OK, imagine a 2s pack. You stack the cells like so for running:
Code:
(-)======(+) ******* (+) (To ESC)
/
\
(+)======(-) ******* (-)
On the left is the jumper, on the right are the wire leads to the ESC.
Now, let's say you forget to re-orient the cells and install the jumpers for parallel charging, like so:
Code:
(-)======(+)
/ \
\ /
(+)======(-)
* *
* *
* *
* *
* *
(to charger)
That
will cause a major issue!