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Forum Index : Electronics : Turning a Toyota Prius into a "portable" generator

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Haxby

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Joined: 07/07/2008
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Posts: 58
Posted: 12:31am 15 Jul 2020
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Hi all,

I have recently discovered the world of the EG8010 and EGS002 modules. What great little components.

For a long time I have thought of converting a Toyota Prius hybrid into a 5KW portable generator. The benefits include the fact that the engine is super quiet, super efficient, super reliable, and with the built in battery as a buffer, it turns on and off as required, so does not run at full duty. Coupled with an off-board battery, this would seem to be a great combination for off grid living, or to power an off-grid cabin or weekender.

There was a product on the market for this purpose but they seem to have shut up shop. (Converdant power) So I guess I'll make my own.....

There are two main hurdles:
1. Convert 220V DC to AC
2. Isolate the 240V AC output from the rest of the car.

I'm thinking of going a similar way to the Ozinverter but with mosfets and transformer to suit the higher voltages.

One product that is half way there is this one:

3KW inverter

It's designed to take 340V DC in and create 240V out. I'm thinking this can be modified to take 220V in and 240V AC out via a large toroid transformer.

One benefit of the 220V DC supply is that I might be able to get by with a 110V to 240V commercial step up transformer, like those used to run USA devices in Australia.

Just looking for any thoughts, comments, or interest at this stage.
 
Davo99
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Joined: 03/06/2019
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Posted: 04:42am 15 Jul 2020
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It is an interesting concept and I have read about it before. The yanks have done all sorts of things with The Priarse like adding bigger battery's and making them an EV that can be charged from the grid.

I drove an old hacker around NZ for 10 days and was surprised by the thing. Loaded up with 3 People whom have no idea of the concept of travelling light and a bit more equipment to really fill the thing up, I was impressed how it pulled up hills especially when there was some charge in the battery and generally got along leaving many larger vehicles behind.  I flogged the thing and still got good economy and performed quite well for a Dunger.

I spose a lot of what you want to do would come back to cost and practicality.
I have read of people using these cars to run off grid holiday houses and using them as power plants or battery chargers.  I have read about added discharge Cycles on the battery but given how small the batterys are and how many times they charge and discharge when driving, Probably not a concern.

I have seen Vids on the net where they remove the engine/ alternator setup from a wreck and mount and run that as a generator. Supposedly economical but I wonder how so when compared to a little Multi Cyl Diesel Generator? Something like a Lister is Very economical but those single Cyl China Yanmar copys are not so much. Probably because of the amount of energy they turn into making a god awful Racket when Running.  I have about 8 of the things, ask me how I know!


I wonder if the battery pack could be connected to a solar array to reduce the engine running and make it even more economical?
That would seem to be the best of all worlds. Have solar power through the day and have a an auto generator kick in at night or with heavy loads.

From what I have read ( and the more I have forgoten) the battery packs on those things Varied a fair bit in size. I seem to recall the early ones were around 7 Kwh and the later ones were substantialy larger. I have also read that these vehicle battery packs can be had quite cheap in the states but are around $1500 here depending on used or refurbed. For that money one could buy a much larger LA pack from a forklift.

Fathers neighbour got an off grid inverter that will charge from Solar or the mains. I _ think max input on that was about 150V DC but that may have been the start up voltage. The system was a 48V battery but the DC input was MUCH higher. From memory the battery packs on the early Priarses was about 208V but the alternator could go to around 650.  I think you would have to look at the exact model you had as I believe the specs on the things changed a bit.

Be interested to see what you find and what can be done with them though.
I read a piece in the extra battery and EV conversion and there was a LOT to it in making all the electronics talk. It's almost anything but just plain electrical with these things.
 
Grogster

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Joined: 31/12/2012
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Posted: 08:40am 16 Jul 2020
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A very interesting idea and thread!  

I would be inclined to find a Prius or Leaf that had been in an accident, buy it cheap, push it into a new permanent home, and use the hybrid engine/alternator for EXACTLY the purpose that the OP mentions.

