Make the i3 battery an emergency home power source

[jadnashuanh]

I read somewhere that EV's sold in Japan (may only be vehicles built there) are required to be able to be a backup power source for the grid. This, in response to their nuclear power plant problem, is supposed to help should there be a future power outage. Especially with the larger batteries in the upcoming 2017 MY i3, would provide 2-3 or maybe more days of power for the typical home, if you were being somewhat conservative. Now, it would also require some interface in the power panel and grid to get the phasing proper and prevent electrocuting someone, but with the built-in cellular connection, this could be managed from some central location, and if you had a power transfer switch, at least provide local power if not available to help out the grid. In some ways, much safer than having a fossil fuel burning generator that kills operators with CO, and much quieter!

 

[Schnort]

I recently had a 28 hour power outage. Such a thing would have been nice, and spared the contents of my fridge and freezers.

 

[PluviaPlumbum]

Interestingly Nissan are trialling this technology here in the UK ! Auto Express article last week

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj4n8-QgPvMAhVMAcAKHVWMCsgQFggcMAA&url=http%3A%2F%2Fwww.autoexpress.co.uk%2Fnissan%2F95493%2Fnissan-reveals-future-electric-tech-including-car-to-grid-system&usg=AFQjCNHntiyQ4S4F--92hd3TnYOhP0ijBA&sig2=mA9weybIDbSsO12tiAfoAQ&bvm=bv.122676328,d.ZGg

 

[jadnashuanh]

The Nissan concept is an interesting long-term goal, but, I think, the first step is to provide an interface in the car to power the home in an emergency. Once that is more commonplace, extending that to the whole grid makes a lot of sense, and a good goal. Inductive charging built into our roads and or parking spaces on any scale is a very long ways in the future. On an individual basis, could happen very soon. There have been some standards meetings and a draft design for a common system of inductive charging. Hopefully, that will happen sooner so that we don't get multiple, incompatible standards like we have with level 2 and DC fast charging stations.

The solar energy hitting the earth is way more energy than needed to power everything, but it is not on 24/7 in any one location. The hassle has always been load leveling, energy transmission, and storage technology.

 

[fdl1409]

I have been thinking about that a lot. Would love to have an emergency power supply. With only 300 - 500W I could run heating ( have a wood pellet heating which needs 300W for 12 minutes to start, then only 40W to run continuously ), fridge, LED lighting, PC, TV. Enough to get through a longer power outage comfortably for several days with a fully charged battery. All of those have a plug or are available with a plug, so one could easyly operate a small power island independent of the grid.

All one would need is a sufficiently powerful 12V outlet on the i3 which can deliver 300W ( 500W peak ) continuously. Small power inverters of that size are available at prices of only some 100-200 $.

In theory very easy and low cost to implement.
Probems:
- powerful 12V socket
- ought to be operating with the car switched off
- must run with minimum standby losses in the car. Car remains sleeping, only DC-DC inverter is active, maybe intermittendly when using the 12V onboard battery.

I believe such an emergency power function would be another very tempting argument to buy an EV.
One could even use that for 24h solar power supply. Charge the car during the day, use some of that in the night. If not for 100% of all power consumption in the house, but for a good share of that.

Frank

 

[psquare]

Using a car battery like this would severely impact its lifespan. While using EV batteries for home provision would be a great solution, I have severe doubts that the current generation of batteries can cope with the charge/discharge cycles. It will also have implications for the manufacturers warranty, which is based on using the batteries for transport. It's a also not practical. What do you do if you have a power cut, but your spouse is away on a business trip with the EV?

Imagine someone would constantly use their car engine to drive a generator to power a house (or part of it) and then complain to the car manufacturer that the engine breaks earlier.

In the medium to long term, I believe separate home storage systems would be a smarter solution.

 

[PhilH]

Using a car battery like this would severely impact its lifespan.

