I did a video showing fitting a supercap in a M100 and I have also refurbished them with a NiMh cell. In the course of researching supercaps to pick out the correct one I learned a lot about them and their ‘hidden’ quirks.
The biggest drawback to a supercap is the very high self-discharge rate, especially in the first 72 hours or so, then it tapers off considerably. I don’t recall the name of this particular specification, but it gives you something like the discharge rate after 72 hours and seemed a bit wishy washy form manufacturer to manufacturer. The main point being that you will lose a lot of the charge in the first 72 hours even with no load. The tiny load of the M100 RAM is dwarfed by the self-discharge rate. It was fun to learn enough about supercaps to be able to specify one for my M100 but the humble NiMh cell will last MUCH longer. Both capacitors and batteries will leak eventually so pick your poison 😊. For me I’m content to use a NiMh cell from now on. Speaking of NiMh cells, while the original battery is NiCad given the low charge rate a NiMh cell works perfectly as a substitute and they are available in the exact size. I bought a bunch of them from a manufacturer as I was working on a number of M100s at the time and put the rest on my website. Arcadeshopper, who is also a list member carries them as well. https://www.soigeneris.com/memory-backup-battery-mbat1 Jeff Birt (Hey Birt!) From: M100 <m100-boun...@lists.bitchin100.com> On Behalf Of Josh Malone Sent: Sunday, February 23, 2020 7:25 AM To: m...@bitchin100.com Subject: Re: [M100] NiCd Battery A quick estimation of 200mAh cell vs 30uA standby current gives life of less than a year. But there are lots of variables, most importantly presence of primary power. However, even with a low dropout voltage diode, 2.6v might be more for Vb rail. I'm not sure. Since capacitors can also leak, I've never seen the point in going the supercap route. I've also seen anecdotal evidence that a 5v Vb might cause issues with the power-off circuit. These reasons are why I prefer to replace the memory battery with a rechargeable NiMh. (yes, technically there are issues with the charging circuit but I don't care enough to source a NiCd). On Sun, Feb 23, 2020, 6:05 AM Ben Strewens <bungop...@gmail.com <mailto:bungop...@gmail.com> > wrote: I was wondering about the supercap since I saw someone on a Youtube video use one. I'm currently trying the lithium cell with a diode. It works, although I'm not sure how long the lithium cell will last.
