The cells are all connected anyway, but it sounds like you mean one of the old "resistor bank" controllers from the early 20th century, but with no settings below full... You can't run a brushless DC motor or AC induction motor straight from a DC battery. With a DC brushed motor, you'd probably damage the commutator at low speed due excessive arcing, or overheat the armature winding due to lack of airflow at low speed. This isn't a problem with cheap powertools because the inertia is low enough to spend minimal time at lower speeds, and because they're cheap and essentially disposable.
The above assumes the rest of your drivetrain is capable of surviving max torque at 0rpm.
Acceleration is where you'll need most torque, and if you're going to carry the weight and mechanical drag of a second motor, you may as well use it. Doing a smooth transition from one motor to two might be difficult. If your motors don't match, you may need separate controllers or at least some extra circuitry to avoid pushing either motor beyond its limits.
Keep it simple: one big motor mounted where the IC engine was, with an adapter to mate the motor's (normally male) shaft to the original (ideally manual) gearbox's (normally male) input shaft. This would let you vary the gear ratio according to payload weight and terrain.
Not impossible, but people rarely bother, since DC systems are meant to be cheap and simple.
https://ieeexplore.ieee.org/document/6360991/
https://electronics.stackexchange.c...-implement-regenerative-braking-of-a-dc-motor
http://www.electric-cars-are-for-girls.com/electric-motor-brushes-and-regenerative-braking.html
Electric forklifts normally operate within short distances of their base stations so maximising range isn't normally in the design brief. Easier to just add more battery, especially since adding more weight helps you balance heavier loads.
It's been done before: https://www.maximintegrated.com/en/app-notes/index.mvp/id/1951
A single-phase AC induction motor could be driven by a single-channel class D amp, but you'd probably need more than one amp and some kind of logic-controlled switching to drive 3-phase AC motors or brushless DC motors (commonly 3 connections).
Not sure where you'd find an amp capable of more than a few kW (normal household plugs here are only rated to about 3kw)
Either use your pickup's existing (probably hydraulic) power steering by fitting a small motor to drive a short belt, or fit an electric or electro-hydraulic steering rack from another road vehicle. I'd expect a forklift to use hydralics for the lift and any power steering probably forms part of that system.
Industrial AC motors are usually conservatively rated for constant 24/7 running, often with limited airflow. Those motors may be capable of much more in a vehicle, which typically only needs max power for a minute or two unless you're climbing a mountain, and will have plenty of airflow (unless you're lugging a full load up a mountain). If you can find the brochure or datasheet for the motor, I expect there'll be another motor in the range with the windings configured differently for the same power rating at higher RPM, less torque. Both models would have the same bearings and casing, so with the right inverter/VFD/VSD you could drive your "800rpm" motor to 1800rpm by running 3x mains frequency.
Yes, but it sounds like you have access to the right part sources to do your first conversion using a DC system, then drive that around while you work on an AC system!
Most commercially-available controllers are configurable but not all are user-configurable. People designing and building controllers will often test with low voltages and small motors. This lets them prove the design and construction are good with less risk of damaging components and do it before spending lots on batteries and mounts.
If you misconfigure the controller you could damage the motor and/or battery if you're careless or unlucky. Higher-rated controllers cost more and are usually physically bigger.
