ROV Hybrid AAA's - not graceful agers!

Turbo DV8

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Sorry, no fancy graphs and charts to be found here. You'll just have to read the whole story :sleepy:to see the big picture! :eek: I have 56 ROV Hybrid AAA cells that I purchased in Feb 2007. They are almost all in use in various applications, kept charged and never allowed to stay in a deeply discharged state. My Hybrid AAA cells are basically used very lightly and have gone through perhaps a half dozen charge cycles since 2/07. I happened to have available three back in August that I took out of rotation and decided to do a capacity check to see what type of degradation the Hybrids experienced in a year and a half of easy-cheesy life.

The batteries were in an LED candle, used regularly. I use the LED candle until it begins to pulsate, at which point the battery voltage is about 1 volt, then I charged them on the BC-900. The first thing I noticed was that one of the cells finished charging after only 398 mAh had gone "into" the cell. So I did the discharge half of the refresh mode @ 250 mA discharge, and the cell only delivered 329 mAh. On the second discharge, the capacity jumped to 664 mAh. I charged it a third time and decided to let it sit for two months, and measure the capacity. I tested it yesterday, and it ain't looking good.

After sitting for two months, the cell was only able to deliver 460 mAh @ 250 mA discharge current. I have also a couple other ROV Hybrid AAA cells that will no longer properly terminate on the charger at 200 mA charge rate. I must use the 500 mA rate. These are just a slice of the picture, but when I note the general trend of how the capacities of my ROV Hybrid AAA cells has declined much faster and less evenly than my Eneloops AAA's (purchased at the same time) I have to come to the conclusion the Hybrids are not as robust. When new, my Hybrids appeared to have substantially more capacity than the Eneloops. Almost all were over 800 mAh, with many approaching 850 mAh. The Eneloops more closely, and tightly, mirrored their rating, between 800-820 mAh. However, of the Hybrids I tested recently, capacity has dropped to between 710-760 mAh (not including the 664 mAh cell) while the Eneloops are between 790-810 mAh. I note the Eneloops are deteriorating much more gracefully than the Hybrids. Where the Hybrids came out of the gates appearing stronger than the Eneloops in terms of capacity, they have dropped faster and farther, and with more disparity between cells, than the Eneloops. The Eneloops have never failed to terminate at 200 mA charge rate, and have never given me any indication to suspect high self-discharge or development of high internal resistance.

The fact that the Eneloops are turning out to be more robust than the ROV Hybrids doesn't surprise me, and probably won't surprise others here, either. What does bother me (because I own 56 of the little buggers) is the rapidity these cells are deteriorating so quickly with such few charge cycles on them.
 
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Re: Graceful agers, the ROV Hybrid AAA's are NOT!

Interesting. Guess I should do a discharge test (C9000) on some of my ROV Hybrid AAAs and see how they are doing. They were last charged 3+ months ago.

Using the Maha C9000, my Hybrids have never come out showing more capacity than my Eneloops.

My Hybrids are only about 7 months old and are used mainly in Dorcy 3xAAA 9-LED lights.

They all received a break-in cycle on the C9000 before they went into service.

EDIT: Discharge test completed @200 mA on 3 ROV Hybrid AAA cells. The cells were charged sometime in June or July (before I started keeping track of charge dates) and were used occasionally since then.

488, 529, and 520 mAh capacity
 
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Re: Graceful agers, the ROV Hybrid AAA's are NOT!

I have a small fleet of Hybrid AA, and they have performed well.

However, recently I noticed that the digital camera seemed to poop out faster than expected. This has happened twice, and I wonder if the bats are beginning to falter. I have a Vanson speedy Box, so I cannot analyze them.
I will certainly keep an eye on them.

I wonder how the Titanium Enduros have been holding up?
 
I would bet the charger is killing them. How hot are they after a charge an what charge rate are you using? I own both the bc900 and the mh9000 and I never use the bc 900 any more due to overcharging.
 
I would bet the charger is killing them. How hot are they after a charge an what charge rate are you using? I own both the bc900 and the mh9000 and I never use the bc 900 any more due to overcharging.

Hmmmmm....

I own 2 MH-C9000's (0H... revs) and 2 BC-900's (v33). Have never had any problems with 'over charging' using the BC-900's.

Both chargers are fine chargers. Both chargers have their advantages and disadvantages.

But most important.....

Each has its own personality, the same as each brand of batteries have thier own 'personalities'.

Now what I mean by that is....for example;

A MH-C9000 will miss termination MUCH more often if you do not stick within the .5C-1C MAHA recommended charging rate no matter what condition the batteries, new or fairly used.

A BC-900 terminates quite reliably at 200 mA....when using AA batteries that are still in good to very good condition AND have already been recently cycled a few times. But it is terrible with AAA cells at the lower rates. Although, I really think this is more the fault of the smaller cell than the charger.

The MH-C9000 rarely misses termination BECAUSE......it IS NOT terminating on -deltaV most of the time, like it originally did. Instead it is terminating on a voltage set point which is 1.47V.

The BC-900 can miss terminating more often because it ACTUALLY IS terminating on -deltaV more often than not, which is why the batteries are a bit warmer (they are actually fully charged when it says 'Full).

ALL regular NiMh batteries can and do suffer from missed termination problems especially on the first few (1-3) cycles. The newer LSD batteries also suffer from this problem but to MUCH lesser degree because they have already been charged at least two times. The problem can be minimized by using higher charger rates (i.e. .5C-1C). But new batteries should be closely monitored the first few charge cycles. This is not such a problem if you use the .1C@16 hours rate, since this uses a timed termination method instead of looking for -deltaV.

Definitely stick with a .5C - 1C rate on the AAA cells when using either charger, but especially with the BC-900 (because of the -deltaV termination). My experiences have been that an AAA cell will miss termination much more often than an AA cell when using the lower rates.

Now, assuming you are talking about 800mAh AAA cells;

I would take a few of them and run them through a B/I cycle on MH-C9000. If capacity is lower than say 750mAh, then run it through another B/I cycle. Do this from 1-3 times. If you can't get 70% capacity (560 mAh) after 3 B/I cycles, then they are trash worthy at that point.

I would also take some and put them in the BC-900, set it to Discharge/Refresh and set the discharge current to 250mA. This will automatically set the charge rate to 500mA (about .6C). The BC-900 will charge/discharge the batteries and compare the capacity after each cycle, repeating until no further improvement is detected. If you don't get 80% then repeate the Discharge/Refresh run one more time. If you can't get 80% (640mAh) after 2 separate Discharge/Refresh runs on the BC-900, then they are trash worthy at that point.

Note - I tend to use 70%-75% as my throw-away threshhold when using the MH-C9000 and about 80% when using the BC-900 because of the differences in their capacity estimating methods.

Also....its not a good idea to try to compare the capacity ratings from the BC-900 to the capacity ratings from the MH-C9000.

Its not a matter of whcih is more correct, rather it is a matter of the differences in the way each unit calculates the capacities. For a variety of reasons the BC-900 will almost always be higher when testing the same cell on both.

Last but not least.....NiMh batteries seem to work better when they are consistently 'exercised'. Letting them sit for extended periods of time makes them 'lazy'...hehe. Run a few complete charge/discharge cycles on them and the tend to rebound pretty good.
 
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Are you noticing less drop off in cells that are used in higher amp drain applications. Like running at 1C or close to that? I think batteries, rechargeable batteries, like to be exercised, and well not perform at their best when set at a low idling speed for sustained periods of time. Just my thoughts here.

Bill
 
Are you noticing less drop off in cells that are used in higher amp drain applications. Like running at 1C or close to that?

I haven't kept tabs that close. All I observe is that of all my AAA Hybrids and Eneloops that are the same age and generally used the same, only my Hybrids have begun to give me problems.
 
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