Hey, it's not gonna need to be street-legal again, right?
And you have a fully self-contained quiet kW generating machine.  
I have no idea what a wrecked Prius or Leaf goes for though, but so long as the engine/alternator and battery-pack were OK, who cares about the rest of the body shell damage?! (rhetorical!)

The members here would no doubt come up with a design to take the output from the alternator to the battery-pack, and use that as the basis of the DC-to-230v AC inverter '2nd Stage'

I will be watching this thread to see what people suggest or come up with.
Might keep my eye out for crashed Prius's or Leaf's!!!!  
Smoke makes things work. When the smoke gets out, it stops!
 
Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 58
Posted: 11:37am 16 Jul 2020
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Since millions of them are on the road, it's very easy to find a slightly crashed one for say $5k. Right now there are a few up for auction in Australia due to being written off from hail damage. All panels have dents but the engines and internals are perfect. The engines themselves are quite cheap on the used market too, mainly because they are so reliable that nobody really needs to buy them. The built in "alternator" is really 2 incredibly well designed, high quality, permanent magnet electric motors that work as either generators or traction motors as required. They total 60kW but I only need a fraction of that.

My thoughts are now to design a DC to AC inverter with the help of the EGS002 board and some optoisolated MOSFETs. The good thing about the high voltage 200-230V DC of the Prius battery is that there will be about 4 to 5 times less current than a 48V system, so the electronics can all be smaller for the same amount of power. Less MOSFETs, less heatsinks, less current but the same amount of power. I'll keep the group posted. I ordered some EGS002 modules today. Shame there is no local supplier for them like RS or Element 14. I'll be waiting a month before I can start any tests.  :-(
 
wiseguy

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Joined: 21/06/2018
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Posted: 02:13pm 16 Jul 2020
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I also like the electric vehicle approach, either on blocks in the shed or still registered and being used on the road too.  I was considering building a 96 or 120V DC car that would double as battery storage when not being used to commute,

My Inverter (5+ KW) is a 48V input, using one of Poidas nano micros on my own design controller pcb and power stage. This would suit a HV dc design such as you are contemplating with little to no modification.

When Poida kindly provided the nano code to create the waveforms I required and I devised suitable gating for the 4 quadrants I needed for my inverter. I later realised that the 8010 appears to provide the same 2 x pwm waveforms just like the nano and could also be a solution

I must confess that despite not liking a lot about the EGS8010 and having found some design flaws with it, I have not totally discarded them to the waste bin as yet.

When I have some spare time, out of curiosity, I will try out an 8010 IC in a modified application where it provides just the 2 x 20kHz PWM fundamental drive waveforms, feeding my own gating circuitry & power stage. If it works as I hope, it may offer another approach to a successful inverter.

It will be interesting to see where this thread goes.
Edited 2020-07-17 00:14 by wiseguy
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
Davo99
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Posted: 03:30pm 16 Jul 2020
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  Haxby said  Since millions of them are on the road, it's very easy to find a slightly crashed one for say $5k. Right now there are a few up for auction in Australia due to being written off from hail damage.


$5K is a LOT for a wreck for that value of a road going vehicle. It's also a lot when you consider what you can get in a diesel generator for that money thats ready to go.
I saw a 9Kwh Forklift battery pack for sale the other day that was described as being near New for $1000. When one considers what they could do with that and a pretty straight up charging setup, The prius may not be such an economical proposition.
I would think you would want to source the Vehicle for a lot less than 5K.

Were the Auctions you saw general Auctions or Dealer Auctions?  You need a dealers Licence for the salvage auctions but they are far and away the best place to buy.
I would expect a write off for a car of that value to be under $1000 these days but being what they are, maybe there is a much higher than average demand and also far more saleable parts. Once they have a yellow sticker ( Non repairable write off) The main thing is the running gear in them.

