Assessing cell balance
Unlike lead-acid batteries which require little maintenance and are very forgiving of neglect, Lithium-based batteries require care and vigilence if reliability and long-life are to be realised. In a worst-case scenario, a poorly maintained Lithium battery can spontaneously catch fire if given sufficient provocation.
As a Lithium battery is charged and discharged repeatedly over time, its cells will begin to diverge in their state of charge. This occurs even though the charging and discharging currents for all cells are identical.
If a battery is repeatedly charged and discharged without any regard for cell balance, some cells may be overcharged and some may be undercharged. Overcharging damages cells and reduces the battery's lifetime, and undercharging means that the battery is not storing as much energy as it is capable of. More catastrophically, overcharging damaged cells is a risk factor for spontaneous ignition.
In summary, cell balancing:
Millswood Engineering makes two UAV battery balancers:
6S Battery Balancer. A precision instrument that can be used as a hand-held battery verification tool, or installed inside a UAV to balance a battery's cells as well as report the cell voltages and battery temperature via the vehicle's CAN bus.
Available soon from Millswood Engineering.
15S Battery Balancer. In development.
This is a new product that is being developed in partnership with VISIONAIRtronics of Austria. Available third quarter of 2021.