Charging laptop battery to 80%?

[Fordulike]

The existing battery on my laptop is pretty much past it's best, so I've got a new one on the way. My current usage is to always have the laptop plugged in on charge, and 2-3 times a day I will use it off charge until the low battery warning comes on. Then it goes back on charge till 100% charged.

My laptop has a feature where it will charge to 80%, then stop charging. Now the new battery I have on the way is a bigger capacity battery, so charging the new one to 80%, will be pretty much the same as charging the old one to 100%.

My question is, should I carry on charging the new battery to 100%, or use the 80% feature?

What made me doubt about whether the 80% charge is a good idea, is a recent post, where I think d8veh mentioned that a battery won't balance in this mode. Forgive me if I have got that wrong, I don't want to cause an argument, just want some advice based on facts, whether this 80% thing is worth it.

 

[Deleted member 4366]

I reckon that 80% is the voltage, not the capacity, so everything should work right.

 

[Fordulike]

I reckon that 80% is the voltage, not the capacity, so everything should work right.

You've confused me a little there d8veh, could you explain in layman's please.

 

[anotherkiwi]

How thick is your laptop battery? It may be a couple of pouch cells not 18650's, just let the software take care of it.

 

[Fordulike]

How thick is your laptop battery? It may be a couple of pouch cells not 18650's, just let the software take care of it.

The battery is clearly thicker than the standard one. I'm assuming 3S3P cells. Here is the link to the battery:

http://www.duracelldirect.co.uk/m/laptop-notebook/samsung/np-p530-battery-extended-life--3nta2k.html

 

[Fordulike]

just let the software take care of it.

Yes, but considering I charge to 100%, then empty to 5%, do you think It would be better for the cells to use the 80% charge feature?

 

[anotherkiwi]

For £50 use it till it stops working then recycle... That is what i did with my Vaio batteries for 10 years.

 

[Fordulike]

Hee hee, I know this is probably a bit swings and roundabouts, but how about this. Would it be better for the battery, to charge to 80% and discharge to 5%, or charge to 100% and increase the discharge level to say 25%?

 

[Deleted member 4366]

100% is 4.2v per cell (say). 0% is 3.2v per cell (say). That would make 80% 4.0v per cell. How much capacity the cell has is irrelevant. 4.0v is always 80%..

Let's complicate it a bit. Some cells get their extra capacity by adding ingredient X, which allows you to charge them to 4.35v without damage. That would be 115%. Your laptop would still charge to the same voltage, so you wouldn't get that extra capacity unless you could tell it to go to 115%.

 

[Deleted member 4366]

If you're already on a replacement battery, the laptop must be old. By the time that battery runs out, the laptop won't have enough processing power to meet the demands of the day, so you'll chuck it. Battery life isn't an issue. Do you keep your car engine at constant revs so that your oil lasts longer?

 

[Fordulike]

100% is 4.2v per cell (say). 0% is 3.2v per cell (say). That would make 80% 4.0v per cell. How much capacity the cell has is irrelevant. 4.0v is always 80%..

Let's complicate it a bit. Some cells get their extra capacity by adding ingredient X, which allows you to charge them to 4.35v without damage. That would be 115%. Your laptop would still charge to the same voltage, so you wouldn't get that extra capacity unless you could tell it to go to 115%.

So, is it down to the software/BMS as to whether it will balance the cell at 4.0v?
I'm sure I read somewhere, probably wrongly, that the BMS will only balance the cell when fully charged.

What I'm trying to say is, will my laptop still balance cells in 80% mode?

 

[anotherkiwi]

Balancing 2P is going to be a lot easier than 5P, you have a 50/50 chance that one cell is bad in each parallel string and you will know straight away you have a duff battery.

I would suggest that you forget you know anything about 18650 charging and get on with enjoying your new laptop battery a.k.a. "just use it!"

 

[Fordulike]

If you're already on a replacement battery, the laptop must be old. By the time that battery runs out, the laptop won't have enough processing power to meet the demands of the day, so you'll chuck it. Battery life isn't an issue. Do you keep your car engine at constant revs so that your oil lasts longer?

