All Zephyred Up

April 30, 2015

P2 (Large)

My souped up, 80V ‘Ego Scoota’ nearly 5 years on and still going strong

Those of you who have been following my blog might be wondering where I’ve gotten to. It’s not often I keep the bike off-road over the winter, but with the repairs to the BMS, the expired MOT (inspection certificate) and the horrible weather I decided put the bike aside for a while to focus on work and other things that needed seeing to.

Now that the nice weather has returned, I’ve put the bike back together and started breaking in the fresh cells in the rebuilt pack. The perspex that I had screwed onto both sides of the pack had become quite broken up, and needed replacing too. Using little screws to secure the perspex to some of those little orange pegs on the cell holder seemed like a good idea at the time, but stresses from the less-than-even road surfaces I have to contend with daily were making the pegs break off and wearing away at the covers, breaking bits off and sending cracks through them. It was also fiddly having to undo a lot of tiny screws every time I needed to do something to the pack.

 

Li19 [1600x1200]

The 24s2p 76.8V nominal (86.4V charge) Lithium Pack

So now I’ve settled on a more basic arrangement. I replaced the perspex with fresh sheets, but just used clear packing tape to hold the sheets onto both sides. It’s not as pretty and elegant, but has the free play to deal with road vibration and will make servicing of the pack easier in future, though now I’ve got the LVC safeguards in place, cells will probably not need replacing for a good long time.

P1 (Large)

New perspex siding now just held on with strong packing tape

Breaking in the pack has been fairly routine. Because the new cells are out of balance with the others, the Zephyr goes into pulse mode at the end of a charge cycle, and needed keeping an eye on to make sure it didn’t get too hot. But three charge cycles in and it’s almost all balanced out again, with the EOC cutting off promptly with very little pulsing.

I was quit relieved about this, as I’d had to replace a few components on the Zephyr BMS after a weak cell died in mid charge and damaged one of the cell circuits (see last blog entry) something that could have been avoided if I’d been more careful and fixed it as soon as the warning light on the Zephyr LVC system started coming on. Though I was getting resistance readings on the newly repaired circuit  that were exactly the same as the other circuits, I couldn’t be sure all was well until I’d run it on the pack itself. Happily all appears well, the pack is more balanced, and it’s cutting off when it should do at the end of a charge cycle.

The bike has a new test certificate now so I’m finally back on the road, however some work will need doing to the bike soon: The terrible road surfaces, high speeds and a period of carrying 48Kg of SLA (lead-acid) batteries has taken its toll on the bearings of the steering column. There’s just a little bit of free play there, top and bottom, and so I’ll have to get this seen to before its next inspection.

72V36 [1600x1200]

72V23b [1600x1200]

The old arrangement, with six 12V SLA batteries

It’s proving impossible to get the specs for the runners and bearings needed for this bike, so I’m going to have to do it the expensive way and get a proper bike person to deal with this. Though I like to do whatever I can with my own hands, I’d rather leave the more technical mechanical stuff to a proper mechanic. Bearings are particularly important now with the bike being as powerful as it is, and I want to make sure it’s done properly with quality, ‘race standard’ parts.

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