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Does the old battery of an old laptop use a lot of energy when the laptop is connected to AC? Does the power supply waste electricity trying to continually charge an old battery? If I remove the battery, how many Watts of electricity would I save? Would the laptop stay cooler?

The power supply is very hot in both cases. The laptop is a Toshiba Satellite from 2004/2005.

This is a slightly different question than this: Should I remove my laptop battery?, so don't repeat the same answers. I've read about he UPS/power buffer effect, about the life of the battery, etc. I don't care much about the battery and I boot the laptop from DVD. There is no hard disk. I care about keeping the laptop cooler and spending less electricity.

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user13097
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  • How is it different from the [duplicate](http://superuser.com/questions/12358/is-it-better-to-use-a-laptop-on-battery-or-on-ac-power) question? – Ramhound Jun 15 '15 at 12:22
  • Same answer, different question. – Moab Jun 15 '15 at 17:17
  • "should I remove an old laptop battery to *save energy*?, i don't see that in the other question. – Moab Jun 15 '15 at 17:18
  • My question was about the energy inefficiencies of old rechargeable batteries. It is not specific to laptops, except that many laptops are still usable with the battery removed, while other devices (like mobile phones) are not. The more general question is whether a degraded battery requires a large amount of energy to charge to a small energy level, or does it just act like a smaller battery (but not terribly inefficient). – user13097 Jan 20 '23 at 09:51

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Yes, having less equipment under power will save some energy and decrease the overheat. However, the reduction will be so small you probably won't notice it. I don't have the exact numbers for your laptop, but I'd expect that you'll save 1 Watt tops, i.e. about 5% of your laptop power consuption in idle state.

According to Wikipedia the power consumed by a fully charged battery is even less. If we suppose that topping charge occurs once every 500 hours, lasts for 1 hour and uses 4 Watts of power (10% of the maximum charging power estimated at 40 Watts), then the annual consumption will be 365*24*4/500 = 0.07 kWh. Personally I find this estimation unrealistically small, but without the datasheet of your battery it's impossible to make a more precise estimation.

Is it worth the trouble to save 1 Watt and lose the UPS function your battery gives you?

Dmitry Grigoryev
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  • 1 W is not worth worrying about, but do you have any references to document that it is really this small? Old batteries use about 1 W to stay charged? To put it in perspective, 1 W of power turned on continuously uses up 8.8 KWh per year, which costs about $1-2, depending on where you live (I live in Greece, so I naturally pay about twice as much for electricity as I would in the U.S.). – user13097 Jun 17 '15 at 14:13
  • I added data from Wikipedia to the answer, though I doubt it's precise. You will must consult your battery's datasheet or make a measurement if you need an exact value. – Dmitry Grigoryev Jun 18 '15 at 08:44