Product review on reviewseen.com
Price: $40.99
(as of Mar 03, 2026 00:52:56 UTC – Details)
Product description
Kratax 3700mWh AA Rechargeable Lithium Batteries with 3-in-1 Charging Storage Box
Kratax constant-output AA rechargeable lithium batteries offer more stable performance in devices than other batteries, ensuring flashlights don’t dim, toy cars don’t slow down, audio equipment doesn’t become too quiet, camera images don’t become blurry, and game controllers don’t lag.
High-Capacity & Stable Output: Kratax AA lithium batteries rechargeable with 3700mWh high capacity and stable voltage and current output ensure more stable device performance. Up to 3A of current output is ideal for high-current applications, with over 2000 cycles.
Lower Self-Discharge & Multiple Safety Protections: Kratax AA rechargeable lithium batteries retain 80% of their charge even after months of storage, making it easy to replace depleted batteries when needed. They also feature an intelligent protection IC chip, an explosion-proof module, and multiple charging protections to ensure battery and device safety.
Smart LED Display: Ultra-thin charger flashing green light indicates charging. Solid green light indicates a full charge. Flashing red light indicates short circuit, incorrect battery type or battery +/- polarity errors. The charger has a 0V activation function that allows charging even 0V batteries.
3.5H Fast Charging: The Type-C charging port is compatible with various inputs, allowing you to charge using a PC, wall outlet, power bank, or car charger. It charges quickly about 3 hours. A 5V-3A adapter is required.
Widely Compatible: Suitable for outdoor cameras, game controllers, solar lanterns, remote control cars, flashlights, recorders, mouse, keyboard, clock, remote control and electric guitars etc..
Price: $40.99
(as of Mar 03, 2026 00:52:56 UTC – Details)
Logan –
Excellent quality, volts almost identical to alkaline (1.54V vs 1.62V) and runtime almost the same
The quality of these batteries seems excellent, they output almost identical voltage to alkaline (1.54V vs 1.62V), the runtime is virtually the same and the combo case/charger works great.Note, to make this review as concise as possible I have split it into sections with a header for each.• QualityThe quality of the batteries and charger seems excellent. The casing of the batteries has the typical plastic feel, there are no visible flaws and the positive and negative contacts look perfectly normal.The next thing to discuss concerning quality is the combo case/charger. The quality of the combo case/charger also looks excellent and it has a nice black exterior, an easy to use strong magnetic lid, and a USB C input on the left side of the lid.• Size and weightI used a digital caliper to measure the length and diameter of these batteries and found the dimensions are identical to AA batteries made by a major brand; both measure exactly 50.2mm long and are 14.0mm in diameter.I also measured the weight of these batteries vs alkaline on a digital scale and they weigh 18 grams each while the major brand alkaline weigh 23 grams each (so these rechargeable lithium batteries weigh 21.7% less, which is a nice weights savings and is to be expected since lithium batteries typically weigh less than conventional batteries).I also measured the charger and it is a compact 72mmL * 44.5mmW * 70.8mmH (2.83” x 1.75” x 2.78”) and weighs 249 grams including the eight batteries and 96 grams empty.• Ease of useThe combo case/charger is very easy to use; all you do is (1) open up the lid, (2) place the batteries into the cylinders with the positive ends of the batteries pointing upward, (3) close the lid, (4) plug a USB C cable into the right side of the lid (connect to your own 5V-3A charger which is not included), and then (5) there are eight LEDs in the lid that will illuminate red at the start and then will blink green while charging and will then stay green for each individual battery after it has finished charging. And that is it. (By the way, the page for this set says it only takes 3 hours to charge the batteries).• VoltageI used a digital multimeter to measure the voltage of these batteries when fully charged and the voltage output is virtually identical to alkaline batteries (these measured 1.54V vs 1.62V for brand new alkaline batteries).This is important considering some devices require an alkaline level of voltage (near 1.5V) and will not work well or for long at the typical 1.2V that rechargeable NiMH batteries will output when fully charged.• RuntimeI tested the runtime of these AA rechargeable lithium batteries vs some brand new major brand AA alkaline batteries in a pair of identical “COSOOS Mini LED Tactical Flashlights” that only use one AA per flashlight. The test was quite simple, all I did was put one fully charged AA lithium battery into each of the two flashlights and then turned them on and checked on them appropriately every hour. The two flashlights lasted 4 hours and 10 minutes and 4 hours and 12 minutes before shutting off (the flashlights were never turned off during the test and it was one continuous run).For the next test I repeated the exact same test but with two brand new major brand AA alkaline batteries and the flashlights produced a good amount of light for 4 hours and 33 minutes and when I checked back at 5 hours both were quite dim