The batch of Fechter-Goodrum 4.4a Zephyr boards I had made back in November sold out a few weeks ago, and I’m getting enquiries from people who missed out on them. Unfortunately, though, I’ve been a bit short on cash, so can’t afford the outlay to get a fresh batch made.
All is not lost though; I’ve come up with a way round the problem: I’ve set up a pre-order system to help fund the outlay to get a batch of the new, 4.4b boards made. If you want one, just pre-order through the link at the shop. Once I have 6 pre-orders, I can afford to order the batch. The pre-orders will not include shipping – that will be taken care of when the boards are available and ready to ship. If I don’t get enough orders to fund a new run then I just issue refunds to whoever did pre-order. Worst case scenario is some wasted time. [Update: 4.4b boards available here]
So what’s so different about the 4.4b boards, then? A change requested by Richard Fechter – involving the addition of a component – has been made to the board, and there have also been a number of cosmetic changes:
1) A TVS diode has been added to offer an extra layer of protection for those dealing with banks running at higher voltages, such as configurations of 32s and above
2) Square pads have been added for the 47K capacitors, to prevent further confusion about which way round they go
3) Holes have been added to enable jump-wires to be soldered to save on redundant wiring where the top cell of one bank meets the bottom cell of the next. This allows a 24-pin connector to used for a 24s circuit, and so on
4) The component labels and values have been tidied up and moved to the silkscreen layer, where they’re easier to read.
The upgraded control circuit on the 4.4b version of the board
For those of you with 4.4a boards who think you might need the diode modification, you can easily ‘patch’ your existing board by adding the component as described on this Endless Sphere post.
As for my bike, there’s been nothing much to report recently. The bike and pack continue to work fine, and I typically get 15-20 around-town miles before the LVC system (the on-board, Fechter-Goodrum one, no less) starts to trigger the red, warning LEDs that tell me it’s time for a charge. So little to go wrong with these bikes once you’ve got them figured out. I am still on the look-out for a more powerful hub-motor, though, but I’m still finding it hard to come by ones more powerful than the 1500W one I already have.
If I can get hold of a 2000W one, and confirm from the weight that it’s probably more powerful than the one I already have now, then I’ll give it a go and see if I can get more performance. Have a great summer!
What does this change mean?
“1) Square pads have been added for the 47K capacitors, to prevent further confusion about which way round they go”
By convention, the negative end of components goes to a square pad, so you know which way round polarity-sensitive components like capacitors, diodes etc. are meant to go. In an early run of the board, a photograph was shown in the assembly manual of a board that has the capacitors on the wrong way round, which caused some confusion (though, oddly, it still apparently worked fine). The photo was later replaced with one of my own board with the capacitors on the right way round.
However, the holes on the board for the capacitors were never coded, so I’ve made the relevant pads square in line with convention, to make it clear which way round the capacitors should be mounted. See: