I did a silly thing. When I made my 3D-printed custom remote for my board I connected the 1S lipo cell directly to the electronics and a SPDT switch. The switch selected between powering the electronics and connecting the battery to the charging port. The electronics don’t currently include any over-discharge protection because the controller only draws a tiny tiny bit and I was happy to just check the voltage manually.
Yesterday I got my board reassembled with the new trucks and an idler pulley and was all ready to test it out, so I grabbed my controller and switched it to the charging port so I could stick a multimeter on it to check the voltage. No voltage. Wut. Oh right, somehow I failed to get the switch to the charging position…
1.7v. On a lipo cell. 0_o Oh dear.
And then I realised why I’d failed to get the switch to the charging position the first time: it was in the “on” position when I picked it up.
So yeah. I failed by not having over-discharge protection and also by having the switch mounted sideways so when I inevitably sit the controller on something it’s very easy for the switch to be turned on by accident. I’m not actually annoyed that I killed the lipo (they’re cheap and easy to get), more that I have to desolder it and prepare a new cell, and that I couldn’t take the board out for another test. Also the fact that I think I accidentally threw out the other 2 cells of the 3S lipo that cell came from with the packaging. Will have to dig through our bins and see if I can find them because I don’t want our bins to catch fire.
Next step is buying an over-discharge protection chip (or making one, should be pretty easy! Thinking just a voltage divider and a mosfet controlled by the arduino).
Me too, that’s how I designed my remote, by looking at heaps of photos of other people’s remotes Going to make the design and software open source once it’s reliable and a bit more tested. The goal is for it to be as easy to make as possible using the most available parts possible. Currently the brake has too much travel and it’s awkward to apply 100% brakes (not that I think I’d ever want to do that, basically stops the board on a dime when I do that ).
Haha. I’ve got myself on a pretty strict budget at the moment because I have a number of moderately-sized debts that need to be paid off ASAP. Accounting for internet, food, board and fuel costs that leaves me just over $100/week, and this week (because I screwed up a calculation in my spreadsheet) I need that money for my internet.
Well that’s AUD of course and I think you’re in the US so that’s only about 80USD. But yeah, I work full time in IT as a programmer/website engineer dude. In all honesty I would much rather only work 3-4 days a week and have less money but more time. It sucks only having 2 days per week to myself.
Already bought a pack of 5 of those from eBay after you suggested it in general chat, but I didn’t know they did discharge protection as well. Is that what the datasheet means by under voltage lockout? I assumed it meant it wouldn’t try to charge it if it was below a certain voltage.
There are 2 diff versions, with and without over/under protection. The ones with protection have extra solder pads next to batt pads for output to device being powered by lipo. It charges at 100ma if it detects low voltage cell and then ramps up when it hits threshold mentioned in datasheet. You can also adjust charge rate by changing a resistor
Ah interesting. So based on that, the ones I bought should have the undervoltage protection? Ah, with some googling I can see that board has two different lipo protection ICs aside from the TP4056 so I guess it does. I’m not sure why there would be two different ICs that seem to do the same thing though