Laptop replace li-ion cells medion

mathero11

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Feb 4, 2016
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My current battery for my laptop (brand is Medion) has 6 cells.
The battery back says:
10.8V == 4400mAh, 47Wh
model name: A32-C17

So I want to replace all them with Panasonic NCR18650B 3350mAh.
But then the capicity would be [strike]6* 3350 = 20.100 mAh.[/strike] in parallel so 2*3350 = 6700mah
Can the battery controller, chip, I dont know what it's called, handle this capacity?

Thanks
 

Eximo

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Cells can be of different lengths, and they may have opted to only use 6/8 available space to save on weight/money.

Laptops don't run on 10.8 or 14.4 volts. All of that voltage gets stepped down to what the components run on anyway. Pretty sure laptop GPUs and some internal components need 12V so they also have to step up voltage with a 10.8v battery.

You can try looking for reviews, or see if that model was available with an 8-cell battery. My guess would be that it did.
 

Mister_MO

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Jul 28, 2016
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You cant just swap cells and go like nothing happens, you would need first find firmware for battery controller and then way how to solder batteries together without them blowing up.
 

sizzling

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Oct 18, 2006
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Don't mess with lithium batteries, incorrect usage or charging turns them into a real fire hazard. Also 6*3350 would only be 20,100 mha if wired in parallel which would only give you 3.7v. You would need to wire in parallel 2 set of 3 series cells which would give the correct voltage and 6,700mha but how are you going to balance each cell during charge and discharge without a cell balancing circuit?

The whole idea is really bad unless you know exactly what you are doing. I know a little and that's enough to tell me its a bad idea.
 

mathero11

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Feb 4, 2016
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im indeed wrong of the calculation.
6700mah would do the job also.
my original battery is still in tact, but my question was, does the circuit accept the higher capacity cells?
 

Eximo

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Indeed, if you want a higher capacity battery for a laptop, find an aftermarket battery that has more capacity.

Building your own just isn't feasible. Many of the battery monitoring circuits actually have single use security wires, or at least they used to, that prevent user tampering.

While charging/monitoring/management circuits are pretty common, you would need a whole host of tools to reprogram one, assuming they aren't hard set. Not sure what interface they use these days, been a long time since I messed with that stuff. At a certain point it just became cheaper and more convenient to buy off the shelf parts.

Consumer electronics are just not that easy to mess with any longer.
 

Eximo

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Lithium chargers use an algorithm to detect a subtle bend in the charging curve to determine when to stop charging (Any more and they go into thermal run away and risk fire and explosion), or they stop at a predetermined limit, my measuring wattage input, and never fully charge. This is why some batteries can be reset to gain more capacity using vendor specific sequences, usually involving taking a laptop battery well past empty to trigger a reset.

General rule of thumb with Lithium used to be 40-80% charge to get the most longevity. I imagine they go close to 10-90% these days since they are considered disposable.

In all likelihood if you managed to replace the cells and got it to work at all it would charge up to the exact same amount as before.
 

mathero11

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Feb 4, 2016
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thanks for the explanation.
the laptop is from 2014 so it's not the newest around.
so is there anything else I can do to increase the capicity? except buying one with higher capicity because they don't exist.
 

Eximo

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Cells can be of different lengths, and they may have opted to only use 6/8 available space to save on weight/money.

Laptops don't run on 10.8 or 14.4 volts. All of that voltage gets stepped down to what the components run on anyway. Pretty sure laptop GPUs and some internal components need 12V so they also have to step up voltage with a 10.8v battery.

You can try looking for reviews, or see if that model was available with an 8-cell battery. My guess would be that it did.
 
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