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I got an Acer Aspire 5100 and I just bought a new battery (after the stock battery just died yesterday). But I saw something after buying and I'm wondering whether it's really important or not.

My stock battery was a 6-cell 4000mah 11.1v and the new battery is an 8-cell 4800mah 14.8v . I know that 8-cell and 4800mah is okay, but what about the 14.8v instead of 11.1v?

The battery description says it's compatible with my laptop model (AS5100, model BL51), but the voltage difference makes me wonder.

Will the laptop only take what it needs? Or will it be getting 14.8v straight in the brain? I know that my wall plug claims to output 19v, so logically I'm thinking a higher voltage battery shouldn't be a problem. Am I correct in thinking this?

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If it's sold as compatible with your laptop, it probably is. Many battery voltages sag under load, depending on the quality of cells, chemistry, etc. – Paul McMillan Aug 31 '09 at 23:57
R=I/V so your resistance is going from 2.78 to 3.08 which means it will run hotter~10%! But is should still be within tolerance. The manufacture has the recommended range. – Jeff F. Mar 13 '12 at 20:13
@Jeff You cannot calculate the battery's internal resistance by dividing its voltage by its mAh rating. Instead of ohms your calculation gives ohms per hour, so the numbers you give are meaningless. – hdhondt Mar 3 '15 at 0:59
up vote 12 down vote accepted

OK. After some digging, a typical mobile PC (from 2006) can handle 18V to 7.5V at the input either from an AC Adapter or a Battery. Also, the typical voltage for a battery is 11.1V or 14.8V depending upon the numbers of cells. The risk that 14.8V won't work on your laptop is extremely small.

Your laptop supports:

  • 71 W 4800 mAh Li-ion battery pack (8-cell)
  • 44.4W 4000mAh (6-cell) Li-ion battery
  • 29.6W 2000mAH (4-cell) Li-ion battery

Typically, laptops can work over a pretty wide range of input voltages. 14.8V doesn't sound too high to me. I can't find any specs from their website to confirm that 14.8V is OK, though.

Going from 6 to 8 cells will increase the voltage proportionally. Think of going from 6 to 8 AA batteries.

Here is an article on Notebook Battery Cells that presents an 8-cell battery being 14.4V as pretty common.

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Nice, thanks for your answer and nice link ;) I'm now more secure to put it in when I'll receive it ;) – Marc-Andre R. Sep 1 '09 at 1:57

Based on my electrical engineering knowledge, I believe most of the electronic circuitry work on pretty lower voltage than 11.1 V or 14.8 V both. The first stage is adapter which is nearly 5 V higher than the battery rating voltage to charge it faster to the full. Now the second stage is the motherboard or processor which typically runs at 5 V and for that you have voltage regulator inside.

The question is why can not we install a battery of voltage rating of 5 V and why we need a regulator at all? Answer is, unlike power adapter, the battery output voltage constantly decreases as it loses its charge since V = Q/C, Q is charge and C is a constant capacitance. Hence, A fully charged battery can power the laptop for few hours until its voltage drops down to the minimum acceptable level.

Therefore it really does not matter much if you use 11.1 V or 14.8 V. To me, 4400 mAH with 14.8 V would be almost same as 5200 mAH with 11.1 V in terms of time of powering your laptop as what finally matters is WH (watt-hour).

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Aren't motherboards and processors typically 12V, and optical/solid state/hard drives run off the 5V? Then again I'm referring to desktops. – Arthur Kay Aug 10 '15 at 17:15

I've found that power circuitry typically has a little bit of tolerance in the voltage, but it's certainly best to use the recommended voltage. I would err on the side of caution with a 11.1v to 14.8v increase!

However, it's safe to use a power supply or battery of equal or higher amperage. The device will only draw the amperage it needs, and as long as your supply at least meets those needs, you'll be alright.

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protected by bwDraco Sep 19 '15 at 14:08

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