Are my Eneloops starting to die?

[KD5XB]

I have about 6 Eneloops that are in constant use in my GPS as I drive around the country. When I first got them, I used my MH-C9000 to break them in, test them, and I matched them in pairs for closest capacity.

One set, that I labelled #3, is acting strange. For quite a while, if any of them were charged and I put them in the MH-C9000, within a couple of minutes at most, I would get an indication that they were charged. The rest still do this, but #3 has started showing "HIGH" on the readout of the MH-C9000.

Does this mean #3 are ready to be recycled? Or should I ignore it? Or what?

Thanks!

 

[45/70]

Hard to say, KD5XB. Do you run the sets down each time, or is the discharge stopped at an acceptable level (rested voltage of 1.20 Volt/cell, or higher)? My thoughts are that no matter how well matched a set of cells is, if you run them down very low each discharge, they likely will be damaged from reverse charging at some point. This will of course wear out the cells prematurely. NiMH cells (including LSD's) also last longer if not discharged deeply each cycle anyway, as info.

Usually when cells build up high internal resistance, they are unlikely to be recoverable. You might try a few "break-in" cycles on them, but don't get your hopes up.

Dave

 

[KD5XB]

Oh -- what I do is run them until my GPSr gives me the "kow battery" warning, then recharge them. I guess I should look at the charger when I first put them in to see just how low they're being discharged.

And my apologies -- my name is Earl. This is the wrong forum to give a call sign and expect anybody to know who I am.

 

[Apollo Cree]

Try a discharge/charge on the C9000 and see what happens.

If I had time, I'd do

Discharge
Charge
Discharge
Breakin

Record readings at each point.

If you're really interested in experimenting, I'd do a few more charge/discharge cycles before the breakin and see if the capacities change between cycles.

Make a note of the resistance of each cell before each cycle. To measure resistance, put in a cell, hit the enter button until it starts charging. The first voltage reading you get will be the cell's internal resistance. You'll notice that the first voltage reading differs from any subsequent voltage readings, or you haven't done it right. (Or it may say, "HIGH".) You can even do this when you're doing a discharge cycle, just start a charge cycle, get the resistance reading, then take out the cell and restart with a discharge cycle.

Consensus seems to be that if a NiMH ever says "high" you need to say "bye."

If the cell's still flaky, throw it away. You've still probably saved vs. disposable cells.

How many cells does the GPS hold at one time? If it's only 2, there's probably not much chance of getting a reverse charge.

 

[KD5XB]

I might try that -- when iu get home. Being in the truck for several days at a time puts a kink in that due to power interruptions.

 

[Apollo Cree]

I might try that -- when iu get home. Being in the truck for several days at a time puts a kink in that due to power interruptions.

You could probably do the discharge/charge bit, just not the breakin cycle. That is assuming you can get 4 hours to run a discharge cycle. Even if you couldn't get 4 hours straight to run the complete discharge cycle in one chunk, you could still discharge and charge, but you wouldn't be able to measure the amp hours.

 

[cckw]

You didn't say how old these are that would factor in. Also, for the guys thinking that these are running clear down the GPS won't function at low voltages so that isn't going to be the issue.

 

[Mr Happy]

Also, the published numbers of "1000 cycles" or "1500 cycles" for cell lifetime do not line up exactly with real-world results. If you are putting cells through full charge/discharge cycles (as you probably would with daily use of a GPS) then the cells may wear out within maybe 200 charges or so (just as a rough guess). So if you have had cells in daily rotation for, say, a year or two, you might find they are reaching their natural end of life.

 

[TakeTheActive]

I have about 6 Eneloops that are in constant use in my GPS...

...One set, that I labelled #3, is acting strange. For quite a while, if any of them were charged and I put them in the MH-C9000, within a couple of minutes at most, I would get an indication that they were charged. The rest still do this, but #3 has started showing "HIGH" on the readout of the MH-C9000.

Does this mean #3 are ready to be recycled? Or should I ignore it? Or what?

It probably means that set #3 is ready to move on into its "Semi-Retirement" stage (remotes, clocks, thermometers, etc...).

