NiMh battery life (cycles)

[Christophe]

Nice guys from forum from the Nicd.net site, cyclic discharge charge tests were carried out on several NiMh batteries of varying capacity. It's this way! Problem is an old (finally ... 2007) subject and a lot of attachments are HS (when I insist on using our host of images and files it is for this reason).

But I managed to find there the datasheet (link HS but findable in google) of the manufacturer Rayovak on NiMh of 2100 mAh which includes:

a) 4 discharge voltage curves according to the amperage
b) 2 load voltage curves 1 fast to 1C and 1 slow to 0.1C (C = current corresponding to the capacity is 1A for an 1000mAh battery)
c) And especially: 1 curve of life cycle in charge / discharge at rated intensity (= 1C)

Charge: 2100 mA to -dv = 8 mv
Rest: 30 Minutes
Discharging: 2100 mA to 0.90V
Temperature: 20 ° C

I assume ordinates are capacity ahs?

https://www.econologie.info/share/partag ... 4KbMUe.pdf

And here is the equivalent at Varta for AA 1800mAh:

https://www.econologie.info/share/partag ... x01YXD.pdf


Conclusion: not to hold at least 300 charge / discharge cycles is therefore not linked to a bad technology or a false advertisement but a bad use of the batteries (bad storage, too strong load, too deep discharge ... etc etc). ..

[Christophe]

And here is a copied / glued one of the nice tester of the forum from the NiCd site:

New Batteries to come (in addition to AAA GP950 / 1000 and Varta 1000mAh, and AA Uniross 2500):

-Yuasa 2700mAh (made in china)
-Energizer 2650
-Sanyo 2700 (true or false I do not know), it will be those of vincebdx

Accus out of the race (summary):

-Varta Photo 2500mAh No. 1 after 115 cycles (980mAh capacity), cause charge considered HS (less than 60% of nominal capacity)
-Varta Photo 2500mAh 2 number after 108 cycles (1026mAh capacity), same

-Varta Professional 2700 n ° 1 after 76 cycles (capacity 2348mAh), plastic cause all melted, and also after that as soon as one tries to charge them they "disconnect" as would do Varta 15 ".
-Varta Professional 2700 No. 2 after 105 cycles (1851mAh capacity), same reasons

-Sony stamina 2500mAh n ° 1 after 140 cycles (1568mAh), because the charger refused them (internal resistance too high), and capacity <60% C nominal
-Sony stamina 2500mAh No. 2 after 118 cycles (1370mAh), same reasons.

-Microbatt Vvpow 800mAh after 96 cycles (713mAh), because the charger refused it regardless of the charging current (internal resistance too high)

-Lacrosse AAA 700mAh after 161 cycles (646mAh). It could have gone on for a long time but the deltaV is messy and the loader does not detect anything anymore at 500mA. The battery was overloaded, it took over 8500mAh before I noticed it. Its capacity is still good but its end of charge is no longer detected. Like what the Lacrosse batteries are finally not so shitty ... Load currents 500mA and discharge 400mA for this battery (did not support the load 700mA)

-Camelion "1100", after 105 cycles (807mAh) Refused by the charger, internal resistance too high.

For the moment I can say that Microbatt batteries should be avoided (at least the "general public" models ... the others of the pack are sometimes refused by the charger for too high internal resistance, however they only have a few cycles. .. and in addition they are expensive!
And the Varta of course

And here are 2 curves of their measurements (capacity / cycle number):





The difference with the curves of the manufacturers is quite important, I think that it comes from the fact that the manufacturers perfectly regulate the T ° during the tests (air conditioning) and that they take perhaps the best tests that they made (can be that some series of batteries are better than others, like for PV panels?) ... nicd testers no.

We will appreciate the consistency and reliability of the Sanyo ... as for the Varta I would say we do not become 1 number (or almost) by chance if you know what I mean

On the basis of all this, I would say that we can therefore reasonably rely on a life cycle number of 300-400 under conditions of current use, that is to say without mistreating the batteries and considering that the end of life is not reached for 65% of the initial capacity but for 50%, and a 2700 mAh battery at 50% capacity is still better than a 1100 mAh battery no?

From there we already have a basis of work to compare with a stack.

[Christophe]

An important remark ...

The fact is that 300 at 400 cycles for most users, it's HUGE!

It's more than 10 years of service life. Indeed; 40 cycles a year it is a recharge every 9 days !!

Personally I am very very far from this on our batteries, I am closer to 100 days !! Only pros uses (or amateurs and enthusiasts) that often recharge their battery. Most lambda users (that I am) will only 10 to 20 refills per year ...

I therefore think that the "number of cycles" is to be weighed against the chemical wear over time of the battery which risks arriving much faster than cyclic wear ...

[chatelot16]

the number of cycles in perfect condition is one thing: the number of cycles in actual use is another, we must see tolerance to abuse

it is even paradoxical: the lithium battery is a tolerance to bad treatment absolutely zero: conclusion a good circuit of charge and discharge limitation is mandatory: result with what is necessary the number of cycle is good

conversely NiCd are much more tolerant so we are not afraid to sell them with bad charger

worse NiMh are less solid and we continue to sell without good charge solution ... but as their price is reasonable we are content with a fairly low cycle number which is still more profitable than the batteries

[lemontval]

Hello everybody
is there any battery not manufactured in Asia please?
A+

[chatelot16]

for NiMh I do not like the automatic detection of end of charge which only works in fast charge

with the slow load there is no end of charge detection possible: only solution load time theoretical: problem with a battery never completely discharged

does it need a charger that fully discharges before each charge? the information you just gave say yes: these batteries are not afraid to do a lot of cycle corect: they suffer a lot more overload

so for batteries that walk from one device to another requires a charger that fully discharge before making a slow charge theoretical

As a result of the problem there are different capacities for the same dimension: a system is needed to identify the batteries: charger even more intelligent to read the label?

numbered battery and even more inteligent charger that records the cycles and will allow a variety of statistics his battery

[bernardd]

To arrive at the stored energy, and also the influence of the discharge rate on the recovered energy, here are very interesting curves, always from the same site:

http://www.candlepowerforums.com/vb/sho ... ostcount=1

The slower it is, the more energy is recovered. As long as we are above the self-discharge ;-)

[bernardd]

And on the Li-Ion, it makes you shudder if you have to buy 15000 € in a car:

http://www.ni-cd.net/accusphp/theorie/lithium/index.php

A big defect appears however: this technology is used even when one does not use it.

According to the opinion of some specialists and the findings that I could make, the life of a Li-ion battery would be limited to a period ranging from 2 to 3 years after the date of manufacture ...

It is clear, at least. And this is the first one I see that is so clear.

[chatelot16]

it's not obvious: I bought a used laptop there 10 years: his battery parraissit dead, but there was only 2 element on 6 death: the remaining 2 still serve me for different experience and one almost normal ability

since 10 years without control circuit plugged on: the self discharge is negligible, I have already left 2 years without charge

I think that the low lifespan of lithium batteries is often due to electronic circuits that consume too much stopped and that discharges the battery below the minimum voltage if we do not use it often enough

[bernardd]

For the energy efficiency of the charge-discharge cycle, I have not found more precise for the moment:

http://www.ni-cd.net/accusphp/baba/gene ... nement.php

The charge as any energy conversion phase is not done without losses. The load efficiency is therefore not 1 but rather oscillates between 0,5 and 0,75 depending on the technologies and the charging mode. It takes more energy to charge a battery than it will be able to return.