Lithium Ion AAs. Will they be any good?

Hi folks,
A while back, I was running around BangGood and found these things:ZNTER 1.5V 1250mAh USB Rechargeable AA Li-Po Battery.




They managed to stuff a Lithium Ion cell, a charge controller, and a voltage converterinto a AA format. I couldn't resist. Had to check these out!







They've even got an LED indicator light.




Each cell draws 0.25A from a USB port to charge, so it makes sense to get theirfunky splitter cable.
I plan to do some comparisons between these and some other rechargeable AA I've got around. For now though, the do charge up, give a constant 1.5V, and work perfectly in my GPS. The fact that they can be charged directly from a portable charger without having to carry along a special USB-AA charger, makes them potentially very useful.

They look cool!

LOL

Then I saw the price



Pretty neat, nonetheless.

Korishan said:

LOL

Then I saw the price



Pretty neat, nonetheless.

Click to expand...

18.21CAD. Not horrible. I've seen basic rechargeable 4 packs go for that.

Also they are 1.5v not 1.2v nominal as NiMh/NiCd tend to be. This is a huge bonus, as many electronics need 1.5v per cell to operate correctly.

So if you need 1.5v, they are excellent value. 1250mah is not too shabby for AA form factor either.

As for price, they work out $18aud about 50% more than brand name NiMh. So not overpriced, assuming they perform.

Charged, discharged, and recharged. Along with three other cells. A Tenergy NiMH, Energizer NiMH, and a Tenergy NiCd. Just because I had them laying around.

Here's discharging results:










Here's charging results:










I've gathered all the stuff I think is important into a spreadsheet and did some math. I'm not really comparing to see which cell is "better". I'm hoping for a clear picture of which cell I'd like to take with me on trips where power is limited. Like hiking for example. Anyway here's the spreadsheet.




Just to be fair, I've listed the approximate age of each cell I tested. So give the Energizer a bit of a break. It's pretty old. I also compared actual capacity vs. advertized. The Znter did pretty well. Discharging all the cells at 200mA, they all did as would have been expected. The larger capacities took longer to discharge, and the smaller capacities took less time.

Now, I had no control over the charge rate of the Znter. It used 5.1V supplied by the USB cable, and 0.24A. I've attempted to "translate" what would have been going on inside the cell. Assuming nominal Voltage, the cell would have received around 0.33A, where the rest of the cells charged at 0.2A. So the Znter got a big advantage there as far as charge time goes.

So conclusions... not really any. I can't properly compare recharging efficiency without knowing the Amps and time from an actual charger for the other three cells. I certainly wouldn't be taking the Opus with me on a hiking trip, LOL. Still, the tests were interesting.

This leaves me with my initial thoughts on practicality.
Pros:
-The Znters charge fast. Way faster than any other cells I have. (Assuming 200 mA is around what regular AA chargers use.)
-I can charge all four at once from a single 1A USB port. Handy for AC chargers and portable battery banks.
- No AA specific charger needed. Less junk to carry and keep track of.
- The Znters give 1.5V constantly throughout their whole discharge cycle. Good for flashlights and sensitive electronics.
Cons:
-Capacity is a little low, so the Znters will need charging more often. This could get annoying.
- The 4-way USB cable must be used or I can only charge one per USB port.
- The Znters constant 1.5V output means electronics will always show the cell to be "full" until its low Voltage cutoff.

Another thought - how about self discharge? I know NiMh don't hold charge for months on end (mine don't anyway - even the Duracell). I imagine the Zenter being LiIon will hold charge for a long time.

That's a good point. I wonder if the Volt converter pulls "phantom" current when its not in use. I'll try that out.
One of my least favorite properties of NiMH is the awful shelf discharge. AAAs are the worst!

There are also pictures that show how they are assembled, they are totally cute
Other formats are available as well! It's not difficult to see why NiMh dominates these formats though. Only their 9V battery at 400mAh looks interesting if 400mAh is anywhere near reality. And maybe the bigger formats like C and D. hobbyking.com has them at cheaper prices as it seems.

NiZn batteries in AA format with 1.6V nominal voltage have been available for some time. Four of them at 1500mAh cost 15 EUR on Amazon. I've never tested them, but I guess they are the better option when looking for a stable 1.5V output.

edit:
Why do you think self discharge is an issue with NiMh batteries? Don't you use Eneloops or similar LSD batteries?

DarkRaven said:

Why do you think self discharge is an issue with NiMh batteries? Don't you use Eneloops or similar LSD batteries?

