not be to worried about the shock. 300vdc or higher would need a lot more safety procedures.

In the future when electricity price is stronger linked to date and time it would be interesting to charge the battery at low energy price and deliver some back during peak hour.

The losses from a grid tie solar system at 300 vdc and two conversions, one more then direct solar charging into battery are not that high and it would be much cheaper to throw one or two panels more on the roof.

Later j


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