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2 Bronze
2 Bronze

New battery calibration

Short version:

I have Dell Latitude 7480 with 60 Wh battery (F3YGT is written on the battery itself, DM3WC is how it is identified by the system).

Tried to purchase new same battery from local seller, and looks like it's new indeed, but initial reported capacity is 95% and I have reasons to think it's actually 85%.

I know I can be wrong, so the hypothesis I try to check, is: is it possible for a new battery to report it's capacity lower-than-its-actually-is? For example, in this topic I see something like this, but I'm not sure, is it a fact, or just some assumption etc.


Long version:

I received my laptop pre-owned (not new). Initially, it's battery reported it's capacity as 96%. Most of the time I used my laptop on AC, so I never bothered to check anything about the battery state. When I tried to use it without AC a couple of times, I've found out, that, for example, system estimated expected work-on-battery time as 5 hours, but, after only 2.5-3 hours, laptop reported critical battery charge (15%) already.

When I started checking, what exactly is happening, I realized that battery wasn't charging and discharging linearly, there were huge spikes/drops. For example, battery discharged "normally" from 100% to 40-45%, and then suddenly it reported something like 10% charge. While charging, it charged normally from 0% to 60%, and then suddenly reported 100%.

As far as I've googled, that's a "usual" symptom when battery wears out, and that's why there is "battery recalibration" term (a series of "charge-discharge-charge-..." iterations, so battery contoller/sensor/whatever will have a chance to re-adjust reported capacity to it's real value). With each iteration, I spectated how battery starts to report lower and lower capacity, but, at the same time, the spikes/drops during charge/discharge also became lower. In the end, the battery went from 96% initial capacity (with ~ 40% spikes/drops) to 56% capacity (and no spikes/drops at all) - from that moment I'm sure, that battery reports it's actual capacity, and that the reported charge percentage is accurate enough so I can actually rely on it.


Then, I decided to purchase a new battery. When I received it, I checked initial capacity reported - it was something like 95% indeed, but, having this "calibration experience" with my old battery, I also tried to perform the full charge-discharge cycle to test battery for any spikes/drops - and, sadly, I found them. During discharge, it went linearly from 100% to 17%, and then dropped to 6%. When I charged it back, it went from 0% to 90% linearly, and then spiked to 100%. Applying the simple math (which worked perfectly on my old battery), I made an assumption that, after a couple of charge-discharge cycles, this spikes/drops will disappear when battery will adjust it's capacity to something like 85%.

For the reference, this is my reddit topic, where I described the situation -


So, on the one hand, I have my own personal experience, when the battery reported incorrect capacity value (resulting in non-linear charge and discharge), and it required me to make something like 10 charge-discharge cycles in order to get linear charge/discharge (and the "real" capacity value).

On the other hand - I have the message from this topic , which says:

Just use it normally - after a few charge-discharge cycles, it will show its maximum capacity.

And also I have a message from the store where I purchased this battery (I'm going through a refund process now):

There is chemicals in the batteries, and that's normal. Once calibrated, the battery boosts its health.

I'm kinda skeptical about this "magical" capacity increases, which, as far as I understand, can somehow happen with the new batteries - but that's why I've came here to ask.

Replies (6)

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8 Krypton

Your battery info is out of date. Today's batteries are designed differently and do not require calibration. (Should not be calibrated at all since it shortens battery life.) Batteries can fail anytime now from 18 months to 2 years old.

Only new replacement batteries purchased from Dell or a trusted supplier should be used. For recent computers, the laptop will still run on just the adapter after the battery is removed. It's hard to buy new replacement batteries and there are scams with private sales of batteries. Your model is 5 years old now. 

See Dell's info here FAQ - Laptop battery articles - Dell Community


@Mary G , thanks for your reply.


Do batteries for my Latitude 7480 also count as "today's batteries", i.e. they don't require calibration?

If so, do you have any ideas, how was it initially possible for my current ("old") battery to show "96% capacity" with 40% spikes/drops during charge/discharge? I considered my experience as a good example of battery recalibration effectiveness. If I hadn't perform those multiple charge-discharge iterations, I wouldn't have had realistic (reliable) battery charge percentages now.


In other words, if new batteries do not require recalibration - how are those spikes/drops even possible, and how can one deal with them.

8 Xenon

Lithium ion and lithium polymer batteries do not require calibration, regardless of age.

The real question is, what is the date of manufacture on the battery itself?  And are you 100% certain the battery was never "remanufactured" with replacement cells?

A battery showing quick discharge relative to capacity may have one or more internal cells that's marginal or faulty -- not uncommon on aging battery packs.  

Somewhere in the Dell PPID string on the battery (starts with CN, KR, etc.) is a three-digit field -- something like 1A5.  This is the date code (the first digit is the year of manufacture, so a "1" is either 2011 or 2021, etc.  Since the model system you have did not exist in 2011, it means the battery is from 2021.  

If you see a date code beginning with a 7 or 8, it's likely an original battery from 2017 or 2018 when the system was new -- and therefore likely near the end of its useful life.



The real question is, what is the date of manufacture on the battery itself?

