Use the Prius as a 12-volt generator during a power failure?

I'm in the middle of a gen3 Prius to UPS project.

I decided to use the HV battery. The HV-12V converter is good for 100A (or so I've read). Of course the car takes some 12V power, especially if the radiator fans run. Even 100A would only be good for about 1000W of AC power after taking the inverter efficiency into account.

If I only wanted 1000W, it would be easier to just run a portable Honda generator and leave the car alone.

The UPS I'm using is this one:
SU5000RT4U - SmartOnline 5kVA On-Line Double-Conversion UPS, 4U Rack/Tower, 208/120V or 240/120V NEMA outlets, Split-phase input

It uses 16 12V batteries in series (196V nominal) so it's a great match for the Prius 201V (nominal) HV battery. It also makes 5000 kVA (W) of 120/240 split phase power so I can shut off the main house breaker and run the house through the normal wiring. The output is pure sine wave.

The UPS architecture is double conversion, so it's designed to always be inverting DC power to make it's output. That means high efficiency design and durable components with good heat removal.

When I'm done, I'll post a full "how I did it" in the gen3 section and I'll also come back here and post a link, since this is common to gen2 and gen3 cars (both 201V HV batteries).

 

Very interesting.

Referring to the spec sheet, it appears that the AC output is rated at 3.8 kW.

Is your intent is to insert the Prius traction battery where the optional battery pack would have been wired?

Do you intend to disable the front half of the UPS which processes the raw AC input and keeps the battery pack charged up?

I suppose you know that the Prius traction battery is not grounded. Both positive and negative terminals are isolated from the body ground. You may want to investigate if the optional battery pack has one side grounded; if so then you may have problems when trying to use the Prius battery.

 

They rated the 5000 kVA at 0.8 power factor to get the 3800W. That's pretty conservative. Maybe not for 100% computer loads, but my house is closer to 0.9 or 0.95. The furnace blower and refrig have caps for pf correction. Most of the rest will be lights or other resistive.

Yes, I'm going to unplug the 16 batteries and connect it to the HV batt via some 6g multistrand and Anderson (75a) connectors.

I'm not going to disable the input side, just not plug it in. The UPS will think the power failed, and yes, this UPS can cold-start. Already tried with the internal 12V gel cells, starts up fine.

The internal pack is not grounded, just two conductors. The packs are low-tech, just generic Chinese 7Ah 12V gel cells wired in series...in 2 packs of 8, literally taped together in 2 flat rectangles between clear plastic trays.

 

Typo alert:

The page says 5000 VA or 5kVA.

It is not 5000 kVA, which would correspond to something like 3,800,000 W. The Prius would melt.

 

We have used a Gen2 for limited backup (120v for up to about 1 kw) for a couple of years. The Halloween weekend snowstorm dropped a tree branch onto the lines about a mile away and the crews took about a day and a half to clear. The car was in the garage, with an exhaust hose out. Unfortunately the heater had been left on, and a lot of energy was wasted! Other than that we had a our heating system (oil burner, wood stove with water heating coils, and circulator pumps), refrigerator, tv, and computers (but not our usual printers) running.

Limited internet was available via an iPhone hotspot. What we didn't have was any 240 appliances (water well, clothes dryer, stove), nor microwave oven (over 1kw).

The Tripp-Lite looks like it would at least run some combination of everything but the dryer and stove. Connection should be similar to the PriUPS project, but with a new rather than refurbished UPS.

Looking forward to cit1991's report.

 

Another Tripp Lite model is less expensive and and has similar specs: SMART5000XFMRXL (found on another thread).

 

Please use the word current rather than amperage.

 

What's a few orders of magnitude between friends?

 

This thing costs $4000. Did you find a deal on it?

 

The Prius makes an Excellent 120VAC generator.

It's as simple as hooking up the HV battery (200 vdc) to a computer UPS that uses a battery pack in the same vdc range.

