Introduction: Poor-Mans Smart-Grid - Blackout Protection by UPS and Electric Motorcycle

Picture of Poor-Mans Smart-Grid - Blackout Protection by UPS and Electric Motorcycle
A while back, the cheap battery charger I was using for my electric motorcycle went on the fritz. I decided to get creative to see if there was a way to not only get a great battery charger for FREE, but also increase the usefulness of my personal electric vehicle.

I came up with the concept of the "Poor-Man's Smart Grid"

Read on to discover how I not only got a great new charger, but can power my detached garage or even my entire house in a blackout, directly from my electric vehicle.

But first, what IS the "Smart-Grid"?

Please keep in mind that this project involves both both AC AND DC power, at potentially LETHAL voltages.
Persons unqualified and uncomfortable with household electrical should keep their hands out of the fusebox, and hire a professional to instal a backup generator system for them.

Electrical Code varies from one place to another. I make no claim on meeting code in your area.

Back-feeding power out to the grid during a blackout is illegal and highly dangerous. Any backup system must make use of "anti-islanding" technology. Connection to the grid MUST be disabled when running backup power.

Step 1: Smart-Grid Concept

Picture of Smart-Grid Concept
The "Smart-Grid" is an interesting concept, which has potential to stabilize the electric grid, due to either times of high demand or the variability of renewable energy sources, through the use of automated equipment, turning devices on and off remotely. One element of the smart-grid we often hear about is using power from the batteries in an electric vehicle to supplement power to the grid.

The Smart-Grid requires smart, bi-directional meters, and electronic components that can either charge an electric vehicle OR pull power from it as needed.

At night, an electric vehicle owner charges their vehicle from wall power. At any time that the grid has sudden demand (or a sudden drop in supply) electric power is instead PULLED from the vehicle's battery pack to meet that demand. Electric vehicle owners will be compensated through special electricity pricing for being part of the program. A great deal of infrastructure is required for the Smart-Grid, as well as standardization between vehicle manufacturers, utilities, and interconnected equipment.

The way I see it, the Smart-Grid is a great CONCEPT, but has a number of issues. For example, what if I can't drive as far as I need to in my electric car, because my neighbor was simply being extra-wasteful with his energy use? How much money will it take to set up the Smart-Grid, when we have continually shrinking budgets in government, and much infrastructure that is already behind on repairs and maintenance?

On the other hand, what about a PERSONAL Smart-Grid? A small-scale concept of the Smart-Grid could be designed using little more than hardware-store parts and salvaged materials.

For my project, I required:
  • An Uninterruptible Power Supply (UPS)
  • Power cables and connectors (typical hardware store components)
  • An electric vehicle - in this case, my electric motorcycle

Step 2: UPS - More Than Just a Delivery Service

Picture of UPS - More Than Just a Delivery Service

At the heart of this system is an uninterruptible power supply, or UPS.

You may have a UPS on your home or work computer. It's typically a box that you plug into the wall, and then you plug your computer into it. In case of a power outage, the UPS instantly kicks over to battery power, giving you some certain small amount of time to continue using your computer, or at least save your work, and shut down the system. When power comes back on, the UPS recharges the 12V battery inside it, so that it's ready for the next time it's needed.

So, a UPS is actually TWO things. It's both a DC to AC Power Inverter (typically converting 12VDC to 120VAC) AND it's a battery charger (usually low power 12VDC.)

So, when I needed a new charger for my motorcycle, could I just use a UPS? And if so, could I use it as a power inverter as well? The answer in both cases is YES!

I called up my buddy Tom, who happens to run a computer recycling company. I asked him if he ever gets any 48V UPS to recycle. He said yes, but that the batteries are always dead, that's why people throw them out. Of course I already had the batteries - in my electric motorcycle.

I asked Tom to keep an eye out for me. Sure enough, in a few weeks, I got a call, and headed over to his shop to collect a rack-mount 2200-watt, 48V UPS which would have been used in a computer server room. There were no batteries with it, and it had several dents and missing screws, but the electronics functioned properly.

