Okay, so I have a wireless mouse that takes 2 AAA batteries. The specs on the mouse are as follows:
Rating: 3 VDC
Min: 30 mA
Max: 80 mA
I just acquired a used Class 2 NiMH battery charger that takes AAA batteries. Since I got it second-hand there is no user’s manual or other instructions to go by. The output specs on the charger are as follows:
Output: 2.8 VDC 160 mA (2 AAA NiMH)
When I went online to purchase rechargeable AAA NiMH batteries, I noticed they come in a lot of different mAh ratings.
What mAh rating should I get? Does it matter?
Plus, any other buying advice (like which brands to avoid and which to seek out) would be very appreciated.
mAh refers to capacity. All else being equal, batteries with a higher mAh will last longer. I suspect a lot of cheaper batteries don’t really meet their rated capacity, especially after a few recharge cycles.
Sony Eneloop batteries are excellent. They’re especially good at holding a charge on the shelf, so if you plan to charge a spare set that might be a consideration.
If all you’re using them for is the mouse then it’s probably not worth worrying about.
it gets confusing. Alkaline cells are nominally 1.5 volts, but they “droop” pretty quickly, and thanks to their internal resistance their voltage declines pretty quickly as they discharge. And if you try to draw more current from them, they fall on their faces (a “2800 mAh” alkaline AA cell might only have 600 mAh at higher current draws.) nickel-based rechargables (NiCd and NiMH) have a nominal cell voltage of 1.2 volts, but they hold that pretty steadily until they get close to full discharge. Also, NiCd and NiMH cells have lower internal resistance so they’re better at maintaining nominal cell voltage as they’re being discharged. basically you want “pre-charged” or “low-discharged” cells; the aforementioned Sanyo Eneloop cells are a good example. They trade off total capacity (they have a lower mAh rating) for not self-discharging so quickly.
the rechargeables have a slightly lower voltage when fully charged compared to disposable batteries. i’ve found in some digital devices that rechargeables don’t run for very long (15 minutes) before the voltage is too low, the design demands the full voltage of a disposable cell.
i find rechargeable batteries excellent in lights and analog devices.
you would need to see for this mouse if they would work. you also would want to have some disposable batteries on hand to give power while your rechargeable batteries recharge.
Anyway, most LSD AAA NiMH batteries generally put out 1.2 volts for most of the duration between charges, and most of the good LSD ones put out somewhere between about 800 mAh, versus the 1100 or so of an alkaline battery.
Sanyo Eneloops are pretty much the gold standard- they’re 800 mAh and can be recharged up to 1000 times. Tenergy Centura batteries are also good, as are the Amazon Basics batteries- they’re all in the same ballpark.
Energizer NiMH batteries are somewhat higher in capacity, but trade off # of recharges. Some Duracells are rebadged Eneloops, so they’re good as well.
Rayovac are generally scraping by- if you have to, get the platinum ones- they’re 800 mAh and can be recharged 500 times. Don’t get the standard pre-charged ones- they have significantly less capacity than the standard 800 mAh.
And finally, make sure whatever you do, get Low Self Discharge (LSD) cells for your mouse- this means they won’t self-discharge and go dead if they’re sitting still for a period of time- they typically have 85% of capacity if they sit unused after a year. They’re usually labeled something along the lines of pre-charged, low self discharge, etc… and usually hawk that 85% stat as well.
NiMH batteries don’t have lower initial voltage- they start out just as high, but drop quickly and usually level out at 1.2 volts, and most importantly, hold that voltage for 80% or so of their discharge duration. That’s why they do so well in things like cameras. Alkalines have a proportional relationship between voltage and discharge- a battery that’s half-discharged will have a voltage exactly halfway between an unused battery and a fully discharged one. A NiMH one will have 1.2 volts generally- the discharge curve looks like a sideways “S” kind of- it drops fast, levels out for 80% of the time, and then drops fast again at the very end before it’s discharged.