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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 02-06-2012, 09:25 PM   #1
Turbine
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Unhappy Cycling Sanyo Eneloop NiMh batteries

Having recently purchased a new 9.6v, 2000mah Sanyo Eneloop NiMh battery, I gave it two timed "forming" cycles, then several charge/discharge cycles with a Sigma 2 EQ charger/cycler to establish it's useful capacity.

The maximum recorded capacity after cycling was 1886mah, ie, well below the 2000mah on the label.

I understand that new batteries do require several cycles to achieve their maximum performance, but even after this, I am still well short of the manufacturers stated value.

Can the "lost" 100mah be recovered in any way, or is this a common experience?
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Old 02-06-2012, 10:24 PM   #2
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what was your drain rate? These aren't high performance cells, What are you planning on using them in?

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Old 02-06-2012, 11:46 PM   #3
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Capacity can be a moving target with NiXX depending on how charged, how long they sat between charges, AND (important) the discharge rate. Too high a D/C rate and you get low results. Low D/C rate and you see more capacity.

What discharge current should you use?
Most manufacturers (Sanyo and Panasonic for example) measure capacity at a discharge rate of C/5, which is called the five hour discharge rate. For example, a typical AA cell of 600mAh capacity would have a 'C' of 600mA and a C/5 of 120mA. Others measure capacity at a discharge rate of C. Like all batteries, the higher the discharge current, the less the available capacity. For example, the available capacity with a discharge at C/5 is about 10% more than that with a discharge at the C rate.

Another possible discharge current would be the actual current drain of the battery while being used. I recommend that you discharge at between C and C/2.

Many high capacity batteries if used at a D/C of C or even C/2 will fall flat on their electrical face.

Eneloops generally get close to their rated capacity, but rarely over in the tests I've seen. More important is how they stack up for the real world use you expect to get out of them.
I suspect that's for a TX pack so it'll work fine as the D/C rate is very low (probably C/10 or lower) and the LSD character is very important.

BTW-Just to make SURE, with a PACK you ABSOLUTELY DO NOT WANT TO D/C BELOW 1 v/cell. To do so risks cell reversal and permanent damage.

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Old 02-07-2012, 12:57 AM   #4
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Originally Posted by Turbine View Post
Having recently purchased a new 9.6v, 2000mah Sanyo Eneloop NiMh battery, I gave it two timed "forming" cycles, then several charge/discharge cycles with a Sigma 2 EQ charger/cycler to establish it's useful capacity.

The maximum recorded capacity after cycling was 1886mah, ie, well below the 2000mah on the label.

I understand that new batteries do require several cycles to achieve their maximum performance, but even after this, I am still well short of the manufacturers stated value.

Can the "lost" 100mah be recovered in any way, or is this a common experience?

Just thinking, let's see, you've got a battery rated at 2000 Mah, and it checks out at 1886 Mah. So that is 2000 minus 1886 divided by 2000 or it's about 5.7 percent short of its rated capacity.

That's assuming you're measuring milliampere hours with a meter that's accurate to ten times better than 5% or 0.5% accuracy. Not many low cost multimeters are accurate to 1/2 percent. I've got a Fluke 87V meter accurate to 0.2% on DC current, and that's a $350 meter.

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Old 02-07-2012, 01:51 PM   #5
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To compare to specifications, you must discharge down to 0.9 volts/cell at a rate not greater than 0.33C. You will get a lower reading if the discharge rate is higher or if you stop the discharge at a voltage higher than 0.9 volts/cell.
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Old 02-11-2012, 03:25 PM   #6
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Unhappy Cycling Sanyo Eneloop NiMh batteries

Many thanks for your responses and advice.
The battery in question is to replace nicads supplied with a Futaba 9C transmitter, so it is a low drain applicaton.
Using the Sigma2 EQ in cycle mode. with the default delta peak setting, and lowest discharge voltage of 1.0v/cell, I charged at 200ma (C/10) and discharged at 500ma, - not too far off the C/5 recommendation.
I really had to push it to reach the quoted 1886mah capacity. I would expect this reduction (from 2000mah) in an ageing battery, not a brand new one!! Anyway, I will keep persevering.