but still going.The longer runtime of the alkaline at the cost of ever increasing dimness levels is to be expected when comparing alkaline to rechargeable lithium because the rechargeable lithium batteries contain circuitry that prevents them from being run down all the way and so they cut off when their voltage is still at a reasonable level and the light is still reasonably bright because if it didn’t cut off and went below a voltage threshold that would ruin the battery and prevent it from being able to be recharged (this is how it is for all rechargeable lithium batteries); while the one time use alkaline batteries on the other hand will simply keep discharging until the voltage in the battery reaches zero.So the bottom line for the flashlight duration tests is the rechargeable lithium batteries lasted 4.16 to 4.2 hours and the major brand alkaline batteries lasted 4.5 hours (at the same brightness the rechargeable lithium cut off at) and then by 5 hours the alkaline were still going but the light was quite dim.• ValueSo even though the alkaline batteries lasted slightly longer in the flashlight tests vs the rechargeable lithium batteries the trade off is once they are depleted the alkaline go in the trash while the rechargeable lithium can be recharged up to 2000 times and at 0.26 cents per alkaline * 2000 that would equate to $520 vs $31.99 for these rechargeable lithium batteries; so the rechargeable lithium are clearly a better value.• ConclusionSo that basically covers it and the bottom line for these batteries and the combo case/charger is the quality seems excellent, the size (length and diameter) of these batteries is identical to standard AA alkaline, the measured voltage (measured with multimeter) of these batteries is virtually identical to alkaline (measured 1.54V for these lithium vs 1.62V for alkaline and only 1.2V for NiMH). In addition the rechargeable lithium last almost as long in a flashlight test (if end test at same brightness level) as the alkaline at 4.2 hours for rechargeable lithium vs 4.5 hours for one use alkaline. And the included case/charger is compact, easy to use and recharges the batteries quickly (only 3 hours). And lastly the rechargeable lithium batteries are a good value because it would cost $520 ($0.26 * 2000) to get enough alkaline batteries to equate to the performance over time of these rechargeable lithium which are supposed to be able to be recharged 2000 times. Hope that helps. Thanks.
Scott –
Better than most
I have multiple smart devises that use AA Batteries. These are better than others, I like the charger, sleek design. Batteries last longer than the others I own and they seem to charge faster. Began thinking these were a 4 and I will give them a five when used in smart devises
Joshua G. –
Better than energizer
So far much better than even energizer lithium batteries. I can’t believe how long they last before needing recharged. Will return to edit review if they only last several recharges.
Jack –
Avoids constant disposal of used batteries.
I use this product for batteries in frequent use such as puck lights. It allows me to rotate batteries in and out if the charger instead of constantly buying new batteries and disposing of used ones.
spockmckoy –
Work in some things, not in others
The charger works fine, the batteries charge fine. I have found the batteries work in some things, but not in others. For example, they work in a flash light, they work in battery operated Christmas lights. I placed them in a remote control on a gas log set valve, and 4 alkaline batteries work fine, but 4 of these won’t work in it. Polarity was correct, 100% charged. One of those things I guess.
Space Marine –
Batteries 🔋
good 👍
Adam Battaglino –
They work
Too soon to know for sure but they currently work very well.
Logan –
Initial impression is good
Tested batteries on a computerized analyzer @ 100ma draw.Capacity was 2530mah @ 1.5 volts.This gives tested capacity of ~3800mwh.Very rare to find imported batteries that actually match advertised capacity.Will update review once I have an idea of longevity.
Keon –
I’ve been using these batteries for about a month now, and honestly they’ve been great. I’ve tried them in my camera, flash, Walkman, tape player, game controllers, MP3 players—you name it—and they all run without any issues. The performance has been solid, and my flash recharges super fast, which really surprised me. Overall, they just work really well across all my devices. I’d recommend avoiding those super‑cheap batteries from China because their cycle count and performance are just annoying.
Buddy Williams –
These rechargable batteries work awesome! Will be getting more later!
Anthony D –
I’ve been using the 3500 blue batteries on my trail cam for about 2 years daily as well as on my remotes and they’re still operating like new with long life between charges so needed more batteries and I got these 3700s and they’re working great so far. Highly recommend the company from experience.
cham cham –
so far so good. all batteries are working and charging. i’m using them for our blink camera hopefully it lasts until i have to charge againedit~ been about a week or less, my blink cam show that it needs new battery. one star down cause it didnt last long
Yar –
Works great. Not sure if the cheaper versions are of equal quality, but this one works just fine.