By powering the UPS on wall-power, I could charge my 48V electric motorcycle, and by running it from the motorcycle, I could create AC power to take my detached garage, or even my house, OFF-GRID!

Keep in mind that not all UPSs are the same. Cheap ones only create "Square-Wave" AC power, which doesn't work well for battery chargers, computers, and electric motors. Higher quality UPSs, and specifically ones sold for use with computers create a very smooth AC sine-wave. In fact, we hooked up this UPS to Tom's osiliscope and found that it made better AC power than he got in his wall outlets from the power utility!

Step 3: Custom Cable - UPS to Wall

Picture of Custom Cable - UPS to Wall

I would need several special connectors and power cables to make my "Poor-Man's Smart-Grid" work.

The first one wasn't special at all. The UPS already came with a standard 120V electric cord to plug into the wall.

Typically, there are several outlets in the back of the UPS to which you would directly plug in devices such as computers and monitors that you would want to keep running in a blackout. On the back of this UPS, there are several 15 amp and 20 amp circuits.

But I didn't want to just plug in a device or two. I wanted to plug in MY ENTIRE GARAGE and maybe even my house when needed. To do that, I would need to make my own "Load-Side Connection".

Alternating Current (AC electricity) changes the direction it flows MANY times per second. In the United States, it's 60 Hertz. That means that AC goes BOTH directions! If you think about it, doesn't that mean that an electric outlet could just as easily be an electric "inlet"? Sure can! All that is needed is a special cable to connect the UPS back TO a wall outlet.

I added an additional, dedicated, 20-amp circuit to my circuit breaker box. The only thing on that circuit is a single twist-lock electric outlet, now being used as an "inlet". I chose that particular style of outlet because is is common enough to be purchased from a typical home-improvement store, yet I don't have any other outlets like that anywhere else on the property. It's a unique and dedicated connection.

I purchased 6' of heavy power cable, a twist-lock male connector, and a 20-amp male connector, which features a turned blade when compared to a typical power plug.

Stripping the jacket and individual conductors of the power wires, I made a dedicated male-to-male power cord that would connect the 20 amp outlet on the back of the UPS to the 30-amp twist-lock electric outlet on the wall.

When not in use, the cable is unplugged from both ends, rolled up, and stored away.

Step 4: Custom Cable - to Electric Vehicle

Picture of Custom Cable - to Electric Vehicle

Most electric vehicles are just a big battery bank on wheels.
Also, they are parked 90% of the time. Lets say you have a long commute, and drive to and from work one hour each direction. That's two hours you use your vehicle, and 22 hours per day that it's just parked somewhere.

While my electric motorcycle is parked it can recharge, OR be a battery backup for my garage and home.

The motorcycle has four 12V AGM batteries rated at 55AH each, or 2.64KWH of theoretical energy. This is a relatively SMALL battery compared to most electric cars or solar battery arrays, but it's still plenty for my use, especially since I use CFL and LED lighting, and efficient appliances and electronics.

On the UPS end, I needed to adapt the original computer-style power connector that went to the four batteries to an Anderson connector. I cut off the original battery spade connectors and crimped the wires in to an Anderson connector.

Next, I built an "Anderson Extension Cord" with two of the same connectors (making sure to maintain polarity) and a length of 6 gauge power cable left over from another project. I plugged in the short UPS to Anderson pigtail into the UPS, and then the extension cable into that. When not in use, the extension cable is coiled up and hangs on the back of the equipment rack.

To connect the motorcycle to the UPS, I added an Anderson connector to the the ends of the batteries in the motorcycle. The plug is accessible, by pulling it up out of the gas tank through the gas filler port.

With the cycle parked near the UPS, I plug the extension cord from the UPS to the motorcycle. I then plug in the UPS to wall power, and it automatically starts charging.

Step 5: Manually Switching Power

Picture of Manually Switching Power
To run my garage or house on battery power, I need to manually route the power.

Here's what I do:
  • Unplug wall power from UPS
  • Plug in the cable from the UPS to the twist-lock load-side "inlet"
  • Turn the main breaker OFF
  • Turn the load-side "inlet" UPS DISCONNECT breaker to ON
  • Power the UPS to ON
At that point, the garage is disconnected from the grid, and running completely on battery power from the motorcycle.

