GTech - battery problem - battery and controller replacement - where to start..

Hi gang, hope all is well with you - was wondering if anyone would be able to offer some assistance?

My wife's much used GTech city has had a problem with the battery for a while. The battery is the one with the digi display on it - V2 I believe. One of the the connectors in the base of the battery had got bent and was preventing the battery from sitting on it's charging base nicely. It needed constant wiggling to get it to stay long enough to charge - it got a bit tiresome...

I took the battery apart and straightened the connectors so that it sits down nicely on the charger now, (for info I had to go in from the bottom of the battery case with a Dremel as the connectors are glued down to the bottom circuit board with silicon sealant - can't get in from the top - although I was able to pull the fuse so I wouldn't get fried), but the charging problem remains. It will charge for a few seconds, sometimes adding one or two percent to the charge number, then will switch from charging back to ECO or MAX with an audible click.

I'm thinking that something is up with the battery so was looking to replace it, but the GTech ones are quite pricey for not a lot of capacity, so I'm looking to replace it entirely - and I understand that the controller is part of the original battery - so will need one of those as well. I'm planning to take the battery mounting rack off, then fit a new rack, battery and controller. I'm thinking 36V battery, and an 18-20A controller to suit the existing motor.

Cuuld anyone help with some questions I have:

- Does it sound like the battery was the issue (not the charger!)?

- Will the controller plug into the motor with no modification to the wiring?

- Can I buy a battery with an integrated controller? Is this one the sort of thing that would work (with controller option)?

Any thoughts/help would be much appreciated - thank you!