[denito]

I've wanted to do an EV conversion and my wife suggested I should use an MGB (small, lightweight British sports car from the 60's). I looked up the MGB and I have to say, that looks like a really good suggestion. In fact, I found at least two electric MGB projects on youtube.

I have some experience with electric bicycles, but this is my first foray into this class of electric vehicle. For instance, the C-rate on the LiFePO batteries I used in my electric bicycles is way too low for this application. Any comments or pointers on where to start? Don't worry, I'll read the FAQ's and the wiki; I mean advice more specific. For instance, supposing I buy an EV kit; how do I know the splined shaft will fit the transmission in the MGB?

• Your skill level with auto mechanics and fabrication

Fair to good; I have some experience tinkering. I've rebuilt the brakes and engine on a '71 Beetle, for instance. Also, I'm an electronics engineer.

• The range you are hoping to get (how many miles/charge)

No more than 20 miles round trip; this would be a car for my wife and I to drive on dates in town. I plan to use a minimal battery pack (maybe even use lead acid?) and upgrade them later if/when the cost of Lithium batteries goes down.

• What level of performance you are hoping to get

I want it to accelerate as well or preferably much faster than the ICE engine version of the sportscar, but I don't need a very fast top speed. It will never be taken on the interstate.

• How much money you are willing to put into your project

I'm hoping to do it for about $8K including buying the car (which seems to go for about $4K).

• What parts you've already considered, if any.

Not really except for some general guidelines. I may go with lead acid batteries while developing it, and add lithium batteries after I get it working. I'm thinking of going with a DC motor, because I already know how to make motor controllers for things the size of an electric bicycle, I would just need to scale up the design. I'd love to find a modern BLDC motor with Neodymium magnets (my custom controller design I'm working on is for BLDC for electric bike) but I don't know if they make BLDC motors that size?

[Woodsmith]

Hi and welcome.

An MGB would be a great conversion to see happen.
There is plenty of space in the front for a nice motor and still have a little space for some of the batteries. The old B series engine is weighty and so there would be enough capacity for some lead.

Your $4000 may mean that you will probably have to look at a forklift motor and Open Revolt controller kit.
It wuld be worth starting to look for any fork lift breakers or finding an old one to strip parts from.
A 9" motor should be fine and 96v to 144v should keep the current down and help a little with the range.

If you get a coupler kit then I would suppose that one end would match the motor and the other end would need to be made to fit the clutch plate centre to give you the splines that you want.
Personally I would be tempted to keep the flywheel and clutch if possible as, depending on the age of your MGB, it may not have syncro on all the gears so shifts could be troublesome.
You could look around for a friendly machinist to make a coupler for you.

Post up some photos of the car if you have it.

[denito]

Originally Posted by Woodsmith

Hi and welcome.

An MGB would be a great conversion to see happen.
There is plenty of space in the front for a nice motor and still have a little space for some of the batteries. The old B series engine is weighty and so there would be enough capacity for some lead.

Your $4000 may mean that you will probably have to look at a forklift motor and Open Revolt controller kit.
It wuld be worth starting to look for any fork lift breakers or finding an old one to strip parts from.
A 9" motor should be fine and 96v to 144v should keep the current down and help a little with the range.

If you get a coupler kit then I would suppose that one end would match the motor and the other end would need to be made to fit the clutch plate centre to give you the splines that you want.
Personally I would be tempted to keep the flywheel and clutch if possible as, depending on the age of your MGB, it may not have syncro on all the gears so shifts could be troublesome.
You could look around for a friendly machinist to make a coupler for you.

Post up some photos of the car if you have it.

Is that a 9" diameter motor or 9" radius motor? Anyway I'm glad you mention that because one of my concerns is that without a reference point I might be looking at motors that are way underpowered or way overpowered for the application.

Here's a thought - might be a crazy idea but a lot of neat things get done just because someone didn't realize it was "impossible": why not get 2 or 3 smaller BLDC motors and use the gear teeth on the flywheel to transfer power? I could use 2 of these, for instance: http://www.electricmotorsport.com/st...otors_pmac.php Maybe I can get a machinist to cut gears for me to match the flywheel teeth (the gears would be larger than were on the original starter motor).

[Woodsmith]

Sorry, the 9" would refer to the motor diameter. You could go as far as probably an 11" diameter but in that range would be good.

The smaller motors are more able to to be made to spin faster then the bigger motors and so you would have reasonable road speed. For economy of energy you would be looking to gear so that the motor is running faster, near the top end of its speed range. Don;t risk over speeding though as motors tend not to like that.

