Just got the wife a 501 pass-through this weekend. They have a 1CR10440 battery inline with the pass-through. On one the battery got hot, quite hot even to touch, when it was on the USB on the computer. It quit working after what appeared to be thermal runaway. Does anybody know why there is a battery inline on the pass-through? The 901's I have don't have a battery on them like this and I was wondering why there is one on the 510's.