EEVblog 1419 - Sinclair C5 Restoration - Part 2

[EEVblog]

RIP Sir Clive Sinclair.
Dave finally gets around to starting to take apart and restore the classic Sinclair C5 electric vehicle.

[coppercone2]

rolling dirty on that contraption with a bottle of jack on the starship enterprize. i think it needs a starfleet logo. and magnetic wheels for 0 gravity driving

[floobydust]

The subframe cracks, maybe ask AvE for suggestions but Malcolm Faed's C5 in EEVblog #501 also has the same tearing 14:33. It's like unintentional torsion bar suspension lol.
The Ferranti ULA IC's battery low voltage alarm at 12.5V seems high, today we run a UPS battery down to say 10.8V

[thm_w]

The Ferranti ULA IC's battery low voltage alarm at 12.5V seems high, today we run a UPS battery down to say 10.8V

Way too high, as soon as you hit on the gas it would dip below that.

A nominal 18 milliohms of battery impedance is assumed. The gauge can only decrement and contains a 20 second delay which must time out before a display decrement can occur. This eliminates  spurious  counting.  The  five  equal  incremental  voltage  steps  span  the  nominal voltage range, 12.0 to 10.5 volts.

Apparently the original battery was 35Ahr, range of 20km, motor 200-250W. But this PDF says they'd only get a useful 15-28Ah out of it (340Whr)..
https://erik.gjermundsen.net/PDF/C5-SM.pdf

The  charging  profile  is  shown  in  Figure  6  and  is  implemented  by  a  hybrid  circuit  with  laser trimmed resisters driving 2 SCR's as a phase controlled current source.

wow

If you completely strip out all that original electronics and motor and replace it with modern tech. Would easily be 2-3x performance improvement with the same weight.
All of these parts are commodity, since you could grab a controller and battery from say an electric scooter (350-500W controller with regen, 300-500Whr battery).
Ton of work though..

[floobydust]

C5's have a cult following or something. Turn signals, mud flaps, horn, side mirrors, reflective stickers and Hi-vis mast - all were options.

I woke up thinking it has no regen ability at all? Then I see D4 the 1N4001 

Somebody beat us to it, a MCU-based replacement for the ULA chip. I'll say the board has no -ve spike protection for the LM78L05 so a bit fragile... the LM358 in the Control Box dies a lot too they say.

[thm_w]

I would never have expected it to have regen. On devices this light and small it doesn't make a huge difference though. The nicest part of regen really is it takes load off of the brakes and extends their life massively. If its a 1N4001 though.. lol it won't be doing much.

Commutation  diode  failure.  If  the  vehicle  is  pushed  backwards  at  anything  other  than  a  very slow rate, the motor which is rotating as a generator forces a high current through its commutation diode which then blows open circuit.

I guess we know why that belt pulley was broken:

The  latter  causes  the  motor  to  tilt  slightly  loading  one  edge  of  the  belt  very  heavily.  Never  start  the  C5  under  power  but  always  pedal  a  little  first.  The  stall  torque  of  the  motor  is  very  high  and  strains  the transmission significantly.

[Kleinstein]

The motor is connected by a kind of free-wheeling link, which is needed so one could paddle faster than the limited motor speed.
So regenerative braking would also need some mechanical parts.
It would also need some kind of boost converter to bring the voltage from the motor up to the battery level. Otherwise it would only work at high speed.

[floobydust]

I don't think it has a 'mechanical' diode    The gearbox is a planetary but I see no clutch or reverse ratchet (aside from at the pedals/chain). Looking at the Control Board schematic:
No Reverse- or reverse movement, based on diode 1N5401 D1. They say the diode smokes if it's pushed backwards at anything faster than a crawl.

It's weird with Sinclair stuff, it always has a lot of science when you dig in, if you can push aside the practical aspects being a bit weak.
I think it's the first 1980's Coulomb counter I've seen, in the Fuel gauge. Lots of measurements on the speed, torque, range, acceleration, hill climbing etc.
Like everyone went along with the Emperor's plan- not saying anything about his clothes. Perhaps for the business and money you'd do this kind of work.