There are known issues with a batch of v2 batteries, for a while they were difficult to buy from cycle republic (sole distributor), they may still be... The local shop order bits and what comes in isn't what was ordered. Great front-end service, **** back-end service.
They have many complaints, it's only one batch of bad batch of v2 batteries, inside knowledge, but not nice if it's you.
However, I now have two v.1 (with four led display) from my 2nd hand really old (but mint) Gtech. A v2 that came with my Gtech mtb + a 2nd battery that was difficult to order.
I bought a v2 battery holder for my v1 e-bike so I can now swap batteries between the e-bike + mtb version.
The problem with the v1's was a poorly designed retention mech, it's easy to break the handle on the battery and four leds were fairly difficult to see in daylight, but the batteries themselves are really solid.
The v2's led screen display is easier to see and gives a fair reading of battery left but it doesn't drop linearly. The first few % are burned through very quickly, this gives a good idea of the battery health. Both types like to be treated properly (or at least fairly). The only real way to do that it is to have a second battery. Keep the first charged up and always use the maximum of the battery before swapping to the 2nd.
Just don't expect the rated range. after a while, it does go down, but not anymore than I'd expect out of a really good laptop battery over time, but its over generous to start with especially in 'High' all the time
Real usage on hills is more like half that if you ride it lazily, you know pedal to the whole time at a certain cadence that kicks the power out the most with the least effort
If your battery is acting weird it all depends upon where you bought your bike, Gtech or Cycle Republic. Good luck if it's Cycle Republic, you probably need it. If its Gtech ask for a replacement if it's acting like that.
The working product is basically totally solid, some **** happened to some of them, that may be you