NiMH Battery Life

[Patch42]

In August I bought two sets of Ansmann 2850mAh NiMH batteries from Thomas Distributing. These have been used exclusively in my GRE PSR-500. They have been charged exclusively in a Maha C9000 charger. I put both sets through the "break in" cycle on the charger. All of the batteries initially indicated a capacity of close to 2900mAh.

I generally run a set of batteries in the scanner until the low battery indication comes on. They are then recharged in the C9000. I've tried various charge rates, but generally have stuck with 500mA.

The scanner sees a fair bit of use so each set of batteries has been recharged once or twice a week for the last seven months.

Over the last couple months I've seen the capacities of the batteries start to drop. For the first several months they regularly took close to the full rated capacity to recharge them. Lately, even if I fully discharge them in the charger first, they take more like 2600mAh or less before the charger says they're full. I just ran one set through another "break in" cycle and all the batteries showed a capacity of 2600mAh or slightly less.

I realize the capacity of the batteries will decline over time, but I was rather expecting a bit more time before they would start to show a clearly noticeable reduction. I checked the Ansmann web site but could find no email address or contact point for anything other than OEM sales. I emailed Thomas asking if they could suggest something. To their great credit, they quickly responded that I should return the batteries and they would replace them. Problem is, I'm not 100% certain they're defective. This may well be the normal aging profile for these batteries.

I'm wondering what experiences others here have had along these lines. How many charge cycles have your batteries been through before they start to show a decline in capacity? (I should note here that I have not noticed a clear decline in real life performance. The batteries still power the scanner for what seems a perfectly reasonable number of hours. If not for the digital readout on the charger I wouldn't have noticed any decline.) Have you noticed any specific usage pattern that helps to delay the capacity decline? Maybe charging them every day rather than waiting until they've been nearly depleted?

 

[davidmc36]

I believe the documents that I have read reccomend recharging NiMH when they fall to about one volt, not much less, which is about where the low battery warning should trip in your scanner. What you have described is about 10% decline after 20 to 30 charges. I have seen similar performance where they fall off a bit initially but will likely stay at or near that capacity for quite a while before they get much worse. I guess if they are willing to replace them then go for it. I bet you are getting the best performance and longevity by using a good charger like that.

 

[gmclam]

NiMH Batteries

... They have been charged exclusively in a Maha C9000 charger. ... All of the batteries initially indicated a capacity of close to 2900mAh. I generally run a set of batteries in the scanner until the low battery indication comes on. They are then recharged in the C9000. I've tried various charge rates, but generally have stuck with 500mA.

Lots and lots of thoughts here. I've found higher capacity batteries are more trouble than lower capacity batteries. My feeling is that you should not "fully" discharge NiMH batteries before recharging them. Why not only discharge them 50%, then recharge? You should make sure the low battery voltage in your scanner is set correctly. I've also heard that NiMH batteries should not be allowed to go below 1.0v (or no less 0.9v).

Next is charging. I know the C9000 defaults to 1AMP of current, but why be more harsh on the batteries than need-be, unless 500ma is what is specified by the manufacturer of the specific battery you are using? My scanners charge at 150ma and the C9000 only goes down to 200ma. From the standpoint of battery life, that seems like a better charge rate.

Over the last couple months I've seen the capacities of the batteries start to drop.

Somewhere they'll rate a battery for how many cycles it will last. I usually see numbers like 1000 cycles. What I have not seen is when the capacity starts to drop, or what percentage of capacity the battery has at that 1000th cycle. If you're fully discharging them and re-charging them daily; you'd be at about cycle 250 after several months. That's 1/4 of the battery's life in terms of cycles (which may be different for the exact battery you're using).

How many charge cycles have your batteries been through before they start to show a decline in capacity?

It depends on the (brand of) battery, the amount used (how far discharged) and the rate of recharge.

Have you noticed any specific usage pattern that helps to delay the capacity decline? Maybe charging them every day rather than waiting until they've been nearly depleted?

Don't fully discharge. Recharge more slowly. Life is number of charge cycles.

Side note: I've had quite a dialog with an engineer at Maha regarding their C9000 charger and ultimately their PowerEx batteries. While the PowerEx batteries do a good job, they are really suited more for devices with a higher drain than typical scanners. A lot of things about the C9000 makes it more like a device to sell more batteries than it does a charger per se. Specifically it refuses to charge some batteries that I am still using months later and that display you refer to makes you think your batteries are not what they were when new (which is true); and has caused you to raise these questions that otherwise would not have happened.

 

[Patch42]

Why not only discharge them 50%, then recharge? You should make sure the low battery voltage in your scanner is set correctly. I've also heard that NiMH batteries should not be allowed to go below 1.0v (or no less 0.9v).

