I've waiting long enough to try to find an exact replacement battery pack for your Tiger tank. I'm going to go ahead and try to make one or modify it to take normal batteries instead. I was sure I could find a good replacement, but the only original one i found was, like the one in your tank, not capable of keeping a charge.
I wanted you to know that I have not forgotten about the Tiger tank you sent. It is here next to my desk and I plan to get to it soon. I've just been tied up on another project. I hope I can get it running again.