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Electric Pusher Trailer


66gaza
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Several years ago I read about Mr Sharkeys trial and tribulations with a Diesel powered trailer that he used to push his Electric car around when he went on longer trips http://www.mrsharkey.com/pusher.htm not much good to me but I like reading about people doing things differently and going out on a limb. So enstead of powering an electric vehicle with a diesel powered trailer I suppose you could push a diesel powered vehicle with an electric powered trailer and creating a true hybrid. The trailer could carry a diesel genny and/or a solar panel or just plug it in when you could. The trailer would still be able to carry other things as a normal trailer does but it would be dual purpose. How much battery power do commercial EVs have? I can already hear the cries "This blokes an idiot" any thoughts? comments? Do I just need to sit down in a darkened room?

Gaza

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The way Mr Sharkey does it is correct, the range of EV is limited enough without having to push a diesel lump around town. An EV wants to be as light as possible.

If I were to design a hybrid it would have a de-mountable genny so I could charge from the house for commuting, shopping &c and fit the genny for long runs. The advantage of using a genny is that it can be smaller than a normal engine and would run at maximum efficiency when in use. It could be shut down in towns to reduce local pollution.

You could also use the genny to power the house during power cuts, although I guess the way things are going we will all be living in our cars this winter anyway.

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A solar panel capable of contributing significantly to running an EV is going to cost a number with a hell of a lot of zeros on the end, I'd forget that one and concentrate on the trailer, which is a reasonable idea. I'd vote for a small diesel engine running veg oil.

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A solar panel capable of contributing significantly to running an EV is going to cost a number with a hell of a lot of zeros on the end, I'd forget that one and concentrate on the trailer, which is a reasonable idea. I'd vote for a small diesel engine running veg oil.

Now now Fridge I might be daft but I'm not stupid, the solar panel would just trickle charge when its parked up.

Gaza

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Now now Fridge I might be daft but I'm not stupid, the solar panel would just trickle charge when its parked up.

Even then, it would be making a negligible contribution relative to ~10 seconds of the generator running, and be costing orders of magniture more per watt than the generator.

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I actually heard someone on the radio say a solar panel could charge a battery overnight - he managed to correct himself before I stopped laughing though.

Payback time on solar panels is still far too long, and of course it could get broken or nicked before it pays for itself.

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I was talking to the renewable energy beards at Glastonbury, the very latest solar panels they have can sort of almost power ~30% of your house on a very sunny day - but then they take up half your roof and about £10,000. Given that the most juicy thing in most people's houses is a ~1kw electric kettle, and that 1kw is all of ~1.3hp, you can see why solar panels might not be the answer just yet.

Mind you, there have been a few stories on /. about much more affordable and productive solar stuff in the pipeline, the technology can only improve.

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Are you using some sort of travel kettle John? I think that most are 3KW these days.

Well fair enough, that's still only 4hp and 3kw is approaching the limit for household electrics (240v x 13A = 3120W maximum), the solar stuff is still vastly expensive for relatively low power, the panels would probably not generate enough electric to make up for the electric you use carrying the panels around...

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Even here where it's sunny most of the time, solar electrical panels are mostly seen on top of 4x4s powering the second battery to keep the fridge going.

Although I do have solar water heating panels for my swimming pool. Gets up to 32°c in the middle of summer which is too hot so I have to switch it off.

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Just thinking about this from a financial point of view, rather than a 'save the planet' standpoint - If you were to have a trailer running a small generator, running on either red diesel or waste veg oil, you could then run it at maximum efficiency (effectively full power) and use that to run a motor. Could this be cheaper than running the engine normally? I don't think so simply because of the weight of the trailer, the losses in transmission through a control circuit, and the efficiency of the motor. You would have to run it through a control circuit so that you could go around corners - if you didn't, it would tend to push the back straight on - not nice. If you look at the money for the fuel saved (if any, because of the weight of the thing) and divided it into the cost of the project, I would guess that it would pay back in a couple of thousand years or so.

One thought though - I know that SimonR has thought the same - what do you have to do to make a vehicle 'hybrid'? If you attached a small electric motor to (say) the rear propshaft, and had a battery which was turned on when the vehicle was at full power, and charged (a tiny amount) by a small solar panel - it wouldn't provide any actual savings - and in fact would be a little worse because of the weight of the battery and the motor, but could it be changed to a hybrid vehicle? That would mean lots less in VED, and no congestion charge...

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run it at maximum efficiency (effectively full power) and use that to run a motor.

That was basically my point, but charge a battery instead so the engine doesn't run all the time. Using it run a motor directly means the genny has to be as powerful as the motor in the car, using it to charge a battery means it has to be less powerful, although the work done over a journey would be the same, less any charge in the battery before the journey starts.

