Have you ever wished you could replace your Alkaline cells with Li-Ions?
What device do you have that NiMh or NiCd just won’t do, but your alkaline budget keeps you from using these devices?
If you could adapt Li-Ion to your device cost effectively, would you?
My black hole for the alkaline budget is my blinkie tail lights for my bike helmet.
NiMh don’t last nearly long enough (drain too fast without use too)…
and max power in the alkaline cells wanes very quickly where less than half life maintains that nice bright output.
Maybe try a LiFePO4 cell with a dummy to replace 2 alkalines? Lower capacity than 2 Nimh, but solid voltage of 3.2 vs 2.4 (2x1.2) during discharge. Also, significantly lighter weight if that is of any importance.
Interesting; didn’t know they made LiFePo4’s in AA and AAA. They seem to be about 1/2 the capacity of the available Li-Ions, though.
The LSD sounds like it would help, but the low end full charge 2.4V for a pair is still problematic. I have a small camera that has a huge parasitic drain and it usually reads a low battery at 2.3V. The actual power requirement with the display is about 400ma. And of course, bike lights want to be as bright as possible. Several units I’ve tested seem to stand up to 4.2V just fine. They pull about 200ma at 4.2V ~160ma at 3.6V and drop to 110ma at 3V. Once it drops below that, the light is almost worthless.
AKA the poorly designed device blackhole. If NiMh voltage causes the device to shutdown, underperform, or throw lot’s of warnings about low battery it means they aren’t working well with alkaline for a good chunk of their capacity. I wish that people designing devices for AA would actually design them to work with AA that are at least partially discharged. Li-ion is just a fix for their device being crappy.
I’ve got an older digital camera that’s 2AA and NiMh almost immediately drop below “full charged.” It works fine with them though; better if you use the flash since they keep clicking along while the surge of current draw flogs partially discharged alkalines.
A whole house power meter was not designed to work with NiMH, which is funny since its a recently designed device and its focus is on energy efficiency and conservation.
I use NiMH in the receiver anyways, but it goes to low battery warning in a week and after 2 months it goes into sleep mode all the time even though the batteries are only about 25% used.
Folks have a small replica clock that doesn’t like NiMH AAs
You can use a single Li Ion + dummy spacer in a S1P config, the volts are a little bit high but it will work just fine, did that in my kids game console, needs 2xAA, or one Li Ion and dummy
That worked out nicely. Although it uses a zener, it only has the conventional voltage drop of a diode in this arrangement. At 700ma, the drop is 0.8V; at rest, 0.6V.
I tested the CAM with the XTAR 800mah protected 14500and the 700mah Efest 14500 cells. In my FlipShare CAM, it recorded 1:18 and 1:08. The low voltage cutoff of the CAM was right at 2.85V at the cell. Perfect! Now to test parasitic drain. The device input is sitting right at 3.6V (standby).
The biggest deal about this is resetting the date and time of the CAM. If you take the cells out, you have reset these every time.
The diodes are 1N5333 5W zeners… I made an AA and AAA version. The AAA is 3/8” OD, 1/4” ID acrylic tubing and the ends are from a BIC pen. The contacts are solid copper ground wire from ACE H/W (dia .160). The AA is 1/2” OD and 3/8” ID acrylic. My 1st AA is not quite as nice for the one off, but the 3/8” OD and the 1/2” OD do telescope, so you could just make a long AAA and glue the larger tube to the outside.
This is the full size image of the AAA
Donor BIC pen courtesy of Fidelity and the tubes from TAP Plastics. A batch of zener diodes from ebay.
Might be time to hit tinkercad and whip up a few VERY simple printable “plugs” w/ flanges to prevent them from sinking in the tubes
Would say pieces of 10ga awg copper wiring (2.588mm) from romex be able to be used for the center conductors to solder the zener to? Or would you recommend something thinner 12ga (2.053mm)
Both ends have flanges. The bottom is the part where the ink pen is installed. I just removed the long tail and left just a very thin shoulder.
The ID of the ink side (anode) was perfect for a press-fit of the copper pin (goot-n-tite!). The top (cathode) is the upper cap cover with a .156 hole drilled through. Not a tight fit on the pin but snug.
My second attempt at an AA adapter. This time the negative end is a copper rivet (ACE H/W). Same BIC pen parts.
Turns out that the acrylic tubing is a real pain to work with. It splits at the drop of a hat.
I did find a small and large tube that had a slight interference fit.
Order of assembly; solder copper rivet to the diode; slip green spacer plastic over rivet; solder positive end; clean thoroughly; press small tube into big tube from positive end with subassembly in place; push positive end plastic cap in the small tube. Done.
Yes, there’s got to be an easier way. I just want to make sure that the creepage distance/isolation across the diode is maintained.
For bike taillights I normally use Energizer ultimate Lithiums but I do not do much night riding any more. The Energizers stay bright for a much longer time than alkalines and have the higher voltage compared to NiMH rechargeables. Not cheap though.
Alkalines are reserved for low drain devices such as clocks and remotes where they seem to do well.
I didn’t look into these until now. Those are some serious cells! And yep, spendy.
I was looking for two solutions: one, rechargeable and two, minimal sag. I got the 1st solved and the second is definitely better.
Since I didn’t make this a true regulator, I am only getting the benefit of a reduction of the 4.2V full charge by ~0.7V. It appears that most devices will tolerate this. For most of the performance curve at 500ma in a Li-Ion or Li-Mn is in the 3.6V region, this is just about perfect. Once it drops below this, the discharge curve is pretty steep anyway.
The power density isn’t that much different. An 800mah 14500 Li-Ion is 2.96wh and the primaries at best is 4.5wh. The difference is that you can use 2 so the outcome is almost 3x the runtime. Definitely worth the consideration depending on the application. However, in higher power devices, say at 500ma draw, these still have significant sag at half-life and in my particular CAM, that would terminate at only 2/3rd the capacity.
In my tail light blinkies… the extra 0.6V is very welcome for the increased brightness. Night time riding isn’t the challenge for a blinkie, it’s daytime visibility. 20% more light is always welcome in a being seen scenario. I am pretty much assured that I have at least 3V to the light, meaning it is like having fresh primaries all the time, or better. Now the only consideration for the AAA lights is that the Efest cell doesn’t have protection. I will have to do a weekly replace and recharge routine. The AA XTAR cells are protected and the CAM shuts off at low voltage when the cell reaches 2.85V using the diode.
Each device deserves its own attention to this option. I think I have the same in this experiment than I do in one fun pack of alkaline cells. I am happy with the results so far… meaning I haven’t killed a device yet