Click to expand...

Eneloops are EXPENSIVE! Very good I must admit. Aside of Eneloops I have experienced issues with self discharge in most every other NiMh I own. If the converter does draw Phantom power, which it almost surely does, I wonder if it would be significant?

Very Very tempted to buy these. I could easily forgive their low capacity, given that they charge very quickly and deliver 1.5v until they are completely flat.

That said, it brings about a very inspiring idea for running 3v battery powered things (ie 2x AA, AAA, C, D ect)from LiIon. 4.2v to 3.3v converters are readily available.

Hmm, ok. Sure, non-LSD NiMh have issues with self discharge. To be honest, I've never even considered that someone might think that they are expensive and is not using LSD NiMh in 2017. But hey, that's why other peoples opinions and points of view are always interesting!

A standard AA Eneloop costs around 2 EUR or so. It has no issues with self discharge and can replace hundreds of alkaline AAs. I think it's money well spent, for your own convenience and for the environment.

I've never heard of either of those. Brand names?
Ok, I have heard of LSD, but to me it means something way different than batteries.

LSD just means Low Self Discharge, it's a desciption for the latest generation of NiMh batteries. This dates back to 2005 when Sanyo invented this technology and brought the first commercially available product to the market, these were called Sanyo Eneloop. Since 2013 when Panasonic bought Sanyo they are called Panasonic Eneloop or still just Eneloop as it was before.
LSD NiMh batteries became available from other brands and manufacturers and well, often called "ready to use" or marketed as precharged. Maybe LSD is a trademark of Sanyo and not everybody is allowed to use it. Some manufacturers might also act as an OEM for some brands without own production capabilities. For example, Amazon sells LSD NiMh batteries under their AmazonBasics brand, no clue who makes these for Amazon.

NiZn batteries on amazon.de are available from Ansmann and PK Cell. Ansmann is a german company and they are not available on amazon.com, PK Cell batteries are though and additionally you get Ultracell.
These NiZn batteries get mixed reviews, on amazon.de and .com alike, often because their rating confuses people. Ansmann labels them with 2500mWh and I always wondered why. But now I saw that PK Cell and Ultracell do the same. People are expecting 2500mAh and are disappointed when the see results of 1300mAh or so. I think other than that the NiZn batteries are doing fine if you need constant 1.5V (or at least more constant 1.5V than NiMh can deliver).

Well, my first attempt at a self discharge test failed. I let one cell sit on the desk for a week, then put it on the Opus along with three freshly charged cells. The test cell, along with one of the charged cells, came up null after discharging was finished, and that data was lost. The other two cells finished a bit later, and gave about 1Ah each. It took about 5.5 hours to discharge them at 200mA. Good numbers I think, but tells me nothing about self discharge.

So I'll have to start thetest over again I guess...

I bought one of their 9V batteries and it seems very promising!

Its idle voltage is 9.46V, that's ok. I gave it a full charge, ~720mAh went in. They claim they are shipped at 30% capacity, so it seems to be a 1000mAh LiPo cell, more or less. Makes sense as they state a rated energy of 3.7Wh on the battery. Currently testing at 200mA discharge to see if their claim of 400mAh is actually true. It probably is as 400mAh at 9V is 3.6Wh.

If it is then this is a very decent 9V battery and an improvement over other rechargeable 9V batteries. Until now I'm using a Tensai 9V NiMh battery, it's actually a 8S / 9.6V NiMh. Rated at 270mAh and I got about 235mAh at 200mA from it. It costs about 6 EUR. So the ZNTER 9V is cheaper and has possibly more capacity.

I will definitely keep this in mind if I decide to get a 9V lithium. I hadn't thought about the differences in mAh/Wh ratings before. Makes one think about paying attention to numbers on the packages

The end result is good, but not as good as I initially hoped. 314mAh came out and while it is still an improvement over the NiMh battery (while being cheaper) it is not as good as claimed. The average voltage during discharge was more like 9.4V instead of the rated 9.0V so that gives us a little more energy as it first seems, but still about 0.6Wh short of the target. The output is 0V now, I'll recharge tomorrow and see how much goes back into the battery. Sadly there is no way to measure the voltage of the lithium cell without taking it apart completely.

