# Throttling (reducing) Laptop Battery Charge Rate using ThrottleStop



## popTbop (May 29, 2021)

CPU:  Intel i7-5500U  dual core.  

Older laptop that pulls about 2.5 amps @ 20Vdc, or about 50 Watts max power while charging. I'd like to know if manipulating the CPU using TrottleStop, or tweaking the hardware and/or software configuration (Win10) can REDUCE or limit this maximum charge rate. I want to be able to charge this laptop while turned on, but with a much smaller charger, like a USB-C-PD 30 or 40 Watt charger.  

Any ideas?

Thanks. 
PB


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## Bill_Bright (May 29, 2021)

popTbop said:


> Any ideas?


Yeah. Don't do it. The chargers supplied with laptops are chosen by the engineers to support maximum charge on the battery while the laptop is running. If you put a smaller charger on it, and that smaller charger is faulty or poorly designed, your laptop power demands plus the battery charging demands may attempt to demand too much current and cause an excessive heat (or much worse!) and dangerous scenario. 

Note too that the demand batteries put on chargers decreases as the batteries move closer to fully charged. So my advice is to not let your battery fully discharge (except maybe once every couple months to keep it calibrated with the laptops battery monitoring circuits - as per your userguide instructions).


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## popTbop (Jun 1, 2021)

Thanks Bill_bright, 

But just to clarify, my idea is to down-throttle the CPU so that the laptop does not demand as much power from the charger in the first place, thereby allowing me to use a smaller charger while running the laptop.  I'm not suggesting using a smaller charger on the laptop running normally.  

Whether that can be done by undervolting the CPU, or by other methods, I think this could shave off 5-10 watts from the instantaneous peak power demand of the charging circuit on the charger, as I monitor it on my charging meter in real time.


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## unclewebb (Jun 1, 2021)

popTbop said:


> i7-5500U


You can undervolt these CPUs if the BIOS did not lock this feature. You can also lower the turbo power limits or reduce the CPU speed,

For CPU speed, set the Non Turbo Ratio to 0 and then adjust the Set Multiplier value. Post some screenshots so I can see what options are available.


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## Bill_Bright (Jun 1, 2021)

I guess I need a better understanding of why you want to do this? What is your ultimate goal here? This will not save you any money because eventually, the battery will still require the same amount of energy to charge. All you really are doing is crippling the performance of your laptop. Why do you want to do that? But beyond that, using a smaller power supply introduces potential hazards too. 

Computers (all electronics, actually) pull from the power supplies what they need (if the supply is capable of providing it). This means the computer will demand from the supply/charger what it needs based on the tasks it is currently performing. If you are just surfing the Internet, updating Facebook, watching YouTube videos, editing a Word document, or processing your email, these are all low demand tasks. So right there that will put less demand on your power supply/charger. 

If you are asking the computer to perform demanding tasks, like playing a very demanding game, that will put greater demand on your power supply/charger. 

But of significant importance, if you use a less capable power supply and the computer demands more than it can deliver, at best, you risk having an unstable computer. At worse, you risk overheating the supply and charging/regulator circuits creating the potential for fire!!!   

If you want to keep over all "peak" demands on your power supply/charger down, keep your battery at or nearly fully charged. It is important to note that battery charge rates are NOT constant. The closer a battery gets to being fully charged, the smaller the charge rate it demands from its charger. That is with any battery. 

Another important thing to consider here is the fact the CPU is but one device in your laptop demanding power. Even with integrated graphics, the energy required by the graphics solution to display an image on the monitor is the same, regardless the energy consumed by the CPU side of the processor. Then there is the energy required by the monitor itself - that is significant too. The RAM requires energy. The drive(s) require energy. The motherboard requires energy. So do the network ports - especially if using wifi, USP ports, even the keyboard and mouse/trackpad all are demanding energy too. Then add the demands of the battery. Even if you reduce the power demands for the CPU, when you factor in all other devices demanding power too, you really are not talking about much. 

Let me illustrate this another way by using a regular desktop PC as an example. It does not matter the PC does not have a battery. All electronics work this way. 

If you have a PC and all the component (motherboard, CPU, GPU, RAM, drives, fans, etc.) all require 300W of power, they will demand from the power supply 300W of power. And the power supply will deliver only 300W regardless if that power supply is a 500W supply or 1000W supply. And those power supplies will pull from the wall only 300W too - plus a little extra due to PSU inefficiencies. 

So, assume you have a 650W "Gold" certified power supply that is 90% efficient in that PC. It will deliver the needed 300W to the components inside while pulling ~333W from the wall (333 x .9 - 299.7W). Again, it does not matter that PSU is rated at 650W. That extra 33 watts pulled from the wall is wasted in form of heat being generated inside the power supply. 

Same with your laptop. If your current supply is rated for 90W (a common size), it does not matter if the laptop (including the battery) is only demanding 60W of power. The supply will deliver just 60W. If you replace that 90W supply with a 65W supply, for example, the computer is still demanding and getting just 60W. HOWEVER, you have created a dangerous scenario because that 65W supply is having to work at near capacity most of the time - it surely will get hot because it is not designed to work at near capacity full time. Not good! If you keep the 90W supply, it will still only deliver that same 60W, but it will not have to work as hard to do it. Thus less heat in relation to capacity. And that's good. 

So if you want to reduce the performance capability of your laptop fine. But as I said initially, as far as using a smaller power supply, "don't do it"!


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