@nottinghack And the C5 springs into life for the first time in over 3 decades!

The POD once again showing minimal load as the wheels are off the ground this is all great!

Just now need to tidy up the wiring and get this thing out for a ride.

@nottinghack I was a little concerned; after a few minutes the POD LEDs for battery status would loose an LED, but after soak testing for half an hour it just remained at that, I realise I had the PSU set exactly for 12v, and the battery I have measures at more 12.5v, so in theory if there were losses the POD could be seeing 11.5v and assume declining battery, setting the PSU for 12.5v and I never lost an LED - the POD and ULA appear to be working perfectly!

I then disassembled the test setup; and started putting the control box back together; this was a little awkward, the plastic case had been welded together and I had to cut these welds, but there were tabs for 3mm self tapping screws, I which I was able to fit some black plastic 3mm screws and nuts in to keep it together and also it kinda looked the part.

Quickly attaching all the wiring in the C5 and remounting the control box, I was ready to give it a test with the real motor.

@nottinghack After making these repairs, I wanted to test absolutely everything to be sure nothing else is about to blow.

I initially started simple, I connected the control box to a power supply, current draw was small and all the voltage lines looked OK.

Moving a little further, I wanted to make sure it could switch a load without issue, but I didn't want to do that with the POD attached in case of damage to that; looking at the circuit diagram for the control box, transistor 3 appears to connect from the coil of the power relay at the collector, and 0 volts at the emitter, with the base coming from the pod from a line named "RELAY DRIVE", so this must be how the pod can disable the motor.

A simple dupont wire between pins 1 (+5Va) and 7 (relay drive) on header X9 (POD connector) ensured the relay was always enabled, also shorting pins 4 and 5 on X6 (thermal cutout switch), then just adding a small 12v motor to the motor terminals, and shorting pins 5 and 6 (motor switch feed/return) on connector X8 resulted in the relay making a nice clear click and current draw at around half an amp - perfectly fine.

Then I just quickly popped the POD off and with some dupont wires connected it to the control box, with a 10k ohm resistor between pins 1 and 2 of X6 to simulate the thermocouple in a good state, and everything worked as expected, the POD LEDs behaved just as expected, showing full battery and low load.

@nottinghack And repair/PCB pics!

There was some solder bridges on the PCB, but after checking the schematic, these actually seem intentional

@nottinghack After that, I again connected up the lights and the POD and then applied the battery and everything lit up as expected, whew.

This is good, the control box on the C5 is a simple circuit with all readily available parts and is the best thing to go wrong, to see the POD still working which uses a custom ULA chip is a relief.

I have just popped back home from Nottinghack to write this update and also grab my laptop and some tools I intentionally left at home so I could carry the battery; my next steps are to get food for once today, and also connect the control box, isolated, up to a bench power supply just to check everything is working as it should, no components are an unexpected current draw, and maybe even connect the POD to do a full dress rehearsal with a small 12 volt lamp or small motor, once I am happy with that, I will do a test with the main motor.

@nottinghack After consulting the schematic further, it looks like the POD uses a +5Va line in driving the LEDs, this is generated in the control box by a LM342 off of the larger +12V line which was of course, still lifted form the overcurrent; that might explain how the LEDs went off but the lights didn't, I put another bodge wire in there but I also thought I should check R1 and D4...

R1, which was supposed to be at 2.2ohms was more like 500k, not good, and D4, which was incorrectly listed in the schematic as D3 (there are 2 D3s, the one connected to the coil of the relay is the real D3, they are both 1N4001s), was open in both directions, and connected between the smaller and larger +12V lines, and thus explaining why the traces blew;

When the power relay connected D1 to the negative terminal of the battery, D4 also being a dead short would have started pulling current from the smaller +12V line, damaging the quite large trace to the smaller +12V line and obliterating the small trace from the LM342 to the larger +12V line.

I had a direct rep for R1, bit D4 I could only find a 1N4002, which as far as I can tell from the datasheet is basically the same thing but rated for a higher voltage.

Whilst I was at that, I did the same with D1, similarly again replacing the original 1N5401 for a higher rated 1N5406.

@nottinghack Diode D1 sits between the positive line coming straight in from the battery and the negative terminal of the motor in reverse bias, this is a problem, as when the motor relay clicks closed, it connects the negative terminal of the motor directly to the negative terminal of the battery...

