[FujiPedaler]

Work with me on this but looking at your pictures, you have wires going all over the place.

Think of your 2 batteries as one big battery except that one batteries positive is connected to the others negative .

Now all of your positive (hot) leads go to the one positive side and the negetive leads go to the one negative post of the other battery.

If you draw yourself a picture of your two batteries side by side, you should be able to use the drawing as a guide to hook up correctly.

Your positive to negetive jumper should not have any other lines (wires) going to/from them, then negetive wires to negetive termanel and positive wires to positive termanel.

Hope this works for you.