NiMh Battery Shoot Out

[TorchBoy]

That result of 78%, SilverFox, would you immediately retire that cell, or is your limit 80% of initial tested?

 

[Anders]

Hello 1dash1.

Welcome to CPF.

I am sure that your Maha 2700 cells perform a lot better than this DigiMate 2700.

I wasn't suprised to see mediocre results with noname cells, I'll suppose they where cheap?

Anders

 

[SilverFox]

Hello Ian,

When I get new cells, I form them. If they are from a battery manufacturer, I will send them back if they are below the minimum specified by the manufacturers data sheet.

On the other hand, if they are re-labeled cells, I use my forming results to give me an idea of the re-labeling policies of the brand. In this case I can "live" with cells that start out at 80% of their labeled capacity, because the label is not based on reality. However, I expect the cells to be consistent from cell to cell.

I now have a little more work to do in record keeping. I need to record what their capacity actually started at and use that as my reference. When they drop below 80% of their starting capacity, then it is time to retire them.

Tom

 

[1dash1]

Anders:

Thank you! It's a nice community that you have here.

The DigiMate's were $9.99 for a pack of 8. The manufacturer's inflated rating doesn't bother me too much. I'm more concerned about the variability from cell to cell. It doesn't say much for their QC.

 

[1dash1]

Silverfox:

Do you recommend that I match the cells with similar capacities? Do I have to worry about exploding batteries if I don't match them, or is that just a problem with the Li and 123 batteries?

* * * * *

I'd like to check on how fast the batteries self-discharge in a month. Any suggestions on how I can accomplish this with the C9000?

If I understand it right, the "Discharge" mode runs the batteries down to about 1.1v, then stops (I guess this is a safety feature?). Whereas, the "Cycle" mode runs the batteries down to 0.9v, so the two results are not comparable.

* * * * *

I have this growing itch to know more about my batteries, even when they are just sitting there doing nothing, and to purchase more flashlights than I will ever need. Do you have any pharmaceutical recommendations for this affliction? :green:

 

[Black Rose]

I have this growing itch to know more about my batteries, even when they are just sitting there doing nothing, and to purchase more flashlights than I will ever need. Do you have any pharmaceutical recommendations for this affliction? :green:

It's called flashaholicism....it's very difficult to treat.

My recommendation: Charge 4 NiMh cells and check back in the morning

 

[Power Me Up]

I'd like to check on how fast the batteries self-discharge in a month. Any suggestions on how I can accomplish this with the C9000?

If I understand it right, the "Discharge" mode runs the batteries down to about 1.1v, then stops (I guess this is a safety feature?). Whereas, the "Cycle" mode runs the batteries down to 0.9v, so the two results are not comparable.

In my experience with the C9000, the discharge is the same in both modes - in all but the first versions, they discharge down to 0.9V under load.

Things could change with a new revision, but I don't see any reason why it would and I haven't seen any reports of what you're saying...

 

[TorchBoy]

Thanks for that clarification Tom.

If I understand it right, the "Discharge" mode runs the batteries down to about 1.1v, then stops (I guess this is a safety feature?). Whereas, the "Cycle" mode runs the batteries down to 0.9v, so the two results are not comparable.

The Discharge mode on the MH-C9000 runs the batteries down to 0.9V, as does the discharge part of the other modes (where applicable - obviously the Charge mode doesn't have a discharge part).

 

[1dash1]

Torch Boy, Power Me Up:

Thanks! I'll keep a closer eye on the discharge cycle, the next time I use it.

========================================

Preliminary results on BTY 1200MAH AAA NiMH batteries:
Under 400 mAH for sample of four tested batteries.

I'll post the results after the second cycle is done, but it's going to be ugly.

:toilet:

 

[SilverFox]

Hello 1dash1,

Yes, I would recommend matching cells as best you can in multi cell applications.

With mismatched cells, one cell will empty first, and runs a risk of being reversed charged by the other cell(s). This will ruin the cell. With NiMh, you don't have to worry about "rapid venting with flame" during use, but you could have a venting incident during charging. On top of that, if you use mismatched cells your performance will suffer.

