Once upon a time, before spring of 2010 – Controllers from EBikes.CA had progressive regen, also known as Variable Ebrake. After that time these controllers were no longer available anywhere on the market.
Traditional operation was as follows:
- Throttle-only, no ebrake -> works just like a throttle should.
- Ebrake depressed, no throttle -> low amount of braking force
- Ebrake depressed, full-throttle -> maximum electric braking
The aim of this thread seeks to restore what once was: Give us back our variable ebrake capability!
<cue pastoral anthem with lots of French horns>
I have a dream! <whoa that’s heavy!>
It’s a tiny dream <that’s better>
The way to solve the problem is two-fold:
- First we investigate how to adapt present common ebike controllers to trick them into providing variable ebrake,
- and second – come up with a clever circuit that we can spoon in.
Using “Hyena’s parallel resistor calculator for LVC and high voltage regen mod” spreadsheet, I was able to extrapolate an interesting fix to the problem. Depending on which controller you have, most depend upon modifying the value of R12 with a piggyback resistor and some tinkering with two parameters in the Firmware configuration to fake LVC and HVC.
I figured out that for my own system I could do this with a 5k POT parallel to R12; when the POT is at Zero, Ebrake will be maximum, and conversely when at 5k Ohms, Ebrake will be the softest – but not below the preset HVC in the firmware.
Presuming we run without any ebraking effects, LVC should be set to match this condition – however we don’t care that it goes all wonky when ebraking is maximum. With my conditions (15S/63V LiPo using a 100V-capable controller),
- No Ebrake: R12 @ +5k Ohms, LVC = 49.5, HVC = 64.9
- Max Ebrake: R12 @ +0 Ohms, LVC = 75.5, HVC = 98.9
The next part of the problem is how to intercept The Throttle and use it like a tool. My thought is that the Throttle always has power, it always has a value – it’s wired that way! The controller through some internal application programming decides to ignore (or cut off) the Throttle signal inside the chip, but we can still read the value even if the MCU doesn’t care. All we have to do is trigger our variable R12-mod to react when –EBS goes from +5V to GND and maybe with a few milliseconds of delay.
As the throttle is increased, the resistance at R12 drops – and there we have it, Throttle-controlled variable ebraking!
Now for the part that I’m weakest on… Circuit Design. I know how to do this with hardware, and it crossed my mind ever so briefly to employ a mechanical device that spins the POT relative to the throttle and… hand me another beer, let’s think of something better. Perhaps a passively sensing circuit could read when –EBS goes to GND and that one could read Throttle without a lot of loss. In the most primitive, we’d have High Ebrake and Low – though it would be quite novel to have several point in-between wouldn’t you think? A voltage-controlled resistor circuit albeit in reverse.
When –EBS goes High (+5V), then obviously we’d return R12 to max ohms and Throttle would be a throttle again with no delay.
Anyway – that’s my dog & pony to a solution. Actually, I thought it would be really nifty to just remove R12 altogether and a hack mini-board would tap right in-between, and borrowing some from the +5V bus as well.
Does this make sense, or am I way out in left field… ?
Missing my variable electric brake, KF