Then, plug in a 12 (or make a 10 gauge) extension cord from the UPS to your house. Limit yourself to 50 feet with a 12 gauge, since you'll be splitting in the house off that extension cord to Other cords.

That style of UPS is what is used for servers, come in various sizes. Costs over 1k$ w/o batteries. Best deal is getting used from eBay, and telling the seller you don't want the batteries, to recycle them.
Save $$$ on freight charges.

See PriUPS.com, and yes, his website can be confusing. You can keep your Prius running 24/7, something you cannot do with a regular car.

Don't try anything fancy, and in doubt, ask an electrician to do a quick-snap hookup. Perhaps another 500$.

Great for camping too ! Hookup a tent to your open hatch, run the exhaust hose far away with the special plastic attachment you can get at mechanic stores. Turn car on, AC on, and sleep!

 

On Newegg it's selling for 2700$

Hunt for used on eBay, the biggest cost is the batteries, which for an easier setup, you don't want that extra weight in your car, if you want just the converter VDC to VAC unit, and be able to use it anywhere.

 

I have a 1200 watt invertor and use it during the frequent outages under apalachian Power. It does well with sump pump lights and fridg. But cannot operate tv that has direct tv box. I wonder why . Any answers?

 

If your inverter is not producing a pure sine wave (instead it may be producing a square wave) then the TV's power supply will not work very well.

 

Gen 2's 12 volt is on the same side as Gen 3.

 

I'll be looking forward to this! Your solution sounds great, although it's expensive, and requires more modification or at least disassembly of the Prius to gain access. Big inverters are heavy, too.

Since you're doing this, are you subscribing to Toyota's TIS to confirm the size and location of any fuses or fusible links in the Gen 3, to see if they're the same as the Gen 1 and/or 2 (mainly interested in the 12V system here). I'd want to try to avoid blowing any of these. If nobody else finds out, I might pay for access and look this up, plus explore to see what else I can learn. Another question, is the jump point under the hood wired directly to the battery, or is there any fuse in between? I'd guess it might be best to tie an inverter directly to the battery if there is, to avoid the possibility of blowing fuses during any transient peak loads such as when starting a motor attached to the inverter (assuming the peak current would come from the battery during the time the car's charging current is maxed out). Connecting to the battery introduces some possible voltage drop in the wires running to the back of the car, so if I know there's no fuse between the battery and jump point under the hood, it would be better to connect under the hood.

While not as good as a big inverter tied to the HV battery, tapping into the 12V is easier and costs less. I'm thinking this could meet my needs for basic backup during a storm. I'm looking at getting a 1000W pure sinewave inverter, since this seems to match the max available 12V power from the Prius, and is also close to the needs of the largest single loads I'd want to run.

This 1000W sinewave inverter is available for $280 from Lowe's (special order), and doesn't require modifications to access the HV battery: Power Bright - Pure Sine Wave Power Inverters. I've already tried a modified sinewave inverter on my heating system, and it didn't seem to work well (hummed a lot, and drew much more current than off utility power), so I think I'd much rather get a pure sinewave inverter. It should have no problem with my heating system and refrigerator (both well below 1000W, should even include startup). I have a small microwave that consumes about 1000W, so that might be usable too (but not at the same time as the others). I'm even wondering if I could run my 220V well pump off it, by using a step-up transformer (commonly sold as a travel converters) between the inverter and pump (less than $100 for this). This transformer would introduce some loss, but hopefully work with a pure sinewave input without tripping off the inverter due to inrush current on startup. So far I haven't determined how much power I really need for the well pump (and it would be more with transformer losses), but it's possible it could work. It's 1/2 HP and the control box says max current 5.9A, but if that's only during startup as I suspect, the inverter's surge capacity might handle it. I suspect the 1/2 HP pump is probably not over 1000W once running. Add in a couple of single-circuit transfer switches (the rest could be run off extension cords), and I might have a good enough backup.

I could get by for a few days running heat & refrigerator (plus a light or 2) most of the time, and switch to microwave or water pump when needed (even if the water pump doesn't work, heat & refrigerator alone would go a long way to lessening the impact of a power outage, since I could go out for food and water).