Output of "dmidecode -t 22", linux-world tool to get such information, where type 22 stands for "Portable Battery" for my new battery (the one I've purchased recently, and then returned to seller):


$ sudo dmidecode -t 22
Portable Battery
        Location: Sys. Battery Bay
        Manufacturer: SMP
        Manufacture Date: 12/22/2021
        Serial Number: 1A92
        Name: DELL DM3WC64
        Design Capacity: 60000 mWh
        Design Voltage: 7600 mV
        SBDS Version: 1.0
        Maximum Error: 8%
        SBDS Chemistry: LiP
        OEM-specific Information: 0x00000801


QR-code from the front of the battery: "CN0DM3WCSLW001CM832NA10"


Same information for my old battery (the one, that was in my laptop when I received it - the one I still use at the moment):


$ sudo dmidecode -t 22                                 
Portable Battery
        Location: Sys. Battery Bay
        Manufacturer: SMP
        Manufacture Date: 04/26/2021
        Serial Number: 1AB7
        Name: DELL DM3WC64
        Design Capacity: 60000 mWh
        Design Voltage: 7600 mV
        SBDS Version: 1.0
        Maximum Error: 2%
        SBDS Chemistry: LiP
        OEM-specific Information: 0x00000801


QR-code from the front of the battery: "CN0DM3WCSLW0076S831RA01"


I am very-very suspicious about "manufacture date: 04/26/2021" in my current battery info, by the way, because I received this laptop in June 2021, and I'm sure nobody touched it's contents (battery included) since then, and:

1. Battery is in a kinda "bad" state (I mean, physically - visible scratch on the front side, some other marks - looks like it was saved from fire :D)

2. There is marker label on a back side, which says "3926 mA" - I suspect, somebody understood that this battery is far from "excellent" state, since it's original capacity should be 7500 mAh, AFAIK.

But, I had no chances or reasons to check it in the past (when I received this laptop initially), so it's not worth any further discussions IMO. My "old" battery came from very unreliable source indeed, so let's just take it as a fact.

And are you 100% certain the battery was never "remanufactured" with replacement cells?

Talking about my old/current battery - absolutely not. Talking about new battery - well, only local seller's reputation, and yes, it's not official DELL distributor AFAIK - so, answer is "absolutely not" too. I see no ways to check it objectively, one can only rely on seller/distributor reputation and honesty.


Lithium ion and lithium polymer batteries do not require calibration, regardless of age.

Sorry for the wall of text below this line

I want to believe this, I really do, but I can not. At least, so far.

I mean, if we talk about "recalibration is dangerous/undesirable for Li-Ion/Li-Po batteries, because full discharge can cause damage to battery capacity" - I am absolutely okay with that wording.

But, if there is no "recalibration" for Li-Ion/Li-Po at all - why did my old/current battery adjust it's capacity after ~ 10 charge-discharge iterations? I used this battery for months (99.9% of the time on AC), and it always showed 96% capacity, so I had a feeling "something is wrong" when my laptop went to "critical charge" much faster than I expected, but I never bothered to check it until recently.

If "recalibration" for these batteries, as a "process", does not exist "by definition" - I guess, battery would not change it's reported capacity after those charge-discharge iterations? But it did.

And, I understand, one can say "there is a chance you actually damaged your battery in the process" (i.e., my ~ 10 charge-discharge iterations did something like 40% capacity damage to the battery) - but:

1. I don't believe 10 iterations can cause such a high damage.

2. The main point: charge percentages went from "linear with huge spikes" to "linear without any spikes".


Both "capacity" and "current charge percentage" - are the values, which come from the battery itself AFAIK. I mean, they are not OS-specific, they are not stored anywhere on my disk, etc. - they come from the battery controller. So it's not my OS, who suddenly realized "oh wait, this battery is actually worse, than I thought" - it's the battery controller itself, isn't it? And, if it is - then, we are talking about controller, which did not adjust any reported values for months, but suddenly adjusted some reported values after a couple of full discharges - in other words, "calibrated" them! If this logic is incorrect, then looks like I'm totally missing something.

Again, sorry for the wall of text - I just didn't see any way be more laconic.



In any case, most of the information above is "general discussion", which I'm very interested in, but it's kinda "optional" for me.

Going back to the "new battery", which I received and sent back (refund).

So, I have received a battery. It's initial reported capacity is 95%, but I see 10% spikes/during charge and discharge. I find this situation "suspicious", and, I think, this battery is not in desirable state for a new battery (i.e., new battery should not have this strange properties). Also, I think, the chances of "spikes are magically gone, battery magically restores it's original capacity" are pretty low, if not zero. Am I correct?

2 Bronze
2 Bronze

Just an update. I've successfully refunded the battery I mentioned in this post initially. Then, after a month, I've decided to test my luck again and to buy the battery from the local polish store again (but from the different one, though). Looks like I wasn't lucky enough   Serial numbers for the new battery are completely different, but the manufacture date is absolutely the same, and the symptoms and initial readings are same too - looks like both batteries were created/transported/stored together. Same initial reported capacity, same spikes during charge and discharge.


This time I've decided I'm not going to make a refund (buying the battery from "official" store will be around 30% more expensive, so I'll just stick to what I have). I started using this new battery, beginning with a couple of recalibration cycles. And, my theoretical calculations are confirmed. After a couple of charge/discharge loops, reported total capacity dropped from 95% to 85%, but spikes during charge/discharge went from 10-11% to 0-1%.


In the end, the only thing, that I can't understand, is: where did this "Li-ion / Li-Po batteries do not require calibration" idea come from? My experience with 3 different batteries (of the same model DM3WC / F3YGT) proves, that calibration IS a thing, and you actually need to do it sometimes, or, otherwise, you'll get unreliable current battery charge readings and unrealistically optimistic full capacity reading.


I'm not going to argue, is it "dangerous"/"damaging" or not (it can be), but I claim that the statement "recalibration of Li-ion / Li-Po batteries is not required at all" is false. Or, at least - I claim that "recalibration for Li-ion / Li-Po batteries does exist" (dropping the "required"/"not required" part away).

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