Not necessarily - it depends on how far you discharge them, what voltage you charge them to, their temperature and other factors. It may slightly impact their lifespan, but careful management would allow a huge benefit from using EV batteries for storage. MacKay's book (Sustainable Energy - without the hot air) regards this as a potential way of making renewable power work as a replacement for carbon-based power.

The reason they make more sense than separate battery packs is that you've already bought the battery, so using them for two purposes rather than just one makes a lot of sense.

 

[Schnort]

It would have to be an 'almost free to me' feature to interest me. My house has had one long term power outage in the 15 years I've lived in it. It would be tough for me to justify spending much more than $200 or so for this feature. Maybe $500 for the peace of mind, but rationally, my economic loss from power outages in 15 years was two fridge/freezer contents.

Sure, others may have more spotty power (like gulf coast inhabitants) where a day or two from hurricanes/tropical storms every few years is pretty common, but not for me.

 

[psquare]

MacKay's book (Sustainable Energy - without the hot air) regards this as a potential way of making renewable power work as a replacement for carbon-based power.

Not disagreeing with what you're saying, but the book you've quoted is old now and in some aspects - especially PV Solar - out of date.

Generally (and I've mentioned this already), I don't understand and find it impractical to rely on a storage power that has wheels and could potentially be away when you need it the most.

 

[PhilH]

Generally (and I've mentioned this already), I don't understand and find it impractical to rely on a storage power that has wheels and could potentially be away when you need it the most.

I accidentally hijacked this thread somewhat, because I was thinking in terms of electrical storage on a national scale, rather than as an emergency single location thing. I agree the latter isn't worth much, since in most locations where i3s are likely to be purchased, the electricity supply is likely to be pretty reliable. As a national way of storing wind/solar produced energy, it's a much better proposition, since your car may not be at home, but on average other people's will be at home, especially at night, when there is no solar...

 

[bwilson4web]

My first Prius and its first modification: http://hiwaay.net/~bzwilson/prius/priups.html

During the April 2011, tornado power outage, 4 days and 6 hours, we camped out in the house burning 2 gallons/day. We had heat because it could run the fan and electronics of our natural gas fired heater.

I had thought about doing a similar modification for the BMW i3-REx but it has automatic shutdown options which I don't fully understand. So I am taking a different approach.

Source: http://www.costco.com/Honeywell-17-kW-Automatic-Standby-Generator.product.100144364.html

Fueled by natural gas, this unit will provide automatic cut-over in the event to a power outage. At 17 kW, it has enough power to handle the house and put a Level 1 charge on the BMW i3-REx. The only drawbacks:

• air cooled engine - I want the latent engine heat for hot water and space heating but I don't want any engine heated air that might contain carbon monoxide from a leaking seal.
• muffler is another opportunity - it is tricky because cooling the exhaust condenses water which is highly corrosive. However, a gas fired, water heater might be just the trick. Insulate the muffler and pipe that feeds a water heater to pre-heat water to the bathroom sink and shower.

Our local utility rate is ~$0.09/kWh and based upon the efficiency of this unit and cost of natural gas, it will run ~$0.18/kWh from the generator. The only way to further reduce my costs is to reuse as much of the waste heat as possible in a safe way.

A big part of the inefficiency comes from the air-cooled engine. Unlike liquid cooled engines, they typically run richer mixtures due to their dodgy cooling. But I could not find a liquid cooled engine until the much larger, industrial sized generators.

Regardless, this will be good enough since we'll also update the house wiring at the same time and that includes a NEMA 14-50 plug for our EVSE.

Bob Wilson

 

[jadnashuanh]

You don't have to be in hurricane or tornado alley to be unlucky enough to have an extended power outage! Northern states can get hit with those, as well as ice storms, that can mess things up for a long time as well.

It would be nice if you could just use the i3's battery to power your house. Certainly, their latest product using a detached battery pack could be useful (but not inexpensive!). But, if there were an accessible connection in the car, maybe they could then let it just plug into the inverter and logic of the external one they showed?! Much cheaper than having to buy an extra battery pack! As I said earlier, it appears that EVs sold in Japan are required to be able to do this, at least those built in country.

