Cell Number – Your batteries have to be the same cell count number. Compatible with standard analog and digital servos – as well as programmable S.Bus system servos. You might also notice the current going into each pack might be different at a given time, that’s because nearly every cell has different internal resistance and therefore some batteries can be charged up faster than others. Even if your LiPo charger was not powerful enough to provide high current, parallel charging saves you from hooking/unhooking them up every charge cycle. Use the CIU-3 to update your Futaba gyro and transmitter firmware just as easily. The adapter may be in the form of a generic balance adapter board for their charger or it may be a specific single use adapter.
Charge current can be calculated by dividing power by voltage, I = P/V. But as you can see, voltage is changing all the time as the batteries get charged up, so will the current. Each battery has one discharge lead (main plug), and one balance plug. This is totally fine if you have the correct connectors but finding the correct connectors can be challenging. Of course the bonus with making your own is that you can make whatever you want. Normally parallel charging boards have enough slots for 4 to 6 batteries. Hopefully this short guide gave you some insight into what parallel charging is, and how to do it safely. The way I see it is, every battery has internal resistance, and the charger has to work hard to “pump” electricity into the battery.
Also make sure you are plugging in the balance lead in the correct orientation. They have now literally become a “huge single lipo battery”, with capacity combined. So basically we are just charging up one big lipo pack instead of smaller, separate packs in a sense. Check the datasheet below to see if it will work with your battery.