Disappointed in slow-discharge batteries
 

I just tried out Sanyo Eneloops 2000mA and another brand with similar technology. I know that 2000mA is still pretty high, but I was willing to hope that their claims of 85% charge retention after a year would be legit.

As far as I can tell, it's not even close, on either of the batteries, and I've tried 4 of 'em already. I load them up in a pager which consumes virtually no energy, and within 10 days, the Eneloops and the other slow-discharge battery are down to HALF charge. In contrast, conventional Duracell AAs take 4 months of continuous use to drop that low.

Was pretty disappointed in this result, to say the least. Was wondering if anyone else had any different experiences with them.

(And yes, I know I shouldn't be trying to run a high-amp type battery in a pager which will never require the high amperage, and that it's better for digital cams, LED flaslights, etc.)

How are you determining state of charge? What charger? How many cycles are on these cells?
I've been quite happy with Eneloops, but have not done long term retention testing.

What do you mean by half charge?

Are you reading this charge value off the pager that was designed to use alkaline cells? NiMH batteries have a nominal voltage of 1.2V, and the discharges is fairly flat compared to alkalines. Alkalines have a nominal voltage 1.5V. If the pager is measuring the voltage of the battery to determine charge, it's going to read incorrectly if it was designed for alkaline cells.

I love Sanyo Eneloops. I use them in everything, and they have a cool white design.

Yes - I am using the pager charge value reader. I suspect you're right with the different charge reading.

My Eneloops are pretty new - have been charged/used probably 2x so far, so perhaps they'll get better with time. Am using a Lacrosse charger - on the recharge, it charged 600mA, or 1/3rd of the putative 2000mA value - this was very disappointing, given only 2 weeks in a pager, which should be a very low-drain device.

I've been happy with my eneloops. I think Efficiency has correctly determined the problem. Your charger complains when the charge goes below, say, 1.15 V, and since the eneloops start at 1.2, it isn't long before they drop that far. Although it's at half charge after only two months, perhaps it will keep working for many months after that?

For example, I use eneloops in our little walkie-talkies. After only half a day, the charge indicater goes from full to two-thirds, yet the walkie-talkies work for months after that.

I can confirm eneloops rock the house. once they have been used twice. brandy new you gotta at least use them and charge them twice. not all the way either, just halfway or so.

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I use 8 AA's, only 4 at a time, in my dinotte 140L

I have a Maha 801 8 bay charger. always charges correctly, never overcharges ever.

I will have 4 in the charger all the time, [which is an intelligent charger but does not
trickle charge once they are topped. If they sit there they will 'evaporate']

My dinotte is fussy. If you have the least bit partial charge AA, you cannot get
decent runtimes. certainly not 3 hours.


so...sometimes I go 2 weeks without using the dinotte, and I take the batts out
of the charger and stick them in the dinotte...i take the old batts out of the dinotte
and stick them on the charger.

Now...compared to 2600mah standard energizer AA's:

the energizers would be half-flat or dead if I did this. I always had to plan the day before
I want to use the dinotte, to -repop- the charger so the energizers would be full again

I grab the eneloops and they will run my dinotte after they have been laying about for weeks,
and run right past 3 hours

and old -used up- eneloops from a previous ride, if I leave them laying about off the charger,
when I pop them in, they are always at half or 2/3rd charged ! an energizer would be just
about dead flat and take forever to charge (well, 3 hours on slow)



so my experience with a Maha intelligent 8-bay charger is, the eneloops are everything they advertise
and rock solid and you can let them sit around for a long time and they do not drop much at all.

I have not tested leaving the eneloops in the dinotte all the time. I know the dinotte is always probing the battery, and if they go low, even when the dinotte is turned off, the dinotte will detect a really
low battery and actually switch on into cripple dim mode. this happens in 3 days of leaving energizer
AA's in the dinotte all the time. I haven't tried the eneloops. I know they would drain faster than 'not plugged in' simply because the dinotte has to -probe- the battery periodically, and that eats power.
so i haven't tried.


Maha 800 series 8 bay charger, best ever

127, do you think that the charger makes much of a difference? I have a cheap Sanyo charger that came with the eneloops, a similar Duracell charger, and a Battery XTender charger.

the charger makes a difference in overall battery life

dumb chargers will charge for a default time, often many minutes or even hours longer
than the battery needs. battery gets warm or even hot and just bakes...this is what kills
battery life


the Maha detects when the battery will not take any more charge and stop. it also doesn't
trickle charge (which can cook batteries by over trickling). not trickle charging isn't the greatest
with normal rechargeables because it leaves them flat after some weeks...but:

eneloops won't go flat

and with a maha charger, you can just -repop- the batteries, it will detect
how flat the batteries actually are, and independently control each individual
battery and charge it only as much as it needs

them thar little 4 bay duracell chargers or energizer chargers cannot do this
sanyo charger is the same.
...

summary, yes, those little 4 bay chargers you buy work, but are stone-age
and the one that comes with a pack of eneloops is not intelligent or 'individual slot.'

Typical NiMH discharge curve starts at a little over 1.4v and drops sharply to 1.3. Things level off and they drop very slowly to 1.1v (hence 1.2V nominal value as thats the average voltage during discharge). After than they begin to drop sharply again and quickly theres nothing left. The flat discharge curve makes life difficult for charge remaining indicators, and for high drain devices it means you get little warning that you're going flat. Alkalines have a more steady voltage drop.
Agarose it would be useful for you to install the eneloops after a few cycles and report back in 3/6 months.
To me this is exactly what the LSD batteries are designed for. I started using them in my remotes this year, the Wii gets recharged now and then but the TV I expect only once a year it will need it.

+1 :beer:

incorrect.

After charging the any NiMH rechargeable AA is giong to dip to a nominal voltage of about 1.2 - 1.3. Including the LSD batteries.

The difference is that amount of energy in the battery, not the voltage. The voltage is going to be at 1.2 - 1.3 but the LSD batteries are going to hold their charge much longer than regular NiMHs

also... paper charge value reader???? those things only read the voltages because with Alkalines, a drop in voltage usually means a drop in capacity. Not so with NiMHs.

To really determine the capacity of your batteries you have to use the discharge/refresh function on the lacrosse to see how much energy the charger has to "drain" out of the batteries.

Or a simpler test would be turn on a flash light and see how long the batteries can keep the light going for.