Some photos, the one on the left is the new charger I got from e-rolling, the one on the right is the original one, also the battery input hole.
I never had a spark with the old charger and the new one was fine until I went to charge Tuesday night, got a big spark, freaked out and didn't charge it and then the same today.
The old charger was working but cutting out after an hour hence getting a replacement but I've pushed it in the hole and no spark so hopefully I have an option to use that if the battery is safe.
The battery has GW embossed on the case and the barcode is 36910, google led me to this as the spec:
http://greenway.ecvery.com/products/electric-bicycle-battery/p1475400/e-bike-battery-36910.html
On close inspection of the battery case there is rust on one of the screws that are on the bit that sticks out of the case
I've managed to hobble to the hospital and back on lowest power but the battery is virtually flat now and have another appointment this afternoon, am tempted to try the old charger?