Preparing for Around The Bay 2023 - DIY Bosch Chargers and knee issues

In this video, what did and didn't get used of what I brought along for Around The Bay, how to build a Bosch charger yourself (not recommended or approved by the manufacturer!), how it'll all be packed this time, and the clever plan to have someone else bring me more battery power. And after the machine's in order, a small human issue that threatens to derail everything.

[@Kevin_Aus]

Nice work mate. I wasn't aware that a bosch battery could be charged off 12v so that is interesting. I wonder if its possible to charge a shimano battery in a similar manner.

[@DropTableAdventures]

The LiFePO4 pack was 12v (with all three of those "bricks" in parallel) - it's been rewired in this application to put all 3 in series so the DPH5005 only has to step up from 36v to 42v, as there's a 10A input limit to contend with. However you could use it with 12v input - 12v 10A is 120w, so you'd have a bit under 3A at the battery end at 42v. Provided you wanted to wait a bit longer to charge it, that'd work. As for Shimano STEPS - I cannot find anything about DIY'ing a charger (I thought info on Bosch was thin on the ground)... I would think it'd be similar as overcomplicating the charger would increase cost, but I really can't be sure.

[@robzyb]

I have so many comments on this video.... 1) You're tempting me to get a DPH5005 to replace my DPS3003. In blatant violation of the YAGNI principal I'll probably get it with the Bluetooth module too. 2) Instead of that Pololu 5V step-down, or even a resistor/zener, I would've thought that an LM7805 would be the way to go. If the device is really that low current you might be able to do without any input/output decoupling caps too. 3) Does the Bosch battery have onboard BMS? I'm not sure I'd trust a DPH to be accurate enough with its voltage limiting. 4) Is that a Seiko SKX171? Not a common watch, but cool! 5) I too have issues with my knee. Not exactly sure what's caused it, but the cartilage in my knee is fractured, perhaps from similar issues to what you had. Yoga has helped me to work the right muscles to avoid pain these days.

[@DropTableAdventures]

1) You can always use both! Haven't used the BT module but maybe for something like this it would have been handy to log I and V over time, for a nice graph (in addition to the timelapse) 2) 7805 is usually max of ~25-35v in, even at negligible current, Pololu module will take 50v in. All 3 batteries in series so could be wired across just one... though if any significant current is drawn, will flatten one asymetrically (maybe in practice this may not matter, those 3 packs do differ a little in capacity...) 3) Yes the onboard BMS on the Bosch side should disconnect above 42v - it doesn't even connect until you supply the 5v - but the voltage did seem to be pretty accurate when I checked with my meter. While testing I had it top out at 41v just to be safe. 4) Yes it is a SKX171 - used to be my watch before I got a Pebble Steel, then a Pebble Time, then a Pebble Time Steel, then a Garmin Fenix 6X. Nice solid chunk of metal, water resistant to 200m, fully mechanical and self winding. Actually, it's funny how I thought that was a big watch when I got it, the 6X makes it look tiny! 5) In the months since then, I've resumed running and it's getting better. Don't think I have problems with the cartilidge - that sounds painful, hope you can keep it under control.

[@robzyb]

Good pick-up re the 7805. My oversight is why voltage regulators cower in my presence.