If I wanted to run power to the house, I would need to first turn off the main breaker in the house, then I would go through the same sequence, only leaving on the garage main breaker, allowing it to feed back to the house.

(If for some reason the UPS was "plugged into itself" by accidentally connecting it both to AND from the fuse box, the GFI will trip, breaking the circuit, preventing any damage to the UPS or creating an unsafe condition.)

Step 6: Real-world Application

Picture of Real-world Application

So, what's a REAL-WORLD application that would make the POOR-MAN'S SMART-GRID useful?

I'll give you an example.

This summer, we had a terrible heat wave. Everyone on our block was using their central air-conditioning, which is a very heavy electrical load. My wife has a heat sensitivity, and can get physically ill from being too hot, so staying cool in a heat wave is that much more important.

It was still over 100 degrees F. in the evening, when the neighborhood transformer blew.

In the house, I turned the main breaker off to disconnect us from the grid*. In the garage, I plugged in the UPS backup cable and turned on the UPS, but did not turn off the main breaker back to the house. That way, the garage simply fed AC power back to the house and any other circuits on the same 120V "leg" of household power.

In the United States, typical home electric power has TWO 120V wires coming into it. Each one goes to every other circuit in the house. High power electric circuits, such as for an electric stove, are on a double breaker, which combines both 120V "legs" to give you 240V.

Since my UPS is only 120V, and on a single circuit, it only powers EVERY OTHER circuit in the house. Knowing that, all the IMPORTANT circuits are on that leg.

During the blackout, the refrigerator, kitchen light, living room ceiling fan, kitchen electric outlet, furnace (for winter blackouts), and water pump, were all on power backup.

We had cold drinks, running water, the ceiling fan and box fan running, electric light, and the radio for both news and entertainment, all thanks to the POOR-MAN'S SMART-GRID!

*Please note: as with ANY kind of backup power system you MUST be disconnected from the grid during blackout using any type of generator or battery backup, whether that's with an automatic disconnect or manual system.

Step 7: What's Next?

Picture of What's Next?

The POOR-MAN'S SMART-GRID has been a great experiment, which has expanded the usefulness of my electric vehicles and made my home more functional at nearly no additional cost.

But what would it take to make this setup even better?

Here's a few ideas:

Solar power is a great way to create electricity from a renewable source of energy, but the right amount of solar panels seldom fit on an electric vehicle! Typically, you are better off with them permanently mounted in your yard or roof of your house or garage. (Here's an exception, that I built as a solar-powered vehicle for my daughter - Solar Power Wheels.)

If you have solar panels on your garage, they can be connected to a solar charge controller, and a battery bank. Since 48V is a "standard" DC voltage common to solar equipment, solar panels can be routed to DIRECTLY charge a 48V electric motorcycle.

 A solar charge controller like the Xantrex C-40 can run 12,24, or 48V systems. Instead of using it as a typical charge controller, it can also be set to use as a DIVERSION controller. When fully charged, instead of disconnecting power between the solar panels and electric vehicle, it would simply RE-ROUTE power to a different load. If the secondary load was a small Grid-Tie inverter, the excess solar energy would be routed to the grid (or deduct from the amount of energy my home is using) instead of simply being wasted.

While my system works well, it is not AUTOMATED.
A typical power backup system would use an Automatic Transfer Switch. An ATS is usually installed between the power utility and the home main breaker box. It is a "break-before-make" switch that automatically disconnects grid-power during a blackout, and then connects power to the backup generator.

On my system, a typical ATS wouldn't work, due to having a detached garage with separate breaker panel. However, the system could be automated through some clever use of relays and automated breakers, such as what's used in Recreational Vehicle power systems. At that point, I could simply always leave the UPS running and connected, and allow the automated equipment to kick over to backup power during a blackout.

I already have some solar panels, charge controller, a small grid-tie inverter, and some RV parts around. It would only be a matter of a little more work and study to automate the system. 

