The battery plug was simply a very tight fit in the socket. My problem was the tablet not turning off properly when we wished. It would appear to switch off but was drawing about 250 mA from the battery which flattened it in a day or so. Unplugging the battery, waiting for a minute or so and re-connecting it solved the problem at least so far.

My Asus Transformer is a T100TAF which doesn't have the yellow tape over the battery connector and the plug attached to the battery appears to be firmly fitted into the socket mounted on the Main Board. I have yet to work out how to remove the plug but the photo nearest above is a help as it shows the little spigot attached to the plug and which fits into the notch in the socket is in fact part of the plug. Back to the work bench.