Cycle Testing Observations…

[SilverFox]

Hello Bfg,

The CBA units are an analog load.

I believe on PWM lights, the pulsing comes from the converter board and effects the LED. The load on the battery is constant.

Tom

 

[bfg9000]

Thanks Tom!

I do know that most DC-DC switching regulator designs use either pretty large smoothing caps on both Vin and Vout (with an inductor on Vin) or a high frequency multi-phase design. The PIR1 looks to be single-phase + low frequency (for efficiency) with only a couple small tantalum caps and this thread reveals the caps on the prototype were only filtering power for the microcontroller! Since Willie Hunt's LVR is supposed to be similar (explaining Newbie's delightful contempt of it), I was wondering if anybody has actually measured the battery load profile from the A2 or PIR1?

OTOH I wouldn't expect the Hotdriver, which is a linear regulator, to put anything but a constant load on the battery. But then I only know just enough to get in trouble...

 

[Ergolator]

And I wonder if battery charger/analyzers like the Cadex, BC-900 or MH-C9000 use resistor banks or digitally pulse a load into a fixed resistor.

bfg9000,

A very interesting find...

The BC-900 uses pulse width modulation on both the charge and the discharge functions.

-Jerry

 

[B612]

Does anyone know how the self discharge relates to C or D cell capacity, can the same technology be used in larger cells so could you say a 10 Ah D cell has better self discharge properties than a 12 Ah one.

I've weighed some duracell copper tops purchased at the same time and assumed a capacity of 2000 mAh for the AA cell, then divided it in to the weights for a rough guide.

AA 24.2g 2000 mAh
C 71.5g 5909 mAh
D 145g 11,983 mAh

 

[LuxLuthor]

Tom, I'm glad you quoted this thread in the C9000 discussion. I now understand what happened to my 9 x IB-1400's. Really great work, even if it takes "noobs" like me a lot of thinking to figure it out.

:rock:

 

[Led_Blind]

Does anyone know how the self discharge relates to C or D cell capacity, can the same technology be used in larger cells so could you say a 10 Ah D cell has better self discharge properties than a 12 Ah one.

I've weighed some duracell copper tops purchased at the same time and assumed a capacity of 2000 mAh for the AA cell, then divided it in to the weights for a rough guide.

AA 24.2g 2000 mAh
C 71.5g 5909 mAh
D 145g 11,983 mAh

Remember the casing has a bit of weight, tho when you say copper top you mean Alk right? The only numbers i know for alk's is AA's at c\20 go for about 2700ma. D's go for about 24000ma at the same rate. (i think)

The cell size should have little to no impact on self discharge. Its all about construction and chemistry.

 

[knot]

Tom,


As an exception, they define maximum charging current for HR-4/3AU and HR-4/3FAU as 3.0A.

Is there any flashlight use for this battery size? I bought a used 10.8V 4000mAH MiMH battery pack at a thrift store thinking there would be AA inside.

 

[SilverFox]

Hello Knot,

There is not a standard flashlight that uses those size cells. I believe those are used in RC cars and trucks.

Tom

 

[knot]

I have some other batteries. They are the same length but slightly larger in width - and 4 volts. Flashlight use?

**edit - I think it's a lithium battery since it's the exact same size as 18650

 

[Handlobraesing]

Silverfox, the Duracell simple charger + 4AA pack contains 1800mAh batteries.

 

[mdocod]

this is a really neat test you've done here.

I often find that you set out to find the answer to a question, but during, and after, the testing, more questions come up.-Silverfox

man, is that ever true, lol.


This thread gives me even more compelling evidence to just stick with my vanson "speedy" box. (SLOW charger). I think when need more cells, I'm thinking maybe just using cells that are designated "high current," or "low self drain," or "~2000mAh" because they all seem to go hand-in-hand.

 

[HexiumVII]

Have you guys found the average life of NiMH regardless of cycles? Alkalines have an expiration date of about 5 years. Lithium seems to last almost double. Never seen any expiration date for rechargeables though.

 

[bob_ninja]

Re: Cycle Testing Observations…

Well it is all over the place. I don't even think that battery makers give any guarantees or even estimates.
For example, many of us had to throw away Energizers after a couple of months. People keep talking about a bad batch, but then many other high capacity AAs don't last a full year.
On the other hand there was a thread about NiCds that are 10 and 20 years old. I certainly have some older NiMH AAs that are about 10 years old and still work.

