Ok here we go.
Well first you have to know a bit how and what a Battery Management System does.
Usual functions:
- Control max. Pack Voltage during charging cut of charge when pack reaches max voltage for your pack should be around 42V
- Control max. cells voltage during charge cut of charge charge when any cell reaches over max. voltage around 4,25V for your cells.
- Control min. pack voltage during discharge, cut of current when pack reaches min. voltage for your pack around 30V
- Control min. cells voltage during discharge, cut of current when any cell reaches min. voltage around 2,5V for your cells.
It can have more functions or less than this but this are the basic ones like:
- Temperature control, if the pack temperature passes 60ÂșC will stop charge or discharge.
- Balancing function keeps cells valanced in voltage.
Now how to check it:
Firs you need acces to the cells or at least to the balancing connector of the pack.
And you need a voltmeter.
The blanacing connector is something like in the picture with more pins in your case.
You can check directly on the cells or on that connector the voltage of the full pack and the voltage of each cell.
The best moment to check is when battery is almost empty, at that point problems are easier to find.
we are going to find out if the
BMS is wrong or the cells.
First you have to check if all the cells have the same voltage, difference between the cells should not be over 0,1V, so for example the lowest can be 3,6V and the highest 3,7V if the
BMS has balancing function the difference should not be higher than 0,02V
Then connect the pack to the charger for a while, and check the voltage increase on each cell if any of the cells increase voltage more quickly than the others that cells is dead or near to dead.
Now disconnect form the charger and put it on discharge with the motor or something else, and check again voltage of the cells and follow them till the pack empties.
When the pack empties all cells should be around 3V if one or more cells are way under then the
BMS have cut because one or more cells are damaged and reach minimum level per cell, instead of cutting at full pack voltage end that is around 30V
As well you have to been able to see during this discharge if one or more cells droop voltage more that the others under the same load if there is one cells or more than one cell that droops more than the others that cell/s are dead or close to dead (provably are the same as during charge and provably the ones that are lower voltage when empty)
(The voltage, temperature and other values I posted here are the standard for Lipoly cell and packs they can be sightly different on each
BMS model and differently adjusted to battery different models and uses)
Hope it helps and ask if something is not very clear, because my mother tong is not english.