I went out and got 4 of the LFP cells and dummy cells to match. I thought it would be a great option for some of the two AA series devices that I have. BUT, I measured them right off of the charger and they were at close to 3.5 volts. I just checked all 4. Maybe 6 weeks later, they are at 3.418 to 3.420 volts. BTW, I charged them with the MC3000, which has a program for lifepo cells.
Now for a flashlight, I wouldn’t worry much about it. Other things, like radios or other electronic devices… well I worry about over-volting them. Some manufacturers of this kind of device don’t even recommend the Eveready lithium cells because they are close to 1.7 volts when new. (2S= 3.4 volts). But I would think that they drop lots faster than the LFP.
Then there is the capacity. IIRC Shockli ones I got are listed as around 650 mah.
Way less than alkaleeks or NiMh.
The issue here is that 1 cell still has somewhat lower amount of energy stored than single ni-mh cell.
I’ve used this approach and it works, but it only makes sense for devices which do not work with ni-mh at all. Because otherwise, even if device only drains ~half of ni-mh capacity, it will still last longer.
The cells absolutely must have protection circuit too, otherwise they will be overdischarged and ruined at first use.
By the way ni-zn cells also exist, with their own issues/disadvantages, but they do have higher voltage.
IF NiMH works fine, use that. If it throws low-voltage warnings prematurely, if the electronix don’t work with them, etc., then you CAN use LFP+dummy cells instead, else go back to alkaleaks.
I never ever ever use rechargeables of any sort in series without some protection (individual protected cells, BMS, etc.).
Unfortunately, this rules out all of the devices I would I thought I would use the LFP cells in. I read about this a while back. Of course went out and bought cells and dummies… but haven’t found anything that they are good for. For me anyway. It sure seems like they could be a useful option if you have something suitable to use them in. I just don’t.
Yup, all things I was thinking about… but the initial high voltage, no protection (on mine) and no BMS. So I am concerned about using them in any of those. Probably all no issues in the end… except maybe the over discharge. But anyway, mine are just sitting in my battery drawer. BTW, Mine are the AA form factor. I initially thought of them for use in one of the portable radios that I use regularly… but the voltage thing… Anyway, I am truly glad that they work out for you.
LiFe is quite resistant to under/over charge ‘abuse’. That’s why they are sometimes used for solar lights. Can’t get much worse than that.
As the discharge curve is pretty flat, and you can generally take them down to 2.5v safely, I think most devices will stop working when it gets that low. That’s pure conjecture. I only have a couple VERY old A123 LiFe so I haven’t really experimented.
I’ve got a couple devices that are designed for 2S AA that I am running Lion + dummy AA. They run REAL GOOD!
What devices? Just trying to get a feel for what I can use without killing the device. I would really love to use the ones I have…
Again, this may be an irrational fear, but I have actually seen ( for all of the CCrane portable radios) advice not to use the AA lithium cells. Which are usually 1.7 volts new. Maybe they are just being ultra conservative. Sorry for the continuing OT direction.
Exactly. It’s like running with fresh alkaleaks across the entire discharge curve.
Even if the capacity is half or less of what alkaleaks would supply (depending on what you’d consider “cutoff” for them), I’m more than happy to not have LFP cells ruin the device they’re in, unlike hateful spiteful creepy little alkaleaks that’re just born nasty and die that way.
Right now I have them in a travel electric toothbrush (Lion + dummy), and nose trimmer (single LiFe). Short time use motors seem pretty resistant to over volt.
You can’t use the 1.5v lithium in radios and some electronics. The step down converter causes interference.
If the devices are voltage sensitive LiFe +dummy might be risky. Lion + dummy, even riskier.
They have exactly the same issues as other li-ion chemistries when discharged below 2-2.5v (potential internal shorts, very fast loss of capacity/degradation). And vast majority of devices intended for 2xAA will happily run on 2.5v because this would equal only slightly discharged alkaleaks. Those solar lights you mention would have at least the most basic under/over voltage protection, which is what’s also needed to safely use this cells as AA replacements.
As much as i dislike the product advertised in OP (primarily because huge self-discharge) - those batteries are intended for end users as AA/AAA replacements, they include required protections, have exactly correct voltage and are safe to use (will not destroy devices, should not catch fire). What’s discussed here (using bare cells of various li-ion chemistries trying to match voltage of multiple AA in series) is unsafe in a few ways - it can destroy devices because voltage does not match exactly and it can fail/catch fire as this are li-ion cells used without proper protections. This should only be attempted with good understanding of the risks involved and is not really a good solution for everyone.
3.2v is nominal voltage though, they are typically charged to 3.65v which is significantly higher than 3v and can be risky. Not too risky though, because lithium primaries have higher voltage too, with 2 in series being ~similar to fully charged IFR cell. I’ve seen devices die because of lithium primaries were used, but that was a long time ago…
【Update】 About XTAR rechargeable 1.5V Li-ion AA batteries’ discharge current
The max continuous discharge current of xtar 1.5V AA Li-ion battery is 2A. There are a lot of devices that can benefit from the higher voltage and medium draw of this battery. The battery has built-in over-temperature and over-current protections. If the discharge current exceeds 2A-2.5A, the protection system will kick in to safeguard the battery from damage. So for devices that demand instantaneous current exceeding 2.5A or continuous currents exceeding 2A, using the 1.5V Li-ion batteries might not be very suitable due to the battery’s protection systems.