 

[davidzi3]

I got an opportunity to test this out during the October Hurricane in Florida. I bought a 1000 watt inverter at home depot just in case we lost power (we only had the power flicker a few times during the storm). I connected the inverter to the 12v battery and tested running lights and full size fridge from the car battery (let run for a few hours just to make sure it would work if we had a power outage). Below are the steps taken to do this:
1. Remove front trunk plastic storage bin by unscrewing about 4-8 screws.
2. Connect alligator clip to battery. Battery is located just to the passenger side of center, but its under the dash and a little tricky to reach.
3. Run extension cord into house from car. I ran cord under the hood and I was able to close the hood, but if doing long term maybe run underneath the car to avoid pinching the extension cord.
4. I think I put car in ready mode for fear of discharging the 12v battery. But its was 2 months ago and now I can't remember for sure. Keep in mind to leave car in ready mode you can't open driver door, you need to go out passenger door.

I think I drained the main battery by about 5% doing this for a few hours. The inverter did switch off on me once at first but I reset it and it didnt happen again. That could have been inverter issue, the fridge starting wattage peak, 12v battery low voltage, etc. I never identified the cause since it only happened once, I'm not an electrician and I was just happy that it didn't happen again. At least my inverter had an alarm that signaled it was not working, but its something to keep an eye on if you do this yourself in case it had something to do with the car.

 

[abs]

It works. Powered my refrigerator, kurig coffee maker, laptops and cell phones during our almost 3 full day outage from Hurricane Irma. My wife recently purchased a 2014 i3 with a REX (22 KWatt battery) The battery posts on the REX are easily accessible by removing the panel in the back truck. I picked up a 1500 watt inverter from a NAPA Autoparts store, 3 feet of 6 Guage flexible cord wire and some electrical clamps from Home Depot. I also modified an extension cord to provide a ground to the inverter from and electrical outlet. With the larger wattage inverters, it's important to use heavy guage wire and good clamps that can be tightened with a wrench. It was all ready to turn on when power went out at 4:12pm on Sunday. The car did not have to be on. I checked the range before bed and it was still at an almost full charge. The next morning around 9am, 7/8 of the battery remained. We made some coffee (I unplugged the fridge for that) and also charged our devices. I continued that ritual until Wednesday morning when the battery reported 6 miles of range left at around 9am. I disconnected the inverter and drove the vehicle a few miles to a BMW dealership that had power and used their L2 charging station. We drove home with our second gas powered vehicle and connected the inverter and fridge to its battery while leaving the engine running. The Connected app indicated our i3 would be fully charged by 1pm, but power was restored to our house around 12:30pm that day. I also inflated a queen size air mattress one night which along with the coffee maker drew a lot of watts. I'm certain it could have powered just the fridge and phones for 3 full days otherwise. Still many neighbors without power and tomorrow it will be a full week for them.

 

[theothertom]

Good job. Thanks for posting. Hope you didn't sustain any damage from the hurricane

 

[prettig]

smart thing to do.......
Always found it strange that no vendor has done this..... only a 12v cigarette socket !....... should have a standard wall socket ......or high power 12V socket to connect an inverter, ideal for outdoors, backup, running/charging tools, etc .....

in Europe they are running smart-grid test. Cars connected to a grid to power the net (and your house).
Goal is to get more out of PV systems and flatten high-peak usage (morning and evening).

I guess future EV's will be standard "grid-enabled", would be nice and your backup problem would be solved.

 

[alohart]

Always found it strange that no vendor has done this..... only a 12v cigarette socket !....... should have a standard wall socket ......or high power 12V socket to connect an inverter, ideal for outdoors, backup, running/charging tools, etc .....].

I believe that Nissan offers this capability for its Japanese Leaf via its CHAdeMO port. The external inverter seemed to be quite expensive, though.

 

[MikeB]

It bothers me no end that I cannot use my 5.4 kW solar array for backup power without a $15,000 modification to add a transfer switch, some really expensive batteries, and associated equipment.

