If you were going to build an DIY electric car.

Maybe have a look here

at what they're using and the Lynch connection. IIRC having spoken to them a few years ago the motor is nowhere near its limit in the application as it can be run at upto 70V and produce significant power. Also the electronics pack could run the motor as a generator to recharge the battery in some situations.

I've heard of 48v fork truck motors being run at 90-144v DC in homebrew car projects, and as long as they are kept sufficiently cool, not suffering any shortening of life.

Depends on the specifics of the motor. Some just wont turn fast enough. Some are only efficient at certain speeds and loads and so range would be crap. Gears seem like a good idea since you wont be pulling hundreds of amps pulling away in top!

No thats fine.

Non. They will all be slow, heavy, expensive and need better than lead acid batteries to stand much chance.

Its all self defeating. The taller the gearing (to make it faster) the more amps you pull trying to move about at slow speeds. And the more batteries you need for capacity which makes it heavier increasing current draw (start again at the beginning)

Yep.

Try a small toy bedford van with a layer of batteries on the bed and rear drive. Auto is a bad idea as the torque needed to pull away comes from loading the motor and the wasted energy in the slippage is wasted range.

Are you going to remortgage your house for the batteries?

No you recharge the batteries with the emf on a decent controller.

They cannot supply enough current. You need ideally AGM batteries such as the Optima yellow top. Or maybe MK Gel or Sonnenschien GEL mobility / EV batteries.

Plus you cannot recondition a battery. When it is sulphated through being left slightly discharged its toast. When its "cycles" are used up its got no active material left on the plates.

You need Deep Cycle batteries with a 400 to 500 cycles at 80 percent discharge level. Preferably ones that have a cca rating as they can give you the amps to accelerate too without voltage drop or creating voids in the Gel.

Yes. Thats all milk floats, golf carts, powerchairs or scooters use. But you will need a speed controller. Probably 48v and say 500 amps absolute bare minimum. Read up on robot or EV vehicle controllers.

I dont see the point! A) C02 is NOT changing the climate! B) Battery technology isnt yet even close to being good enough. (unless you spend 30k on fancy lithium polymer or ion batteries) And it takes more energy to create them and to dispose of them than your petrol car uses anyway during the typical 1 year life of a deep cycle battery. C) Slow D) Massively more expensive than running on pump fuel E) They still need charging anyway! And that uses MORE energy than just putting the fuel in the tank due to generating losses, transmission losses, charger inefficiency, battery charging inefficiency.

Probably! Powerchairs are also EVs...

I knew you would know your stuff.

I'm not considering it because it would make a practical day to day replacement. I'm thinking of doing it because it might be fun to learn something new.

And electric cars aren't slow, don't think milk float and fork truck just because I might be using the motor from one.

I know a lot about batteries and motors. Electric cars using batteries you can afford without sponsorship (deep cycle lead acid) are either fast or have range. Not both unfortunately.

Fast is no problem as long as you are happy with one run down the strip. Distance is no problem if you are happy with low gearing and low road speeds. Both is no problem if you have 30k worth of lithium batteries and 96 percent efficient direct drive brushless motors etc. All which costs a fortune.

Doing it the cheap way with say 20x 55 ah Optima batteries or similar and low slow gearing for usable range of say 30 miles will give you about an 80 percent discharge level daily if you just go shopping. Meaning new batteries every 200 to 300 days. You will only get 300 cycles under very controled conditions and with careful temperature compensated fancy charging etc. Anyway they are about 189 quid each 20 x £190 every 10 months is the first of your problems. You may get half that in practice until you figure it all out. Thats over 4k a year to keep it in batteries alone. How do I know Because I do the same to my 2 identical wheelchair batteries every 10 months...

Lesser batteries (cheaper) will either not give you the amps required on say inclines or away from a standing start or wont give the cycle life at high depth odf discharge you need.

Of course lithium batteries are the real answer but then they are 10 times the price!

Of course leaving the engine it already has, using the electricity to make hydrogen from water, and fitting a lpg kit and altering the fuel pressure to work with hydrogen will give you better range, better performance, less expence, less weight, etc etc...

I like the idea of this sort of hybrid. Almost like the old diesel electric trains.

Running a small diesel at peak torque into a generator and then a direct drive motor to the driven wheels. Regeneration from the motor under braking into the battery pack as well of course.

Having said this, that's pretty much a Toyota Prius I've described there. (Diesel asides).

No, not massive, just miraculous :-)

What's a horse power, about a kilowatt - well within 10% of it I think.

So a 1KW 40V motor only uses about 25 amps so if you have a 75amp/hr battery you can run it for three hours (ignoring inefficiencies as it gets used). You would be better using a lawn mower engine, say 2.5hp, and get better performance. But lets say you want the performance of about 100hp, that would use your battery in about 1.8 minutes and I suspect you would need to replace it well before that time was up :-)

So we really need some form of storing energy that has a higher power density/weight ratio, hmmm, something like petrol...

