Use needle nose pliers and gently squeeze the leads from the connector together until you can easily remove the battery, but NOT so it can come apart with little to no effort.
That would work but be very careful with this exercise.
If the leads are squeezed only a little too much, the battery connection becomes unreliable. I had a DJI battery that was very easy to connect and disconnect. But in mid air it lost connection several times and caused my FC40 to loose it's startup data (engines kept running fortunately) and it was about to 'fly away' (at least, it didn't know where to go or what was up or down). This was on the second day I had it. Nearly lost it in the lake. The startup tune sometimes sounded twice instead of once after connecting the battery. That's how I found out. Wiggling the leads exposed the problem. With the tiny amount of vibration in the quad the connection can just drop for a millisecond, but that's enough to get your Phantom in trouble. It really acts weird if you encounter this. After a few seconds you realise it flies in full manual, without home point or nose direction. Not even Atti mode. If you manage to keep it long enough in the air it will probably go back into Atti, once it settles again with barometric and compass data but the first couple of very long seconds it is totally uncontrolled, except by you.
I have a short video of this fly away and if you look at it you see what i mean.
https://www.youtube.com/watch?v=IyL9CTMJwMs
I had to do the opposite trick and widen the leads just to have it make better contact. The connectors are now as they should be, firm and quite difficult to pull from another. But I never had a problem again.
All I'm saying is: don't mess too much with this, there's a reason why the connectors don't pull apart that easy.
I ended up using dual 2200 lipos. I never trust only one battery again. And since I have both connections on the outside (used a T cable and made notches in the side of the battery door). It is easy to connect and disconnect. My battery door is always closed now and haven't opened it for months. If one battery or it's connection would fail I wouldn't even notice it while flying, other than that my Lipo alarm would sound sooner than expected.