Running them until the scanner indicates they're low is more a matter of convenience than anything else. I suppose there's no reason I couldn't simply change them every day or two, but that would double or triple the recharge cycles in any given period. I've never been sure if that would be better or worse for the life of the batteries.

The scanner actually signals low battery and eventually shuts itself off long before the batteries get close to 1.0V. I've fully discharged the batteries in the charger on occasion and it always shows them at 1.1V or greater right after being removed from the scanner. I was considering changing the scanner settings to allow them to discharge further before shutting down. (Or just switching to the NiCad setting which allows a deeper discharge.)

Next is charging. I know the C9000 defaults to 1AMP of current, but why be more harsh on the batteries than need-be, unless 500ma is what is specified by the manufacturer of the specific battery you are using? My scanners charge at 150ma and the C9000 only goes down to 200ma. From the standpoint of battery life, that seems like a better charge rate.

I read somewhere that charging at less than 0.1C is not advisable, though I believe that had more to do with the charger accurately determining when the batteries are full, something that does not seem to be a problem with the C9000. Still, it doesn't seem that charging at 0.2C would do much in the way of damage to them. The batteries aren't even what I'd call warm when charging at 500mA. Just barely above room temperature, if even that.

Somewhere they'll rate a battery for how many cycles it will last. I usually see numbers like 1000 cycles.

This raises a question I've never seen adequately answered. Is that 1000 cycles from full to empty (say 1.0V) and back to full? And would you get the same 1000 cycles and no more if the batteries were only run down to 50% and then recharged? Or would you get twice as many cycles doing it that way? Is the limit strictly based on how many times they are charged or is it a function of how much total energy is passed through the battery?

What I have not seen is when the capacity starts to drop, or what percentage of capacity the battery has at that 1000th cycle.

I suppose, ultimately, that is my question.

If you're fully discharging them and re-charging them daily; you'd be at about cycle 250 after several months. That's 1/4 of the battery's life in terms of cycles (which may be different for the exact battery you're using).

It varies somewhat depending on how much I'm using the scanner, but I generally get at least two days' worth of use from a single charge, sometimes three or four. It's a bit of a guess, I'd say on average each set has been charged about once a week. I'm pretty sure I'm still somewhere south of 50 charge cycles on each set. I'd guess more like 5-10% of the expected life, assuming the 500-1000 charge cycles they always mention is correct.

A lot of things about the C9000 makes it more like a device to sell more batteries than it does a charger per se. Specifically it refuses to charge some batteries that I am still using months later and that display you refer to makes you think your batteries are not what they were when new (which is true); and has caused you to raise these questions that otherwise would not have happened.

To a great extent I believe you are correct about the display. On the other hand, the display, if correct, and I have no reason to doubt it, is simply keeping me informed of the situation. I'm not sure I buy into the ignorance is bliss thing.

I thought the BatterySpace batteries I was using before were decent enough. Then I got the C9000 and learned the actual capacity of the batteries wasn't remotely close to the claimed capacity, even when brand new and sent through multiple "break in" cycles. They claimed 2600mAh capacity, but I never saw anything over 2100mAh, with a fairly rapid reduction to about 1800mAh.

As to the C9000 refusing to charge some batteries, that is a bit of a problem. I have another charger I use when that situation arises. Odd thing is, when I got that charger, it refused to charge some batteries that the stupid timed charger I bought ages ago at Radio Shack would bring back to life without difficulty. I guess it's all relative.

 

[davidmc36]

The scanner actually signals low battery and eventually shuts itself off long before the batteries get close to 1.0V. I've fully discharged the batteries in the charger on occasion and it always shows them at 1.1V or greater right after being removed from the scanner.

I suspect that while under load in the scanner just before they shut of they are likely somewhere near 0.9 or 1.0 volt. When you take them out and put them on a meter they recover a bit, and the meter is not putting anywhere close to the same load on them when it checks the voltage.

Very nice to hear some detailed experience about using NiMH's and the C9000 charger. I just recently got one with 8 Powerex's. I like how the C9000 brought some AAA's back to life that I use in my cordless mouse. Seemed to have doubled their life.

 

[Hoofy]

I use theMAHA powerx 2500's and have had only one failure since about 2006. I run them in a pro 96 and run them until they are dead or so low that they shut the scanner down. I'm not sure which MAHA charger I have but I run the batteries through the conditioner feature every once in a while.

I also use everready and some kodak 2500 also with good results. I also use the everready slow charger about every forth time and I think that helps. In fact that's the only way a couple of them will charge.

 

[gmclam]

NiMH, C9000 & Battery Life

... I suppose there's no reason I couldn't simply change them every day or two, but that would double or triple the recharge cycles in any given period. I've never been sure if that would be better or worse for the life of the batteries.