Now all we need is to make petrol using electricity. Ah, yes well we can do that but we have to heat the air to 1,500C to persuade the carbon and oxygen to part. Well they are doing that at a test facility in New Mexico using sunlight and mirrors and some form of catalytic cracker.

So if we build nuclear power stations near to oil refineries and put loads of these cracker things there we can make this stuff called petrol by using co2 in the atmosphere. Then all we need is something that can use this petrol stuff and turn it into motion and someway of getting this petrol to people all over the country... Well would you believe it - we already have those.

What you have described is a series hybrid, rather than swap between ICE and battery motor, it runs on electricity all the time, but the battery range is increased by using the diesel/petrol motor to produce electricity. There is no link from the ICE going directly to the wheel only into the generator. Much like a diesel electric train.

So get a sodding great big supercharged V8 fitted to that chair of yours then.

You think an electric vehicle that can achieve 70mph maximum, and have a range of 70 miles is miraculous? How so, these vehicles already exist. Or are you saying that miracles can't strike twice?

It is miraculous as far as I'm concerned at 170 grand or something.

It was merely a comment on the use of the word massive in this context since it is massive for an electric vehicle, hence the smiley.

Be popular in the pub...

740watts ish

Nope its possible with the correct equipment. But not using an old car and an old brushed fork truck motor and lead acid batteries. At least not on the same trip! The one blat to 70 is going to take all your charge. The slow 20mph crawl with suitable gearing might just get 70 miles on a flat runway at constant speed by exhausting your batteries comnpletely which you can do roughly half a dozen times before replacement.

To get that kind of range you need really Good batteries (think many thousands) and high efficiency motors (dont think fork truck!) and a very efficiant light car with everything in its favour. Things like hard narrow tyres, very hard suspension, (all that movement and damping comes from your batteries you know) excellent aerodynamics and everything taped over and slippery. You also need a clear road and brand new freshly conditioned and formed batteries and a lot of luck!

So on a 72volt system, 10a per hp, or 5a for a 144volt system. Hmm. something to think about

And remember that if you take more than half the battery capacity out at every cycle they wont last long. So count on 25 amps from a 50 amp deep cycle. That allows for occasional escursions to the 80 percent discharge level or more to get home...

Remember that you have half the battery capacity if you double the voltage with the same weight of batteries) so no real gain other than a very small wiring resistance loss decrease.

And also remember that as you take current out of a battery its own internal resistance adds some losses too. The reason your starter battery reads about

9 volts when cranking your car is exactly this resistance. And it increases on crap batteries massively as they become more discharged. Less so with good ones.

Brushed motors with cheap ceramic magnets are not too efficient either -- they make good heaters. Hence having to cool them. Especially once you demagnatise them by upping the voltage... So you get many more losses here. And yet more in many designs of speed controllers.

In reality you will need nearer 15 to 18 amps to get your 72v single hp.

Thats 72 volts, 10.347222 amps, 6.958 Ohms, to get 1hp or 745 watts. Or about 50 percent or so more when you take the inneficiencies into consideration.

6 X 100ah batteries with 50 percent nominal usable capacity means one hp will last about 3 hours. If that due to the capacity of a battery being rated at a 20 hour rate...

Thats why you need good low resistance batteries (Hawker Oddysey, or Yellow Optima Deep Cycle or similar) and thick cables, a switcing pulse width speed controller with overun charge capability, and high efficiency rare earth brushless motors, preferably direct drive rather than wasing power in a dif or gearbox to increase efficiency.

See those are the kind of numbers that very few of the diy ev sites mention. Sure they talk about range and weight and speed and battery cost, but a lot of them seem to be going by the suck it and see build route. Lead acid if they are doing cheap prototyping, then once they have a working vehicle, Lithium polymer if they are going big budget with the associated charge monitoring gear, and working on massively saving weight/bulk of batteries.

I have seen some of the guys who a big salvagers using thousands of Ni- Mh laptop batteries, putting together loads of the cells to make bigger hi amp/hour blocks, then using the blocks to make up the voltage through seriesing them. A lot of time needed to build the units, but it seems quite a useful re-use partially working Ni-Mh batteries as quite often it seems to be misuse that shortens the battery life. Wonder where you would find 2000 used 6 cell Ni-Mh batteries in one lot to make sure you had similar if not identical cells to build into bigger units.

How do they make sure all the packs are a) the same b) the correct type of cell (lithiums and nm/h come in a large variety of variations) c) the same capacity e) the same condition (cycle life etc)

A lot of time needed to build the units, but it seems

But permanantly

Wonder where you

The factory is about the only place. Robot battle packs are another source. It will still cost you thousands and give you a crap electric car... Its one of those jobs where you may as well do it properly.