Panel damage means nothing these days. Once they get the canary, that's it. You just don't sell panels/doors nor anything in the interior. Headlights, tail lights, Mirrors, sensors and the running gear is where the money is. The rest is scrap. Other thing with buying at auction is all the fees and charges. They will easily run $400 on a $1000 vehicle and then you have to have the thing towed to where you want it.  You would be lucky to go get it yourself with a car trailer these days, the OH&S and the fall back of responsibility to the auctioneers  to see all proper procedures and practices are met before they leave their gates makes that a rare proposition.

There are 11 Up for Auction at pickels atm, mainly in NSW and VIC and most are the older models.  Curiously, most seem to have only one side at the front taken out. most look similar damage which is pretty unusual. Maybe there is a Blind spot or something with them?

Looking at the damage, I think one would want to be careful with damage to the wiring looms and computers. I know what normal vehicles have in them, I can only imagine the electric and electronic nightmares one of these things could hold. Just removing a loom is a multi day job and on a lot of vehicles now you REALLY need to know what you are doing if you modify anything. Can't just go chopping off wiring that would go to the blinkers or brake lights because a lot of systems expect and check to see resistance in the tail lights etc and if it does not find it....

Other problem could be if the air bags have gone off which Id think the majority of the ones I just saw have.  That can Kill the computer or throw fault codes that -may- need the dealer computer to clear and I think one would have a hard time convincing one to do that to a wreck. I think you'd want to look at keeping the car together but thats going to be a big, ugly lump sitting round.

I would strongly advise looking into these things on relevant sites and forums with people whom have played with them to make yourself aware of any Pitfalls with the things. I can potentially see many so you would want to know what will be OK and what will be a deal breaker before you bought one that's for sure.

One thing with these is that would be an Ideal basis for a Co-gen setup where you use the engine heat in winter to warm the house. Should be plenty of power to plug in electric resistance heaters as well which would help the coolant energy levels and you could take that from the DC side as long as you didn't switch the appliance on and off internally or with a thermostat.

Interesting project for sure!
 
Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 58
Posted: 02:06am 17 Jul 2020
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The co-gen idea did cross my mind. It would be a shame to lose half the petrol energy in heat. I've got a comical vision in my head where there is a water tank installed in the back seat of the car, with a heat exchanger running from the radiator hoses....

As comical as this would look, I wonder how low the cost per KWH could get. Assuming 10KWH required per day, and a 5KW generator, the Prius will run for 2 hours per day. Say 1 hour in the morning and one hour in the late afternoon to replenish the battery packs at the highest energy usage times per day. I'm guessing that might be enough time to heat enough water for the average family.

I actually own a Prius as my daily driver, but wouldn't mind buying a wreck to tinker with. There is an auction finishing on Monday here . Storm damaged. We'll see what it goes for just out of interest. Can't be too much for a 13 yo car.
 
CaptainBoing

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Posted: 09:54am 17 Jul 2020
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sort of related... years ago a mates father had a large workshop heated by an old cast iron pot-bellied stove - once it was going it would get the whole place like a sauna. The roof was about 14ft and he had the flue from the stove run up the inside wall and exit fairly near the top to maximise the heat output - effectivley.

Later he added a lagged c/h water tank and coiled a load of copper micro-bore c/h pipe around the flue so he had a supply of hot water for free as well. A little water pump cycled the water. The thing stayed hot for days

You could do a similar thing on the Prius (if it was static) perhaps - maximise use of the waste heat from the ICE.
 
Davo99
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Joined: 03/06/2019
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Posted: 09:23am 18 Jul 2020
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  Haxby said  

Assuming 10KWH required per day, and a 5KW generator, the Prius will run for 2 hours per day. Say 1 hour in the morning and one hour in the late afternoon to replenish the battery packs at the highest energy usage times per day. I'm guessing that might be enough time to heat enough water for the average family.


Having forgotten more about this than I remember.....