Electricity is a wonderful thing. It can light up our living room, heat our home, cook our food, and transport us from one place to another. It's hard to imagine living without it. Because of so much of what we do is based on electricity, it's nice to have a backup plan and learn all one can about batteries, generators, and electrical power.

Please visit for all my clean transportation projects or click HERE for my other Instructables.


GeneB21 (author)2016-07-11

You had me @both AC AND DC power, at potentially LETHAL voltages. Let me change my underwear now Keymoslobie, my sloppy liTTle friend! Awesome apocalypse survival technique, seriously good stuff

cricketol (author)2016-04-27

have you thought about using a arduino or raspberry pi to automate it any?

LawrenceH8 (author)2015-10-04

Good fun project - HOWEVER - most people should NEVER try what's in this article and may lead to many DEATHS. FIGHT the BS Propaganda of "GREEN" instead. SEEK TRUTH.

I worked for Elgar Corp in San Diego CA they design, manufactures, intalls and maintains Commercial UPS units. In the. Millions of cubic feet of racks of Gel Batteries, NOT to replace fossil fuel or coal - ONLY to support Motor/flywheel/Generators and the NORMAL Grid for critical DOD and Corp equipment.

"Smart Grid" = the National Enquirer. "Smart Meters: (really for spying) are inferior to the standard glass meters and catch fire all over!!! Coal and Fossil fuels are GOD's gift to mankind. Solar without batteries = FRAUD. Wind? ENRON in now GE Wind Turbines. Global Warming by man is BS. No cavemen with SUVS! :=)

Mjtrinihobby (author)2015-04-17

super excellent. my congrats!

Wildfire-Phoenix (author)2015-02-18

Where can I get some of those ups consoles?

hi-line (author)2014-12-03

Super creative. this instructable site in general has made me realize that solutions to our ever increasing energy/pollution issues will NOT come from big business.....but a bunch of backyard geniuses might just pull it off....if the rest of the world is paying attention.

bahi (author)2014-01-21

One of the most complete instructables ever.


espdp2 (author)2014-01-10

Great demo! This sent me on all kinds of rabbit trails. I found used UPS units on eBay up to 40 kVA(!) without batteries, transfer switches, and all kinds of useful stuff. I want to start experimenting by powering my camper this way, and then when I buy a house, I'll set up a bigger system. Now I just need to figure out how to convert my Suburban to an EV... Cheers! :)

PS: Gotta jump on the bandwagon, Ben. Please update us with the news that you have changed that damned cord by now.

brettj1 (author)2012-09-10

Thats all very nice to experiment on running things off your inverter & extending the time you have usable power from it but what you are doing is extremely dangerous & highly illegal.
Just run extension leads & don't plug into your house you will kill an electrical worker if your power feeds some where he expects it to be dead.
I don't care how many disclaimers or warnings you post up it is not appropriate to instruct people on how to do dangerous work when you obviously are not qualified to do this work.
Personally I am a qualified electrician & there are rules & regulations that are there to keep everyone safe & what you suggest brakes many of them

astral_mage (author)brettj12013-11-29

actaully there is a device called grid tie inverter. lets say power goes when u have this device pluged in. ok it senses the power has stopped comin into the home( wat ever the structure u may at this reading be calling yr home) then itill stop feeding power into the grid. thus saving some one husband / father / family member. then u keep the power 4 yr self. when the power come back on. the unit senses the power an it then begins to fed the grid. if it done right u can turn yr home power useage into a zero power home. thus only paying 4 wat u actaully use.

brettj1 (author)astral_mage2013-11-29

For starters the connecting cable he uses with a male plug on both ends is highly illegal & dangerous. This should never be used because if it is pluged in to either socket with the power turned on there will be live power on the other end . There is power inlets for connecting power, as in caravans But you are required to use a change over switch that isolates your house from the main grid while you are useing the alternative supply so no power can be fed back to the other system for saftey reasons.
Next supplying power into your house electrical system can feed power back into the grid & if some1 is working on the power lines down the road, then you risk electrocuting them when they think the lines have no power (this has happened).
The poster has not stated he is using an inverter that can sence the grid power state & it would still be unsafe & illegal to use these inverters without an isolating switch to stop the power from feeding back to the grid to stop electrocution.
Here in Australia if you were caught doing some thing like this you would be disconnected from the grid & charged / fined for your actions. You would also risk being banned fron connecting power to your house for an indefinate period because it brakes many laws & regulations, it also risks the life of other people you may never meet.
Doing this on your own house that is not connected to the supply grid is your choice you only risk your own life. but if you risk your family or other peoples life it is not acceptable in any society.

