Powerex 2700 capacity issue?

Hi;
2yrs ago I purchased 8 of the Powerex 2700 mAh batteries. These are not labeled Pro or Pre-Charged. Just Powerex.
I also purchased a Maha MHC-9000 smart charger, and have been using it exclusively since.

The first thing I did when I received the batteries was to run them on the Break-In cycle.
The capacities reported at the end of the cycle ranged from 2501 to 2555, which is within the spec for the 2700 mAh batteries.

I have charged the batteries at 500mA, which is actually lower than the recommended minimum of 0.3C, but that has never been an issue.
I also use 500mA for the discharge rate as well.

Every few months I have run the Refresh/Analyze cycle on these batteries.
I see the capacities dropping gradually over time; this is to be expected.

These batteries were used regularly (every night) in my Diamond LED headlamp for the first year, then not much at all for the next year, but I ran them through the Refresh/Analyze cycle every few months while in storage.

Then, in June this year, I returned to using the batteries on a daily basis.
The capacities are down to a range between 2230 and 2275, but one battery of the 8 is at 2338.
All the while I have been charging (and discharging in the charger) at the 500mA rate.

The other day I did some reading on the Maha website, and learned that the optimal charge rate is 1300 mA (0.5C) and discharge of 700 mA.
So I decided to run 4 of the 8 batteries through the Refresh/Analyze cycle using those figures.
The result was significantly lower capacity than at the 500mA charge / Discharge rate.
The range was 2022 mAh to 2075 mAh with the one battery (the same one that has always had a higher capacity) reading 2194.
So I'm seeing a drop of 200mAh after running them through R/A at the higher rate.

After this result, I ran them again through the R/A cycle, but lowered the rates to 800 charge 500 discharge. The result was pretty much the same as it was for the previous - higher rate cycle. One battery actually read "HIGH" when I first put it into the charger for the R/A cycle after the higher current one, so I ran them all through Discharge before running the R/A at 800/500 mA.

I decided not to run any more cycles on these batteries for now; just use them in the headlamp until they drop below a comfortable brightness - which is usually when the battery indicator on the headlamp turns red when the high brightness beam is on.

My thinking is that the higher charge rate may have temporarily re-formed the batteries so they have a lower capacity. I have no idea why this would happen - or if that is actually what happened; it's just speculation at this point.

So the next time I put them into the charger, I think I am going to run them through the Break-in cycle.
Perhaps I should even allow them to discharge to a lower level (in the headlamp) before doing this. Since the headlamp is electronic, it will never allow the batteries to go completely dead - unless one is weak and does go to 0V before the other are low enough to shut the headlamp off.
The discharge cutoff voltage of the MHC-9000 is 1.0V. Is this low enough? Maybe I should build myself another discharge circuit that could bring the batteries down to a lower voltage. Or perhaps hack the MHC-9000 so it will do that.

Any ideas?

Thanks

FW

Let's face it, the PowerEx 2700s are/weren't all that great. Like most HSD batteries, you'll perhaps get 2-3 years out of them before their internal resistances start to creep up.

What is their I.R. number (in volts) when you first insert them and hit 'charge?'

I got my Maha C9000 in Jan. of '12, but went with some AccuPower 2900s (1200 AAA) and I got just about 3 years out of them before I chucked them into the recycle bin.

My buddy bought his C9000 right after me, but went with the PowerEx 2700s and I remember him telling me that some of them were already going dwanky on him and that was maybe a year, or two, after purchase.

If you need higher capacities than the standard Eneloop type jobbies, get the Eneloops/Fujitsus high-caps, but even they won't last nearly as long as the standard LSD batteries made in Japan.

I think my Maha cuts off discharge at .900v.

What you can do, apart from noting the I.R. numbers, is to charge them up and do a 1A discharge and see how they hold up. No doubt your I.R. numbers should be creeping up to that 2.00v rejection range the Maha uses to reject high I.R. batteries.

Chris

Thanks Chris;
I never record the initial I.R. number, but I am fairly certain that it was at least 2.00V for these Powerex. There was one that read "HIGH", which was somewhere around 2.3. I will add a column for I.R. to my Access database I use to keep battery info.
I will also run the batteries at 1.0A discharge and see what I get.