As I recall, 1/3rd of the energy is wasted as heat and 1/3rd is mechanical energy.
Standard practice is to put half the generator KW onto the HP rating of the engine.
Ie, 6 HP engine will drive a 3KW gen head. Not the mixed power ratings.

Don't know what that works out at in heat energy but I'm guessing your 5kwh of electricity will generate about 8-9 Kwh of heat. the 2nd or 15th trick to this is an amount of that heat is in the exhaust so you need to be able to try and recover from 2 heat sources.  A lot of what I have read says that exhaust heat recovery isn't worth it and others say it is. I guess a lot would depend on the size of the engine and the output it was generating.

Without the exhaust, you are probably back to somewhere around 5 Kw of heat in the coolant.

If you are talking about hot water for a family, 10Kwh is going to give you very loosely somewhere around 200-220 L per day of hot water.
You could easy Plump up a 30 Plate FPHE to the coolant ( Heater) lines of the engine which is where the hottest water is and run a circ pump into a regular HWS.
You could drive the water pump electrically or use something like a a brass impeller Jabsco pump off the engine like they use on boats.  3/4 Hose would do it as there is not going to be much heat/ load from the engine.


Is this a theoretical or a practical application you have in mind for a real world setup you want to use it on?

Just thinking that if you only want 10 KWH a day, You could buy a LOT of solar panels for what the prius wreck and the conversion is going to cost you and you would certainly have enough power even from a 5Kw array to charge your battery's and heat your water in summer. 10Kw of panels should cover your needs most of the year round.
No fuel to buy and the batterys wouldn't even be discharged at all during the day and it would all be automatic.

Be interested to see what the prius goes for.
Right now it's at $1100 which with fees and charges is $1300 plus getting it home.
Still not bad for the potential it has.

OTOH, for the price I buy panels for atm, that's 20 KW worth!  :0)
 
Warpspeed
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Posted: 09:53am 18 Jul 2020
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Down in the Antarctic the diesels generate power, and the engine cooling water heats the buildings and provides domestic hot water through a heat exchanger.

In summer there is a problem.
Its daylight 24 hours and there is minimal electrical load, and the diesels hardly work, so the building heating gets a bit marginal.
The solution to that is to switch in a big electric boiler. That loads the diesels and at the same time produces even more hot water.

A Prius system could be adapted in many different ways, including adding solar panels.
I think the whole idea certainly deserves looking into.
Cheers,  Tony.
 
Davo99
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Posted: 04:09pm 18 Jul 2020
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Honda and Yanmar among others have done co gen systems.

Honda co gen

yanmar

Prius Generator setup:
 
Haxby

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Posted: 12:12pm 25 Jul 2020
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Davo99:  The Prius went for $2325 plus auction fees. Not cheap but not too bad.

I already have a Prius so this project is more about building an inverter that can run off it’s traction battery.... The real world application is to use it for camping, and as a generator for building houses, so it’s got to run a decent air compressor, chop saw, microwave...

The dream is to build a cabin with the PriVerter and then to use the cabin as a weekender, powering it by the Prius.

In another thread, Warpspeed suggested building the warpverter, and after reading multiple posts about it,.... I’m hooked. I have acquired one AeroSharp 3kw inverter just today, And have immediately started to take it apart. Warpspeed kindly gave me a PCB for the warpverter, and some components have started to arrive from RS.

The aerosharp seems to have a stock transformer that Is extremely close to what I need.

Now the minimum voltage of the Prius battery is 200vDC so In an ideal world I need 4 transformers with voltages of:

200:225
200:75
200:25
200:8.33


But if I use the stock aerosharp  transformer, without re-wiring it, it is rated at 230:250v then I can use it as a lower voltage 200:217 volt transformer without modifying it right......? This approach is tempting as there is less work. Obviously it will have a lower power output but should be plenty for power tools.