Any thoughts on the Pro-peak Sigma2 EQ and the other very similar computerised charge/discharge/cyclers? My experience with other Pro-peak products has been good so far.
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Old 02-11-2012, 05:38 PM   #7
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Originally Posted by Turbine View Post
Many thanks for your responses and advice.
The battery in question is to replace nicads supplied with a Futaba 9C transmitter, so it is a low drain applicaton.
Using the Sigma2 EQ in cycle mode. with the default delta peak setting, and lowest discharge voltage of 1.0v/cell, I charged at 200ma (C/10) and discharged at 500ma, - not too far off the C/5 recommendation.
I really had to push it to reach the quoted 1886mah capacity. I would expect this reduction (from 2000mah) in an ageing battery, not a brand new one!! Anyway, I will keep persevering.

Any thoughts on the Pro-peak Sigma2 EQ and the other very similar computerised charge/discharge/cyclers? My experience with other Pro-peak products has been good so far.
H'mmm
After a discharge test, you might try charging that battery with a simple 1/10 C rate of 200 milliamperes for 15 hours, and re-run the battery cycle test. Could it be your charger is shutting off before it actually fully charges the battery

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Old 02-12-2012, 07:55 PM   #8
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Factory data

http://www.eneloop.info/home/perform.../capacity.html


The last 8 Eneloops which I tested before use as a DX7 Transmitter battery were cycled in a Maha C9000 which is a 4 channel channel (slot) charger so each cell is tested indivualy. Discharge termination is 1.0V

As received Discharged at 500 mA rate 1375-1385

Charged at 1,000 mA and discharged at 500 ma 1851 / 1966 / 1981 / 1923 / 1881 / 1893 / 1875 / 1884

Charles
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Old 02-13-2012, 01:15 PM   #9
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Smile Cycling Eneloops

Thanks Dennis and Charles for your advice and information.

I will try a few more cycles as you recommend, however the graphs in Charles link to Sanyo are very revealing.

There are several variables in all of this, with each one providing a different answer!!!

However, this has been a useful and informative learning exercise.

Thanks again for taking time to help and advise.

Eric
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Old 02-13-2012, 03:57 PM   #10
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Before everyone went LiPo .... it was well known that charging of NiXX would be better if charger dropped to a trickle charge when it reaches "charge" cut-off when using a higher than 1/10th rate.

Most chargers are set to be "safe" on the cut off and as soon as the delta peak blips - OFF it goes. Decent chargers in past didn't actually stop - they dropped to a very low 50mA or similar trickle charge.

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Old 02-13-2012, 04:35 PM   #11
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I use Eneloops in my JR XP9303. Fully charged I get about 11.2v reading on the TX display, but it quickly drops off to 10.3-10.5v. But once it gets there it usually stays there for a good 2 months with me flying every weekend and having the radio on a lot over the 2 months for testing setups.

I love my Eneloops!

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Old 02-22-2012, 05:34 PM   #12
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Smile Cycling Sanyo Eneloop NiMh batteries

I acted on Dennis' advice and cycled twice with a Mainlink Digiliser 2000 - a high quality nicd/nimh cycler.

This does not use delta peak detection, but simply gives a timed charge at 220ma for 10.5 hours, then discharge at about 250-450ma (not sure of exact rate).

The results at 1971mah and 1988mah were very close to the 2000mah stated capacity of the battery and well above the capacities realised by cycling using delta peak detection.

It appears that (in my experience) with a delta peak charger, the battery does not receive a full charge, unless the delta peak detection setting is at a figure above what is the default or recommended setting. (not advisable as the battery may then be overcharged.)

My only concern is that some capacity results achieved after cycling with delta peak, may lead some to believe that otherwise perfectly good batteries may be below par, and less than satisfactory for RC use.

Any further comments or advice?
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Old 02-22-2012, 05:47 PM   #13
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Originally Posted by Turbine View Post
I acted on Dennis' advice and cycled twice with a Mainlink Digiliser 2000 - a high quality nicd/nimh cycler.

This does not use delta peak detection, but simply gives a timed charge at 220ma for 10.5 hours, then discharge at about 250-450ma (not sure of exact rate).

The results at 1971mah and 1988mah were very close to the 2000mah stated capacity of the battery and well above the capacities realised by cycling using delta peak detection.

It appears that (in my experience) with a delta peak charger, the battery does not receive a full charge, unless the delta peak detection setting is at a figure above what is the default or recommended setting. (not advisable as the battery may then be overcharged.)

My only concern is that some capacity results achieved after cycling with delta peak, may lead some to believe that otherwise perfectly good batteries may be below par, and less than satisfactory for RC use.

Any further comments or advice?
That is good information! One reason why I like those A123 cells. By actual test using the same Astroflight wattmeter for both charge and discharge testing, it takes about 2 or 3 percent more to recharge than what was taken out during a discharge test.

LiPos are likely very similar.

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