The general rule seems to be that SOME lower capacity AAs that have a robust constructions (maybe like Eneloops) can last many years, over 10 years.
As an example, Toyota Prius has a massive pack consisting of C or D size NiMH cells of a very high quality. Most owners have no problems with them. The cars was introduced about 10 years ago. However, the computer controls SOC to the 20%-80% range to extend their lifespan.

So the right type of cell that us treated well can go 10+ years.

 

[HarveyRich]

Re: Cycle Testing Observations…

This is a very interesting thread, that I've just read for the first time. Thanks Silverfox for starting the discussion with your excellent NiMH tests. I have a question that I don't believe was answered in the posts. It is my understanding that you can extend the life of NiMH batteries which have lost some of their charging cycles by doing a few refresh cycles on them every so often. That is doing several very slow discharges and charges tends to rejuvenate older batteries. I've had this experience using my BC-900 charger. So, wouldn't it be possible to take a battery which has lost some amp-hr and voltage capacity over time and bring it closer to original specs? Would this actually extend the life of the battery over time?

Testing batteries this way would take a lot of time and require at least two to four batteries and then run them for 100-150 cycles, refresh half of them, then run them for another 100 or so cycles, refresh the same ones and keep doing it for 500 or more cycles. The refresh discharge and charge rates would have to be very low--on the order of .1C or .2C, I think.

Harvey

 

[SilverFox]

Re: Cycle Testing Observations…

Hello Harvey,

I actually did that during the second round of testing, and I don't believe it helped at all.

I have tried a variety of methods to try to get the Sanyo cells back to normal performance, but have had no luck.

The main purpose of the slow charge and discharge is to redistribute the electrolyte within the cell, and allow the separator and electrodes to absorb it. Electrolyte starvation is usually a result of storage, or partial charges. I was going through several full cycles each day, so I don't think the slow charge would be beneficial in this case.

I think I just wore them out.

Tom

 

[radellaf]

...thinks a 3GHz machine is better than a 2GHz...Rechargeable cells seem to be following a similar trend. The average person on the street knows little about self-discharge (at least until they go for a camera which has been sitting a few weeks only to find the batteries are dead) or cycle life. However, they are easily wowed by large capacity numbers.

IOW, if we combine the laments here and and on dpreview, we will have 30mpixel pocket cameras with 4Ah batteries that will take a 1000 photos of pure noise for a couple of hours before the batteries die, whether or not the camera is being used.

 

[SilverFox]

Update:

I have started another round of cycle testing.

Since Eneloop cells have become very popular, and there have been some discussions on fast versus slow charging of them, I decided to see what the effect of fast charging on them is.

I have modified the test procedure, a little, to single out the effect of fast charging.

With this test I am charging on the Energizer 15 minute charger, until the fan stops. I then rest the cells for 30 minutes before discharging them. This time, I am using a 1 amp discharge rate. I don't think a 1C discharge rate is hard on a cell, but by limiting the discharge rate to 0.5C, I can minimize this variable.

Other than the change in discharge rate, this test will be very similar to the test using the Titanium 2000 mAh cells.

Does anyone care to venture a guess on what will happen?

I will give you a hint... after the first 25 cycles, the capacity of cycle 25 was about 99% of the capacity of cycle 1.

Tom

 

[Black Rose]

Does anyone care to venture a guess on what will happen?

I will give you a hint... after the first 25 cycles, the capacity of cycle 25 was about 99% of the capacity of cycle 1.

Impressive.

Assuming the cells lose capacity in a consistent fashion (1% every 25 cycles), it would take 500 cycles for them to lose 20% of the cycle 1 capacity.

 

[Anders]

Hello Tom.

Interesting....

I think they will hold their charge until........cycle 160.

Anders

 

[tino_ale]

Can't wait to see the results. The tests you are making is an awesome addition to CPF shared knowledge about batteries :twothumbs

I'm beginning to play with my newly acquired CBA but I don't have the time or equipment to run tests like you do. I'm still very happy of this tool to find out the health of the cells I own and determine how they behave under different loads.