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Old 11-09-2018, 12:11 AM   #1
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Default How do you Count Battery Cycles

I was looking at a new B with a lithium option. The 600 amp Lithionics battery claims a minimum 2000 cycles.

What exactly is a cycle? Every time I stop for 30 to 60 minutes during the day and leave the a.c. running and the battery has to recharge a small amount is that a cycle?

I read claims of how lithium batteries will seemingly last forever but it seems they only assume 1 cycle a day.

They way I figure it on a two week trip I would go through 50 to 75 cycles and several hundred a year. Any Thoughts...
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Old 11-09-2018, 02:35 AM   #2
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Lithionics has tested their 600 AH over 4000 cycles, they go from full charge to 5%.
The average RV user should get 15 years out of the Lithionics Lithium. After the 15 years you can send it back for a reman. At this time the charge is $3,500.00 in 10 years most likely 1/2 that.
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Old 11-09-2018, 11:28 PM   #3
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A battery cycle is a complete discharge and a complete recharge. It does not need to take place in one event. 5 discharges to 80% and recharges to 100% is 1 cycle. 1 discharge to 50% and 1 recharge to 100% is not a cycle, but 2 of those would be.
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Old 11-10-2018, 12:10 AM   #4
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Default Batteries

Difference being, the Travato Lithium can only do down to 20%, Lithionics can be safely discharged down to 2% with no concerns or battery harm.
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Old 11-10-2018, 12:11 AM   #5
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A battery cycle is a complete discharge and a complete recharge. It does not need to take place in one event. 5 discharges to 80% and recharges to 100% is 1 cycle. 1 discharge to 50% and 1 recharge to 100% is not a cycle, but 2 of those would be.

That is certainly not the way I think any of us here think of a cycle, nor do most of the battery manufacturers.



If you look at the cycle life vs discharge depth charts the have the curves drawn at specific discharge depths. Marko just post one of the charts in another thread on the forum. The curves plot the full capacity left in the battery vs the number of cycles. Nowhere is there any kind of calculus style integration done to get the number of cycles.





Many of us agree that the total energy in and out is what counts the most, not number of recharges, but that is not the way the "cycles" are determined in any of the life charts I have ever seen.
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Old 11-10-2018, 12:21 AM   #6
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That is certainly not the way I think any of us here think of a cycle, nor do most of the battery manufacturers.

This is a quote from Apple.

"A cycle count is one complete charge and discharge cycle on the battery."
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Old 11-10-2018, 12:28 AM   #7
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This is a quote from Apple.

"A cycle count is one complete charge and discharge cycle on the battery."

Where does it say how deep the discharge is? That can easily be interpreted as the "complete charge and discharge cycle" means that the discharge and recharge of whatever depth has to be completed to count as a cycle. That just means you discharge to 50% and then recharge to 80% it doesn't count as a cycle because the charge wasn't complete, or as is often stated it would be a short charge.


Did you look at the chart?
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Old 11-10-2018, 12:36 AM   #8
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Where does it say how deep the discharge is? That can easily be interpreted as the "complete charge and discharge cycle" means that the discharge and recharge of whatever depth has to be completed to count as a cycle. That just means you discharge to 50% and then recharge to 80% it doesn't count as a cycle because the charge wasn't complete, or as is often stated it would be a short charge.


Did you look at the chart?
If you discharge to 50% and recharge to 80% that constitutes 30% of a cycle, according to Apple.
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Old 11-10-2018, 12:49 AM   #9
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If you discharge to 50% and recharge to 80% that constitutes 30% of a cycle, according to Apple.

That is nuts because nobody would ever be able to figure out how many cycles they had or test specs without an accumulating data logger. Look at any RV battery or charger site and see what they say about cycles and cycle life, and it is not as you say Apple is saying. Apple is probably trying to make sure they can't get held accountable for crappy battery life, as they got in trouble for that before.
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Old 11-10-2018, 12:12 PM   #10
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It is a great question.

I suspect Apple's definition is for a particular purpose. It might be warranty or explaining how an app tracks cycles etc.

I think it is too simple to be accurate in the long term as all cycles are not equal (rate, depth, temperature) but it's probably good enough for a iPad or iPhone.

If you look at Trojan LFP battery chart here:



You can clearly see that there are penalties for both rate and depth.

Similarly, this PDF from Lithionics shows that there is a depth of discharge penalty: WhatIsLifeExpectancy.pdf

The rainflow algorithm seems to have been adapted to simulate capacity loss in scientific modelling.

There's an illustration on Page 15 of this paper that shows common aging effects. FULLTEXT01.pdf

A weak point may end up being the BMS in some systems as it too is subject to continual stresses. Failure of the BMS could lead to failure of the battery.
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