When you have a printed circuit board (PCB) made you can have markings and labels put on the board using screen printing. This labeling is often just referred to as the silkscreen. However the methods of silkscreen labeling are generally not as sharp as the photo-imaging methods used to pattern the solder mask. For this reason I generally like to use the solder mask layer for labeling more than the silkscreen layer. That being said, on the last batch of LCD charger boards the solder mask looked awful! This is definitely not the norm, but it made me think that I should really change the way I do labeling so that it is not so dependent on the quality of the solder mask. My solution came from the fact that the etching of the copper is the most precise (it's an actual spec you pay for). Now the copper defines the edges and the sharpness of the label is no longer dependent on the quality of the solder mask (or silk screen for that matter).
I had a single AA size Energizer Ultimate Lithium battery sitting around (like the one pictured right) and decided to run a little test with it. This isn't super formal but it is informative nonetheless. I used one of my non-LCD chargers as I am currently running test on the few LCD chargers that I have out, so the discharge was not constant current, only into the on board resistor which is 3.9Ω. Either way it gives a general idea of the discharge characteristics between Lithium (blue), NiMh (orangish-red) and Alkaline (gray). The thing to note here is the higher voltage the lithium maintained during discharge than the other two, which in this case means it was actually delivering more current into the load. As you can see it also lasted quite a bit longer than the others. So why don't we all switch over to using Energizer Ultimate Lithium?... well first off they are expensive but more importantly they are only one time use. So except for when you wont be able to recharge batteries or when you want a really long shelf life (like in emergence equipment or something) then I still think that most of the time a good set of Low Self-Discharge NiMh batteries are the best choice for AA and AAA battery needs.
I got back the boards for my first 50 LCD chargers. These will all go to Kickstarter backers who have been waiting VERY patiently... if they want them. Why wouldn't they want them you might ask? Well, although they work electrically, the firmware is still very much in the works and there were some cosmetic issues with this batch. One of them being a messed up silk screen on the bottom.
The latest charger is on the left and the last prototype is on the right.
I will be sending off for more black boards as well as some white ones sometime over the next few weeks.