As an alternative, I’m looking into using my 2015 i3 (BEV) as a home backup source. I bought a 12V inverter and made some initial measurements which I’d like to share with you. My concern is I don’t know how much power I can pull from an i3 without damaging the DC to DC converter or some other component. I can not locate the specs for this converter and have seen only brief posts on using the i3 as a backup source.

Since the i3 has three 12V accessory sockets and they are protected by 20 amp fuses (I believe), a simple calculation would indicate it might be safe to pull 720 Watts over a long period (12V x 20A = 240W, 240W x 3 = 720W).

I purchased a VertaMax Pure Sine Wave 1500 Watt (3000 W surge) 12V Power Inverter from Amazon for $261. I picked this particular model because it included battery cables and a 150 amp ANL fuse.

Connecting the inverter was more difficult than I expected. After removing the two mesh covers and frunk (6 hex screws) and disconnecting the negative (black) and positive (red) terminals from the 20 amp-hour accessory battery, I couldn’t easily connect the black inverter cable to the negative terminal. After some research I determined it was safe to attach this cable to the chassis (the attachment point I used had just 0.1 ohms of resistance to the negative terminal). The red inverter cable easily attached to a bolt on the forward part of the positive battery terminal. I don’t believe battery clamps are sufficient for a good electrical connection. Also, I wouldn’t connect a 1500W inverter without a fuse.

As a load I used a ceramic space heater that averaged a draw of 700W on its low setting. Before powering on the inverter I disconnected the front running lights (it’s easy to do, just press the tabs on the sides and pull back). The goal is to use the High Voltage battery as backup power for the house so we want to minimize the drain on the battery from the i3 accessories.

I put the i3 in READY, turned off the lights (position 0), fan, A/C and radio. The seat heaters and all other accessories were off. Note that it is necessary to exit the i3 from the passenger side and leave the key fob in the car in order to keep it in the READY state. It is also best to have the car windows rolled down.

I used a multimeter to measure the input voltage of the inverter and a watt-meter (kill-a-watt) to measure the load. The State of Charge (SOC) was displayed on the instrument cluster (press the button on the end of the left steering column stalk repeatedly until it appears). The i3 was at 100% SOC when the inverter was turned on. Ambient temperature was between 50 and 60 degrees F during the measurement period.

Minutes--SOC(%)--Load (W)-------Input (VDC)
0-----------100----------710----------- 13.81
108---------90----------701----------- 13.85
210---------80-----------694-----------13.74
292---------70------------691-----------13.61

At the end of the measurement period the inverter was turned off and the input voltage jumped to 14.39 VDC.

After removing the inverter I took the i3 for a one mile test ride. It functioned without fault but I noticed the SOC was 55% after this test drive.

If the load were a constant 700W then the energy used during the 292 minutes (4.87 hours) would be 3.4 kWh.
A 30% discharge of a 18.8 kWh HV battery should be 5.64 kWh. This discrepancy might be explained by the the losses in the inverter and the DC to DC converter as well as the power draw of the i3 electronics.

If I were to use the i3 for backup power I would probably limit it to 3 kWh or less per day in order to make it last for three days.

A few questions:
How much power can be safely pulled from the i3 without damage or degradation to the car?
How many kWh can be realized for the load if the i3 is discharged from 100 to 10% SOC.
Is the SOC indication inaccurate under this test setup?
Is there some other way to determine remaining battery capacity?
Does anyone have the specs for the DC to DC converter?

I don’t believe the EV manufactures are aware what a strong selling point they would have with EVs designed to provide backup power. At least they should provide terminals for easy connection of a 12V inverter along with info on the limits of its use. EVs already have inverters. Would it be so difficult to modify them to provide a single phase of 60 Hz power along with suitable outlets on the outside and inside of the vehicle?

MikeB, 3/2/2018, owner of 2015 BMW i3 (BEV) with parking and technology packages.