Advice on Hybrid Kit Car

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Chris King
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Advice on Hybrid Kit Car

Postby Chris King » Wed Oct 01, 2008 11:20 am

Hi there

I am about to start building a Hybrid kit car. I am seeking the best combination between a battery pack for plug in top up, and a 5kw diesel generator for longer runs and battery top-up when/if needed. The thinking behind this is:-

1. The battery pack only would be used for short every day trips in town and to the shops, and be capable up top-up from the home using the grid.

2. The diesel generator would provide the ability to travel extended distance and top-up the batteries if needed. The generator provides 12, 110 and 240 volts.

3. The combination of both the battery pack and the generator would give better performance if/when requiried for motorway speeds.

My idea at the moment is to have a 7.5kw motor running on 110 volts using lead acid batteries. Any views on the size of the battery pack and/or my choice of voltage?

I also need advice on what sort of motor, as I intend to use the present gear box with four forward and a reverse.

Chris

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ChrisB
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Postby ChrisB » Wed Oct 01, 2008 6:53 pm

Sounds familiar :lol:

Image


Really need more specs on what you want to do i.e are you planing to carry the genny all the time or like me just have it when required ?
Also what sort of range are you after 300kgs Lead Acids at that voltage with that sort of motor size will only give really about 30miles tops I recon.
Again what sort of top speeds do you require and for how long ?

I had a Fiesta running 2x10kw lynch motors which was good for 75mph and had a usable range of about 25-30 miles but that was @ 30mph . At 75mph the batts gave up the ghost at around 10miles :cry:

ChrisB
I reject reality and substitute my own !!!!!!

Chris King
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Postby Chris King » Wed Oct 01, 2008 7:49 pm

ChrisB
My choice of kit car is the Brooklands Pembleton see:- www.pembleton.co.uk
Follow this link through to the Pembleton Motor Company. which shows the light frame and low weight. This is based on the 2CV and is under 400kgs. By taking out the two cylinder 602cc petrol engine and the associated heavy parts for this - I hope to be able to replace with batteries and the 402cc diesel generator to take the total weight to say 550/600kgs max.

I only require 15 to 20miles @ 30mph or so on batteries. But wish for a top speed of 70mph with the 5kw generator. This can run for many hours on a tank of diesel, so the distance appears to be no problem. Especially when adapted to run on cooking oil - but that is another project in the future!

The generator in the photo appears to be the same and I have shaved off half its weight by shedding the frame, cover and frills.

Chris K

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qdos
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Postby qdos » Wed Oct 01, 2008 9:55 pm

Interesting choice of kit. The 2CV components have some rather neat design features and I must say I wondered about it as a basis of an EV though I'm not sure the pembleton is an ideal candidate but I'll be interested in how it goes for sure. How are you going to site the generator ? I'm assuming it's not going to be all on the front.... What's the total power output you're anticipating ? I don't think 5kw will get you to 70 I run a 15kw petrol 2 cylinder car which could be said to be a modern 2CV and it manages just over 70mph but I can't see it achieving it with a third the power. oh mine's 370kg too and probably more aerodynamic than the pembleton

MalcolmB
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Postby MalcolmB » Wed Oct 01, 2008 10:40 pm

Hi Chris
The Pembleton is a great looking car in my not so humble opinion. Not exactly the most aerodynamic shape, but you can't have everything. 12.5 kW (motor plus generator) might not be enough to get you to 70 mph. I'd estimate that 15-20 kW would be closer to the mark. Is there a particular reason you chose 7.5 kW for the motor, and is that continuous or peak? If continuous then you naturally have a lot more headroom.

Given the right motor and batteries 110V should get you in the region of 70 mph if you're keeping the gearbox. For a range of 20 miles with lead acid I'd suggest using 12V batteries with a minimum capacity of 100Ah.

MalcolmB
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Postby MalcolmB » Thu Oct 02, 2008 7:18 am

Thinking about this a little more, 100Ah lead acid batteries should be ample since you were only asking for 15-20 miles at 30 mph.

Chris King
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Postby Chris King » Thu Oct 02, 2008 1:14 pm

Malcolm(B)
Many thanks. I think your 'humble opinion' is spot on. The Pembleton Brooklands is about fun motoring and goes in a different direction to the V8s, wide wheels burning rubber, BHP/MPH in treble figures and lots of noise.

OK - Batteries first. If I went for lead acid or similar, producing 100Ah, what sort of weight are we talking about and how are they made up? I wish to charge up at home on the grid and also whilst on the move by the inboard generator (12, 110 and 240 volts) and regeneration if possible?

I thought a 7.5kw electric motor to be middle of the road (forgive the pun), and do not understand the 'continious or peak' element you mention. However, I could easily easily opt for a 10 or 12kw motor at this early stage. I chose 110 volts as I thought I could then use a 110 volt battery pack (made up of 9 x 12v batteries) and the generator together for more umphhhh if needed and motorway speeds of 70mph. The generator produces 5kw at 240 volts, and I understand the easy way to increase performance is to up the voltage, but I think this would mean an increase in weight in the battery pack!!!???

As to the gear box I am still trying to get hold of some one local who has the coupler knowledge for the motor/gearbox link. This is necessary as the Pembleton uses the inboard disc brakes off the gearbox drive shaft.

Chris(K)

Chris King
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Postby Chris King » Thu Oct 02, 2008 1:26 pm

qudos
Also many thanks. Clearly your modern and streamlined car will be more efficient. For that reason I am interested in your suggestion of a 15kw motor. Malcolm recomends taking it up to 12kw. The generator is diesel and will run at 5kw output all the time, even when stopped. Hence my thoughts that it would charge the batteries even when the motor was not drawing full power. Is this possible, what do you think?

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qdos
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Postby qdos » Fri Oct 03, 2008 11:18 am

Hi Chris,

The generator could be used yes there's a number of people thinking and doing things with them but they tend to be 'range extenders' ie they charge up the battery whilst you have the genny running, not sure about the boosting voltage thing and if it can be simply done or not.

My main thought on the Pempleton though is the physical room for all this. Are you considering a 3 or 4 wheeled one? The 2CV is quite a smart design with some really nice features but the motor hangs out the front a long way unless you turn it all around which a 'friend' of mine you may have met as he's a total 2CV H Van nut has done with a couple of 2CV specials.

Are you dead set on the Pembleton as I think there's some other fun machines out there that you might like to consider.

MalcolmB
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Postby MalcolmB » Fri Oct 03, 2008 3:14 pm

A 100Ah 108V lead acid battery pack made up of nine 12V batteries would weigh somewhere around 225 kg.

A 60Ah 108V lithium phosphate pack (which would give you slightly better range) would weigh around 80 kg.

The series DC motors that are most often used for conversions are generally rated for continuous use, i.e. running all day. They can usually be run at higher voltages and currents for short periods as long as the windings do not overheat or the maximum rpm is not exceeded. The peak power output can be 5 to 10 times the continuous rating, but you can only maintain it for short periods of say a minute or less without additional cooling.
DC permanent magnet motors, such as the Lynch type (Agni, Etek, Perm etc) that are sometimes used in smaller EVs have less headroom for pushing beyond their rated specs, mainly because they are so light – they have less thermal mass.
If you haven't already done so I'd recommend looking at vehicles of similar weight and speed in the EV photo album www.evalbum.com to see what they have used.


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