Nobody has replied and that's OK. Just wanted to follow-up my own message by saying that I discovered that my problem wasn't the charging unit after all. I just realized that I'd forgotten that I can't power my CMC5 mics, which need 48V phantom, with the m118 that supplies 18V. So obviously, the batteries weren't supplying enough voltage (which I initially thought was an undercharge) so the sound through the mics was severely distorted. I keep forgetting that I can only use my CMC6 mics with the m118! Doh!