Well, I’ve been using various NiMH batteries in the AA (aka LF-91) and AAA (aka LF-92) form factors for over a decade now. They are a great way to save the environment and they are cheaper too. We have the LaCrosse chargers and there are really two limitations to them:
- If you don’t get the Eneloop or other low discharge batteries, they will run down in a month or so.
- They generate 1.4V, so slightly lower than the 1.5V so some things won’t work with them as they need that much voltage. For instance, our Brother P-touch is a label maker that really wants to see 1.5V
- They have gotten quite cheap at less than a $1 per cell, so never as cheap as alkaline batteries, but they last over 500 charges, so you are saving a lot.
However, the big move now as with all things is to Lithium Ion, this has some advantages and then some disadvantages:
- Not that it matters in these applications, but they are definitely lighter, so if you have something that is weight critical like say a set of Garmin Powertap bike pedals, then this is a big deal.
- They are all internally really running at 3.4V, so they need step down electronics to get to 1.5V
- They do need new chargers which are tuned for this new battery chemistry and some just have a microUSB sticking out so you don’t need to buy a LiPo battery charger.
- They are pretty hard to find and expensive because everyone (cough, the EV, phone and laptop industries need them).
- They have less capacity than NiMH but they produce their 1.5V uniformly before failing, so this is nice for applications that can’t deal with gradual voltage loss.
Get NiMH for long life and low cost, LiOn for high voltage or light weight
TL;dr, the main point is get the Panasonic Eneloop if you have things that don’t need constant voltage, so for instance flashlights great, it will be slightly dimmer (1.5V for Lion vs 1.4V going down to 1.2V for NiMH). It is the default choice. Lithium ion is much more expensive and is best for the opposite case, where you need constant voltages and lightweight such a sensitive electronics. A great example of this are my PowerTap P1 pedals for the bike or the Brother P-Touch label makers or my blood pressure monitor the Omron BP7000 which works fine with alkaline but not with NiMH, you get all kinds of errors with those low voltage batteries.
The electronics on these are sensitive and need a 1.5V minimum voltage. And with the Pedals, the difference in weight of 10 grams matters if you are a weight weenie and want your bike to break the 1999 UCI weight limits for events like the Tour de France of 6.8 kg or just under 14.99 pounds. These days, you can get climbing bikes like the old Trek Émonda 10 which is 4.6 kg or 10.1 pounds!
Well there are a lot of recommendations (see Michael Blue Jay and Right Battery) for these, but most folks seem to like the original batteries made in Japan for Panasonic. For a long time folks really like the Maha/Powerex series of batteries but some have reported loss of charge over time, I have buckets of these and it is hard to tell, but they definitely haven’t just died which is nice. The PowerEx Imedion which I do have for instance is a 2400 mAh 1.2V Low Self Discharge with 1,000 cycles and in testing seem to meet their ratings at least when out of the box. Note that this rating of 2400 mAh is with low current like 0.2A, if you go to a say 2A load, the available capacity shrinks to more like 1900 mAh which is common with batteries like this. Also note that Panasonic does make the Eneloop Pro which is 2500 mAh but lasts only 500 charge cycles and has slightly higher capacity than the Powered Imedion (and is made in Japan)
Also Sanyo (now Panasonic) who made the original Eneloop (4th Generation) now has a 2100 charge cycle version so way more than the typical 1,000 cycles. But that does seem like a nice advantage, they are $3 each for AA 2000 mAH at Amazon and AA 750 mAh are $2.70 or so at Amazon.
Note that the Eneloops are now made in China for Asia distribution, but there is the original factory in Takasaki City Japan that are supposed to better but more expensive. They source the Japanese batteries from FDK (and beware there are many counterfeit Eneloops around, so don’t buy this on eBay). You can still get these original Sanyo/Panasonic cells though as a different brand. And there is a long history of Sanyo buying the Toshiba factory in 2001, then this was acquired by Panasonic.
Finally, you can now get 9V replacements as well which is nice for things like smoke alarms where I feel guilty about using so many 9V alkaline. As an example the Powerex Imedion 8.4V 250 mAh does well in these low current draw situations hitting that number with a 50 mA draw.
I have a bunch of different charges, but the SkyRC MC3000 is super expensive but customizable. It even has a bluetooth connection to your phone so you can charge NiMH, LiFe, Lilo etc. It’s expensive at $105 at Amazon but as with all geek devices hard to use. The other one which I do have and that is pretty much plug and play is the Opus BT 3100 and it can handle AA, AAA and LiIon cells like the 18650 and lots of other sizes so its probably the right one to get for most mortals. Finally if you don’t need Lithium charging, then the Powerex MH-C9000 is a good choice. I have one of these and it works great but note that the Opus is the same price and does Lithium cells.
Perhaps the biggest problem though is a lack of reviews, the number of sites (geekydeck.com)_ that do more than a quick survey of Amazon scores is incredible and it doesn’t pay to do deep reviews much anymore. Plus, some of these are going to need a longevity test which takes time and patience.
The two best sites I’ve found for this topic are Project Farm which does all kinds of random things, in particular he tests a huge number of brands which is great because none of the common household brands are doing this. The long and short is that he really like the Vapcell and the SmartToools for both the charge capacity and the how long they lasted.