This would cost less than a generator, be quieter than a generator, and I wouldn't have to maintain the generator. Honda makes nice generators from what I've heard, but they're not cheap. There are cheaper generators, but every one I've heard is very loud.

 

As a G3 owner, I'd be really interested in a permanent, no-extra battery, installation.

I travel a lot, go to various fairs, and have frequent power failures at home or our small office. Having a permanent solution in my car is to me a plus.

Ideally the project should be able to do at less 2000w @ 120vac, easy-peasy.

If someone wants a CHEAP 12vdc-to-inverter solution, why not do this?

1) use 2 sets of jumper cables, the first set is hard-wired to the Prius 12vdc battery in the back, pos & neg terminals. The other end of that cable ends in a high quality female Anderson jack connector.
The 2nd set ends in the male jack, the other end stays as-is, for clipping unto a car battery.
Connectors: Anderson. (weblink)

2) buy multiple 12v car batteries, smaller and cheaper ones.

3) use Prius to "charge" outside the car the 12v car battery(ies). You could probably daisy chain more than one battery with extra jumper cables, as long as you don't overload. Each "chain" would halve the charge time though.
Stick with 1 battery at a time.

4) unplug the extra car battery, put inside your home, and use whatever 12vdc-120vac inverter you want.

5) multiple batteries, multiple inverters, mix & match.

The "load" on a stationary Prius will be so small. Turn of your Daytime Running Lights (Canada) with the parking brake.

​

IOW, using a cheap car battery with a cheap inverter, yields a system similar to a computer workstation UPS system, for cheaper, and a stronger system too.

You could heat a home with a Granule Slow Burning Stove. Use a 12vdc fan with another battery to blow cold air unto the stove.

Use a car battery + inverter in every room of the house to power lights.

Use a car battery + inverter to power your Internet DSL modem and WiFi router, and keep your laptop charged.

You carry the batteries to be charged outside, turn your Prius on, go back inside and wait 2-3 hours.

Get a car battery tester to "know" your state of charge of the extra battery.
​

With the Double Length cable boosters, you can even charge another battery while using the Prius to drive around. Also, easier to boost someone else's car with double length cables.

1000$ buys a lot of 50a Toyota Tercel-sized batteries and high quality inverters that do upwards of 1000w.

Though, doing something similar, but tapping into the Prius HVB is still the better deal, power loss wise, however requires some electronics to do safely.

Someone could devise a Prius HVB to 12vdc car battery charger.
Or - get the Enginer.us PHEV system, that works backwards.

What I don't like - are standalone generators. Noisy. Back in 1997 I saw many people buy them at huge premiums during our Once-In-A-Lifetime icestorm, and burnt them out by running them 24/7 for just a few days.

 

My apologies if the PriUPS.com web site is a bit confusing. It got built piece by piece as I was putting the system together. A few notes:

1: The "modification" of the Prius itself is pretty simple. Other than adding a connector to the battery after the relays, there's nothing to do. The remainder of the system hardware can be located wherever desired. I have put systems in the hatchback, and also in the house. Here's info on the mod:
PriUPS Site Navigation ("Part 2" has links to the pictures)
2: A number of inexpensive UPS units can be used. Some are directly compatible with the Prius battery pack. Some require voltage step-down, but the hardware to do this can be found on eBay. Here are links to a few of the portable versions:
PriUPS update 08 Jan 2006 and Portable Priups: Several Examples
3: High power UPS units can be expensive, but they're often almost free on eBay. I've written an eBay "guide" on finding them. (Please check the "helpful" link at the bottom if you find it so.)
eBay Guides - Buying BIG Uninterruptible Power Supplies

A number of people have successfully put together a PriUPS system. If you do so, I'd love to add a writeup to the site. ( Son of PriUPS ). Please send pix!

Richard

 

Richard, thanks for your pioneering work and for documenting it all.