astral_mage (author)brettj12013-11-29

use of a grid-tie inverter takes care of all that look them up.

brettj1 (author)astral_mage2013-12-01

For a start the OP says he is useing a UPS.
Secondly maybe YOU should look up a grid-tie inverter
On wikipedia it states "Grid-tie inverters are also designed to quickly disconnect from the grid if the utility grid goes down. This is an NEC requirement[2] that ensures that in the event of a blackout, the grid tie inverter will shut down to prevent the energy it transfers from harming any line workers who are sent to fix the power grid.

the grid tie inverter would be useless for the purpose that the OP is trying to achieve

zappenfusen (author)2012-12-03

The cord is nuts but easily rectified. The use of old UPS systems is something I've been saving old units for. The harping of licensed electricians on homeowner D.I.Y. projects is a mantra promulgated by unions and folks who have forgotten in our world most of us will continue to assume the right to kill ourselves and even someone else when attempting to further comfortable living sans interference from the "Experts" and local authorities. Yes, I'm a licensed electrician who has yet to kill anyone but will support anyone else's right to do so.

Lectric Wizard (author)2012-09-11

Basic idea is good but that cord is deadly. There are male panel mount connectors available,i use them at work all the time. That way the power is always "hidden" inside a female end. Adding larger heat sinks & a fan will allow you to extend the run-time without overheating problems. I'm doing this to a 400w UPS ,as I write, for a small camp lighting / TV.

Cabe (author)2012-09-04

Its this sort of crazy thinking that might just save this blue pearl of rock we call home.

Side note, the hole in the top of the gas tank looks ripe for a nice C16 "commando" connector if you ever need to change them.

Lectric Wizard (author)Cabe2012-09-11

How does this save the planet ??? It merely stores energy for use during the blackout. The energy would have to come from solar, wind etc. to "save the planet".

dfranks (author)2012-09-10

Thanks for the instructable. Nicely put together and the video really helps to explain how it all works.
I would definitely add a transfer switch to the mix. It appears that you've already received LOTS of GREAT electrical information so I will not add to it.
Keep the instructables coming

dalesd (author)2012-09-06

Very nice setup, but be extra careful with that special cord you made. When one end is plugged in, the other end is live, making it a powerful cattle-prod.

bennelson (author)dalesd2012-09-06

The one end isn't live until you turn on the UPS, and the other isn't live until you switch a breaker. Neither end is powered up until you connect both and activate power.

cstruthers (author)bennelson2012-09-10

The real problem doesn't come from you using this cable for it's intended purpose, it comes from some unknowing person using it.

The one end will fit into any standard T20 outlet, so, it is very possible for someone to grab that "nice short extension cord" from the garage, and plug it in. Then, when they grab the other end to plug in the thing with the the short cord, the BIG SURPRISE (hopefully a visual surprise).

I've made cables like this for short lived needs, then disassembled them to avoid accidents by others.

-A-N-D-Y- (author)dalesd2012-09-06

That cable has to be the dumbest thing I've seen in a long while and not just on instructables. That's a Darwin award if ever there was!

Reminds me of people that used piggy-back plugs as sockets for extension leads rather than a actual socket (see here photo 4)

chrwei (author)2012-09-06

If you keep your eye open, there's 5KVA and bigger UPS's that can power 240V, and run the whole house for a short time. might be a little much draw for your bike's batteries alone though

bennelson (author)chrwei2012-09-06

Now that you mention it, I DO remember my friend having a pair of more powerful UPS, but they were worth something. He was selling those for something like a couple hundred dollars each.

The one I got was free, powerful enough, and works just fine.

