This was what was removed from the post I made in the Simple BMS thread. I like the idea however I want more... more flexibility as well as a single decision maker. The post removed part of that post follows:
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What I'm thinking is there are 2 basic types of battery voltages, the single cell battery access (eg lipo, nimh,li-ion, etc) and multi cell access batteries (agm, sla's etc) The hardware differences between the two as far as a BMS node are concerned are not too much different and if your running a multicell battery a simple addition will keep the voltage in spec.
For each cell variation the differences in voltage are not that extreme so the hardware can have an adapter for multi-cell batteries, and for single cell batteries it wouldn't need it. The rest seems to mostly be a software issue. If we need to change a resister to handle a different battery that is fine by me, and seems to be a reasonable solution to that problem as well. The software can take the input (adjusted or directly) and compensate for it in SW. I'll write up a block sketch of what I'm talking about and go looking for parts. I plan to buy the pickit 3 and a few parts to get me going on Friday, but I may just get them when I get off work
I think PIC's are awesome I can't believe I never knew about them or took notice if I did....
For software and input what I'm thinking is each cell when it starts will be numbered. Master (0) the nodes will simply add 1, and when communicating will identify which cell it is. The numbers I care about are number of reporting nodes, highest voltage, lowest voltage, highest temp, lowest temp, and average temp, and average voltage.
There will be an extra non daisy chained node that should detect current flow and volts of the entire pack. If we take the average voltage from the nodes and the voltage of the pack and it dosn't add up (accounting for voltage drop/resistance in lines etc) then we know something is wrong!
I'm not sure if it can work that way and right now I'm at work on my netbook so when I get home like I said I'll look at what and how I want it all to work.
I personally want the master node to monitor the controller, charger, and motor, as well as actually control them in as simplistic a way as. Plus be the main input/output. This way it handles all energy decisions, from a single source and I think in the end will be cheaper as an entire system. You would always be able to omit whatever you wanted from the module sets (EG controller module, BMS node modules, charger module, input module, output module). I think this would give everybody the most amount of DIY flexibility while having the potential to be the cheapest. Any one component can be redesigned without mucking up everything if one device is the decision maker, and it can be reprogrammed if needed for updates or an 'exotic' module that I can't think of currently.
Thankfully most of the work is done, I just need to 'dumb down' the open source charger, controller(s) (both DC and AC when its done), etc... The input side of it should be straight forward. Output can be added at any time, as well as data logging (which I think can be very helpful!)
This way you have a mix and match system tailored to your current needs and if they change you just add or subtract a (cheap!)module, the SW does the rest.
Feel free to correct me when I'm wrong (I'm sure I'll give you plenty of times to do so...) And give suggestions! I'm just getting restarted in electronics (which I never really did anything with anyways) and just learning PIC's! I would wait until Paul and company has everything done but I want something to do too