I swapped to NiMH for my replacements mainly because NiCd was hard to find. Before doing so I did some research on manufacturer recommendations. This doc is pretty good http://data.energizer.com/pdfs/nickelmetalhydride_appman.pdf If you look at the Recommended Charging Rates section (pg 11) it gives this recommendation on trickle charging:
'Finally a maintenance (or trickle) charge rate of less than 0.025C (C/40) is recommended. The use of very small trickle charges is preferred to reduce the negative effects overcharging.’ The NiMH and NiCd self-discharge very badly so if the trickle charge < self discharge rate things should be fine. Looking at the charge circuit on the M100 it is basically a series diode, resistor (1.8K) and the battery. If the battery is at 0V the max current is ~2mA, at full charge (3.7V) the current is ~300uA. Based on the recommendations of Energizer the charge should be <C/40 for a trickle charge. The battery is ~60mAh, which gives ~1.5mA trickle or maintenance charge well above that produced in the M100, in fact the NiMH might sell discharge at that rate. So I went ahead and updated the batteries. If you trickle charge at very high rates then NiMH might fail earlier but so too would NiCd. The initial charge might be slower for NiMH compared to NiCd but that is not really an issue in this application it is merely acting as a backup battery. From: M100 <m100-boun...@lists.bitchin100.com<mailto:m100-boun...@lists.bitchin100.com>> on behalf of George Michael Rimakis <grima...@gmail.com<mailto:grima...@gmail.com>> Reply-To: <m...@bitchin100.com<mailto:m...@bitchin100.com>> Date: Monday, March 12, 2018 at 10:10 AM To: <m...@bitchin100.com<mailto:m...@bitchin100.com>> Subject: Re: [M100] batteries... The thing about NiMH, is the level of trickle charge that they can tolerate is a bit less than NiCD. Might not be good in the long run. On Fri, Mar 9, 2018 at 5:00 PM, Jim Anderson <jim.ander...@kpu.ca<mailto:jim.ander...@kpu.ca>> wrote: > -----Original Message----- > > This brings up an interesting point. Having just replaced my NiCad I > think I'm going to use my label maker to leave a note about when it was > replaced under the battery door. I like to do this anyway (and not just with m100s), because I find myself struggling to remember later which machines have which things replaced, and when they were done... jim
