I’m a little behind on my blog as I’ve been busy with other things these last few days. So now it’s time to do some catching up…

If you recall from Part 1 of my report detailing my 72V upgrade, things were basically up and working, however it was clear that all was not well with the 12V electrics. The first indication of this was that the indicators would no longer blink. This was perplexing as I couldn’t imagine what I might have done to damage them. The only thing that had changed was my substitution of the homemade 72V-12V converter for the one that used to serve the 48/60V electrics. This was puzzling. The lights all worked fine, so clearly 12V of power was getting through okay.

Eventually it became clear what was happening when I tried to connect my new battery meter to the 12V system: The battery meter would not work unless I reversed it’s own red/black power wires: It appeared that the polarity of my whole 12V system was now reversed. The homemade PSU was producing -12V, not +12V.

At this point things took a turn for the worse. A misunderstanding about what I needed to do to rewire the PSU solution so I got +12V instead resulted in me feeding 90V to the 12V system. When I tried the lights, the headlight bulb promptly exploded. The rear bulb and two of the little bulbs on the instrument display got blown too. I really should have used my multimeter before doing anything as daft as turning things on, but I was tired and getting impatient.

Ouch! Stupid… stupid… stupid…

At this point I decided to abandon the PSU solution altogether. It’s a perfectly good way to get things up and running, but the PSU does consume quite a bit of energy. I wanted to preserve the range as much as possible as well as increasing the performance, so I wanted a more energy-efficient solution than this. Andy (the Sparklight guy) had already said that he could probably come up with something better suited for the job, and so I thought I’d see how that turned out first. In the mean time, I decided to just use Battery 1 for the 12V power source, via a cable hooked up to the three-way connector that powers the bike’s 12V system.

Battery 1 hooked up to a mini-connector (bottom right) serves the 12V system for now

Another cable hooked up to the one powering the 12V system can be used to check the battery level and top it up using a separate charger if it needs balancing.

Securing the Power Cables to the Anderson Connector

The main thing left unfinished before was the main power connection. My Anderson Connector was properly plumbed into the battery system on the bike’s side, but the connections to the controller had yet to be properly secured. For the purposes of my test-drive, I’d just rigged up a temporary connection, like so:

The ‘bodge’. Fine just to just check that it works, but not a permanent solution…

This is really the most important connection of the whole bike. However the wires from the controller are quite a bit thinner than the crimps for the Anderson connector, so – like others in the Electric Motoring Forum – I elected to ‘double-crimp’ these by using the existing connectors on the wires as ‘fodder’ for the larger crimps.

Here’s the main motor power cable as it came on my controller. It came as one of three spade connectors housed in a triangular-style three-pin plug with the ground and the low-current feed-wire for the controller. Since this connector isn’t in use on our bike, it needed dismantling into its component wires. This and the black (ground) wire need to be crimped into an Anderson Connector to connect with the one served by the main power cables on the bike, and the low-current wire has already been connected up to the two-pin mini connector that also takes the the brake wire (see blog of 22/08).

First I just folded over the spade  so it fits inside the Anderson crimp.

To pad out the crimp for a tight fit, I’ve used 10mm lengths of thick copper wire I took from an old cooker cable.

I pack the spade connector in with this ‘filler’ then crimp it for a good solid connection.

Next a bit of heat-shrink for insulation before it is clipped into its Anderson connector along with the black ground-wire.

The Anderson Connector (left) for the controller power cables, connected to its counterpart (right) which takes power from the main battery bank via the breaker switch.

So the 72V system is properly up and running. The only other thing I’m missing now is the regen braking, which does not appear to be supported by this controller. The makers of the chatparts.com controller that I also have insist that regen is working on theirs, but I have to add all the right connectors to it before I can try it out on the bike.

For now, though, I’m just glad that it’s all working. I should hear something soon from Andy about the prospect of a custom 12V adapter box, but for now I’ll just have to keep unplugging and re-plugging that underseat connector that I’m using for the time being…


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