arber333 wrote: Huh that is not a bad idea actually. LEM would be mounted on a side PCB powered by 12V. Optocouplers would be used to output signal to cell comms for isolation. You could also use a boost converter to fully supply 5VDC from one cell. Only i dont know how much it drains. You dont want that cell unbalanced!
Software would have to be accurate to 1A though. Should be signal at least two byte in length with identifier.
In Nevilleh's thread
about building a charge count device he mentions using the Tamura sensor (Datasheet
) which only uses - gnd, +5 and signal.
I was thinking of putting the battery packs positive cable through it and using cable ties to secure it from sliding up or down the cable then just a 3 wire fly lead from the device to the nearest cell which would have the combination celltop module rather than the standard celltop module.
Datasheet says the current draw of the device is 15mA, should be able to work out a method of turning this current draw off when current measurement isn't required (when not driving or charging) to reduce any cell imbalance.
Might order one and see what hapens when running off of 3 volts. The datasheet says 5v but that may be just to maintain the 0-5v output signal.
Even if it does need 5v then a small dc-dc converter for 15mA shouldn't be too hard to find.
The sensor series has different versions with different current ratings right up to 600A.
You could hook it up in series with cell modules. That would have PIC12F the code and all but would only repeat other cell voltages/temp. It would code and put LEM value in the comm string using identifier. Master would read and interpret it as a value separately from voltage array.
I bet master code wouldnt be that much longer and comms time also.
SOC would be displayed in the same master LCD together with Amps. You would just have to tell what is the cell value first.
Reset could be a small signal relay triggered from charger shutoff function of BMS or manually.
I was thinking of a celltop module that does the normal voltage and temperature measuring but also interfaces to the hall effect device so it can also measure the current. So all communication (including SOC resets) would be over the existing BMS comms link.
Well you could make Arduino micro SD module (could do it with PIC12F also) that would store to SD card. Its just you have to change array to ascii, decode it to mV and separate it by comma to be read as .csv. Hm shouldnt be a problem for you, but i am still learning programming in C.