So the other 3 transformers to wind or buy come down to:

200:72.5
200:24.15
200:8

Or if I used 240v commercial transformers could I use:

240:87
240:29
240:9.7


Is that how it works or am I way off? I know the inverter output with these transformers would be 218v, instead of 240, but I could live with that.
 
nickskethisniks
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Posted: 03:08pm 25 Jul 2020
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Yes you could try that but Warpspeed mentioned to respect the output voltages,they need to be factor 1/3 of eachother.

But you could achieve that by simply remove or by adding some extra turns. It would still save you an enormous amount of time.
 
Haxby

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Posted: 06:29am 26 Jul 2020
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How do I get the potted core out? Wack it with a sledgehammer?

I don't want to damage the windings.
 
Warpspeed
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Posted: 07:16am 26 Jul 2020
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  Quote  But if I use the stock aerosharp  transformer, without re-wiring it, it is rated at 230:250v then I can use it as a lower voltage 200:217 volt transformer without modifying it right......? This approach is tempting as there is less work. Obviously it will have a lower power output but should be plenty for power tools.


If you do that, with 200v dc you get 217.4v just as you say, for the largest transformer.

If the other transformers ideally go down in exact steps of three from there, they would be +72.46v, 24.15v, and 8.05v.  Total peak voltage would be those four voltages all added together 322.06v achievable peak.

Final Rms voltage will be 227.7v with a 200v dc input.
Sounds like a reasonable suggestion.

The second transformer would theoretically need to be 200v to a third of 217v or 72.33v.
Cheers,  Tony.
 
Haxby

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Posted: 07:53am 26 Jul 2020
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Thanks warpspeed!

Ok the second transformer is the one in the pic above. It comes from a 1.5kw aerosharp. Without mods, it's 93v:230v

So at 200v it's output is 80.86v.
That's tantalisingly close to the required 72.33 but not close enough. I wonder if I can unwind a few turns?

If there is a trick to get the core out, let me know!
 
Warpspeed
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Posted: 08:06am 26 Jul 2020
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O/K 80v is a bit high, but usually the winding with the fewest turns is on top, so it should be possible to remove a few turns to bring that down.

Usual way is by brute strength and ignorance, aided by a BFH.

(BFH = big flamin hammer)
Cheers,  Tony.
 
Haxby

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Posted: 08:59am 26 Jul 2020
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Well that sounds good to me... Two transformers in and I haven't had to do much work yet. For the third toroid, I'll propose to buy a 300va 240:30v transformer toroid. This will give me 200:25 and I can back turn 1 volt to get 24.
 
Warpspeed
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Posted: 09:44am 26 Jul 2020
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Yup !

Altronics have a 30v + 30v 300 Va toroid, and also a 9v + 9V 160 Va toroid.

A slight tweak +/- here and there with the turns, and it should all work out very well.

This will all be excellent for initial proof of concept testing and give you a much clearer picture of how this all works.

Start with the largest inverter first, then add each new inverter successively to that.
Don't be too surprised to see massive overshoot and ringing on the secondary from just the first big transformer all by itself.

The second transformer will give you nine voltage steps, but they will look a bit ragged on the secondaries as well.

Third transformer, twenty seven rather wobbly looking voltage steps, not clean steps, don't be discouraged.

Fourth transformer, magic happens.
The final sine wave will look unbelievably good, and that will be a real surprise.

Transformers don't like square wave current, but when all four transformers are working together in harmony, the combined voltage and the combined current through all the transformers will be sinusoidal.

If there is any residual crud on the output waveform, it will almost certainly be on the dc supply as well. Some very large, very low impedance low ESR electrolytics help a lot.
Edited 2020-07-26 20:18 by Warpspeed
Cheers,  Tony.
 
Haxby

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Posted: 02:39am 27 Jul 2020
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Good news is that the potted core came out easily. I rested the transformer on some polystyrene and wacked the centre with a sledgehammer with a bit of timber between sledgehammer and the potted core.

It came out nice and clean with no damage to the windings.

Bad news is the 80.86V winding is under the 200v winding.


Now should I:

Back wind the 80.86v winding to get 72.33

Or

Unwind the whole lot.
 
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