67spyder (author)bennelson2012-09-07

Larger UPS's (I have a 60A 240V one running a sub-panel in my house) use a higher base voltage. Mine uses 120V on the battery side. My shop has an 80A unit that is also 120V on the DC side. Maybe useful for a larger EV?

Spokehedz (author)bennelson2012-09-06

It never hurts to ask your friend to keep an eyeball out for the bigger ones--one might come in with major damage to the metal box, or even some of the power wires inside damaged. A deal killer for a used/recycled equipment reseller, but not for a handy guy like yourself.

anyheck (author)2012-09-06

This is a great re-purposing idea. I will have to keep an eye peeled for a batteryless UPS. Some APC UPSs that I've seen have Power Poles as standard equipment going to their battery packs.

There are a couple of problems with your setup in terms of safety.

Most importantly if you forget to shutoff the main you can KILL somebody. Not just hypothetical, but actual. A search of the internet will reveal stories of linemen getting killed.

A DPDT transfer switch, by design, does not allow backfeed through the main. It doesn't rely on you to remember to switch anything. The transfer switch mechanically either allows your selected house circuits to get power from the main or to get power from the generator, but not both at the same time. It is dummy proof.

The second, and probably only dangerous for you an those around you, is that your input to the structure should be a male receptacle and a female plug instead of a male plug that is potentially energized.

wmchemist (author)anyheck2012-09-06

Excellent solution to the shocking hazards! As for the legal side of all this! I guess if you can find an electrician to install proper transfer switch and male socket that will make things safer. There must be special electronic equipment already manufactured that can be installed to do this safely as in grid connected PV/Wind homes with battery backups?

anyheck (author)wmchemist2012-09-07

A proper (DPDT ie On-Off-On or "Break before make") transfer switch for 30A is ~$250 a Grid tied PV inverter is ~$2,500.

This is the least expensive option I've seen that seems to satisfy NEC, but a bit cheesy and still ~$150

Trike Lover (author)2012-09-06

Having been both an electrician and later getting a degree in Electrical Engineering, I have a couple of "pro" and a couple of "con" comments.

First the Pro:
I love the idea of re-purposing those big server-type UPS's. They're usually very conservatively rated and well engineered. A person in search of might also check out telephone and celllphone/microwave utilities and companies that service cellphone and 2-way radio towers. I've never been in a tower shack yet that didn't have at least three or four large UPS's and a battery bank. They're changed out every few years along with the batteries, as they have a rated service life. There's normally nothing wrong with the UPS's being tossed, although the batteries are defunct. So, it pays to ask around - often more so to ask the site workers, rather than the "management". Amazing what can wind up in the back of your station wagon rather than it going to the dump, if you say please to the guys on the spot.

Second "Pro" - using your electric vehicle as a battery source. Using Anderson Powerpole connectors all around - the big ones rated for 75 amps or better as well as the smaller versions for lower voltage/current devices - can make switching between battery sources quick and easy. Andersons are inexpensive, readily available, and just about foolproof. Definitely mark the the big ones for polarity with something that won't come off. If you find a company that services electric forklifts, you may well find serviceable large ones in the garbage.Just a tip.

Cons: 1) Cord with two male plugs. Extremely dangerous, no matter how "careful" you are, and unnecessary. Male/female connector pairs with a housed male connector are available in several types. Two sources are marine and RV suppliers. Double-male-end cables are called "dead enders" for a very good reason.

1) Transfer switch. It can't be emphasized enough. A proper, UL/CSA certified auto-disconnect transfer switch, installed by a licensed electrician, between your main breaker panel and the utility drop is essential.

Different jurisdictions have different codes, but this one is just good sense regardless of code. There should be _NO_ way that you can connect AC power from your inverter to the house panel without a proper transfer switch disconnecting your utility power line. Not having one unlawful, and endangers the lives of others. Installing a proper transfer switch is expensive, but for a reason - it's a life-or-death item.

The only other way of installing an interconnect semi-safely is forbidden by code in most areas, but if used properly performs the same function. It is not allowed under code because it is not "idiot proof".