Ok, I've recharged it and 790mAh @ 5.1V went in, almost exactly 4.0Wh. That makes sense, ~99% charging efficiency of the lithium cell and ~95% conversion effiency of the DC-DC converter / charging IC from USB voltage to the charging voltage of the cell. I guess the lithium cell isn't fully depleted during discharge. Which is good on one hand, it will last a very reasonable amount of cycles. To be sure I'd have to take it apart, not sure if I want to do this.
It draws 460mA while charging and it takes about 2h from fully discharged to fully charged.

edit: I take that back, the lithium cell probably was, more or less, fully depleted!

Conclusion:
+ Stable ~9.4V output while under 200mA of load, I guess this battery could put out about 1A or so which way above the usual load for a 9V battery
+ Decent capacity, butthe rated capacity isn't reached
+ Bigger capacity at lower price compared to good quality NiMh 9V batteries
+ Less weight compared to Zinc-Carbon / Zinc-Chloride,Alkaline and NiMh 9V batteries (if that is of any importance to you)

- No way to tell the state of charge, cutoff will occur without warning

I think their concept works pretty good in this size of batteries.The smaller AA size is just a bit too small, I guess.I therefore assume that the C and D type batteries will also be quite good, but I have no use for these sizes so I haven't ordered any.

But I also got these:




NiZn batteries from Turnigy, made by some undisclosed OEM. They are rated at 1500mAh (just like all AA NiZn batteries at the moment) and cost 1.62 USD each, or about 1.36 EUR.
So four of them are 5.44 EUR. Amazon charges 16.66 EUR for four Ansmann NiZn batteries (4.17 EUR each) and 51.19 EUR for 20 PKCELL NiZn batteries (2.56 EUR each).
My MC3000 supports NiZn so I will put them through a cycle and see what's what.

I bought some 9V Li-ion batteries a while back.



They don't have the internal circuitry though, that the Znters do. They came with a proprietary charger, and the Voltage is something near 8.4V when fully charged, and it drops as they're used. They may have some overcurrent / undervoltage protection, but definitely not a Volt booster. But on the plus side, I could probably put these on the iMax and compare them with some NiMH 9V I have. I'm kind of a fan of Tenergy cells. I've found they work at least as good as Energizers, but at a fraction of the price. Most of my C and D cells are Tenergy now. Although, these Znter Li-Ion cells are growing on me fast!

I finally worked out a way to compare the efficiency of the NiMH vs. Li-Ion AAs. I was able to find the Watts used by my GPS, and did a timed charge for each type of cell using a USB meter.




So knowing the capacity of each cell, and the Amp draw, and the charge time, I worked out a ratio of "charge-hours" per "use-hour". This means for every hour I use each type of cell, there is a certain amount of time that it will take to replace that charge. What I found is that the Li-Ion AAs take 20min to charge back up per hour of use. While the NiMHs take 37 minutes. I'm not surprised that the time efficiency is worse on the NiMHs, since the energy efficiency is also less. But this means I'm definitely taking the Li-Ion AAs on my hiking trips instead of the NiMH AAs. I can use up two of them in a little over 7 hours, and charge them back up in 2.5 hours. Whereas I can get a little over 10 hours of use from the NiMH, since they have a higher capacity, but it takes about 6.5 hours to charge them.

Here's my math just for fun:

Garmin on USB power: 5.390V *0.080A = 0.431W

Li-Ion cells in series: 0.431W /3V = 0.144A
1.040 Ah / 0.144A = 7.236 hr
Charge time: 2.5 hr / 7.236 hr = 0.3455 "charge hours" / "use hour" = 20.73 min/hr

NiMH cells in series: 0.431W /2.4V (nominal) = 0.180A
1.849 Ah / 0.180A = 10.297 hr
Charge time: 6.583 hr / 10.291 hr = 0.6397"charge hours" / "use hour" = 38.38 min/hr

I actually got around to weighing these things too. Each Li-Ion cell is18g. All four and the charge cable adds up to87g.
This is compared to the NiMH, where a cell is26g, but with the charger and cable four of them weigh211g. This was the lightest "smart" charger I could find.

I wonder if anyone has ever been this anal about which batteries to take hiking.

One final test of the Znter AAs. I finally got a couple to give some readings after a discharge test rather than going "null". What I found was one AA that had set on my desk for a week, maybe a little longer, read 936 mAh, while a freshly charged cell read 1048 mAh. So it appears they do have some self-discharge, but I don't know how significant that is. Also, consider that the Opus is not a precision instrument, and the same cell will give slightly different readings for each test.

Still, I wouldn't buy these to store on a shelf, but only if they're going to get used and recharged at least a few times a year.