Really with a hybrid you only gain by charging the battery first, reclaiming braking energy as charge rather than heat and running the engine more efficiently and intermittently. On a long journey where the distance covered by the initial initial charge is insignificant you'll lose by carrying the extra weight of batteries. For the 10 mile commute you may as well have an electric car and don't lug an engine & genny around.

I like the idea of building a "Nominal Hybrid" for tax reasons though!

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I imagine unless you're a car manufacturer you'll struggle, they never make it easy to avoid tax!

Apparently you just apply to change the taxation class. If you are unlucky, they will want to come and inspect the vehicle.

I had wondered about a couple of options including an extra set of driven wheels that clamp to the rear of a V8 with their own diesel engine and fly-by-wire throttle. On the road, you run on diesel. Off road, you un-couple the diesel drive and chain it to a tree and drive round on Petrol. Hitch it up again and drive home. It would also give you 6WD - which might be useful sometimes.

I have actually just procured a traction motor and controller from a Hybrid Bus. It's rated at 45kw continuous (60bhp) with a peak of about 200bhp.

post-74-1220878302_thumb.jpg

It's not very clear, but it's quite big! Weighs 90kg too - lifting it out the back of my 110 by hand was interesting!

I have all the data to wire it up now - all I need to find is a 68 way connector to plug in to this:

post-74-1220878409_thumb.jpg

One of my friends suggested it looks like an ECU socket - any ideas would be much appreciated! The controllers are no longer made (Siemens SIMotion Inverter) and I cannot source the plugs or leads.

My current plan is to build an electric off-road vehicle. My current build is almost finished - so I'll need a new project in a couple of months. The plan is to try it out in a Suzuki Vitara (cos I fit in them) with SJ410 transmission (cos it's about the right ratio). Why not a Land Rover? Too heavy and there is a lot of drag in the transmission. A Series is an option though.

I'm going to run 18 batteries giving 216v and try to keep it such that it does not require an SVA. My guesstimate is that that should give me a top speed in excess of the speed limit and a range of about 60 miles (a bit more if driven carefully). That will be plenty for 90% of my mileage. the Zero tax on EV's means it doesn't cost me anything if it's just sitting there.

Si

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Ah, you found some more info on the motor then Si? cool... Have you tapped Mike up for info on the Socket?

I have spent quite some time recently reading the site linked to at the top of this thread - there is all sorts of interesting stuff on there...

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Pushers are more popular in America I think. They have trailers with a battery pack and motor for urban 'pushing' and then they tow on the standard car engine on the freeways for long distance. See here.

The risk of a pusher is it pushing the Land Rover over if the tow hitch is high and the corner sharp. It is the same problem I think the 101 powered trailer had.

Also have a look at the Battery Vehicle Society Forum.

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As an OT aside I have a front wheel drive Skoda Octavia and I have been thinking about getting a rear axle from a 4x4 Octavia under the back attached to an electric motor with a load of batteries in the spare wheel well and the storage space under the boot floor. This would give me low range and speed for urban use and Biodiesel for long distance higher speed use.

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I spose you could set it up so that under braking the trailer went in to generation mode and actually pulled the car to a halt - certainly it would be handy in the case of excessive pushing to have the thing pull back a bit with a dab of the brakes. Also perhaps limiting the pushing as the combination turned, so the steeper the turn, the less it's pushing.

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Regen gets complicated though, many electric car conversions don't bother with regen as the effort cost/return isn't worth it. Also if better batteries are used, instead of bog standard lead acid, then the charging system is also complex and would further complicate the regen controllers.

The Push also depends on whether the pusher trailer is used to power the vehicle instead of the ICE or if it is to power itself to reduce load on the towing vehicle.

If it is used to replace the ICE power then it needs to maintain a push around corners. Sharp corners then pose a problem as it begins to push sideways and not in the direction of travel.

If it is used to reduce towing load then it only needs sufficient push to move its own load. This can be achived with a 'throttle' on the over run damper on the towbar. The trailer then only drives when there is a 'pull' on the trailer hitch and brakes when there is a 'push' on the trailer hitch.

I though about doing this a couple of decades ago using a automatic VW camper/beatle back end. The 'pull' would throttle up the engine and the auto box would take care of the rest. The brakes would be conventional over run and the whole thing would drive its own load as a follower, driving only when there is sufficient pull on the hitch.

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The trouble with regenerative braking is that there is a lot of energy released in a short time, batteries like a steady flow of electricity to charge them, so you use an air compressor to brake the vehicle and store the energy as compressed air in a tank. A generator uses this compressed air to charge a battery at the correct rate.

You will of course need a 2nd trailer for the tank.

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