Prius owner uses car to power home during power outage...

You blow the 100 amp fuse between the DC/DC converter and the 12V battery?

 

I have no opinion on the mechanical aspect except it is so complicated and all he powered was a fridge, a lamp and a kettle?

He should have emptied his fridge into his front yard onto the ice. Buy a few flashlights to replace the lamp. And boil water in a small camping stove. Or put water in a kettle and put it on top of an exhaust manifoil of the car to melt the ice. That would have saved him thousands of dollars.

It would have been easier than locating batteries, hooking up wires, hooking up inverters/converters.

 

You need to be more concerned with blowing the fuse between the high voltage battery pack and the 12V battery. Apparently it's not a standard fuse you can easily replace, and if it goes your car is dead. I think that's 100 amps, so you get 1.2 KW (in theory) max draw. Keep in mind that inverters are rated for their continuous wattage, and they have another rating for their max wattage. I just bought a 600 watt pure-sine wave inverter that has 1 KW surge rating (it's my Christmas present, actually), but I don't intend on taking it up to the limit. I also have a kill-a-watt device that I can plug into outlets, and I've measured my appliances to see what I can power if an outage happens. Or if I want to go camping & bring electronics with me.

If you want more power, you need to hook into the high-voltage battery directly, which is a trickier scenario and takes a little knowledge of electricity. For me, I just tap off the accessible 12V battery to the inverter and I'm good to go.

 

Thank you. I always wanted to have a Honda generator. I think I'll get one of them. They are extremely quiet and I don't have to worry about all this. The 1200 watt powers the AC, fans, lights water pump etc so it is unlikely that I can get 1200 watts out of the car. It is not worth it. You set me straight.

 

I'd like to know some more detail about supposed lube problem leading to the ICE failure, before believing it. Plenty of police and service vehicles spend many hours idling at incident scenes, without such problems that I hear about.

Normal car starting batteries will fail fairly rapidly in this type of use. It probably isn't good for the alternator either.

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While driving a high voltage inverter from the traction battery will be much more powerful and efficient than driving a 12V inverter from the Prius' 12V output, others have pointed out that this is a much greater safety and warranty risk. It will void the traction battery warranty.

For ordinary non-techies, a better solution is to acquire one of the modern fuel efficient, inverter stabilized portable generators. While not as fuel efficient as a Prius 'generator', it carries much less technical risk, and likely less financial risk as well.

 

I have heard it will prematurely wear out the catalytic converter because it isn't kept at a warm enough temperature (in standard cars). But this is over the long term, repeated for months. I agree, this supposed lube problem sounds like an old-wives tale to me. (No offense meant to old wives). My old Compleat Idiot's guide for the VW said pretty much the opposite thing - you need to idle for a minute or two before driving so that the pistons are lubricated before you put a load on it. (Note that this was meant for air-cooled VWs, putting a mild load on a cold engine is not a problem on a modern engine).

I disagree, If you don't want to go over 1KW, a DC inverter is pretty easy. This is the one I just bought for $219, and it's even on sale now. Get the cables with it, and you should be able to just hook it up to the 12V battery in the back of the car, and it has two standard 120V AC outlets that you can plug whatever into. As a pure sine wave (not a modified sine wave) inverter, it supplies the signal that electronics expects.

Now you have a portable generator to take anywhere you want to go, and pollutes less (air and sound) than a stand-alone generator.

 

You have to remember that we lost power for 7 to 15 days. Nobody could work, so lots & LOTS of spare time.

This guy was bored silly, and his "setup" was still cheaper than a dedicated generator, that were being sold at a 500% premium.

Some other guy removed his radiator, added hoses, and placed the radiator *inside* his kitchen, and was running his car just outside.

Me, I simply emptied my freezer & fridge in my back yard in plastic bins.
Used my BBQ to heat water, and I had a fireplace in the basement.
The Internet wasn't as fun in 1998 (56k), I made do w/o electricity.

 

This is also cheaper than going the UPS + Prius route. I recommend buying a separate deep cycle 12v battery with an intelligent charger, that maintains the acid battery, so it's always ready.

Then, if the power failure lasts more than a half day, get extra car batteries and use the Prius to charge them, using standard booster cables.

The *best* is a server UPS system, as stated above, but that remains in your garage, and has lead-acid batteries.

Then you can run 10 or 8 gage wires from the Prius HV battery to the UPS battery. Requires a high quality/amp diode to protect the Prius, should the electricity "come back" on. Or, you unplug the UPS unit when you plug in the Prius.

----------------
Prius Bat -> -> UPS Bat stack, voltage must be lower than Prius Bat
++++++++++++
(A diode on the +++ line able to handle 30a, to protect the Prius)
(Hooking in parallel the Prius HV bat should not void the warranty, if it's temporary)

IOW, you have to know your stuff. Too much effort in my opinion. A dedicated server UPS system *with* batteries - to act as a buffer - that can provide a true 15a/120vac draw for at least an hour, is quite expensive. Think 2K$ range.

For a fraction, you can get a bunch of deep cycle 12v car batteries with *multiple* inverters.

