Originally Posted by
Dave H
It seems you are saying that the sparks are from the bannana connectors, not the batteries themselves, then I suspect the connectors are not making good contact. Not cell venting.
Are the connectors getting warm/hot? If so, it seems that they are warming up, and thus expanding slightly. Towards the end they expand enough that ya start losing contact, then the sparks start.
Low budget fix, crimp the connectors with pliers some to get a better contact. Better, new connectors.
Good Luck.
yeah, that sounds like it. also, strange question, but are your batteries vibrating in any way? like, a wobbly table? could be the plugs bouncing round in the sockets.