The idea of using a number of small motors to drive the ring gear isn't new but does throw up some problems.
The first is that the ring gear isn't designed to transmit driving torque much beyond the starting loads of the ICE and also it is not lubricated in any way. It would be difficult to arrange a suitable lubrication system that would work.

That doesn't stop you from using a number of small motors on a large gear but you may find control problems and maybe uneven wear issues with the gear teeth.

Despite your knowledge and experience with small motors it would be easier with one bigger one.

To find out about motors there is a sticky in the motors forum about forklift motors. Have a read through that and see what others are using and asking about.

In power terms an electric motor need not haf anywhere near as much HP as the ICE that you are replacing, maybe only 1/4 or 1/5, or less, of the rated power.
With ICE the power, say 98bhp, is a peak power at one moment and can't be maintained for long. With an electric motor rated at 20kw that would be a continuous power for maybe 60mins. The spec plate would tell you the duty cycle.

But with motor size, try not to be mislead by 'nutters' like me who would be striving to put a 12" monster of a motor into a 500kg trike!

[dtbaker]

to get anywhere close to $8k budget will be a challenge. You'll need to find a basket-case MGB for $1000 or less, and go with an 8" DC motor, and low end 400amp-ish controller. I dunno if the MGB will HANDLE more than 96v worth of lead, which would be the only way to stay at or near your budget. Personally I would suggest saving up for 120v worth of 100ah lithium at this point for way better performance, life, and cost in the long run.

[denito]

Originally Posted by dtbaker

to get anywhere close to $8k budget will be a challenge. You'll need to find a basket-case MGB for $1000 or less, and go with an 8" DC motor, and low end 400amp-ish controller. I dunno if the MGB will HANDLE more than 96v worth of lead, which would be the only way to stay at or near your budget. Personally I would suggest saving up for 120v worth of 100ah lithium at this point for way better performance, life, and cost in the long run.

OK, well $8K budget isn't set in stone, I just made up a number.

One thing I definitely do NOT want to do is go with a $1000 basket-case MGB. I've been there done that with a $1000 basket-case '71 Super Beetle (not electric, just trying to make the ICE run). In the end I spent more money and ended up with poorer results than if I had just bought a $3K+ car to begin with.

It seems like the batteries are the big cost item. I'd certainly prefer lithium (as I use LiFePO already in my bicycle), but it still seems very expensive! Sites I've seen have them for about $250/cell; I don't see how anyone affords to put together a 120V 100AH pack. Couldn't I go with, say, 60AH lithium cells and an efficient motor? I don't need much range so my main concern is just not overloading the discharge rate on the batteries.

[dtbaker]

Originally Posted by denito

OK, well $8K budget isn't set in stone, I just made up a number.

good! spend what you need to get a donor you are happy with.
I think you can do a great job with about $6k of electronics (motor, controller, charger, dc-dc, and bits) plus $2k for lead, or $5k for 120v worth of 100ah LiFePO4 for about 50 mile range. I would not go under 100ah or you will be drawing too much at high accel.

Originally Posted by denito

Sites I've seen have them for about $250/cell;

no.... standard price these days is closer to $1.25/$1.30/ah delivered from stock in the US. I would NOT pay less to bulk order from China by slow-boat.... you can really get burned by scammers like James Morrison (EV Components & Lithium Depot) that take your money and never deliver.

Originally Posted by denito

I don't see how anyone affords to put together a 120V 100AH pack. Couldn't I go with, say, 60AH lithium cells and an efficient motor? I don't need much range so my main concern is just not overloading the discharge rate on the batteries.

exactly.
with even a small car at 120v you'll pull 300amps during accel. So less than 100ah and you'll be running the cells hard enough to risk loss of cycle life.

[Woodsmith]

I avoided considering a cheap, cheap MGB for similar reasons. I've restored them in the past and it is a huge undertaking at the best of times.

However, even some of the 'road legal' more expensive ones need checking over carefully to make sure the body is sound.

Another option would be to buy a new bodyshell and a dead car and transfer parts and convert at the same time. That may use up all of your budget though.

There are ways around some of the costs through classified ads and junk yards for forklift motors. It is even possible to get preused batteries. SimonRafferty on here powers his Land Rover Freelander EV using junk yard Optima Red Top batteries. He buys at £3 and returns them at £2 so for his 10 mile commute he pays £1 per battery!

There are also used controllers and chargers to be had, occasionally, as people upgrade. There are some brands to avoid though.