What I get for sleeping.
(Lots of post to respond to.)
Let me reiterate, I'm NOT trying to push more sophistication on you than you want. I'm trying to design a circuit with enough options that it will work for ANYONE.
Just because an option is there, doesn't mean YOU have to use it!
I'm surprised people think this is complicated. One processor, one op amp IC, however many shunts you need, and a handful of caps and resistors for the main board, plus a processor and a half dozen peripheral components for each serial ID unit (if used).
Rather than using quotes and responses, I just going to make random responses.
Thanks for the link to the diyelectriccar thread link, I'll pursue it farther, but the safety devices I saw so far have already been discussed here. (fuses, GFCI, HVC/BMS shutoff)
The caps should be modern UL listed
RUN caps. They have a switch that opens if they build up pressure.
I have a lot of faith in my programing, especially if checked by members of this forum.
If you want true redundant safety override, it shouldn't share ANY components with the main controller.
A good cheap alternative would be a crowbar (a heavy SCR) across the output, with fuses in front and behind it. Could use a trip voltage higher than any of your packs ever see (could be switch selected, but there's the danger of it tripping when you forget to change it), and it could have a timer that energizes it if the controller doesn't send regular 'watchdog' resets (not to be confused with the processors internal watchdog).
You don't need to use all 6 relay control outputs. Would only be for those who have more than one 'size' battery. You surely aren't going to use the same current on your lite 4Ah battery as on the 40Ah+ motorcycle battery, are you? At an EXTREME it would provide almost infinite current control 'like a commercial charger'. I rerepeat, you don't have to use them if you don't want to! My
immediate plans call for 2 significantly different battery packs, so probably 3 caps would do me fine, but other people might have a wider need, so I'm trying to allow for them. Skippic, are you sure your setup would be ideal for both a 4Ah 4s and a 40Ah 24s?
Good point on the internal references. I'll probably build a prototype with the VR reference, and 'allow' for it's variability when setting my limits. (I don't have a 16F1938)
I can't see why we could possibly need a separate thread to include an HVC input, or why it's 'messy'. One pin on the processor, one line of code.
Evibus is an alternative to CANbus. Involves wires and is much more complicated than adding a serial # IC to the battery. Wake on interrupt would require some form of bidirectional com, which would unnecessarily complicate things (I can live with 20 to 60uA).
My thought on the zener is that it wouldn't have to conduct continuously or even accurately (maybe I'll experiment this afternoon). As long as the voltage stayed between 2.5 and 5.5 volts, even the old 12c508 would be happy. <edit> I would want a different processor for battery temperature measurement.
The more I think about it, the more I like the idea of a wireless serial # ID, because
it's simple (I've pretty much abandoned the idea of an extra connector at the charge connect as being unnecessarily complicated). Programming at the charger would be simple since the one I build would have up/down buttons and an LCD (I would require that the battery being programed for, be plugged in, so you would KNOW you were programing for the right one). And before you jump on me, YOU don't have to spend the extra $5 for an LCD if you don't 'need' readouts or programability.
The reason the processor has a watchdog timer is in case the micro 'takes a dump'. Like Alan pointed out, we just have to make SURE the reset shuts the relay(s) off.
Anybody who wants to is welcome to build a non computer controlled version, (they already are after all), but it's NOT what I'm designing.
I'm thinking that at most this would end up as bare boards, maybe with a programmed processor. Since different people would want different variations, preassembly would be problematic. It's intended to be easily assembled. The resistors are all large 1206 smt, and the smt caps are 805 or larger, which are fairly easy to work with. If by some miracle someone started selling them by the thousands, for sure, SMT would be the way to go.
Moving slightly off topic, I live in bush Alaska, and can't go to the store to buy anything in this project, except maybe a GFCI outlet (I want a GFCI plug), (and would have to pay 2 to 3 times (or more) as much as the rest of you if they had it). I have to order it, usually pay double the shipping most of you would, then hope it isn't lost (not to mention it taking an average of twice as long for shipping).
Farther off topic, we Alaskans have one of the wonders of political idiocy called 'power cost equalization'. They 'tax' the people with more efficient power production, and use it to supplement those of us with inefficient power (our local power is generated with diesel gensets burning $6+ fuel, then distributed over an obsolete grid). Helps keep us from being 'too' conservative! Did I mention that the Alaska legislature pretty much works for the oil companies?
It's warm out (over +20F!!), I'm going to get dressed and go for a ride, just for the fun of it!