Re: Shunt field motors and regen issues

[Victor Tikhonov <vtikhono@lsil.com>]

"Mander, Art" wrote:
...
> Regenerative braking is a worthy goal with at least three benefits:
> 
> *       Improved safety (coasting is not good)

It really depends. Personally, I love coasting.

> *       Increased range (though often debated - Victor have you been able to
> quantify this with the AC drive regen engaged and disabled?)

I'll do all sorts of measurements when by batteries will be routinely
charged properly, that is when Rich finally ships my charger to me.
Rich?

For now I can only track Ah with and without regen. for the US06 driving
cycle (which is closest to my real everyday driving) the most of
the benefit will be in stop-and-go traffic. If you put some Ah back in
the batteries (otherwise lost as heat), you extend your range, no doubt.

If you're coasting on the freeway 'till SOC drops to your favorite
number representing EOR (end of range), then - no benefit.

Realistically, you'll be somewhere in between.

If you only use regen for braking, then energy you spend to accelerate
after regen is *about* the same as the amount regen puts in the pack
in a first place (minus efficiency).

Compare:

A. Regen off, lift the throttle at 55 mph and coast to 35 mph.
You've gone, say, 1000 feet for free.

B. Regen on, lift the throttle at 55 mph. By the time you're at 35
mph you put 3Ah in the pack but have gone 600 feet only.
Got to run remaining 400 feet at steady 35 mph to be at the same
point of first experiment. So you have to spend gained 3Ah to do
that, so net gain is nothing.

In reality, accelerating and regenning 
are not 100% efficient, so you end up spending a bit more that way 
than if just coast.

Result depends on the speed also, by slowing down
sooner, you get away from high air drag effect sooner too, so for high
speeds you *may* gain by regenning and accelerating vs if this all
happens at low speeds where air drag won't matter.

To me regen is not only matter of energy in/out math.

It's a coefficient by which my EV grin width is being multiplied,
and I cannot put a dollar sign in front of it.

Also I save the brake pads. Brake pads dust contamination, I've
heard, is the second worst pollution source along the coast highway 
in California.

I will post my actual energy loss/gain on the web. Your mileage
may [literally] vary. To compare between the vehicles, you'll
have to drive close to as ISO US06 cycle suggest, and then will talk.

Victor