Hobao have recently changed the connectors on their models (which I wasn't aware of) - they used to use the standard Futaba/JR style but now use BEC connectors. Unfortunately most rx packs have Futaba/JR connectors, but there are a limited few available with BEC connectors -
These are the only one's I'm aware of and aren't widely available (and I have only started stocking them since you phoned me!)
If you want to swap the packs you bought for these then please let me know and I'll refund the difference.
I would still however advise you get a switch with a Futaba/JR connector and charge jack built in - like
This one. This means you will have a wider choice of battery packs when you need to replace them in the future, and can charge the rx pack without removing it from the car.
The Core RC battery packs you purchased are better than the Ansmann ones too...... but as I said the choice is yours!