Simply run extension cords, voltage drop for 120vac on a 50' extension is minimal, to power individual items.

Having 2 12v batteries "per system" means you can unplug one battery, charge it, put it back in parallel, and charge the next battery. And so on.

With 1K$ you can easily get a dozen (used) batteries, six 1000w inverters, etc.

Remember that generators need off-duty cycles, or you'll kill it. Plus an oil change every 3 or 4 cycles.

A 4 stroke Honda generator that can do 30a peak, 15a continuous, and non-stop operation for multiple days, can cost 1100$.
They are not meant for 24/7 though. I read the instruction booklet once, and they recommend half day on, half day off, oil change every 3 or 4 cycles, with an additional oil change the first cycle.
Messy work, and noisy machines.

Usually you'll just want a light, power your phone, charge cellphones, and run a fridge.

I'd simply do a 3-batt setup for just the fridge, and a 1-batt setup just for phone/light. Two inverters.

 

This doesn't apply to the Prius, where the ICE spends a lot of time loafing. The Prius control system keeps the catalytic converter warm at all costs, even if it has to burn fuel explicitly for heat. In this situation the system advances the timing and lets unburned fuel make it to the cat, where it is consumed and makes heat.

Tom

 

Here's an old thread on this subject. It's long and goes a lot of different directions, from the 12 volt inverter, to testing the 12-volt system to ascertain how much power you can safely draw from it, to the High Voltage systems, and then a discussion of free-standing generators and whether they are more economical to run than the Pruis as a power source. Many of the contributors to this current thread also contributed to this old thread.

If you are considering using your Prius to provide auxillary power, I think you'll find a lot of valuable information in this thread.

Prius as a power source
http://priuschat.com/forums/prius-te...er-source.html

 

Just for newbies reading through this thread, this is simply a non issue in a HSD (Prius or other), when the ICE is turned on, it is done in a much more "civilized" way than with a regular gas only car: MG1 turns the crank shaft (with no pressure on the pistons from gas being burned), then the ECU wait for the engine oil pressure to be brought back up, then it starts engine gas injections/sparks. The engine is already lubbed when it is "started", the engine wear from quick start/stops is therefore not an issue. This happens in less than 1/4 sec if I remember correctly. Note: If you are also using synthetic oil, even in cold temps the oil is probably still fluid enough to do its job from the beginning of the engine start.

 

Over the holidays I installed a Xantrex 1000 Inverter using 50 amp welding cable connectors, 6 gauge battery wires and an 80 amp fuse assy coming off the rear 12V battery. I suspect I am good up to the 80 amp fuse limit, but I only need to run my pellet stove and a few lights in a real emergency and this setup will be more than enough. I tested it with an electric drill but not for long enough to get the prius to start up and charge the battery...I must remember to: Park the prius outside, set the parking brake (so the headlights dont come on), start the car to Ready and make sure the interior heating system is turned off. I run an heavy extension cord (10 gauge 100 ft) from the inverter through the garage and into the house to my APC1400 UPS that powers the stove....it may be a problem if the UPS is fully discharged but I think as long as the load is low on it. I'll be OK...some pics attached...the whole thing cost me less than $200

 

If you are going to try to draw any where near 50 amps off the small 12vdc battery to an inverter you are going to be asking for trouble.

First, if the Xantrex inverter is not pure sine wave (I don't know about that particular inverter) your motor loads are not going to be happy. You may draw very much more current, as the power factor of the motors is low, AND the inverter efficiency is low. Additionally, the 12vdc battery in the Prius is tiny, and expecting it to power any real loads is asking alot, even with the car running.

Remember the starting loads of a motor load can be in excess of ten times the running load, so if you stove fan draws 5 amps at 120 vac, it might draw 50 at start up, convert that to 12vdc you you might see starting currents near 500 amps @ 12vdc. (For those that don't know, power is measured in watts. Watt is the product of Volts*Amps So if a given load draws say 100 watts, it will draw ~ .83 amps (current) at 120 volts. Drop that voltage to 12 volts, and the current rises to ~8.3 amps. (Double the voltage/halve the current. Halve the voltage/double the current etc)

Personally, I would buy a honda Eu 1000 inverter generator, which will run 4 hours on 1/4 gallon of gas, will deliver ~700 watts continuously. Costs ~$4-500 if you buy it right. Then you are not putting a very expensive car at risk for the sake of a couple hundred $$.

PS I know there are several threads about people who have hacked into the HV battery with "real" sine wave inverters to make the car a large UPS. That too comes at a cost (and potential damage) to the expensive car, but the battery is at least of a size to handle the loads.

 

I went a similar route with my 2003 Prius. The only problem I've found is the 'inrush' current to our TV and cable box. I solved that with a pig-tail outlet and an inrush thermistor.

There are reports of potential motor problems with a modified sine wave. I used a temperature probe with our gas furnace motor and found it only went 5 degrees warmer after several hours compared to line voltage. There is a voltage drop because of the length of extension cord but nothing to 'set your hair on fire.' Also, the digital thermostat got 'cranky.' Still, we're warm in the winter and it has also driven a 5,000 BTU window air conditioner.

