Battery charge cycles
Submitted: Sunday, Dec 18, 2011 at 20:54
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mike39
I have read so much about battery life in relation to charge cycles.
I hope there will be someone here to enlighten me.
So, does a "charge cycle" mean that the battery has been fully discharged then charged back to full.
Or, does it mean that after a (say) 15% discharge, then fully recharged it is "a cycle".
The term seems to apply to all forms of rechargeable batteries, not just lead/acid.
For instance the Li battery in my metal detector is quoted as having a "600 cycles" life, but now
well exeeding that in charge connections it retains its a/h capacity.
The laptop I am using at the moment would have exceeded 1000 cycles if every time it is used and plugged into the mains means a "cycle", yet it still lasts 3hrs. on its battery when off mains.
As Sol used to say, "oils aint oils"
Is this the same for rechargeable batteries?
I am lost in the Great Battery Atmospheric.
mike
Reply By: oldtrack123 - Sunday, Dec 18, 2011 at 22:26
Sunday, Dec 18, 2011 at 22:26
HI Mike
It not so simple
Nicad & small Li batteries can be taken to flat & then fully recharged & for them that is a cycle
Lead acid however should NEVER be fully discharged ,as THAT will seriouslly shorten their life
Battery makers supply figures [no of cycles]for THEIR batteries based on depth of discharge then back to fully charged
Generally with wet lead acids max life is achieved when the battery is discharged by no more then 30<40%
100amphr battery only take out 30 to 40amphrs before fully recharging
Peter
AnswerID:
472843
Reply By: Battery Value Pty Ltd - Sunday, Dec 18, 2011 at 22:30
Sunday, Dec 18, 2011 at 22:30
Hi Mike,
one cycle is completed when the battery is re-charged to 100% of available capacity (which includes a small over-charge).
It doesn't matter from which SOC the charging starts, it's always counted as one cycle on completion of charging.
The cause of your getting confused with your devices high number of charging cycles is that the number of cycles you get from a battery depends on how deeply you discharge it.
So your Li batteries may be specced 600 cycles based on 80% depth of discharge. But obviously you're discharging them less than that before plugging the charger in. So the cycle life increases a lot.
For AGM deep cycle batteries you can expect to get over 1500 cycles @ 30% DOD, but only 700 cycles @ 50% DOD.
cheers, Peter
AnswerID:
472845
Reply By: The Bantam - Monday, Dec 19, 2011 at 00:23
Monday, Dec 19, 2011 at 00:23
The life of a battery can vary so much depending on how it is used, and there is such a wider range of how batteries are used.
SO
The manufacturers have to come up with some sort of method that gives a reasonable comparison.
So they quote the number of charge cycles.........that more or less represents full charge cycles, but that actual depth of the cycle may vary....there should be some sort of standarised procedure.
BUT woith almost any battery is the battery is treated badly, you will get less charge cycles out of the battery than specified, if you treat the battery
well you may
well be rewarded with longer life.
REMEMBER there are other factors in battery life than the number of charge cycles.
Some batteries in certain applications will die of other causes long before the predicted cycle life..but still at a very ripe old age.
cheers
AnswerID:
472855
Follow Up By: mike39 - Monday, Dec 19, 2011 at 07:12
Monday, Dec 19, 2011 at 07:12
Thanks blokes, that does make clarity of the issue particularly when it relates to DOD before recharging.
With my wet cell batteries I have always endeavoured to recharge
well before the 50% DOD level is reached.
For instance a pair of conventional N70 starting batteries used as auxillaries in parallel for fridge and other accessories are still going strong after 4yrs.
At 4mths./yr. daily charge cycle, then 8mths. on float I would seem to have obtained a good result
I also keep the charge rate at C10 which also seems to be a requirement for long battery life.
mike
FollowupID:
747678
Reply By: Peter_n_Margaret - Monday, Dec 19, 2011 at 17:51
Monday, Dec 19, 2011 at 17:51
''For AGM deep cycle batteries you can expect to get over 1500 cycles @ 30% DOD, but only 700 cycles @ 50% DOD. ''
Yep, but that is not as bad as it seems on the surface.
1500 cycles at 30% DOD is a total ''usage'' of 4,500Ahr.
700 cycles at 50% DOD is a total ''usage'' of 3,500Ahr, so while the total life is lower it is not as bad as might first appear, and in the mean time you invested a lot less $s in batteries (and will need to replace them more often) and carted a lot less weight around, so there is a legitimate arguement to work them harder too.
In some aspects, looking at a deep cycle battery as having a total Ahr capacity (use it fast, or use it slow?) is as good as looking at cycles.
Cheers,
Peter
OKA196 Motorhome.
AnswerID:
472912