Please read: Interpreting Maha MH-C9000 Impedance Check Voltage

1. What's the ICV of set #3 in the DISCHARGED / cool (room-temperature) stage?
   .
2. What CHARGE RATE do you use?
   .
3. Are the set #3 cells HOT (over 120°F) at the end of their Charge stage?

BTW, how many (estimated) CYCLEs do you have on these cells? (i.e. Charged DAILY, or every 3rd day, 5 days/week, 50 weeks/year, 1,2,3,? years.)

Try a discharge/charge on the C9000 and see what happens.

If I had time, I'd do

Discharge
Charge
Discharge
Breakin

Record readings at each point...

I wouldn't bother with all that effort ('Been There, Done That!'). Once a cell reaches the HIGH stage, it's pretty much already moved on into "Semi-Retirement". Now, *IF* the user had been MONITORING ICV along with CAPACITY, it would be interesting to see if the ICV proportionately increased as the CAPACITY decreased. :thinking:

...To measure resistance, put in a cell, hit the enter button until it starts charging. The first voltage reading you get will be the cell's internal resistance...

Not true. The first voltage reading is the C9000's IMPEDANCE CHECK VOLTAGE (Measuring Maha MH-C9000 Impedance Check Voltage), measured in VOLTS, which is somewhat PROPORTIONAL to the cell's Internal Resistance. Internal Resistance is measured in OHMS via a different method (2 are listed in my Sig Line LINKs).

...Consensus seems to be that if a NiMH ever says "high" you need to say "bye."

It depends. Many of us get *MANY* more years of service out of HIGH (and even MODE!) cells in low current devices.

...How many cells does the GPS hold at one time? If it's only 2, there's probably not much chance of getting a reverse charge.

It all depends on the 'Voltage Cutoff Point' of the device. Wherever there is more than ONE cell in SERIES in a circuit, the POTENTIAL for a reverse charge exists.

Also, the published numbers of "1000 cycles" or "1500 cycles" for cell lifetime do not line up exactly with real-world results. If you are putting cells through full charge/discharge cycles (as you probably would with daily use of a GPS) then the cells may wear out within maybe 200 charges or so (just as a rough guess). So if you have had cells in daily rotation for, say, a year or two, you might find they are reaching their natural end of life.

Do you really believe that, even if one is REGULARLY USING and PROPERLY maintaining the cells, they may wear out after only ~200 cycles?

I always refer to the example of "Charge a cell WEEKLY for 10 years and that's 520 cycles" and probably the end of the life of the cell TIME-WISE. Thus, I always believed that folks who recharge DAILY (i.e. police, fire, EMT, etc...) *WOULD* get 1000-1500 cycles.

__________________________________________________​

KD5XB,

Just out of curiosity:

• Are you an Amateur Radio Operator?
  *AND*
• Is the truck you're referring to an 18-wheeler?
  *AND*
• Per your avatar, are you also an F-18 pilot?

 

[45/70]

Oh -- what I do is run them until my GPSr gives me the "kow battery" warning, then recharge them.

As Mr Happy suggested in post #8, and I mentioned in my previous post, if you do run them down each time, cells will wear faster and these may very well be at EOL.

There is not much point in doing any charge/discharges on these cells, that is what they've been doing in your GPS all along. It would of course give you a capacity reading, but you already know somethings up with these cells. Further cycling will just wear the cells down. The only chance for recovery (if any) is with break in cycles.

......for the guys thinking that these are running clear down the GPS won't function at low voltages so that isn't going to be the issue.

A cell could still be reverse charged, depending on at what voltage the GPS signals "low battery". I agree though, that only running two cells, this is unlikely.

Dave

 

[KD5XB]

Easy questions first -- yes I'm a ham, yes it's an 18-wheeler, and no I'm not an F-18 pilot. I believe that picture is an F-22 though, but I can't see it whil messaging on my BB.

As for voltages -- I haven't been watching. However I till get usable capacity from #3, it seems to be about 2/3 what it should be.


650 miles todayn GN all.

 

[etc]

Mine are. They are from 2006. I get poor runtime in Garmin GPS 60CSx.