D1 was directly shorting the battery, and was probably why I saw smoke, I subsequently removed D1

For any C5 owners out there, check D1 (the big diode when you remove the upper potion of the control box cover where all the connections are), if it's shorted, just go in there with a pair of pliers and cut it.

Now time to look at what other damage I had done; the C5 has two +12v lines from the battery, one of these is intended to power the auxiliary circuitry like the lights and POD and is fairly low current, the trace for this looked to have been lifting and might be why the POD LEDs were turned off, after putting a bodge a small wire in there, I plugged the POD and lights back in and applied power, lights came on all as before but no POD LEDs :/

@nottinghack Sooo, that was a wild ride.

Just after this video I pressed the power on button one more time (dunno what I was expecting), and all the LEDs went off and only the lights remained on.

THAT'S NOT GOOD

So, first and most obvious place to start is to take off the control box, after removing the cables and 2 screws it came straight off.

Unfortunately the lid on this one appears to be plastic welded on to the base, but it still had tabs where it looks like you can screw them together, so I had to cut those welded joints to get it off.

Inspecting the board, apart from 2 burnt traces going towards the power in (explains why the LEDs in the control box went off at least) there wasn't much I could see that would have blown, other than diode D1.

I had read about D1, it's a common diode to go on it, simply pushing it backwards at more than a snails pace will kill it; and I had measured last week when it was on the bench to be a dead short in both directions, for those screaming why did I not replace it there and then; everything I had read emphasized how unimportant D1 is and how it can be left in temporarily if blown; then I read the schematic...

@nottinghack Update, the motor runs!

@nottinghack Update, the toolkit has arrived but not the battery this should make disassembly of the body for cleaning a little easier.

As for next steps, Halfords has assured me that they will have my battery by tomorrow, hopefully with that I can chock up the C5 and connect the battery straight to the motor and hopefully it should turnover, and if so, we should be good to connect it up to the main battery terminals and do a full "system test"

I am fairly confident, the test with the power supply whilst flawed, showed that; a motor on signal was received from by the ULA, the ULA determined that there was no problematic flags from the motor and battery sensors, it sent a motor on signal to the control box, the control box gave 12v to the motor, and then the motor tried to turnover, just that the start-up current of the motor killed the PSU

Also, my partner pointed out that the stall current of the motor is 140 amps, and the (original) installed wiring loom gauge to the battery is only rated for 100 amps, so I used this as an excuse to get a fancy safety wiring loom that also protects against accidently wiring the battery up backwards https://www.ebay.co.uk/itm/235040436116

@nottinghack Update: I caved

@nottinghack On to the battery itself, as this has come up as a few times about retromods; since the original lead acid battery (now long gone) got a decent range, and I only intend this to be a cool little joyride thing around the City of Nottingham, I don't see a reason to go too extreme just yet, but I do always have options -

The battery in the original C5 was just a pretty standard lead acid battery with a custom hat that had a custom connector on it, it was simply thrown in the back of the left footwell and held in place with a fabric strap, with 2 wires coming out the back compartment to connect to it - there was no internal charging circuit, you had pop off the connector from the C5 and attach the external charging adaptor.

This is excellent, since all that is needed to retrofit a modern battery is to fit the correct fittings on to the wires, and to throw a 12 volt high current battery in the footwell and away you go! No fancy mods to charging or battery management circuit, just 12 volts and the ability to deliver a decent amount of current and it's happy.

Mr Fusion mod still pending on cold fusion to be experimentally proven.

@nottinghack So if the speed and range were the same as a modern mid range e-scooter, why did it flop?

I can see 2 reasons for this; the first and most obvious is that people and the media were expecting Sinclair to launch a car, the marketing advertised it as a "vehicle"; so it goes without saying, it was widely seen and judged as a car, and that's a problem, because whilst it is amazing for a peddle assisted e-trike in 1985, it's absolutely terrible as a car!

The second problem came from that fact that it's performance and concept were so ahead of it's time, there was literally nothing else in it's own class to compare it to, the concept of an electric assisted peddle vehicle was not in anyone's head at the time other than probably Sir Clive's, everyone just saw a dangerous, slow car that could barely go anywhere. We of course unfortunately now know in hindsight that there is absolutely a market for something like this (albeit, a maybe a little less bulky).