The method is to have a pair of spring loaded master disconnect switches. The first master switch is in line between your utility drop and main breaker panel. (Throwing the main panel master breakers is not good enough). The switch must be the type that disconnects all three wires. It must have provision to be locked or padlocked "ON" _AND_ it must be the type that is spring loaded to "OFF" or OPEN" if the key or padlock is removed. i.e. if it's unlocked, it's "OFF".

The lock or padlock is important - you can use only ONE padlock and it can have only ONE KEY. At the other end. your tie from the alternate power inverter to your house panel has a similar switch. It's a switch like the other, using a padlock to hold it in the "ON" position. You must set a routine where you use ONLY the padlock from the utility line disconnect switch to lock "ON" the alternate power source.

Because someone can use a second padlock to turn it "ON", or haywire it, it's not "idiot proof" and against code. Also, because it requires an exact routine to be safe, it is far from ideal to use during a power outage.

When you want to transfer to off-grid power, you first disconnect the utility line by removing its padlock and opening its switch. A spring-loaded, normally off switch, it cuts all thee wires of the utility connection. Then, you use the same lock & key to lock "ON" or "CLOSED" the switch connecting your alternate power to the main breaker panel. This switch is the same type - spring loaded, normally off, with a padlock fitting to hold it in the "ON" position.

In this way, if you do not cheat and have two locks or two keys, you cannot simultaneously connect your utility line and your alternate power source line to your main breaker panel. As I said at the beginning, this method is contrary to every electrical code I know of, although safe if done properly.

However, it depends entirely on one person - YOU - having a single lock with only one key that fits the two switch panels and remembering that order really is deadly important..

It also depends on having switches that are spring-loaded to be "OFF" unless a padlock is holding them "ON". But if you do not have an automatic transfer switch, this method, used correctly, will prevent connecting your alternate power to your utility line. It is a stopgap method only.

(If you can find them, three wire switches mounted in boxes with actual spring-loaded key-lock activation are more foolproof. But they're hard to find and expensive - no saving over an automatic transfer switch. With these switches, there is a single key and no padlock. Power is cut when the key is removed. Since the single key must be in the switches' lock to turn power "ON", it is impossible to turn both switches on at the same time).

With power outages and rolling blackouts becoming increasingly common, using re-purposed industrial UPS's is an excellent idea, all by itself. I know I'll be making the rounds with one eye out, quite apart from using some of your other ideas.

Thanks for a most interesting article

Serendipty (author)2012-09-06

Nice article. Enjoyed reading it.

Correct me if I am wrong. You are using a UPS to power the entire house, instead of just one or two pieces of equipment. And using additional storage (battery packs) from EV.

In India most homes in the cities are fitted with what people generally call an inverter. It is essentially the same as what you have described in the
article, except it is packaged as a complete product (the UPS box with battery pack).


drichard58 (author)2012-09-06

Maybe I'm getting old, but I remember seeing those "suicide plugs" when I worked in construction 25 years ago. It was typically the welders who had these rigs but I can't remember what they used them for.

I do know some people who have made these for their gas generators (lots of us have generators here in hurricane country). When power goes out, they flip the main breaker at their breaker box, plug the plug into a 240V outlet (like an electric dryer), and crank up the generator.

I am an EE also, and I do cringe at the thought of that.

Good Info though....

ScottyAlmanjoy (author)2012-09-06

It will also make the life of your electric car battery shorter, since you're constantly charging and discharging it.

bennelson (author)ScottyAlmanjoy2012-09-06

It's not constantly "discharging and recharging".
At this point, I'm mostly using the UPS as a charger for the electric motorcycle. DISCHARGING with the UPS is only when ACTIVELY using the motorcycle as a power source, such as in a blackout.

actionjksn (author)2012-09-06

If you have to turn off a switch before turning on the system in order to prevent back feeding and killing line workers, then I think this system may be illegal. Because that would mean it is not idiot proof. Somebody could theoretically turn it on during a power outage, without first hitting the switch to disconnect from the grid. And it could back feed power into the grid and light up some power line workers. I don't believe you're dumb enough to do that, but the government doesn't know that. So it's a huge fine if you get caught. And believe me there are many many people who are dumb enough to do it. I heard about a guy getting an $8,000 fine and was facing prison time and he didn't even shock anybody. All I'm saying is don't get caught. Also I think your kill switch that disconnects you from the grid also has to disconnect the main ground wire as well. If I understood correctly you also have a power cable that is male on both ends? The nickname for those is known a a dead man, and for good reason. They are also illegal and if that's what you have I would change it out.