Unfortunately, neither of these brands are available, but Tenavolt is all over Amazon right now. There are specialty folks like LiIonWholsale.com with a huge array. Most are the really common 18650 (of early Tesla fame) and also the newer 21700 (now inside the Tesla Model 3/Y) but they have a few AA Size but the Vapcell P1418A is out of stock at $9 each (so they are way more expensive than NiMH). CandlePower Forums has a deeper parameter analysis of this one and it looks pretty at least the 2020 version.
The other recommended battery is the SmartToools (yes that’s three ‘o’s in a row) is also not available that I can find. It is a 2600 mWH battery with 1200 cycles. And, it is MicroUSB charged.
They do have the Opicplus AA with 2800 MwH which is $10.49 in a dual pack for LiIonWhosales. And the Tenavolt INR which is all over Amazon at $35 for four plus the charger at 1850 mAh claimed and 1692 mAh measured). As well as the Pownergy which is micro USB and is $22 for four with a claimed 2960 mWh (or 1973 claimed and 1751 mAh actual)
So, get the LiOn if you need constant voltage, that is it is sensitive to voltage or it to be light weight. The best idea is to first stick some NiMH in and most equipment will work fine. For instance, in a flashlight or in a PS5 or Xbox controller or in a clock. Switch to LiON if you discover the electronics won’t run at lower voltages (Brother P-touch Labelmaker) or if you need it to be light (PowerTap P1 pedals)
The test done by Project Farm does two things, tells you the capacity of the battery at at a given current draw, so at 250 mA Discharge (at 1.5V), how many mAh does it have, in other works, the Vapcell as an example has a capacity of 1999 mAh, so that means it will last 1999 mAh/250mA or about eight hours discharging like that. In comparison, the Smarttools has 1470 mAh so it will last 1470/250=5.9 hours:
- Sorbo, 959 mAh
- Safeloop, 1103 mAh
- Maxwel, 1438
- Smartoools, 1470 (does much better at high drain)
- MaxLithium, 1593
- OpicPlus, 1606
- Tenavolt, 1692 (much worse at high drain)
- Pownergy, 1751
- Blackube, 1830 (worse at high drain)
- Amptorrent, 1988
- Vapcell, 1999
The second test is how long will you run with high drains, more like 500mA and then they have a fan test which also measures the Voltage as well (via the RPM). So in the test, the Eneloop NiMH runs longer, but runs down to lower voltages. Note this list should be about the same as the previous one if the current drains are close:
- Sorbo 102 minutes, $5.50
- Safeloop 115, $6
- MaxLithium 144, $6
- Tenavolts 154, $7.50
- Blackube 168, $7.50
- Maxwel 172, $7
- Pownergy 179, $5
- OpicPlus 186, $5
- AmpTorrent 188, $7
- Smartoools 193, $4.25
- Vapcell 233, $8.8
- Eneloop 278 minute but much lower voltages at 1.4 down to 1.2
So, given all that and the availability issues, what makes sense to buy now:
- Pownergy. These are $22 for four at Amazon, so a decent $5.20 and they are mid-pack in terms of lasting at 179 minutes in high current drains and 1751 mAh at low drain scoring #8 and #7 respectively highest. These use micro USB to charge.
- Tenavolts. It’s hard to tell the price since they bundle a charger, but it is $35 for the charger and four batteries. It scored #7 and then #4 highest on these tests, so a notch below the Pownergy
Finally, there are bunch batteries on Amazon that didn’t get tested:
- Lankoo at $19 for four claiming 2600 mWh (which is 2600mWh/1.5V = 1733 mAh) but it does have USB C connections instead of microUSB
- Deleepow. This is $14 for four claiming 3200mWh or a whopping 2,133 mAh but it is 4/5 rating on Amazon and requires it’s own charger (for about $2!). Also it says 1500 cycles (vs the normal 1,200 cycles of charge and discharge). It’s not clear if you need that charger or something that understands Lithium
Battery chargers for Li-ion and NiMH
Names for Batteries from AA to AAA…
As aside, the standard formula is the first two digits are the diameter and the second two are the length, so an 18650 is 18mm diameter and 65 mm long. So the AA form factor is also called a 14500 which is 14mm diameter and 50mm long. So if you want to be cool instead of saying AA, you can say L91 or 14500 if it Lithium 😅. And if you are using the International names IEC, then the names vary by battery chemistry so AA is the size, but an LR6 is an Alkaline battery, R15 is Li-Ion, HR6 is NiMH and Li-Fe (Lithium Iron) is FR6. For American standards, the ANSI/NEDA name are 14500 for Lithium, 15A for Alkaline (the traditional one-time use batteries), 15H for NIMH and 15K for NiCd. In China, it’s called a #5, a UM3 in Japan. Confused yet?
If you want to be a complete nerd, then there is an entire list in Wikipedia on this topic, for instance the smaller AAA battery is called the HP16 in the UK. The C battery is HP11, #2 in China, UM 2 in China, LR14 Alkaline. A D battery in china is a #1.