No hysteresis on cell overvoltage reported through Charge Enable over Canbus/RS485

[delboy711]

Using diyBMS ver 16-08-24 427a56

I am using Pylon protocol over RS485 to regulate my battery charging from an AC power supply unit using a home built PSU regulator. It all works beautifully but while testing edge conditions I found there is an issue when a cell goes overvoltage.

The function Rules::IsChargeAllowed() tests for cell overvoltage using the variable mysettings->cellmaxmv from the Charge Settings page where it is described as "Charge target cell maximum voltage"

When any cell reaches that voltage the Pylon protocol reports the 'ChargeEnable' flag as false and charging stops. But because there is no hysteresis on that test as soon as the cell voltage drops charging will immediately resume and charging will bounce off and on.

I suggest instead using Rule::ModuleOverVoltage as the test which allows the user to select an appropriate hysteresis value before resuming charging.