So, to clarify some questions I had.
- NiCd and NiMh batteries can be charged in series. However, make sure you properly limit and regulate the voltage if you do this.
Lots of interesting search engine adventures in thrashing around trying to rediscover one of my already logged links uncovered some new and interesting articles from Instructables. Yes, it turned out that the article I was looking for was not from Instructables, it was from an entirely different website.
20180304/DuckDuckGo instructables battery backup alarm clock
20180304/DuckDuckGo instructables nimh battery charging alarm clock
20180304/DuckDuckGo instructables dc battery charging alarm clock
20180304/DuckDuckGo instructables dc battery charging alarm clock
This article is really interesting. It covers how you can make your own switched mode power supply of a sort from fundamental circuit components. Hey, wait, is it saying that you don’t need motor control ICs if you use MOSFETs as your interface units? Maybe. But yes, if you’re trying to save space, you should definitely go for the ICs.
20180304/http://www.instructables.com/id/Build-Your-Own-Battery-Power-Supply/
20180304/DuckDuckGo dc battery charging alarm clock site:instructables.com
20180311/DuckDuckGo line power battery charging backup site:instructables.com
SAVE your print, about saving 20-hour 3D prints from power outages that effectively ruin them.
http://www.instructables.com/id/SAVE-Your-PRINT-When-the-Power-Goes-Out-Longterm-B/
20180310/DuckDuckGo line power nickel metal hydride battery charging backup site:instructables.com
- Important! This article mentions that you can use a single state-of-the-art IC for both NiCd and NiMh battery charging.
20180310/http://www.instructables.com/id/How-to-Make-a-NiMH-NiCd-Battery-Charger-Circuit/
20180310/DuckDuckGo line power rechargable battery switch site:instructables.com
20180310/DuckDuckGo battery charging dc input jack site:instructables.com
So, good news for the overall battery backup system design. The switched mode power supply? You can buy a board with all the integrated components on them. The battery charging limiting design? You can buy an IC to properly control that. The power source switching design? You can buy an IC to control switching that too. So, the remainder of the design comes down to creating a printed circuit board with a few more diodes and resistors, and you should be all set. Plug in your 12 V DC wall power supply on one end, and route the other end to your network equipment. You should be all set.
Wait, don’t you want to conformal coat your circuit boards? Okay, okay, now you’re talking. Yes, you do, since the Raspberry Pi itself is conformal coated.