I've been trying to pin down some (battery) engineers on this question with no luck. So I'm running several sets of batteries all differently to see what I think. Of all the basic things you can do to them, overcharging is the worst. I think cycles vs deep discharge depend on the batteries, charger and recharge rate.

I was considering changing the scanner settings to allow them to discharge further before shutting down.

I've been told not to do that with the PowerEx NiMH batteries. When the batteries are new, they rebound ok. But after they age a bit, they might not want to take a charge after being discharged too much - especially in the C9000.

I read somewhere that charging at less than 0.1C is not advisable, though I believe that had more to do with the charger accurately determining when the batteries are full, something that does not seem to be a problem with the C9000.

Yup that's a C9000 recommendation. They told me to recharge the PowerEx 2700s at 900ma because the C9000 has trouble determining end of charge at a lower rate. When I pressed the issue that I felt it was being more harsh on the batteries than need be, the reply was ' .. well the thermal sensor of the C9000 will terminate charge anyway.'. I feel there is a lot more to this and those with the knowlege are reluctant to share it.

Still, it doesn't seem that charging at 0.2C would do much in the way of damage to them. The batteries aren't even what I'd call warm when charging at 500mA. Just barely above room temperature, if even that.

How about after the batteries have aged? (500th cycle)

This raises a question I've never seen adequately answered. Is that 1000 cycles from full to empty (say 1.0V) and back to full? And would you get the same 1000 cycles and no more if the batteries were only run down to 50% and then recharged? Or would you get twice as many cycles doing it that way? Is the limit strictly based on how many times they are charged or is it a function of how much total energy is passed through the battery?

All great questions that I think lots of us would like answered.

I'm pretty sure I'm still somewhere south of 50 charge cycles on each set. I'd guess more like 5-10% of the expected life, assuming the 500-1000 charge cycles they always mention is correct.

So the million dollar question here is: "is the capacity drop you're seeing normal with so few charge cycles?". Or would the batteries be better off if you only discharged them 50% as much and recharged them twice as often? Or would the batteries be better off if you recharged them at 200ma instead of 500ma?

To a great extent I believe you are correct about the display. On the other hand, the display, if correct, and I have no reason to doubt it, is simply keeping me informed of the situation. I'm not sure I buy into the ignorance is bliss thing.

I'm not saying the display is a battery seller - I am saying that the charger is a battery seller. If someone only has the C9000 to recharge batteries, what do you do when the charger refuses to charge them? Buy more batteries.

I thought the BatterySpace batteries I was using before were decent enough. Then I got the C9000 and learned the actual capacity of the batteries ... They claimed 2600mAh capacity, but I never saw anything over 2100mAh, with a fairly rapid reduction to about 1800mAh.

This is something the C9000 is good at - rating your batteries (when their voltages are not "too high").

 

[Patch42]

I'm not saying the display is a battery seller - I am saying that the charger is a battery seller. If someone only has the C9000 to recharge batteries, what do you do when the charger refuses to charge them? Buy more batteries.

With my better quality, newer batteries I've never had a problem. The only ones that give me that "High Voltage" issue are lesser capacity ones that are probably five or six years old.

I've had limited success with "jump starting" these batteries by cranking up the charge rate. I'll put them in the charger at the max rate. They'll fairly quickly indicate "HI". Then I do it again, and again. Sometimes it forces enough juice into them that they'll then charge normally. It isn't always successful, but it has worked a few times.

It's probably not good for the overall life of the battery, but if the alternative is to throw it away then there's little lost in the attempt.

 

[N1SQB]

For what its worth!

My Maha MH-C801D Charger allows for Deep battery conditioning which I do on all my batteries once a month.In case you are not familiar with conditioning, the batteries are cycle charged,discharged, then recharged. It restores them so they charge better and last longer, to a degree of cource. I use the Sanyo 2700 Mah ones. I have had my oldest set of 4 @ 2 years now. Obviously not like when they were new but still they last me quite a long time between charges.

Manny

 

[RayAir]

I got some NiMH 2600 mAh batteries in my Pro-92 and my Kenwood TH-K2. They last quite a while in the PRO-92, but the battery life blows in my TH-K2 and I don't TX very much (mostly used as a receiver).

 

[methusaleh]

Very interesting thread! I use NiMHs in a lot of my hobbies so I find this stuff intriguing.

Anyone familiar with Sanyo Enerloop batteries? Why do they seem to be touted as the next great thing in the battery world? I've seen them at specialty camera shops and online, but hesitate to try them without having a good reason.

 

[rvictor]

Very interesting thread! I use NiMHs in a lot of my hobbies so I find this stuff intriguing.

Anyone familiar with Sanyo Enerloop batteries? Why do they seem to be touted as the next great thing in the battery world? I've seen them at specialty camera shops and online, but hesitate to try them without having a good reason.

