A123 ANR26650M1-B 2400mAh 3.3V 26650 Bench Test Results...an extraordinary battery, with issues

Hello!
I find this somewhat odd, in the likes of that discharge HKJ made for the APR18650M1-A.
The battery is supposed to be charged up to 3,6V, and start dropping voltage steadily down from there but, there's something else. I mean, if you look at the discharge curves, you can clearly notice there's some sort of unusually steep initial voltage drop even for the lowest amp rating curve. The more or less even voltage drop spacing for each adjacent +10A incremental curves makes sense yet, in general, all of the curves seem to sit somewhat lower than I'd have expected.
Mooch, did you ever thought about making no-load voltage measurements on the cells at steady intervals? I mean, very brief pauses while discharging for voltage measurement. I think this can give very decent feedback about cells' internal resistances and how do they progress on the discharge curves. Well, not that it's that difficult to do by observing the slope evolution of adjacent curves, yet actual numbers can make calculations waaay easier than reading a limited resolution graph to the naked eye.
Well, just trying to figure out the reason for such an steep initial voltage drop.
Thanks for the review, I linked it to BLF the other day: A123 ANR26650M1-B reviewed by Mooch :-) | BudgetLightForum.com

Cheers

 

Thanks for the tip on taking a peek over the pulsed discharge graphs.
I'm going to settle on calling this phenomena “voltage sag inertia”.
It seems that after an initial steeper voltage drop (which seems greater for LiFePO4s vs Li-ions), the steepness on the discharge voltage curves reduces (less steepness on LiFePO4s vs Li-ions).
The 20C (50A) discharge curve on the official datasheet is quite close to the one you attained. It would be safe to say this is a 50A continuous cell too.
A tad expensive maybe, but with a good array of these cells a good starter motorbike/car battery could be made. Mmm, maybe a mixture of lead-acid plus some 4SxP ANR26650M1-A/B LiFePO4 array could more or less fix the fragility of lead-acid starter batteries against deep cycling and their weakness under cold environments…
Tad off-topic, yeah.

Cheers

 

Thanks for the info mooch.
BTW enjoyed the true vapors show episode. Keep up the great work.

 

Mooch, let me explain:
I can observe a delta of ≈0,55V between the 10A and the 60A curves on the continuous discharge graph. Therefore, from such data I can infer the battery has about 11mΩ of internal resistance, isn't it?
Good, but, as I was trying to explain before, if the battery starts discharging right at around 3,6V, shouldn't we be measuring the first 10A load voltage(s) at the battery terminals just below 3,49V in the graph?
Hope this is more clearly understood now.

Cheers

 

Mr. Mooch, about internal impedance of the battery:
I bought a little Chinese tester @ 1000Hz and it seems to do OK.

Before that, I made a simple voltmeter. Solid stainless steel construction with 10 AWG wire inside.

Pretending that my copper mechanical mod has no internal resistance, I would measure my battery voltage under NO load first U1. Then I would attach my 0.5Ω 100W resistor, that I made for that purpose.

And take down the voltage under load U2. I would then subtract U1 - U2 to determent the difference U3. Then I would calculate my current under load: U2 ÷ R = I.
Then I would divide my voltage sag U3 ÷ I to get my battery internal impedance.
Example: U1=4.16V, U2=3.86V, 4.16 - 3.86 = U3 0.3V. Then 3.86V ÷ 0.5Ω = I 7.72A. Then 0.3V ÷ 7.72A = 0.0388Ω = 39mΩ (rounded up). It wasn't the best battery, I might add.
Based on my internal resistance and my coil resistance (for example 0.2Ω), I would imagine that at the first push of a button, the current will jump up to 4.16V ÷ 0.2Ω = 20.8A. Voltage drop, on internal battery impedance, will be:
20.8А × 0.039Ω = 0.8112V. Therefore my running voltage will stay at: 4.16V - 0.8112V = 3.3488V and current: 3.3488 ÷ 0.2Ω = 16.744A and I will be vaping at 3.3488V × 16.744A = 56 Watts.
But my Chinese tester shows much different results (usually lower). I also have Opus BT-C3400 and SkyRC D100 that can measure internal battery impedance and their measurements are much higher that the other two. What am I doing wrong? How do you measure internal resistance? I hope I'm not boring you...

 

Why can they not be used in regulated mods? I'm trying to understand.

 

Because their working voltage is too low for most regulated mods. Their highest voltage is 3.6V and lowest 2.0V

 

Thanks- just so I understand, if you can adjust the discharge voltage on your regulated mod, this still wouldn't allow you to use such batteries? On my dicodes mods, I think the battery discharge voltage can be adjusted between 2.5v-3.0v (depending on which Dicodes chip is being used, it might go up to 3.5). Perhaps I'm not understanding accurately how this feature works, but my initital thought was that such a feature would allow you to use batteries with variant voltages. But I think that such a feature would have to allow you to set the minimum discharge all the way down to 2.0 for this to work, to not get the low battery message very quickly, if I am grasping this properly.

