Prius as a backup generator for the off-grid home.

[PriusGuy]

I've been off grid for a while and generators generally suck. I've recently used a midnight classic solar charge controller to convert the high voltage Prius battery down to the 48 volt house battery Bank. I've had some success with this and it's replaced my regular backup generator for the past two weeks. I've been running it 16 hours a night and it's reduce my generators fuel bill by half & the Prius is much more powerful.

You can read about it here https://www.solarpaneltalk.com/forum/of ... r-possible

Currently there's been some talk pointing me to openiverter.Org where I've been reading & its expanded my ideas for this. You'll have to forgive me I'm a total beginner when it comes to this stuff. Is it possible to replace the 200 volt Gen 2 Prius battery with the 48-volt house battery by gaining control over the Priuses inverters output? This would eliminate the need to do any DC converting like I'm doing now and from the sounds of it would enable higher wattage charging then I can do with a single MidNite Classic.

I assume the communications between ecu's in the Prius would have to be spoofed to make the engine cooperate and this is a whole nother level I'm a beginner in as well. Using raspberry pi or adreno and writing a script to run things it's something I've never done before.

If this could be accomplished successfully it would be a huge success for the off-grid world. everyone's running out of battery power and running their generators from time to time costing them lots of gas and smell and noise. since I've been using the Prius instead I've enjoyed it silently running there not bothering The Neighbors and no bad smells coming in my windows all night. These cars can be acquired wrecked for cheap and converted 4 less than the cost of a quality generator. Although I still drive my Prius everyday. So it would be nice if the alteration could be enabled with the flip of a switch when you get home and plug the car into the dock.

[xp677]

Very interesting idea. You're right that a Prius is likely cheaper than an equivalent generator, depending on how you set it up you could see an easy 20kw from such a machine, and maybe up to 3-4x that.

Short answer is yes, its possible. Long answer is that it would probably have to be MG1 only unless you locked the planetary gearset inside. And likely quite a bit oc custom code. As for the engine, you might be on your own for that, its likely outside the scope of this forum. Plenty of aftermarket ECUs around though, including open source units like the Speeduino.

[MattsAwesomeStuff]

Is it possible to replace the 200 volt Gen 2 Prius battery with the 48-volt house battery by gaining control over the Priuses inverters output? This would eliminate the need to do any DC converting like I'm doing now and from the sounds of it would enable higher wattage charging

I'm impressed that the Prius is 2x as efficient as a normal generator. Didn't know genny's were that bad.

So you want run the Prius engine, but instead of it charging the normal Prius battery, just have it directly charge the 48v house battery?

I think you're better off just using a DC-DC converter and otherwise leaving it as-is.

The Gen2 Prius should have a DC-DC converter in it, that's used as a boost converter when driving. You could repurpose this as a buck converter instead, but that's no different than using the DC-DC converter you're using now (except faster charging I suppose).

I'm trying to picture what happens if you just straight hook up a massive 48v house battery in place of the 200v Prius battery. Does that just appear to the Prius to be a really weak Prius battery? It should. Is it dangerously low? Will it still let you charge it? Probably?

At that point, all you need is a relay that (really, really reliably) will trip the charging lines when the house battery is full, so that the house battery doesn't ever actually reach 200v. That shouldn't be difficult or expensive to do.

Will the Prius intelligently only pull as much power from the engine as it should to keep MG1 at a reasonable temperature? Probably?

I'm tempted to say just go do it to experiment, and standby ready to shut the Prius off when the battery voltage reaches max.

Don't trust anything I say though.

[Kevin Sharpe]

Don't trust anything I say though.

[NiHaoMike]

Rather than an expensive charge controller, you can use cheap telecom "rectifier" modules to step down the high voltage. Or even some modified server PSUs in series:

The simplest solution, if your home inverter supports "AC coupling", is to get a 240V induction motor and connect it to a small car engine. The gear ratio should be such that the engine will be running at about 1000-1200RPM or so. Spin the motor faster than its "synchronous speed" and it will turn into a generator. If you mostly run the generator during the winter as is usually the case, having a separate engine makes it much easier to set up a CHP system.

[PriusGuy]

Using the classic make selling its output voltage so simple. for anyone off grades you could easily change the voltage output to 12 volts or 24 or 60 volts right through the menu on the classic. Using Telecom rectifier modules seems like I would have to add a variable potentiometer somewhere in order to dial in the correct voltage for charging house batteries. I'm not against doing this it's just that I'm not quite sure how.