I bought the Powerex because I was becoming somewhat disappointed with the Eneloops. What I would really like is Lithium rechargeable AA's, but I don't believe such an animal exists.
Perhaps doing the 1A discharge, then Break-In cycle will revive these a bit...
I have a whole slew of Eneloop AA and AAA's; some dating back 5yrs. I need to run them all through Refresh-Analyze and get rid of the ones that have lost more than about 25% of their capacity.
Many of my uses for these batteries are not very demanding, so lower capacity isn't going to bother me all that much. I do use them in my Nikon flash, but I rarely use the flash anyway, so it's not really a problem.

It's too bad that with all the advance in technology, it's batteries that still lag way behind. Sure, they're much better today than they were even 10 years ago, but still not ideal.

FW

ultrarunner2015 said:

[...] What I would really like is Lithium rechargeable AA's, but I don't believe such an animal exists [..]

Click to expand...

They do exist (Kentli, Jugee, Zntr) and some have been discussed briefly here in the past.

I have run the 4 Powerex batteries through the discharge cycle on the MHC9000 at a rate of 1A*. The results are as follows:











All of the batteries had been run through the Refresh-Analyze cycle at 500/500 mA yesterday and were not used during the interim.

* Battery #1 is displaying symptoms of high I.R., so I re-started the discharge cycle at 500 mA.

ultrarunner2015 said:

Thanks Chris;
I never record the initial I.R. number, but I am fairly certain that it was at least 2.00V for these Powerex. There was one that read "HIGH", which was somewhere around 2.3. I will add a column for I.R. to my Access database I use to keep battery info.
I will also run the batteries at 1.0A discharge and see what I get.

I bought the Powerex because I was becoming somewhat disappointed with the Eneloops. What I would really like is Lithium rechargeable AA's, but I don't believe such an animal exists.
Perhaps doing the 1A discharge, then Break-In cycle will revive these a bit...
I have a whole slew of Eneloop AA and AAA's; some dating back 5yrs. I need to run them all through Refresh-Analyze and get rid of the ones that have lost more than about 25% of their capacity.
Many of my uses for these batteries are not very demanding, so lower capacity isn't going to bother me all that much. I do use them in my Nikon flash, but I rarely use the flash anyway, so it's not really a problem.

It's too bad that with all the advance in technology, it's batteries that still lag way behind. Sure, they're much better today than they were even 10 years ago, but still not ideal.

FW

Click to expand...

They're not coming back, so stop worrying about them and move onto another set(s) and enjoy life.

Batteries/cells are consumable items, which means that they will wear out/stop working and need replacing, like gun barrels, or a gallon of milk. The more you shoot, the closer you are to rebarreling and the longer you hold onto that milk, the closer it comes to being sour.

When I revamped everything in early 2012, I did the 'buffet' style of choosing batteries. I got a bunch of different brands and fiddled with them for a few years. My usage is still low to moderate, so cycle life isn't a problem, but that's not the only component in the degradation of a battery/cell--time is a problem for us and things can sit unused and still go bad, like the gallon of milk.

I've sworn off, unless there's a great deal, my Sanyo 2700s (died the fastest,) AccuPower 2900s/1200s (3 years,) Energizer 2300~Japan (love these), PowerEx Imedions (decent/still working) and GP ReCyKos (pretty good.) Now I'm just sticking to Eneloops or Fujitsu, standard capacities to boot, but the latter are a bit harder to find these past 24 months.

It doesn't have to be that difficult, but we're all different.

Chris

Live and learn

Chris;
This is a project. I am performing these tests out of curiosity. If I can recover a little of the capacity then that's icing on the cake.
My use is non-critical. I use these Powerex in an LED headlamp, which I am using mainly for walking my dog at night. They last around 5 walks, which are usually about 20 minutes each. Then I throw in the 2nd set and recharge the 1st set.

I am going to measure the current that the headlamp uses, just for curiosity.

I do have a more 'critical' use for rechargeables though: I own two amateur radio HT's, which each use 6x AA cells. I have used only the Eneloops in the radios. I think the radios could benefit from the higher instantaneous current that the (new) Powerex could deliver, as the radio will draw about 1.2A when set to high (5W) power. But the high self-discharge rate of the Powerex (compared to the Eneloops) prohibits their use in the radios.
Unfortunately, the radios I own came with NiMh and not Li battery packs. I 'build' my own packs using a tray that holds 6 AA's and fits onto the back of the radio, just like the OEM packs do. I select the Eneloops so they have nearly the same capacity when I build these packs, so I get the most from the cells.