[brian_]

Since many electric cars managed to be built before the computer age my interest in electric power for this project pretty much hinges on being able to forego anything with a chip.

Those pre-electronic electric vehicles were really undesirable, which is why modern power electronics (and, of course, better batteries) enabled the return of electric vehicles (which were successful until about 1912, but then lost out to engines).

Fortunately, you don't need to understand how the electronic bits work internally, if you buy a controller which is designed to work with your chosen motor.

 

[brian_]

The problem is controlling the power from the motor - the only really good way of doing that is by an electronic motor controller

If you couple an electric motor to a battery - without any sort of controller - then you will get a lot of torque which will reduce as the motor revs rise

If you can arrange things so that you can use that type of power delivery then you can simply use a big switch...

• The next step toward something which is actually usable without electronics is a set of switches for resistors to restrict the motor power in steps - this is very wasteful of energy.
• A solution for commercially-produced electric vehicles (such as trains) before electronics was to make motors with multiple windings, and to use a complex set of large switches to control which windings were powered, and thus how much power the motor produced.
• Some schemes even used switched parts of the battery bank between series and parallel to crudely step voltage to the motor, requiring large switches or relays and lots of high-voltage high-current wiring.

For examples of these old solutions, see Lee Hart's EV Motor Controllers page. I wouldn't want to build any of them.

Any of these schemes are not only less efficient and less driveable than a modern electronic controller, they are also more difficult to build with and to use. For overall simplicity, hidden electronic sophistication is the solution.

There are chips inside that controller - but if you leave the lid on you won't have to see them

 

[brian_]

I think one aesthetic challenge, when trying to follow the original style, is packaging the battery. The motor is no problem: an exposed motor running a chain drive would work fine, and look right. Even a modern electronic controller is no problem, because it is small and can be tucked under a seat; it could also be housed in finned cast aluminum box which would look right at home. A charger could be housed like the controller, or just left at home or carried in luggage".

The battery is big, and doesn't look mechanical. I suppose the answers could include:

• use a modern lithium battery of moderate size and enclose it in what looks like a fuel tank (although a cyclecar would not have a large fuel tank), or
• use a modern lithium battery of moderate size and hide it under the seat, or
• use lead-acid batteries (accepting the resulting short range), mount them in the open, and insulate all connections for safety, or
• use LiFePO4 prismatic cells, install them like the lead-acids, and manually check their individual states of charge after use and after charging.

One of the old control schemes could look interesting, but it needs to be kept safe (safer than those old electric cars were).... and seriously, I wouldn't want to build one, especially the kind with resistors.

With a 48-volt (nominal) battery in four sections (such as four 12-volt lead-acid batteries or four 4-cell lithium modules), you could use a "golf cart" motor, and arrange relays to implement the voltage-switching scheme shown on Lee Hart's controller page (from the Henney Kilowatt) or a variant with more contacts and no diodes, if you can stand only crude steps in power (12V, 24V, and 48V). The pile of cables and relays would look vintage and suitably primitive. It would be more expensive than a ready-to-use electronic controller.

 

[brian_]

If you really want an old-school solution that's in keeping with the cyclecar era you might enjoy this thread: http://www.diyelectriccar.com/forums/showthread.php?t=31134

A mechanical PWM controller! That's brilliant... but the reality is that to make this work you still need to understand enough to handle the arcing problems which are discussed in the thread, and you end up doing electrical design which would not be required with an off-the-shelf electronic controller.