[PriusGuy]

I'm impressed that the Prius is 2x as efficient as a normal generator. Didn't know genny's were that bad.

So you want run the Prius engine, but instead of it charging the normal Prius battery, just have it directly charge the 48v house battery?

I think you're better off just using a DC-DC converter and otherwise leaving it as-is.

The Gen2 Prius should have a DC-DC converter in it, that's used as a boost converter when driving. You could repurpose this as a buck converter instead, but that's no different than using the DC-DC converter you're using now (except faster charging I suppose).

I'm trying to picture what happens if you just straight hook up a massive 48v house battery in place of the 200v Prius battery. Does that just appear to the Prius to be a really weak Prius battery? It should. Is it dangerously low? Will it still let you charge it? Probably?

At that point, all you need is a relay that (really, really reliably) will trip the charging lines when the house battery is full, so that the house battery doesn't ever actually reach 200v. That shouldn't be difficult or expensive to do.

Will the Prius intelligently only pull as much power from the engine as it should to keep MG1 at a reasonable temperature? Probably?

I'm tempted to say just go do it to experiment, and standby ready to shut the Prius off when the battery voltage reaches max.

Don't trust anything I say though.

One complication is the Prius uses its 200 volt battery to start the engine so it would have to switch over like you're saying. And if I were to switch it over without commanding the Prius to do the correct voltage output it would put out so many watts it would force the battery's voltage over its safe maximum very very quickly. It wouldn't even charge much before reaching that voltage. Mechanical relays wouldn't do. It would require a solid state relay so pretty much a pwm charge controller. the thing is the Prius has everything it needs it's only a matter of telling it what to do and installing a transfer relay and that's why I'm asking in this thread.

I got four of these cars now and I'm likely to get a 5th soon. So I've got parts to mess with. I'm trying to make a system that I can quickly easily duplicate and start helping out my friends and neighbors around here with their generation problems.

[PriusGuy]

Very interesting idea. You're right that a Prius is likely cheaper than an equivalent generator, depending on how you set it up you could see an easy 20kw from such a machine, and maybe up to 3-4x that.

Short answer is yes, its possible. Long answer is that it would probably have to be MG1 only unless you locked the planetary gearset inside. And likely quite a bit oc custom code. As for the engine, you might be on your own for that, its likely outside the scope of this forum. Plenty of aftermarket ECUs around though, including open source units like the Speeduino.

While the Prius is in ready mode in park when I watch the power meter it's dumping 4000w into its battery while the engine is running. if I put it in drive and forced charge the battery basically by holding the brake and pushing the gas pedal like is very well known to do to charge the battery it charges at 25000 Watts. The 4000 Watts it normally puts out is increased up to 5000 Watts when the air conditioning is on so it can definitely compensate for loads and I think it can go much higher all on its own if the loads are present but Honestly 4000 Watts is plenty for this purpose. To get greater fuel economy I suppose if you had a large enough battery Bank you could utilize the 25000 Watts but that's going to be a hell of a lot of expensive lithium batteries to handle that kind of power and will be out Of reach for most people anyway.

The lithium batteries I ordered 250 kilowatt-hours arrives in 3 weeks.

As far ascontrolling the engine I don't think it's that complicated because I've read about people converting them to full-time electric vehicles by adding extra lithium batteries and having a small computer spoof the communications between the battery computer and the rest of the communications system. They basically interrupts the communication and replace the messages with their own in order to accomplish the desired result of when to run the engine and when do charge the batteries.
They'll have their own controller sending the message into the system that the batteries are full. That way the rest of the system prioritises electric mode. This type of information is very well known among few people and I would likely Post in the appropriate forums on other web pages on this topic.

But for here what I'm looking for is somebody that knows about the controllers spoken of on this website that are available for the Prius inverter. What are this inverters limitations? can the output voltage be commanded to drop all the way down for someone that's off grid with a 12-volt system, a 48 volt system?

[MattsAwesomeStuff]

if I were to switch it over without commanding the Prius to do the correct voltage output it would put out so many watts it would force the battery's voltage over its safe maximum very very quickly. It wouldn't even charge much before reaching that voltage.

