Yeah IR testing is difficult and can only be used relatively, meaning you results will be different than mine kind of thing.
I’ve had rayovac and energizer NIMH batteries and those have been trashed long ago.
However I do still have a couple rayovacs, as they were lower capacity than the energizers.
I also have some old eneloop pros that still work great, but I don’t know where they are ATM lol.
Also, my brother has/had some Powerex NIMH, forget what capacity, but i know they were less than 4 years old before they got throw away because they could hold a charge.
Also i don’t know of any other decade old battery tests other than eneloops, probably because other would be trashed before then.
12 year old eneloop test:
If you do have a good IR setup, getting consistent results, it can be pretty useful. I finally got the ZB206+ and holder due to inconsistencies in capacity testing between various chargers, and even the same charger using the same settings.
That said, the inconsistencies were often the result of testing OLD batteries. Termination, cut-off, and self-discharge can be highly variable for old, high IR cells.
Those need recycling I found. Be rid of the headaches.
Thanks folks for your reply Re. IR.
My first attempts to measure it with my Opus BT-C2000 charger used to give very widespread results.
Now I use my BT-C100 to test batteries one at a time, 5 times in a row and pressing hard the slider against the battery, following advice given somewhere else on BLF. This gives me much more homogeneous results, and I keep the lowest value obtained.
With this method, I find that the worst I have are my 12-year old Maha Imedion AA (700-900 mΩ for two of them, 350 mΩ for the other two), and the best are 4 out of my 8 13-year old Varta Ready2use (around 150 mΩ). The 14-year old ReCyko+ are also around 150 mΩ, still not bad for such old batteries.
9-year old AAA Varta Ready2use are still below 100 mΩ, whereas 12-year old Maha Imedion reach 470 and 770 mΩ (but these two were used for a long time in a DECT phone, i.e. permanently charged at 100 % which is not good for battery life).
Those Varta looked interesting. Unfortunately on Amazon they are $28.47 for 4.
Fujitsu 1900mAh were $23.54 for 4.
Eneloop 2100 were $18.99 for 4 (plus the fake issue.)
Most of the ‘cheapies’ with more capacity, that I don’t trust, are much less expensive. Make your choices according to information collected + your belief system. 
In Europe we can get them as low as €6.45 (nkon.nl), but the shipping cost to the US (€19) is a strong deterrent unless you buy many units.
A little more shopping and found the Varta 2100 on eBay for $12 for 4. WAY better. Free shipping from Lithuania. Huh!
If If If you got a buck-boost driver to adjust to 6V, then yeah you can use 2 cells in series, but keep in mind the voltage will range from 8.4V out of the charger to as low as 6V or lower when completely spent.
And they’d better both be protected cells because when Li-ion cells are in series, likely one will get discharged too low and fry it or get it fizzing.
Hmm. I always thought a larger capacity would give longer life. For example, I had a new battery that I had put in a 6 cylinder car that was of larger than necessary CCA. Car bit the dust just a few months later so I kept the battery & put it in a Honda Civic. There was a prety good system in it. 2 amps (about 2200 watts), & that battery lasted a really long time. This includes listening to the system with the engine off for a couple hours at a time.
I do however have Tenergy 9v 200mah in my smoke detectors that are at least 5 years old. The only other type of NiMh I have used is Energizer.
I was going to buy some of the 1000mah AAA from Tenergy, but after reading this I may buy the smaller mah ones.
Car batteries are completely different. Not to mention you are comparing different things.
Amp Hours are not Cold Cranking Amps.
Think of lithium batteries in flashlights. A Samsung 30T won’t have to “work as hard” compared to a Samsung 50E in something like a FW21 Pro that can pull almost 20amps. But the 30T has waay less mah.
That Samsung 50E won’t be as bright on Turbo, not to mention will kill the battery and make it unusable after several cycles running crazy hot on the verge of blowing up.
That Samsung 30T won’t break a sweat for its entire lifetime because its rated for that output.
Overkill in the correct way will make something last longer.
That’s indeed a great find, I see Eneloops and the Fujitsu batteries at the top of the chart for “regular” AA rechargables
Can’t really compare Pb life to NiMh life. Pb likes to be kept fully charged. All it takes is a few deep discharges (lights left on kind of thing) to ruin even a good one.
NiMh does best kept to 20-80% if you REALLY want it to last, but that’s very difficult to manage. It’s quite happy between full and 1.0v. LSD types are damaged by constant trickle charge.
I have a dozen Tenergy 800 AAA from 2017. They get regular use and are OK. Most are now in the 600+ - 700mAh capacity.
I saw they now have a Premium Pro 1100. I’d only buy them if the were $1, to check them out. Doubt they would hold up for the long haul, which an important variable to me.
So are you saying that 4 1.2s are not a good idea? I also was thinking of running 4 in my 2 way walkies as well.
4xAA or AAA is fine. Just be aware that in series they are a ‘chain’, and a chain is only as good as it’s weakest link.
When a battery ‘pack’ is pushed until one cell goes dead, then continues to be used, assuming the device will still function, current is forced in reverse through that cell. The weak link now takes further damage, making it even weaker, further compromising the battery pack.
NiMh do not require full discharge. Re-charge them before they get that low, then you’ll be fine.
your walkies likely have a low battery indicator.
pay attention to it.
a led light can run normally on 3 cells.
on 4 cells it can still be producing plenty of light while it reverses the first cell that drops.
some cells like eneloops are well matched and very consistent.
with these its less of an issue.
anything else and there are wide enough variation in capacity and self discharge to get in trouble.
and of course the abused cell just gets worse on every cycle of abuse.
I usually pull/rotate my 9v in my smoke detectors every 6 months. Guess I could add that to the rotation. On the walkies, what mah would be good for those?
You get 6 months out of “Tenergy 9v 200mah in my smoke detectors that are at least 5 years old”?
Come on…really? Do you know they are still working? Maybe they have died.
I had a bunch of 9v NiMh. There were universally pathetic. They would self discharge to dead in less than 6 months, let alone get any functional use out of them. Hated them.
I’ve moved on to 9v (8.4v) iPowerUS Li-on. They are vastly superior, and I actually do get ~6 months in a smoke alarm or DMV.
Yep. I bought those the same time I bought my rechargable RCR123’s. I do rotate them, so it’s not like they are being used 6 months & recharged to put back in the same day. I did have 1 that went bad. The detector was beeping only a couple of weeks after I changed it out.
Actually, use > recharge > re-use is maybe the best case for them. Kind of like the Project Farm constant use trial.
I have a Prius with a $4000 NiMh battery in it. The ones in cabs go hundreds of thousands of miles. The ones that get erratic and occasional use sometimes go dead in less than $100K.
I make sure to drive it more than a 3 mile jaunt to the store at least once a week if possible.
I also have a Nissan Leaf I try to keep around 30-60% generally, try to seldom exceed 20-80%, and only fill it if I’m going to use it immediately and pull it down a fair amount. That’s an $8K battery, and the car is pretty worthless with a bad battery.