Balance Charging Two 3S packs
last updated 12-6-2009

Okay, at first it does not sound complicated and you are right, it is not complicated.... but you have to pay attention! Do you want to know what happens when you do not pay attention?

Actually this and more could happen. This is what happend the first time I connected the batteries to the charger. I was lucky all I had to do was replace the connectors. However it could have damaged the charger and batteries. The problem was that I criss-crossed the battery main wires with the balance connectors. Looking at the two diagrams below you will see the difference between the correct setup (on the left) and the wrong way on the right. You can click on the pictures for a larger view. In the 'wrong' picture you can see the dashed green lines indicating the electrical path that causes the problem. The positive side of Battery 2 gets connected to the ground side of Battery 1 through the Y-adaptor's middle wires. In the Y-connector you see two wires are connected together. And since Battery 2's ground is connected to the ground of Battery 1 through pin 1 of the balance adaptor, you have just connected the positive voltage of Battery 2 to its own ground.

correct	wrong

In the picture below you see a photo of the correct setup. Notice that in the green circles I have marked the balance connector, main wires of Battery 1, and the Y-adaptor. This way I can visually know I am correctly connecting all of the plugs.
Things to note!
1. Battery 1's negative main wire needs to connect to the negative side of the Y series adaptor.
2. Battery 1's negative wire of the balance plug needs to connect to the negative side of the Balance adaptor (green arrow).
3. Battery 2's negative main wire connects to the short wire that joins the Y series adaptor.
4. Battery 2's negative wire of the balance plug needs to connect to the middle wire of the Balance adaptor (yellow arrow).