So we have established what this actually is, an e-trike, and actually not a very impractical one, particularly in a flat city. Still, I'd still own it if it was impractical, as it's a weird part of engineering history, and I love that.

@nottinghack Wow this got popular, I haven't really done a massive writeup like this since I was working on the PDP-11, and I forgot to finish that in the excitement that followed when I got it to boot, so now I feel obliged to continue.

Sadly I can't really do much active tests without the battery; I ordered one from Halfords for next day in store pickup, but that was on Friday, and still no word; for now it's just a standard 12v lead acid car battery just to make this thing go, but I at least for now know the control electronics are working from my rather flawed test with the power supply.

I'll take this time to talk a little more about the C5 and what I'm planning on doing with it. To start, I've had a couple of people repeat some misconceptions about the C5 and question why I am doing this.

The C5 uses a custom motor made by the Italian company Polymotor, who did make washing machine motors, and also torpedo motors; it very likely needed this custom motor as for the time, it's efficiency is incredible...

In 2022 I used to make a daily 10 mile (16km) round commute on a first generation Pure Air e-scooter, it could just about manage it doing 13mph (20km/h), coincidently, this is almost exactly the average performance and range of the C5 with it's original 80 AH lead acid battery, and yet the Pure Air is 40 years newer, weighs half as much and is absolutely packed full of lithium batteries!

@nottinghack Now came time for the actual tear down and maintenance part, retroworkshop.uk has a fantastic guide in written and video format on how to inspect, take apart, service and put back together again every part of the C5 https://www.retroworkshop.uk/sinclair-c5-restoration/sinclair-c5-restoration-part-1-vehicle-check-over/ this was really an amazing resource and I'm sad they're not on Fedi (or at least I can't find them)

After reading up on the electronics involved, I figured it was mostly safe to throw some electrons at it with the wheels off the ground and see where this takes me

Sadly the car battery I had ordered is taking it sweet time in arriving, so I figured why not use my 30 amp PSU I use for my radios...

**WILD GOOSE CHASE BEGIN**
Applying power, the POD light for battery status and motor power draw all came up as expected, indicating the ULA was functional, front and rear lights worked; giving the motor on switch a press did something a little weird, the wheel slowly jumped forward in stages, drawing a massive amount of current each time and causing the power supply to cutout

Oh well, something must be amiss with the motor, thankfully retroworkshop.uk has a very good guide on how to strip and service the motor, mine is an older one, so the front end gearbox cannot be removed without it breaking, but that shouldn't be a problem here, taking apart the motor, and removing the brushes, rotor, and stator, I got them all cleaned up

Luckily the wheel I had removed was the one which needed a new inner-tube, easy fix and in the process I noticed the tyres were actually the original Sinclair branded ones!

The original inner tube wasn't actually punctured, rather it has just degraded and appeared to, well, expand like a balloon when inflated, which was the reason why it didn't appear to be taking any pressure.

With the new inner tube installed and all tyres inflated to the correct pressure (thankfully given on the all to the boot box when opened), I was able to cycle this the 1km from my house to @nottinghack - it was quite a nice ride, albeit the chain was slipping quite a lot (suspected and later confirmed to be the tensioner wasn't engaged) and the awfully large number of police and traffic wardens about, but I got there no problem and had it up on the workbench

Bringing it back to Nottingham Hackspace so I can have a once over at it, 2 out of the 3 tyres were fine, the rear left one needed a new inner tube, thankfully it is just a 16 x 2 inch inner tube that is needed and I was able to get a decent one the next day for £5, but since the wheels are made of plastic, I didn't wanna try and ride it back home from the Hackspace (~1km away) so I had to push it;

That was surprisingly easy, what wasn't however, was when I finally got it home; I had planned on keeping this in a smallish landing area in the entrance to my flat, in a warm dry climate and safe, however it simply was too wide to fit through the door with both the back wheels on/with the door still on it's hinge.

Faced with the prospect of the fact I might have made the most impractical eBay purchase ever, I reluctantly took off one of the wheels and carried it in, before then assaulting my bank account even further with the purchase of a £400 decent bike shed for my back garden, with a plan to purchase an £800 Asgard next pay period to really keep this thing safe, oh well, I was probably going to have to buy something of the sort anyway since my dad keeps pestering me to take my 1960 Excelsior Consort out of his garage

The C5 was safe for now at least