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Li ion 18650 battery discharge

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BILLPOD:
I have found that the best way, (for me), to charge, discharge and test cylindrical batteries is with the SKYRC MC3000 battery charger.   It does ALL the chemistries and most battery parameters can be measured.
Some may consider it overpriced, but for what it does, is worth the price.
I operate it through a USB cable to my laptop, but it can be programmed using the 8 push buttons on it's face.   I especially like it for categorizing my large collection of 18650s which I have harvested from laptop batteries.   Here is the Amazon USA listing, but it may be found cheaper elsewhere :popcorn:

Peabody:

--- Quote from: VEGETA on June 08, 2023, 10:48:30 am ---
there are certainly better LDOs which can do nano amp quiescent current such as AP7354-33W5-7 but they are of course a bit more expensive.

is there any real gain from switching the LDO to a better one with lower Iq? or would it be just an overkill.

--- End quote ---

Well, you would come close to doubling the life of the battery.  The better LDO will cost four or five times as much, but still not a lot of money in absolute terms.  So I guess it depends on whether you will be making a million of these devices, or just one.  The MCP1700 is another one you might look at that might be more readily available.

VEGETA:

--- Quote from: Peabody on June 09, 2023, 01:36:10 pm ---
--- Quote from: VEGETA on June 08, 2023, 10:48:30 am ---
there are certainly better LDOs which can do nano amp quiescent current such as AP7354-33W5-7 but they are of course a bit more expensive.

is there any real gain from switching the LDO to a better one with lower Iq? or would it be just an overkill.

--- End quote ---

Well, you would come close to doubling the life of the battery.  The better LDO will cost four or five times as much, but still not a lot of money in absolute terms.  So I guess it depends on whether you will be making a million of these devices, or just one.  The MCP1700 is another one you might look at that might be more readily available.

--- End quote ---

your suggested MCP1700 is very good. ground current is about 4 uA and quiescent current about ~2uA so total would be < 6 uA compared to 29 uA from before. it is 3 times the cost though but still good enough as the board will not suffer from < 0.3$-0.5$ price increase.

I will make say hundreds and sell them, in batches according to demand.

However, in this experiment I am doing, I am seeing if the cheap (and still very good) LDO of 29 uA will be that much effective or not.

if we assume total current consumption from everything is just about 60 uA total, then what will that be for a 18650 battery? my assumption is that it will be literally nothing. if so then changing the LDO won't be much of a change.

yesterday at this time it was 4.112v and now it is 4.110v so a 2 mV drop which is less than before where it dropped by more than 5 mV, and very early was more than that.

to my understanding from explanation above about chemical characteristics... this should be normal and will settle at some point, after that will be mere self discharge + my 50-60 uA which in reasonable assumption won't be dropping battery voltage in any effective matter.

I would be very happy if the battery will last for a year, which by all reason and calculations it should do much more than that.


 

radiolistener:

--- Quote from: VEGETA on June 09, 2023, 05:07:49 pm ---yesterday at this time it was 4.112v and now it is 4.110v so a 2 mV drop which is less than before where it dropped by more than 5 mV, and very early was more than that.
--- End quote ---

This is not a drop but just a noise due to chemical processes inside battery. Don't be surprised if the voltage can rise by 2 mV in some conditions.

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