JST Parallel Charging Board 2-3S

Parallel Charging FAQ: What is it all about? Parallel LiPo charging allows you to charge more than one battery at the same time (with an appropriate charger). The big advantage of parallel LiPo charging is it saves time. You can charge your entire collection of (same cell) LiPo batteries on one charge cycle. For example, if you charge four batteries, the charge current is four times of that you used for a single pack, and you need only approximately 1/4 of the charge time if you were to charge every battery separately.

Is parallel charging safe? It is as safe (or dangerous) as charging a single lithium battery pack, indeed many argue that it’s kinder and indeed safer on your batteries than serial charging (one pack at a time). The drawback is if something were to go wrong during the charge cycle it could affect multiple packs; lithium battery chemistry is a volatile mixture – one battery setting on fire because of unsafe/improper charging is bad enough, never mind several batteries all hooked up in close proximity! Charging your LiPos, in fireproof containers and monitoring the process is therefore imperative.

Can I mix and match my batteries? Parallel charging will only work on same cell count batteries, but they can have different capacities (within reason). They can also be at different states of discharge – again within reason. It isn’t advisable to parallel charge a pack that was 5% discharged with one that was 80% discharged. As a rule of thumb, don’t charge batteries with more than a 0.1 volt maximum difference. This for example would be very close to the voltage difference between a cell that is 80% discharged (around 3.75V) and cell that is in a 50% storage state (about 3.85V). The larger the voltage difference between packs hooked together in parallel, the greater the amount of current that flows between packs as they all equalise.

What voltage and charge rate should I set for parallel charge? Think of charging multiple packs in parallel as similar to charging a single large capacity pack. The cut off voltage remains the same as that of your single pack since they are connected in parallel. The capacity becomes the sum of all your batteries. Because of this you can increase charge rate according to the total capacity. For example, if you charge one 3S (11.1 V) 2200 mAh LiPo battery at 1C, the charge parameters you set should be 3S (terminated at 12.6 V) and 2.2 A. For six of these packs, they should be 3S and 13.2 A (2.2 A × 6 = 13.2 A).

Is my charger up to it? High power chargers are generally required, especially when charging multiple high voltage batteries, as the wattage requirements are typically high. For example, charging 6, 3S batteries at 13.2A will require 166.32 Watts, and that’s only at 1C. Hence just because your charger might boast a maximum current of 10 amps or even 20 amps, if it doesn’t have the adequate power potential, it will never be able to provide that current to your battery during the whole battery charging process. As a consequence your overall battery charging time will be much longer than expected.

To summarise some general do’s and don’ts:

• Do not mix cell counts (i.e. do not try to charge a 3s and 4s pack together).
• Do ensure that all cells are within ~0.1V of each other before connecting.
• Do connect the main charge leads of the packs to the board before connecting the balance leads.

For further guidance, check out this helpful video.