Flyhal FX1 drone battery hacking

To get a line over high branches here I've been using a cheap but decent drone out of China called a Flyhal FX1. They are about AU$300 but seem to have gone up in price since I purchased.

I've used it quite successfully to inspect the roof and solar panels. The camera isn't great. It's 4K but not very clear. Live video is sent back over Wifi which doesn't have good range but I tend to fly just by eye anyhow.

Here's some video of me using it to raise a line over a tree:

As a result of this activity, the drone has suffered damage from a few heavy landings. One arm broke and has been glued a few times.

Today, for some reason, the battery pack will no longer charge. It has convenient USB-C charging and a set of LEDs to show what it's up to. Now the LEDs just all flash together and it doesn't charge. I pulled the battery pack apart and it seems that the 12V is simply connected to the far left and far right pins so a standard Lipo battery connector was soldered in place.

A 3S battery can be connected and held in place with velcro or rubber bands and the drone appears to power up as normal.

As I write this I haven't flown it yet (the glue on the broken arm is still setting). I'll update this post when I do take it up. Update: It looks like two other pins are needed to measure the battery level. I tried to fly but the controller thinks the drone is flat.