If you’ve owned a Lithium Polymer (LiPo) battery you will have noticed a small connector on the battery pack in addition to the traditional positive and negative leads. What is it and how do you use it?
This balancing plug comes with batteries that are at least 2s and up. It is configured such that any two adjacent wires will give you the voltage of a single cell. The wire on one side is the negative terminal of the pack and the one on the far side is the positive terminal. The wires in between are placed at the points where the positive end of one cell contacts the negative end of another cell. That’s all there is to the balancing plug but it serves an important purpose – to keep your battery cells in balance!
A balanced cell is a happy cell! Consider that with LiPos it is very important to know what the voltage of the battery is – you MUST use an ESC that is ‘LiPo Safe’ or ‘LiPo Ready’ or use a Low Voltage Cutoff (LVC) with your ESC if the ESC is not LiPo Safe. When it comes to charging you MUST use a charger that is specifically designed to charge LiPo batteries like the ProTek “Prodigy 65″ and “Prodigy 65 AC” battery chargers – this is all in consideration of the battery’s safe operating parameters. Discharging LiPos too much or over charging them can produce a hazardous condition (ie: a fire!) and diminish the service life of the battery.
A battery pack is made up of its cells so if the pack must be within certain parameters then its cells must also be within certain parameters! Generally the cells within a pack will charge and discharge at a similar rate and so will read the same voltage as its neighbors – the cells are balanced. But every now and then a cells voltage can deviate from its neighbors – the cells become unbalanced. When the cells voltages are different by more than 0.1v they are sufficiently out of balance and will need to be balanced to bring them into line. Charging a pack with one cell that has a voltage lower than the rest could cause the other cells to be over charged and cause damage. Likewise, discharging the same pack could cause the cell with the lower voltage to be over discharged, also causing damage.
To keep the cells from being unbalanced or to bring them back to a balanced state you will need to use the balancing plug and a balancing charger or a standalone balancer. The balancing charger uses the balancing plug to monitor the individual cell voltages and adjusts the charging rate to the other cells to keep the voltages the same. This monitoring is done continuously until the battery is charged.
It can be as simple as selecting the ‘balance charge’ option instead of the regular ‘charge’ option to balance charge a battery. Refer to your chargers instructions for specifics on getting your charger to do a balance charge.
There is some debate on the internet as to how often one should balance charge their Lipos – from every charge to none and somewhere in between. I say, if you have a balancer or charger that is capable of balance charging why not do it every charge?! The equipment is there and it is no more difficult to do a balance charge than to do a regular charge. A down side, however, could be that your battery may take longer to charge if the battery is unbalanced.
So, LiPos are way cool and powerful but they require some steps like balancing that other battery types do not require. Lucky balance charging is a simple process and if you have a balancing charger I’d recommend balance charging each time. If you don’t have one yet you can nab one for pretty cheap (Thunder AC6 – great little charger).