Hi, guys. As above, is this normal? I bought some 2450mAh Eneloops from Amazon back in November 2015 for my TN4A. I haven’t used them in quite some time but they weren’t stored empty. I noticed that the low voltage light was flashing on the TN4A so I decided to charge them. Much to my surprise I’m getting some really odd readings - 1.40v at 1549mAh, 1.39v at 1275mAh, and the other two are still charging both at 1.41v at 1639mAh, and I predict they will stop charging shortly as I did a test discharge on them and I got similar readings. They’ve been left at room temperature the whole time. Has the TN4A done this or have I completely noobed out and storaged/used them incorrectly?
I’ll be completely honest - I didn’t look at the voltages when I chucked them in the charger. Could it be the case that I’ve let them run too low for too long? The last time I charged them was months ago and I just left them in the TN4A, but I remember a selfbuilt review stating the parasitic drain for the TN4A was extremely low. Hm.
Indeed there was. The TN4A had stepped down to High, which is around 550 lumens while the low voltage indicator was going off. I charged them up today and noticed the readings looking a bit…low. So I did a discharge test and the above readings are circa what I got. Unless the charger is faulty (which is doubtful as it’s been fine with all of my other batteries) I’ve done something to these Eneloops that has significantly reduced their capacity, and I can’t figure out for the life of me what I would have done.
Okay, it wasn’t clear to me if you did a discharge test. (actually i didn’t read your OP too well… :person_facepalming: )
But you did.
Then i also don’t know what’s going on…
I killed some Eneloop PRO AAA batteries in cordless phones, but that’s because those damn phones overcharge them continuously…
Apparently cheaper NiMH batteries do survive that kind of abuse…
But in your case, they may have over-discharged, but that usually is not a big problem.
None the less, i think NiMH cells shouldn’t be discharged below 0.8 Volts.
Many AA and AAA lights have low voltage protection, set at 0.8 Volts.
Are the high capacity Eneloops maybe sensitive to abuse?
I don’t know…
But i’m an Enelong fan now.
Much cheaper and similar capacity. https://www.fasttech.com/product/1140600
Check the reviews.
Hi Jerommel - It seems that from Old Mate’s post that the high capacity Eneloops are indeed prone to losing their charge in a less convenient manner.
I’ve just remembered something; I did see the voltages of some of the batteries when I first stuck them in the charger - none of them were uniform, but additionally, the lowest I remember was for around 0.99v. I’m going off my memory hear so I can’t be 100% sure. I’m currently performing a discharge refresh to see if this will revive them.
Also, thanks for the link to the Enelongs (great name).
I am not able to give a figure as it is hard to truly measure resistance of a cell.
The resistance can be measured on your opus charger but is only useful if you check their resistance when brand new and compare as they age. This has proven not to give absolute correct or accurate ir readings, but is good to compare.
Some of the signs of high ir -
Wont accept full 1.50v charge
Voltage wont exceed 1.4v and low ma cap
Gets very hot when charging
Will get rejected by some chargers
Straight off the charger it will invoke the blue low battery warning immediately
Driver will be noisy trying to power the light
I would just buy the standard eneloops they are bullet proof- everyone likes a higher capacity, i like my cells to work for a long time and being able to deliver full current a couple of years or five from now.
Hey I had a similar issue with a different brand they sat discharged for months and came back with really low 1200 capacity. From a 2400 cell. I ran a refresh cycle on them on the opus charges and discharges 3 times and got them back to over 2k. I recommend that at 1 amp charge rate. Sometimes they need to be woke back up. One cell went back to original capacity completely. For my eneloop pros I will drain them at least once every 6-8 weeks. Even if I don’t have a use. I’ll put them in a light or lantern and run them down. Or just do a discharge cycle on them. Same with my 18650s to keep all the chemicals in a active state not stay stagnate for to long. I’ve seen a lot of 18650 specs sheets talk about permenate capacity loss after just 30 days of storage sometimes down to 80% recoupable. I have no idea if nihm is the same. But every 1-2 months just run them. The eneloop pros are rated for like 400 cycles. I probably have some with 40-50 cycles and still test at 2500mah its easy enough to take your tn4a and use it as a lamp in a room once a month and cycle the cells.
Yes, I’d do a discharge/refresh @ 500mA. Then do a charge/test again.
You can do an internal resistance with the Opus. The battery should be fully charged and not hot. I only use one channel since the various wires and contacts in the charger are part of the equation. I also HOLD the battery TIGHT in the slot to optimize contact. If the reading looks weird I do it a couple more times to try to get a somewhat consistent reading.
On my Opus a really good/new AA will read ~40. Used but very good batteries will be 80-100. As it climbs from there the battery gets less effective for output. I do have some that register 300+ but they work OK in situations like a solar charge light that is very abusive. I’m not about to put a good battery in there.
FWIW, higher capacity (more than stock Eneloop @2000) cells have a known shorter life. It’s even printed in the specs. Really high capacity cells; 1. Probably aren’t 2. Have a MUCH shorter life, high discharge rate, and internal resistance goes up soon and fast. Not worth it unless you really need that 300-400 extra mA……which you will soon lose anyway.
Thanks for the responses, guys. They’ve been discharge refreshing at 500mA for the past 15 hours now and it would seem the capacity is indeed slowly climbing. I can see that one of them is now at 1900mAh. Everytime I’ve checked them they don’t appear even that warm. It looks like this discharge refresh is going to take a very long time - the manual says it can even take days.
Thanks for the info on the higher capacity cells having a shorter life span. I actually did not know this at all.
@Speed4goal - it looks like these will indeed need to be refreshed charged periodically if they behave like this in future. I’m going to post the readings I get once the refresh is done.
I too prefer low self discharge over high capacity… if forced to choose one or the other. I also have some really old 2000mah eneloops that still run great in various lights / devices.
From the review: [DISCHARGE REFRESH: Discharge and charge the battery 3 times.] @500mA it could take a long time to cycle. Lower would take even longer. Too low and the charger has more risk of missing termination, more so if the internal resistance has gone up too far.
I just did a few tests on 2-3 year old stock eneloops. On average just doing a [Charge/Test] cycle bumped the capacity ~50mA. These are good batteries in good shape, but not used much.
