Coast USB-C Rechargeable lithium ion 1.5 volt AA and AAA batteries

[larslhansen]

Having a need for AA rechargeable batteries with higher sustained voltage output than typical NiMH cells, I saw these on sale at Costco and decided to give them a try.

Sadly (and interestingly), these particular cells are not regulated at 1.5V output like the many other AA rechargeable lithium cells that are available these days. Rather, they likely have several diodes in series (or similar) to drop the output voltage to ~1.5V resting at full charge. It then drops throughout discharge, making these no better than NiMH, and perhaps worse in some respects.

I have other AA lithium rechargeable cells that regulate to exactly 1.5 volts, and will remain there throughout discharge. I use these in particularly finicky devices that object to the lower output voltage of my beloved Eneloops. Was hoping that these were similar in this respect and was disappointed when I learned that they're indeed not. If I didn't loathe standing in lines, I would probably return them.

See attached CBA discharge curves for my 4 AA cells at .5 and 1.0 amp loads and very low .9V cutoff. If I didn't loathe standing in lines, I would probably return these.

Cheers,
Mark

@mrforsyth: Is it correct you measure a capacity over 2500 mAh when discharging at 0.5A? and around 2100 mAh @ 1A?

The design of the voltage curve output is optimized to enhance the user experience, allowing you to accurately determine when the batteries will be depleted. This can be challenging with other rechargeable batteries, especially if the built-in indicators do not support, for example, Ni-MH voltage curves, or if the battery constantly maintains 1.5V, leaving you with no indication of the remaining energy. Additionally, the design ensures broader compatibility by mimicking the behavior of alkaline batteries, which are the most commonly used type of battery.

 

[mrforsyth]

@mrforsyth: Is it correct you measure a capacity over 2500 mAh when discharging at 0.5A? and around 2100 mAh @ 1A?

The design of the voltage curve output is optimized to enhance the user experience, allowing you to accurately determine when the batteries will be depleted. This can be challenging with other rechargeable batteries, especially if the built-in indicators do not support, for example, Ni-MH voltage curves, or if the battery constantly maintains 1.5V, leaving you with no indication of the remaining energy. Additionally, the design ensures broader compatibility by mimicking the behavior of alkaline batteries, which are the most commonly used type of battery.

Correct, although do note that this is at an exceptionally low (and completely unusable for my application) cutoff voltage of .9 volts. My device shuts down at ~1.3V, so these particular batteries perform poorer than my NiMH cells. Conversely, the regulated lithium AA rechargeable cells that I purchased work perfectly until they are fully depleted, at which time I simply swap them out and recharge the empty cells.

As for the marketing hyperbole ("voltage output is optimized to enhance user experience") - I'm not personally buying this, but others may. Suffice it to say that far less expensive NiMH cells will have equal or better voltage curves, without the headaches of these particular cells. I suspect that some have found that these cells work great for their application, which is wonderful. I'm not among this group so I cannot recommend them.

Cheers!