I may have misunderstood your description of your system and if so please just disregard everything I said. But my information is still relevant for anybody who is planning to do something like it. Back feeding from generators and other power sources has killed power line workers, I think quite a few times.

bennelson (author)actionjksn2012-09-06

Please see footnote in BOLD at the end of the INTRO page.

ricks (author)2012-09-06

This is most interesting to us. We hooked up a power-out connector from our Prius using a plug like you have on your motorcycle, but the inlet is currently going to a 12v to 120v converter. The output of that is just a single plug and 1800 watt max. We wired this into the 12v accessories battery to keep the system simple. The Prius self-starts when the volts drop which is what is great about this system and our basic (low watt) needs.

I would love to add a "port" to our house panel so that we can feed one house circuit at a time, rather than running cords throughout the house. I was under some impression that flipping the main breaker switches really doesn't stop back-feeding to the grid, since the common (white) lines are not broken. Am I confused (likely)?

Can I just create the inlet like you show? Switch the main breakers and turn on the Inverter?

bennelson (author)ricks2012-09-06

I've heard of a number of people using a Toyota Prius as a backup power source.

You can pull energy from the battery, convert it to AC for use, and when the battery runs low, the engine comes on automatically to recharge it. It's like having a hybrdi generator. Just make sure to park the car out in the fresh air.

I seem to remember seeing a commercial product once that was a backup power system based on a Prius like that, but I don't recall the name.

Enginer makes aftermarket plug-in kits for the Prius. They now sell an inverter with the idea of using it as a home backup system.

sephelie2 (author)2012-09-06

love the idea!
please be careful, some UPS systems are rated for 20 minutes backup, 'upgrading' the batteries will extend the cycle rates of the UPS but most of the UPS systems have the 20 minute rating for a reason - BC the internal transformers will overheat after 20 minutes! I am an electrical engineer and coming from the power plant industry, so if you upgrade batteries in UPS systems please make sure the internal transformers in the UPS systems are not overheating and catching on fire.

everything else - GREAT JOB, i disagree with the 'plug / plug' wire, there are better ways, maybe check into CEE plugs, they come as plug and socket in both directions, just a suggestion, everything else good job!

bennelson (author)sephelie22012-09-06

I checked the UPS during and after a four-hour blackout. There weren't any issues with heat internal to the UPS or the transformer. Good idea to check though.

I think that since this was originally a UPS designed for a computer server room that the components are beefier and designed for a longer run time than a smaller/cheaper UPS would.

swereska (author)2012-09-06

As a thought, you might move your UPS disconnect circuit breaker to be opposite your Main Disconnect breaker, and fuse the two so that they can't both be on.

In your case this would mess up which leg the live circuits are on and limit you to only having power in the garage, but for people who don't have a sub-pannel, or who's sub pannel provides power to enough of the house to get by, it would keep them from inadvertently back feeding the rest of the grid, and lighting up some nice electrical worker who's trying to repair the break.

I'm guessing you know enough to manually do this safely, but what about the guest who want's to see if the power's back on?

londobali (author)2012-09-05

That's really great!!
I was just wondering what alternative is there to buying charge-controller for when i build my own electric vehicle (your other i'ble will be my blue print for that project)..

Another great instructible from bennelson...

Thanks for sharing man!
I'm a huge fan!!

bennelson (author)londobali2012-09-05


mikesoniat (author)2012-09-05

Great idea! I have a couple of old UPS's lying around the office. I guess they're coming home with me!

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Bio: Ordinary guy with no special skills, just trying to change the world one backyard invention at a time. See more at: On ... More »
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