mwkeefer wrote:Y have you been hanging out with Amberwolf cause your photoshopping is getting better?
philf wrote:Sheesh. I just can't keep up with this place. Really. I just started playing with LiPo this summer, after wading in (deep) to all that's been posted here on ES. I finally gave up and just started playing.
I hit the same poser that everybody else does - what do you do for a BMS? Then, realizing that the chargers I'm using look after the ugliest task, I was taken by the elegance of Gary's solution for pulling the e-brake low when any cell hit 3V. Brilliant - I placed my order with Digi-Key right away, and went to work on a board - I wanted it to look after a 12 cell pack. Meanwhile Knuckles started this thread (synronicity!).
Here's the board:
It had to meet two special criteria - it had to fit in a small Hammond box, and I really felt I could make it SINGLE SIDED. And I did.
For giggles, I added an extra resistor and an LED to each channel. Funny thing to do - when any cell is over 3V, the draw of the circuit is in the micro-amp range. When you get down to the LVC, not only is the opto-isolator activated, but the LED glows. The draw is 9ma. Obviously something you wouldn't leave plugged into the pack at this point, but I thought it would be useful to see WHICH cell is pulling the e-brake. In a perfect world, when you're finally "dead", you'd look at the board and see 12 LEDs alight. In reality, I'm sure there's ultimately gonna be one cell that goes first - and it would be nice to be able to glance and see if it's always the same one. Dunno if this is gonna be useful or not. We'll find out.
Populated, it looks like this:
After doing a quick Dremel job to round out the corners for the Hammond box (my drill press snapped its belt while I was building this), I realized that the box was probably overkill. So I stuck the whole affair inside a piece of clear heat shrink tubing and just stuck it to the pack with Velcro. (It would have been tidier if I hadn't taken out the corners, and if I hadn't hit the tubing with the heat again after cutting out the connector hole).
Will post about the usefulness of those LEDs when I can get out for a good run. We've been living with torrential rain for the last few days. No fun.
heathyoung wrote:Also - quick question - what are you using for tinning your boards? I've been trying to find something cheap that works well, TINNIT is not available in Aus, so I've almost resorted to making my own with Stannous Chloride 5 grams/litre, Sulphuric Acid (66 Be - 96%) 10 ml/litre and Thiourea 50 grams/litre.
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