Some users may have AA/AAA lights which use linear drivers without current limiting features. They could produce an instant output of 300lm or more, requiring a current output of around 2.5A or higher. Then, these kind of lights will need unprotected batteries. For many EDC AA/AAA lights, max output below 250lm, using 1.5V Li-ion batteries will be fine, which can also keep the light stable & brighter.
In fact, for 1.2V NiMH AA/AAA batteries, even with brands like Eneloop, the continuous output above 2A will also greatly shorten the battery’s life. Generally, the cycle life of 1.2V NiMH batteries is about 500 times, while the cycle life of xtar rechargeable 1.5V Li-ion battery is around 1200 times, with longer life and eco-friendly choice.
I use one of these as an external thermometer, inside a Ziploc as I’m not sure how water-resistant it is, and with a fully-charged AAA Eneloop it starts showing 60% battery and lasts about 6 months before turning off. Recently I replaced it with an AAA Ultimate Lithium and it started at 100%, and after 6 months it’s still at 100%, so I’m thinking it will probably outlast the thermometer itself
EDIT: I just checked and the AAA Eneloop actually lasted about 7.5 months to go from a starting 80% (as shown by the thermometer battery sensor) to zero, while the Ultimate Lithium has been about 3.5 months at its starting 100%:
I’m really impressed with the Ultimate for this use case and I expect it to last at least double the Eneloop – which would be great as swapping batteries for this thermometer is a PITA due to its location.
【Updated】 XTAR rechargeable 1.5V Li-ion batteries’ low-voltage detection function
Some people tried out many rechargeable 1.5V Li-ion batteries on the market. They told there is a big one of the characteristics of some to go from 1.5V flat horizontal output line, directly to straight vertical line drop too low instantly, without warning when the batteries runs out. Then the devices will also just suddenly stop working with no warning.
For this shortcoming, we have made improvement on xtar 1.5V Li-ion batteries. There are low-voltage detection function on these batteries. That means, when the capacity of the xtar 1.5V Li-ion battery is within 5%-100%, the battery can keep stable & constant 1.5V output. If its capacity is less than 5%, the battery voltage drops to around 1.1V. Then your devices will remind you of power out, if it has a lower battery reminder function (such as smart doorlock). And you may also find the change after voltage drop. For example, if you use these batteries in a AA/AAA flashlights, the lighting would be dim when the power is used up. And users can charge them timely. So this function avoids devices shutdown without warning.
How do you think of this low-voltage detection function?
I just bought some of these types of batteries (a different company whose name I will not mention here) and tried them in a couple of flashlights (a Nichia Tool 2.0 and a Sofirn SP10 Pro). The same thing happened in both lights - the initial brightness was great, which dropped slightly after about three seconds. Then at about ten seconds, the lights shut off. I’m guessing some internal protection was tripped, as all I had to do was quickly reconnect them to the charger and they worked again. But clearly, 3 amps draw is way too high for this type of battery (at least this company’s version).
As for the idea of dropping the voltage to 1.1v to signal low battery warnings in devices that have them, that’d be brilliant. I was going to install these in my number pad door lock (as the old alkaleaks were giving low power warning and the lock doesn’t work with NIMH) but I am too concerned about the day when the batteries suddenly die and I won’t be able to unlock my front door.
I’ve tested a number of these. 1.5v support is generally, but not always, quite good. Current support is all over the place. I haven’t tried the Xtar but the claim of 2.0A would put it on the high end. 1.0A>1.5A for AA is more the range I experienced.
The conversion electronics overheat and it trips protection.
Whether your lock would still actually WORK, when you get the low voltage warning is another question needing answering. Electronic door locks seems to be a potentially useful niche for these batteries.
【Update】 Multiple safety protections on xtar 1.5V AA/AAA Li-ion batteries
The xtar 1.5V AA/AAA Li-ion battery integrates a high-efficiency charge-discharge management chip. It adopts 1.5MHZ synchronous rectification and step-down discharge. This ensures the steady and continuous 1.5 volt output, more powerful than regular AA/AAA cells, suitable for devices that require long-term, steady high-voltage output.
And this 1.5V AA/AAA Li-ion battery has a range of protective functions, such as over-discharge, short-circuit, and over-temperature protection. These features significantly reduce the possibility of accidents caused by battery malfunctions. Besides, for xtar 1.5V Li-ion batteries with indicators, these LED indicators show charging status. And they can also remind users of safe-discharging state, such as short-circuit in quick flashing.
It’s also leak-proof, suitable for any devices where you won’t encounter battery leakage or corrosion, like water flow meter, game controllers, camping laterns. Next time you need to power your devices, could consider the XTAR 1.5V Li-ion batteries, which don’t compromise on safety and performance.
That is the thing, low voltage warning would not work in locks, or anywhere else, cuz it is always 1.5v, until it shuts off. it would shut off unexpectedly. not something you want a lock to do.
It would be cool if cells themselves had low voltage warning, since LVA on devices used with those cells will not work. A beep when li ion cell drops to 2.7v would be very convenient. cuz there is absolutely no way to tell SOC with those cells.