:devil: As far as a pharmaceutical recommendation goes... I usually find that a good strong cup of coffee goes a long way to clearing my head... :devil:

Tom

 

[Black Rose]

:devil: As far as a pharmaceutical recommendation goes... I usually find that a good strong cup of coffee goes a long way to clearing my head... :devil:

Ummm....Isn't there a post on here somewhere where you said that you usually have 10 chargers on the go at any one time? Might need a stronger cup of coffee

P.S. Love the Battery Operated Moderator title

 

[Black Rose]

Another set of 4 ROV Hybrid AAA cells finished the discharge portion of the Break-In cycle on my MH-C9000 this morning. Capacities reported were:

754, 769, 777, 735 mAh

Cell #3 is the best result I have achieved so far with the ROV Hybrid AAA cells.
Cell #4 is the worst.

 

[1dash1]

I just discharged a brand new pack of Kodak 2100 mah hybrid AA's last night. When I looked at the results this morning, they were all in the 1.1v range. That's not right. So, I ran the discharge mode again. Within a few minutes they drew down to 0.9v and terminated. Aha!

The values shown on the C9000 display after the discharge mode are energy discharged (mAH), elapsed time that it took to discharge (minutes), and voltage. The first two values are fixed upon completion of the discharge mode. The last value is real-time. I had mistakenly thought that all three values were fixed upon completion.

So, I learned two things. It really does discharge down to 0.9v and learn to write things down BEFORE acting. (I lost all the data to check how good the batteries were fresh out of the package, when I ran the second discharge test.)

 

[TorchBoy]

1dash1, the 1.1V is the resting voltage while the 0.9V is the voltage under load. Normally cells will bounce back to around 1.2V unloaded after a C9000 discharge.

 

[1dash1]

Okay, the results are in on the BTY 1200 mAH AAA NiMH batteries:

A set of four batteries were selected randomly for testing from the 12 batteries originally purchased. All batteries were in original plastic wrap, prior to testing. The batteries were conditioned using the "Break-In" mode, with the following results:

Btty #1 ..... Btty #2 ..... Btty #3 ..... Btty #4
290 ........... 304 ........... 286 ........... 281 (mAH)

Batteries were subsequently discharged at 0.5 mA, rested for 2 hours, then tested in the "Cycle" mode (2 cycles, discharged at 0.5 mA, charged at 0.5 mA). The test results were as follows:

Btty #1 ..... Btty #2 ..... Btty #3 ..... Btty #4
286 ........... 295 ........... 278 ........... 283 (mAH) CYCLE No. 1
284 ........... 291 ........... 275 ........... 281 (mAH) CYCLE No. 2

The results were less than 25% of the purported 1200 mAH battery capacity. :thumbsdow

I contacted the vendor and asked for instructions for getting a refund.

 

[MattK]

1dash1 - not that I think those cells are 1200mAh but a .5mAh discharge rate isn't appropriate for a claimed 1200mAh AAA cell. A Discharge rate of .2C, or .24Ah would have been the correct choice by which to rate the cells by as that is the IEC standard which is used by battery mfrs.

 

[Bones]

...
The results were less than 25% of the purported 1200 mAH battery capacity.

I contacted the vendor and asked for instructions for getting a refund.

You may be dealing with counterfeit cells 1dash1.

Although I could locate a number of online sources for a BTY 1000mAh AAA cell, I could only find a few vendors on eBay selling a 1200mAh version.

Images of both the 1200mAh cell and the 1000mAh cell for comparison:



There is even one vendor on eBay, Broadway.HK.Shop, who is selling both versions.

Conversely, UK.Battery.Co, sells only the 1000mAh version.

 

[Mr Happy]

1dash1 - not that I think those cells are 1200mAh but a .5mAh discharge rate isn't appropriate for a claimed 1200mAh AAA cell. A Discharge rate of .2C, or .24mA would have been the correct choice by which to rate the cells by as that is the IEC standard which is used by battery mfrs.

I suspect 0.5 mA is a typo and it was in fact 500 mA. Discharging 300 mAh at 0.5 mA would take about 600 hours.

 

[1dash1]

MattK:

I've been running tests on 2700 mAH AA's. I forgot to change the protocol for the AAA's. Newbie mistake.

... or early signs of Alzheimers. :tinfoil:

Nonetheless, I doubt if performance will pick up very much if I change the cycle protocol. After all, the C9000 automatically set the 0.2c and 0.1c rates during the break-in mode (the 1200 mAH capacity was properly inputted) and look at those results by comparison.
.
.
P.S. I originally planned on running tests on all 12 batteries purchased. However, the initial results are so bad, I think testing the remaining batteries would be a waste of time.
.
.

 

[1dash1]

Mr. Happy:

Good catch! Indeed, the cycle mode was run at 0.5 A, not 0.5 mA.