Mmmm no. That's not how that works.

The voltage on the battery will only rise as it gets charged.

There is no such thing as a battery that has "too high of a voltage" but that is "not done charging". Not to a significant degree anyway, maybe the last couple percent.

Think of it like a bucket of water. You can't say "The water level in the bucket is over the top!" and "The bucket is mostly empty" at the same time. Adding water to the bucket is what raises the water level. If you were pouring water from a hose at chest-height into the bucket sitting on the floor, you would definitely overfill the bucket before the water level reached chest high, but that doesn't matter, as long as you shut the water off when the bucket is full. The bucket will both be filled with water and have the water at the right height at the same time.

Provided that the Prius can handle the current steadily at that lower voltage (like an empty Prius battery that appears to never increase its voltage), there is no issue.

I got four of these cars now and I'm likely to get a 5th soon. So I've got parts to mess with. I'm trying to make a system that I can quickly easily duplicate and start helping out my friends and neighbors around here with their generation problems.

Yahoo.

I think it can go much higher all on its own if the loads are present but Honestly 4000 Watts is plenty for this purpose.

4000 watts is a pretty small generator. Especially compared to what the Prius is capable of. That might be below the optimum efficiency of using the Prius as a generator. Plus it's a lot longer for the noise of an engine running.

I suppose if you had a large enough battery Bank you could utilize the 25000 Watts but that's going to be a hell of a lot of expensive lithium batteries to handle that kind of power and will be out Of reach for most people anyway.

The lithium batteries I ordered 250 kilowatt-hours arrives in 3 weeks.

... wait, what?

You bought a 250kwh lithium battery? That's enough to go 10 days off-grid for an average family before needing a recharge.

25,000 watt generator would charge up an average family's energy needs for a day, in about 1 hour. That seems to be about the right amount of time to be running a generator.

But for here what I'm looking for is somebody that knows about the controllers spoken of on this website that are available for the Prius inverter. What are this inverters limitations? can the output voltage be commanded to drop all the way down for someone that's off grid with a 12-volt system, a 48 volt system?

The controllers Damien sells on the http://EVBMW.com webshop are 3phase speed controllers. They use the code from Johannes (OpenInverter) to tell the Prius inverter what to do.

Damien also sells a (only slightly tested) DC speed controller, which presumably just uses PWM and might be more suited to just being used DC-DC converter.

There is also just a plain DC-DC converter in the Prius inverter that might be easier to use but I don't know if anyone's written a way to do that yet.

For 12v... the Prius's have 12v batteries in them still. So there's presumably some auxilliary DC-DC converter that can at least handle the typical alternator loads.

But you want to do this without using a DC-DC converter?

Honestly, since you only want 4000 watts, I'd just leave the Prius intact, tap the 200v battery, presume that that's close enough to the 170v peak you'd get out of most rectified mains, and just use an old, junk 48v UPS to charge your batteries. Problem solved. (Better yet, get a unit that was tolerant for 120-240v ac input). An old UPS has to be cheaper than even what Damien is selling speed controller boards as, and you'll have to do zero modifications to the car.

[PriusGuy]

Just thought I'd throw an update in here. I remember I was using the Prius high voltage battery connected to a midnight classic solar charge controller and it was working for 2 weeks? Well yep it worked very well for nearly six months until I upgraded my system with my lithium batteries. I changed my houses inverter to a inverter that requires 500 volt battery. I made a 500 volt battery utilizing the lithium's that I had ordered and it total 65 kilowatt hours. The rest of the batteries I've been selling to friends and family. My new hybrid inverter system has been working so well I have forgotten that I'm off grid until recently it's been cloudy for the last two months and I'm finally running low on power. Now I need a way for backup power with a 500 volt system.
Brusa chargers that can charge up to 520 v battery have a AC input but I'm wondering if I feed the 200 volt DC from the Prius battery Into it if that would work? Or maybe use the openinverter system and get a spare inverter from my other Prius and use that inverter to boost DC up to higher voltage. Will the openinverter.Org idea be able to utilize a DC source instead of AC mains?

[johu]

Yes it can use a DC source but so far there is only current control. You can however limit the maximum dutycycle so that it doesn't exceed a certain voltage.
Boost converting needs a little tweaking as there is an inverse relationship between duty cycle and current in Prius converter in boost direction.