In either case, after reading your review more carefully, I guess it still looks like the iJoy would be a better choice, since these only fire up to 20 amps, and you say the iJoy is superior in that range in any case, even on a mech mod (which I don't use.) Just liked what I read about the chemistry and technology here; I wonder if it is technically possible to produce batteries of this kind in the normal voltage range for vaping?

 

Let me also point out for anyone interested that these batteries are available from official U.S. distributor here: Authorized Online A123 Battery Cell Reseller...
For 10-99 26650 batteries, they sell for $9.30 each with a flat $20 shipping. If you need an absolute ton, you can get 100 for $8.75 each, with the same flat $20 shipping.

They also have the 18650 version of the batteries.

I think they do come out slightly cheaper from nkon, which charges 8.50 euros (roughly 8.88 USD) and generally 30 Euros delivery; though for about 10 or so, the a123 should come out cheaper because of the lesser shipping, though this may depend on your location.

 

Thanks for this info on the LFP chemistry, and the clarification about adjustable cutoff voltages.
I might try this, after I have some time to research some of the other issues you highlight. Unfortunately, it does look like the adjustable cutoff voltage on the Dicodes chips I have can only be set as low as 2.5, at present. Plus The chip will also start gradually reducing the wattage gradually once voltage dips below the cutoff point plus 0.5, dropping to 10 watts once the cutoff point is reached. So if I tried using these, I'd be able to get full 60 watts of power with a full 3.6 volt charge, but power would quickly drop to 50 watts once I drop under 3.0 volts and hit 2.9, drop to 40 watts at 2.8 volts, 30 watts at 2.7 volts, 20 watts at 2.6 volts, and 10 watts at 2.5 volts. So even though the battery has 1.6 volts to drop from full peak voltage until cutoff at 2.0, I'd only be able to actually drop 0.6-0.7 of those volts before my wattage also started to drop, which is about 45 percent of the full voltage range of the battery, and would only be able to drop about 70 percent of the actual volts before wattage dropped below 20 watts. Conversely, if I used one of the iJoy batteries, then even if one set the minimum discharge 0.1-0.2 higher with the iJoy (back to the factory settings) to avoid fully discharging it, the iJoy would have a significant advantage in how much voltage can fall before getting wattage dropoff or becoming unusable--starting from 4.2 volts, the iJoy could drop slightly less than 60 percent of the volts before wattage dropoff, and could drop slightly less than 90 percent of voltage before wattage drops below 20.

Plus, the MaH is almost 60 percent higher on the iJoy; while I don't quite yet understand what the MaH figure means, I gather that it means usage should be 60 percent longer at most settings. So even with adjustable batter cutoff on a mod, the a123 is still probably currently bested by the iJoy, barring very high amp usage over the iJoy's 40 Amp MDR; but if a future chip allowed one to adjust the battery minimum cutoff all the way down to 2.0, then the advantages might start to outweigh the disadvantages for the a123. Having said all this, I'm slightly suspecting I may have completely misunderstood how voltage discharge works, because I don't understand what you mean with this sentence: "The voltage of this cell is very steady for most of the discharge, very similar to LiPo's." In my untutored understanding, I had thought that voltage drops proportionately with the discharge of the MaH for all batteries, but now it seems that it depends on the battery type? If voltage holds steady until the MaH are mostly discharged for the a123, this might make it more attractive (at least for my usage) because I then would not have to worry about wattage dropping steadily as voltage drops (the bane of my existence), which generally leads me to recharge my batteries as soon as voltage drops low enough to start dropping wattage.

Sorry if any of this was totally off-base or far too long-winded; I'm just learning about batteries recently and have been trying to figure them out and see if I've understood their arcane, esoteric workings.

 

Minor technical note to add, on your review.

You write: "The datasheet has a "maximum continuous discharge" rating of 70A in the datasheet. But at that temperature, about 85°C, the cell will have a significantly reduced cycle life. This rating is an absolute maximum, not a level you should operate the battery at for every cycle. To allow direct comparison against other batteries I am rating this cell at a level, 30A continuous, which limits the temperature to 60°C to ensure good cycle life. Above this temperature the cell's aging accelerates significantly. The cell can easily be pulsed at levels above 80A though."

I checked the datasheet you post above, and it indeed claims 70A as the Maximum continuous discharge rate, just as you say. However, I just wanted to note that, interestingly, the datasheet presently posted on the a123 website (this might be from their official reseller's website, actually) now lists an Maximum Continuous Discharge Rate of 50A, not 70A: http://a123batteries.com/v/vspfiles/images/pdf/26650.pdf

Perhaps battery salesman are reading Mooch's reviews and deflating their overrated CDR claims! Still lists a max pulse discharge rate for 10 seconds of 120 A, though.