If you do update your site, the #1 thing that would help the most is to put a list of known compatible UPS units somewhere easy to find. Your links above don't include PriUPS update 15 Jun 2005 (where you describe your Lucent UPS) so even though I knew I saw it somewhere, I had a hard time finding what model UPS you used. The reason this would be very helpful is as you noted, it can be very time consuming to sort through all the UPS units on ebay, trying to find one that has a compatible voltage range, when most UPS makers make it very hard to find their battery voltage (you even say this on one of your pages). So doing an ebay search for models known to be compatible could be a big time-saver.

I'd prefer your direct HV approach if possible (meaning a UPS with a 200+ VDC input, with no additional converters required). Additional step-down converters make this project less elegant, since they become more like using the Prius 12V system (which already has its own step-down converter), with the only possible advantage of more power capacity, and require a spaghetti mess of wires so you don't have a nice clean portable package (unless you mount all the parts to something, and some of these are too big to permanently mount in the car). Unfortunately most 200+V inverters like you used are not very portable (and in my case if they're too heavy to move easliy, might have to be left out in my cold unheated garage, below the normal operating temperature range of some inverters, something Californians don't have to be concerned with).

I'm actually considering yet another approach, since my backup power needs are mainly small, with possible short periods of higher power (occasionally running a well pump, or a microwave, etc.) To do this I have another possible approach... using an external 12V deep cycle battery powering an inverter, and the Prius 12V system keeping it charged during use (and a 120VAC float charger keeping it charged when not in use), with power from the Prius through some sort of charge controller or current limiter so my peak loads don't overload the Prius 12V system (I'd sure hate to damage its expensive inverter if I pull the voltage down too far). The peak loads would come mainly from the external battery, with limited additional current from the Prius, and in times of lower load, the limited current from the Prius recharges the external battery. This could have the side benefit that I could keep limited power on overnight from the external battery (for refrigerator, heat, etc.), without leaving the Prius in Ready overnight (being an external deep-cycle battery, I'd have less concern with allowing discharge overnight). And for a short outage, I might be able to get backup power completely from my external deep-cycle battery, and won't even need to hook up the Prius for recharging it.

My 3rd alternative is to simply connect an inverter to the 12V Aux battery, but I think I need to limit my power draw in that case, probably to 1000W or less, preventing powering some larger items (but an alternative for that is to move to an inverter on a conventional car with a larger 12V starter battery for those occasional peak loads, and use the Prius only for smaller continuous loads)

So many alternatives.. I haven't decided yet which way to go.

 

I'd just completed our PriUPS - when the Prius got munched - front and back. Now, the donor hybrid will be the AWD 400h Lexus (as soon as I can talk "she-who-must-be-obeyed" into letting me monkey with it. Ultimately, I hope to be able to use the UPS to spoof our grid tied PV inverters into running if/when the grid goes down. Yes, there will be a main disconnect to prevent back feeding.

 

That may be difficult for grid tie inverters that aren't also designed as backup (off-grid) systems. Plain grid-tie systems without batteries are designed (required by the electric code) to shut down when the grid goes down. If you try to spoof the inverter to stay on, your PV inverter may try to drive excess power to the grid (that's not there), with possible bad consequences, or your PV inverter may not be able to operate at all, since it may depend on the utility power for voltage and frequency regulation and even the sinewave shape, since when connected to the huge low-impedance utility grid, they may be unable to control voltage at all, all they can do is push current in-phase with the utility. PV systems with batteries are different and use different inverters, since they do have to be able to create their own 120V/240V 60Hz power independent of the utility

I'd also thought with my idea of an external battery with an inverter, that instead of a float charger, I could also use a small PV array with a small charge controller to keep the battery charged (and then maybe even take advantage of this small PV system to power something small, like my garage door opener, which is right near the Prius I'd connect during power outages). This small PV system (not a grid-tie system) would have an oversize inverter (compared to the PV cell and battery capacity), so if I need backup power, I can get more power by connecting the Prius.