Hope this might be of some use I contacted Windcamp a few years back and here below is what they had to say:-

The WLB-817S lithium battery pack has four power cords, two red ones for the positive and two black ones for the negative.It does not lead to the balance detection line, so does not support the balance charge.

However, your B6AC balance charger can still charge wlb-817s, but the charging mode needs to be set to unbalanced mode. LIPO for battery type, 3S for voltage and 1.5-2a for charging current are recommended.