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ReVive Balancing Explained

As ReVive Balancing is now enabled, here you can read a bit more about technical aspects of the algorithm we use to force balancing.

BMS (Battery Management System), which is installed in every electric or PHEV car (sometimes called alternatively by the producer of a vehicle) beside of controlling critical parameters, like the maximal voltage, or current, spends some time on balancing of cells. Basically, it is simple. Most powerful cell (qualified via highest voltage) or usually - a group of such cells are connected to small resistors to reduce their total energy stored and thus - to reduce voltage to be similar (more or less equal) to most of the cells.

This process is not continuous, and also it uses quite low energy consuming resistors to avoid generating heat.

The most crucial problem is that it is not entirely sure (but most probable) that the cell with the highest voltage has the highest capacity. As this may change while the voltage of the whole battery (and state of charge, SOC) would be lower, BMS tries to store some information about the behaviour of cells at various SOC level to be better prepared and predict future needs of balancing. In simple words - a cell with the highest voltage at SOC=100% may be the weakest one at SOC = 10% - so it would be a nonsense to discharge it (balance it), when BMS knows, that this cell will loose that high voltage, along with SOC going down.

As all this information stored in BMS is used to predict the total capacity of the battery, it may start to be inaccurate. Sometimes it is just caused by an error (bug) in the software of BMS (like Nissan Leaf 30kWh before the update, that corrected that mistake). In most cases, it is just because the car is not fully loaded or discharged to help BMS to collect more data and predict real capacity better.

ReVive Balancing uses a semi-random "Pulse-Relax" algorithm, well known from modern 12V battery chargers with reconditioning of battery. The car should be discharged to <10% of SOC (shown at car dashboard). Then - charger pumps battery for a short period, then - relax it with slowest charging speed possible. It repeats with some time variations.

With this schema of charging, all weak cells show their behaviour at various SOC and BMS learns quickly and accurate, how to balance them in the future. We may say it "resets" but to be honest - it just updates all the info about cells behaviour at various SOC.

Last period (usually after 8-10 hours) is just slow charging of the car.

In most cases, usable capacity will be improved, and SOH (State of Health) may go up.

Please use that function overnight, at least twice a year, and you will recondition your battery and keep better usable capacity.