Dell laptop battery question

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dacflyer
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Dell laptop battery question

Post by dacflyer » Tue May 29, 2018 10:00 am

are these batteries designed to shut down and rendered no good after so many cycles ? ( control board inside ? )
i got one here that appeared to be bad, i cracked it open, the cells read 3.3V per cell, they will take a manual charge via my power supply, but they will not charge via the laptop, i seen on the board that there is some communication connections. so i am thinking the board is either bad or it is in shutdown mode,
i got a new battery. same model number, but the new battery is listed as a lower voltage than the original.
old was 14.8 , the new one is 10.8 but much more current capacity.
new battery seems to be working,, it indicates 100% charge.
old battery shows NOT FOUND

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Janitor Tzap
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Re: Dell laptop battery question

Post by Janitor Tzap » Wed May 30, 2018 2:47 pm

Hey Dacflyer,

It sounds very much like the controller board has failed.

I'd look on it for an "Over Current" Diode that has opened up, due too excessive current draw by the batteries.
Or the Current Regulator failed.

That's the thing about these Li-on Battery packs, since the SONY Laptop incident.
They don't want them exploding, or catching fire during charging.
Thus, the Current Regulator Circuit pops at a predetermined current level, before that can happen.


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Re: Dell laptop battery question

Post by dacflyer » Sat Jun 02, 2018 7:58 pm

this battery is a li-ion , not a lipo
i am assuming the board is bad, but it is all SMD stuff, so no luck to fix it, so i'll just salvage the cells for another project..

but what's strange is... the old battery was listed as 14 volts, the new one is only 10 volts, but the seller says that is what is used and will work.. and it is working so far.

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Re: Dell laptop battery question

Post by Janitor Tzap » Sun Jun 03, 2018 10:02 am

dacflyer wrote:this battery is a li-ion , not a lipo
i am assuming the board is bad, but it is all SMD stuff, so no luck to fix it, so i'll just salvage the cells for another project..

but what's strange is... the old battery was listed as 14 volts, the new one is only 10 volts, but the seller says that is what is used and will work.. and it is working so far.
Well when the first Laptops {or Luggables} came out.
The battery packs were more like 14V to extend the run times, because the HDD, and Floppies Drives required 12V to run them.
Later on, 5V versions came out for these drives. Thus, extending the battery life even more.

So, why switch to a lesser voltage battery?

Well, the newer battery has a Higher MaH rating cells in it than the older Battery Pack cells.
So, they don't need to put cells in parallel to get the same MaH rating.
Thus, they don't need as many cells, making the Battery Pack lighter.

Also, since the highest voltages used in the Laptop is 5V.
The Motherboard Voltage Reg doesn't care if the input voltage is 8V to 14V.
It just has to regulate it down to 5V, 3.3V, 1.5V, 1.25V.

So, they cut the weight, without cutting the batteries running time.
Thou, if the Reg board in the 14V pack was okay, and you replaced the old cells with new higher MaH Cells.
The running life of the battery pack would be doubled some what.


Basically the manufacturers are looking for ways to cut the weight of the Laptop.
Yet, keep the battery life as long as possible, or to acceptable running times.
{I believe most are up to 6 hours of running time.}

I'd look at the Accessories Support Site, for this Laptop.
Probably will find two versions of the Battery Pack.
Regular & Longer run time version.


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Re: Dell laptop battery question

Post by dacflyer » Mon Jun 04, 2018 12:04 pm

in the old pack, the cells were in series. it had the samsung 18650 cells, i am sure the new pack is the same way, it does feel heavier for sure..

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Re: Dell laptop battery question

Post by haklesup » Mon Jun 04, 2018 5:00 pm

is there a voltage spec on the laptop itself. In any case the lower voltage should mean less voltage dropped across the internal regulators and it should run cooler and more efficiently. The new battery may have a better buck/boost regulator allowing for a flatter discharge curve rather than a gradual drop off.

the old pack may have had a thermal fuse in it which are typically not resettable. Look for a 2 terminal device with few markings that is open circuit and probably in series with one of the terminals. If it got hot enough to trip a thermal fuse, it has probably got a bad cell too. If you can revive it, I wouldn't bring it on a plane.

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Re: Dell laptop battery question

Post by Janitor Tzap » Mon Jun 04, 2018 6:58 pm

dacflyer wrote:in the old pack, the cells were in series. it had the samsung 18650 cells, i am sure the new pack is the same way, it does feel heavier for sure..
Do you mean it was like this:
Image


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Re: Dell laptop battery question

Post by dacflyer » Tue Jun 05, 2018 3:21 pm

nope, single row, nothing parallel

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Re: Dell laptop battery question

Post by haklesup » Tue Jun 05, 2018 5:15 pm

not all 18650 are equal, you could just have some with heavier walled cases and better discharge specs and other minor construction differences.

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Re: Dell laptop battery question

Post by dacflyer » Thu Jun 07, 2018 7:19 pm

well it's listed as double the current, but what do i know..

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Re: Dell laptop battery question

Post by haklesup » Fri Jun 08, 2018 11:14 am

by way of example, here is an article comparing 2 18650 batteries from the same manufacturer. Initially you can see one has higher max discharge current and the other has a little more capacity but in the discharge tests, they are very similar. Differences between brands I expect would be greater. In any case this is a good characterization and the site has tons more info.

He doesn't show prices but the catalog page is a good chart of max discharge current and capacities of various models.

https://batterybro.com/blogs/18650-whol ... c-18650-be

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Re: Dell laptop battery question

Post by dacflyer » Sat Jun 16, 2018 2:52 pm

well i was more concerned about the voltage..
the battery led on the laptop starts blinking green and red ( to make yellow ? ) can't find out what it means.. maybe it does not like the new battery.., but it shows 100% charged..

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