Their advantage is that they self discharge at a much slower rate than previous NiMH cells. Therefore, longer shelf life and they can be sold with a partial charge already in place. Downside is that, so far, they are available only in somewhat lower capacities than the best "regular" cells.

Dick

 

[icom1020]

Has anyone used the break in cycle to restore or boost the capacity in a set of old batteries? I just purchased the C9000 and only used this procedure with new batteries. I believe it says in the manual that if a HIGH reading occurs, one could try the break in mode.

 

[rbm]

See the excerpt below from the Maha C-9000 instructions. It's worked for me with some older Energizer NiMH that I used to have. Refresh them every 10 cycles or so. If you see the capacity drop off, run the Refresh cycle once or twice and they should come back up.

As far as Sanyo LSD Eneloops go, I've been using them for the last couple years and never had a failure. (I have around 80 of my own and another 40 I've given to my kids.) For 'C' and 'D' size cells I use Accupower LSD cells and like them also. The nice thing about LSD cells is you can use them in devices and not have to worry about them running down on the shelf for a year or more.

Even though the 'AA' Eneloops are only rated at 2000 mAH they outperform many of the older style NiMH batteries that are rated at higher capacity. I run my BCD396T for a week per charge. That's 6 or 7 days each week, 1hour+ travel time round trip.

By the way, I use the default 1,000 ma charge/500 ma discharge for my AA's.

Rich



Maha recommends:

Refresh & Analyze Mode
• First recharges the battery, rest for one hour, discharge, rest, then
recharges again. Charging and discharging rates are programmable.
• Reports the discharge capacity at the end of the cycle.
• Useful when the battery capacity needs to be determined. Also
useful for battery with degraded performance.
• Recommended once every ten cycles for NiMH batteries.

http://www.thomas-distributing.com/maha/mh-c9000-charger/MHC9000_MANUAL.pdf

Edit: If you haven't been to CandlePowerForums, you may find it addictive. Be forewarned you could wind up spending LOTS of money on Flashlights/Batteries/Chargers etc.
It's an excellent source of information. Here's a link to start with.

Flashlight Electronics - Batteries Included - Threads of Interest - CandlePowerForums

 

[icom1020]

I'll try that, I have an set of Duracells that refuse to charge in the C9000 and the cheapo Ray O Vac chargers.

With my better quality, newer batteries I've never had a problem. The only ones that give me that "High Voltage" issue are lesser capacity ones that are probably five or six years old.

I've had limited success with "jump starting" these batteries by cranking up the charge rate. I'll put them in the charger at the max rate. They'll fairly quickly indicate "HI". Then I do it again, and again. Sometimes it forces enough juice into them that they'll then charge normally. It isn't always successful, but it has worked a few times.

It's probably not good for the overall life of the battery, but if the alternative is to throw it away then there's little lost in the attempt.

 

[gmclam]

I'll try that, I have an set of Duracells that refuse to charge in the C9000 and the cheapo Ray O Vac chargers.

I have had several different models of DuraCell and Energizers that the C9000 would not charge. I wondered if it would handle the PowerEx batteries differently. Now I have PowerEx batteries (about 6 months old) that it will not charge. Meanwhile I am charging the PowerEx batteries elsewhere and using them daily with no problems.

 

[icom1020]

Some of the 'smart chargers" are finicky. Maybe too smart but the break in feature could be the best part of them. I had a Emerging Power $70 travel charger that would take forever to charge a set or refuse to at all. The Duracells are crap. I think the advice of purchasing a battery around 2000ma makes sense.

 

[Patch42]

Has anyone used the break in cycle to restore or boost the capacity in a set of old batteries? I just purchased the C9000 and only used this procedure with new batteries. I believe it says in the manual that if a HIGH reading occurs, one could try the break in mode.

I've tried that with the Ansmann batteries that have been losing capacity. It made no difference. They're down to ~2500mAh from 2850+mAh and nothing I've tried gets them back up to where they should be.

My only issue with the break-in cycle is how long it takes. It's at least two full days for each set of batteries. That's a long time to tie up the charger, and a complete pain when you have several sets to break in.

 

[GTO_04]

Edit: If you haven't been to CandlePowerForums, you may find it addictive. Be forewarned you could wind up spending LOTS of money on Flashlights/Batteries/Chargers etc.
It's an excellent source of information. Here's a link to start with.

Flashlight Electronics - Batteries Included - Threads of Interest - CandlePowerForums

Too late. I am already addicted, and my flashlight collection is growing! At least they are cheaper
(for the most part) than scanners.

GTO_04

 

[thewenk]

too Late. I Am Already Addicted, And My Flashlight Collection Is Growing! At Least They Are Cheaper
(for The Most Part) Than Scanners.

Gto_04

+1

Dave