Laptop's performace decreases when on battery (not plugged in)

[Daniel-India]

I have a Acer System Aspire VN7-591G, and when it is on battery the gaming performance decreases (getting lower frame rate). One thing i noticed is that, when i am playing a game and I remove the AC power the frame rate drops drastically but then after a minute or so the frame rate increase much more but still not as good as when plugged in.
I have already done the following:
1) Switching to high performance mode in power options
2) going to nvidia control panel and switching to "prefer maximum performance
please help me. Thank You!

 

[Solandri]

Batteries are not capacitors. You cannot pull energy out of them as quickly as you want. Generally, the more quickly you draw energy (higher power consumption), the less efficient they are and the hotter they get. Draw too much power and it'll overheat possibly destroying itself. So all laptop manufacturers cap the max power the battery can provide.

Usually this is substantially lower than the max power draw the AC adapter can supply. For gaming laptops, it means the GPU can't run at full speed on battery. You can't control this. It's baked into the firmware to prevent you from destroying your battery or even possibly causing a fire.

As for the initial frame rate drop then ramp up to a higher framerate, that's probably the laptop figuring out exactly how much charge is left in the battery. Measuring battery capacity is something of a black art. You estimate it based on the measured voltage, but the voltage changes with power draw (higher power depresses the voltage) and temperature, not just remaining charge. So the charging circuitry is loaded with all sorts of tables to help determine the battery's remaining capacity under different use conditions. My guess would be it can measure more accurately at lower power draw, so initially drops the laptop to extremely low power consumption and gives it some time to stabilize so it can figure out the correct battery state. Then once it's got that figured out and has determined it's safe, it allows power consumption to rise.

You want to accurately gauge remaining charge because Li-ion batteries are not like alkaline or NiCd or NiMH which have fairly noticeable drops in voltage as they run out of juice. Li-ion batteries voltage drops only slightly as they reach what you're told is 0% charge. Because of this stable voltage, they can be used beyond this point, but it will damage the battery chemistry. And next time you try to charge the Li-ion battery it can catch fire or even explode. You may recall a few cases of this happening in the early days of Li-ion batteries in laptops and cell phones. The charge/discharge protection circuitry we have now was developed based on those past incidents, to prevent a situation which could cause a repeat of those accidents.

 

[Wayfall]

Ye this always happens with laptops.

We have an old full large laptop that the family still use, this one came out when SLI was just starting off and its still rather powerful. If it is not plugged in it lowers the GPU frequencies and does not allow SLI even when on high performance but the second you plug it in all the power shoots up to max and SLI comes on.

Whenever I gamed on it as a teen I had to plug it in just to play the original assassins creed

 

[jaguarskx]

All laptops operate at lower performance when not plugged into the A/C outlet. It is likely a built in function of Windows to prolong battery life. But it could also be a hardware power limitation as well; meaning it is part of the laptop's BIOS.

 

[Solandri]

Batteries are not capacitors. You cannot pull energy out of them as quickly as you want. Generally, the more quickly you draw energy (higher power consumption), the less efficient they are and the hotter they get. Draw too much power and it'll overheat possibly destroying itself. So all laptop manufacturers cap the max power the battery can provide.

Usually this is substantially lower than the max power draw the AC adapter can supply. For gaming laptops, it means the GPU can't run at full speed on battery. You can't control this. It's baked into the firmware to prevent you from destroying your battery or even possibly causing a fire.

As for the initial frame rate drop then ramp up to a higher framerate, that's probably the laptop figuring out exactly how much charge is left in the battery. Measuring battery capacity is something of a black art. You estimate it based on the measured voltage, but the voltage changes with power draw (higher power depresses the voltage) and temperature, not just remaining charge. So the charging circuitry is loaded with all sorts of tables to help determine the battery's remaining capacity under different use conditions. My guess would be it can measure more accurately at lower power draw, so initially drops the laptop to extremely low power consumption and gives it some time to stabilize so it can figure out the correct battery state. Then once it's got that figured out and has determined it's safe, it allows power consumption to rise.

You want to accurately gauge remaining charge because Li-ion batteries are not like alkaline or NiCd or NiMH which have fairly noticeable drops in voltage as they run out of juice. Li-ion batteries voltage drops only slightly as they reach what you're told is 0% charge. Because of this stable voltage, they can be used beyond this point, but it will damage the battery chemistry. And next time you try to charge the Li-ion battery it can catch fire or even explode. You may recall a few cases of this happening in the early days of Li-ion batteries in laptops and cell phones. The charge/discharge protection circuitry we have now was developed based on those past incidents, to prevent a situation which could cause a repeat of those accidents.