I have thought about adding a 'stiffening' cap to the 12 VDC system. This might solve the inrush current and also extend the life of the 12 VDC battery (there are lay reports that this works.) But it is one of those 'get around to it' tasks.

I would be interested in your fuel consumption vs kWhr data. If you can get a 'Kilowatt' meter, they are real handy for such measurements.

Bob Wilson

 

The Xantrex mentioned here is indeed modified sine wave with 90% peak efficiency. Motor loads (and switching power supplies) ought to be dealt with on a case-by-case basis. The least expensive pure sine wave inverters I know of in this size class are $300.

Some prefer the additional purchase of a stand alone inverter, and others (including me) have had success tapping the Prius in this way. Seems to me to be a matter of choice, with more options being better. The Honda inverters are excellent (have used them as well), very fuel efficient and quiet. Not quite as low-emission as a Prius, but way better than your typical lawn mower. Must only be operated in a well-ventilated area! (carbon monoxide)

So far I have not read of any Prius main fuses being melted in this way, or inverter damage, so I think that this option remains on the table.

 

"I went a similar route with my 2003 Prius. The only problem I've found is the 'inrush' current to our TV and cable box. I solved that with a pig-tail outlet and an inrush thermistor."


Thanks Bob..it was your post that I originally modeled my setup after. My 1400vA UPS blew my 80amp fuse so it looks like I'll look into your thermistor advice.

 

I'm not following your comparison.

The Honda generator would be running full time. Though its engine is cleaner and more efficient than traditional generators, it doesn't match the Atkinson-cycle Prius.

The Prius owner(s) doing this in the past reported the engine running part time, possibly 5 minutes per half-hour? The initial energy efficiency from tank to the HV battery should be unmatched by anything else. But after stacking on the HVDC --> 12VDC --> 120VAC conversions, it isn't obvious to me whether this will have higher or lower overall efficiency than the portable generator.

Personally, I'm likely to stick with the portable for simplicity, and to get a higher power rating than the Prius 12V system can handle. Tapping directly into the Prius HV is attractive in theory, but carries more warranty and safety risk than I want to tackle.

 

It's a pretty simple equation, the Prius 12v Battery is ~35 ah, meaning, if you could draw it down 100% you could draw ~ 420 wh out. Drawing a starting battery that far will KILL IT!. In fact drawing a starting battery shouldn't be drawn down more than ~5-10% or you will significantly shorten it's service life. (Despite "sales" pitches to the contary, "deep cycle" batteries shouldn't bee drawn down more than ~50% max, and even then most suggest a maximum routine draw of 20% Car and Deep Cycle Battery FAQ, Battery Manufacturers and Brand Names List, and)

So if you only wish to draw the battery say 10% (and the car's voltage regulation system will charge before the 12v gets down that far) that would be ~40 wh before the car needs to charge. Now I don't know how the HV battery charges the 12v but I would guess if you were drawing a 500 watt load, the car would run more than ten minutes per hour.

Even at 10 minutes per hour, you are still using 1800 cc to do what 50 cc would do. Looking at it that way, if the car runs 10 minutes/hour, you would have 1800* .1=180cc/hour. 50 cc for the same hour would be 50cc/hour. Not a straight line comparison, but in simple numbers, the Prius would be ~1/3 as efficient.

All I am suggesting is that given the basic efficiencies/costs/tech advantages, the Honda EU wins hands down. Now if you just want to run a drill for a few minutes away from the grid, great. To use it when the power is out to power the fridge/heater/etc through a cheap MSW is, IMHO, silly.

 

Every load has to be tested and I don't have any experience with a 1400VA UPS. They are supposed to have a 'soft start' but without the unit and test instruments, you're at the 'bleeding edge.'

Many times, I use the audio-input of my laptop as a poor man's oscilliscope. I use 600 ohm, isolation transformers and voltage divider resistors to bring the peak-to-peak voltage to under 1 V. Then audacity, an open source audio recorder, can capture the data.

If your operational scenario is based upon the vehicle inverter feeding the UPS, you may need to consider a more aggressive 'soft start' system.

The usual problem with inrush is charging up the power supply capacitors. Once charged, the equipment steady-state power flow keeps things working. The problem with a thermistor is it bleeds energy because it 'gets warm'. Properly sized, it is a watt for a TV but it needs to be matched to the load. But feeding all power through a thermistor to the UPS could be a challenge.

I tend to prefer simpler systems so I would not use a UPS except for power critical systems. When we have a power outage, I bring up specific loads, one by one:

1. Lights - safety and being able to bring everything else up, ~25 W.
2. Heat/Cooling - to make habitation possible, ~700 W.
3. TV/Internet - to connect to news, ~75-100 W.

With only 1 kW, surge to 1.2 kW, I try to avoid any losses. The TV/Internet has the inrush problem that with the other loads can trip the inverter.

In power systems, especially those working near the limits, stability problems can occur. They can be maddening and each needs to be tested and evaluated carefully. As always, do the testing in 'nice times' as during a real power emergency your diagnostic tools are severly limited.

Bob Wilson