HP 41C series battery issues

[Seisland]

Hi, I'm wondering if anyone has heard of this problem. i have a 41CV and a 41C. I replaced the "N" batteries in the C but it wouldn't turn on despite new batteries. A month later the same thing happened to the CV. I went as far as buying batteries from another place just for comparison but got the same outcome. The contact points don't look corroded or dirty on either calculator. I'm puzzled. If anyone has any suggestions I'd be interested in hearing from you. Thanks

Ed