It is fairly old, but for what I use it for, it still zips along very well. I use my tablet for stuff like YouTube etc. Laptop is for forums and occasional shopping, not too processor intensive.

I'm hoping to run it for a few years yet, as I specifically bought it for the matte screen, which are getting hard to come by these days on laptops.

 

[Croxden]

My Lenovo laptop keeps the charge at 50% when I'm plugged in, and that's most of the time. The battery is working fine unlike th HP before it that was at 100% charged. It soon failed.

But I charge my bikes fully after every ride and although not as they were when new are plenty good enough.

 

[Deleted member 4366]

So, is it down to the software/BMS as to whether it will balance the cell at 4.0v?
I'm sure I read somewhere, probably wrongly, that the BMS will only balance the cell when fully charged.

What I'm trying to say is, will my laptop still balance cells in 80% mode?

Most Ebike BMSs only balance at the top of the charge. Without seeing your laptop's BMS, it's not possible to say how it balances.

 

[Danidl]

Most Ebike BMSs only balance at the top of the charge. Without seeing your laptop's BMS, it's not possible to say how it balances.

d8veh, your responses to this and similar questions presupposes a specific type of BMS .. essentially analogue in performance, where the cells are all charged in a series configuration and then when the voltage accross an tier exceeds an externally imposed limit, bleeds off charge. Such BMS would be used in the long established commodity battery market
Have you considered that there are different topologies, eg ones where the current flow into and out of each tier and or into each cell s recorded, in addition to the voltage. Such arrangements can give redundancy, and individual cell optimisation,at a cost of more data processing.

 

[Fordulike]

d8veh, your responses to this and similar questions presupposes a specific type of BMS .. essentially analogue in performance, where the cells are all charged in a series configuration and then when the voltage accross an tier exceeds an externally imposed limit, bleeds off charge. Such BMS would be used in the long established commodity battery market
Have you considered that there are different topologies, eg ones where the current flow into and out of each tier and or into each cell s recorded, in addition to the voltage. Such arrangements can give redundancy, and individual cell optimisation,at a cost of more data processing.

Are you saying that my laptop is likely to have a more sophisticated charging control system, which is why it can charge to 80% with no negative effects?

I'm getting a little confused now

 

[anotherkiwi]

May have. I swapped out the Vaio battery for a cheap Chinese clone and the only thing it's BMS could do was turn the charger off when the battery was full.

 

[Danidl]

Are you saying that my laptop is likely to have a more sophisticated charging control system, which is why it can charge to 80% with no negative effects?

I'm getting a little confused now

Yes. But .. read what d8veh had said 80%of what. Think of the battery cell as a plastic barrel with a tap in the bottom. As the battery fills up it's weight ( total water or total charge) increases , also as the height of water increases , the pressure or voltage changes . If the barrel is filled and more water is added, the walls of the barrel expand slightly, and more pressure results but with very little extra capacity. Each time the barrel is filled and emptied, it forces and eventually wears out the walls
The li ion cell manufacturers have exactly the same problem, slightly more capacity for reduced lifetime or slightly less capacity and more cycles . They decide on what is to consitute as full capacity and 100%

One could extend this model by considering that there is a material inside the barrel wool or something else porous andThe water going in is dirty, . Each time the barrel is filled, a little bit more of the material gets clogged so less current can flow in or out...

 

[Deleted member 4366]

d8veh, your responses to this and similar questions presupposes a specific type of BMS .. essentially analogue in performance, where the cells are all charged in a series configuration and then when the voltage accross an tier exceeds an externally imposed limit, bleeds off charge. Such BMS would be used in the long established commodity battery market
Have you considered that there are different topologies, eg ones where the current flow into and out of each tier and or into each cell s recorded, in addition to the voltage. Such arrangements can give redundancy, and individual cell optimisation,at a cost of more data processing.

I didn't pre-suppose anything. I said it's impossible to say how the BMS works without seeing it.

If you're referring to ebike batteries, I'm constantly stripping them down. I currently have about 15 from various brands waiting for stripping and analysis. I must have stripped a total of 100 batteries by now. They nearly all have conventional bleeding BMSs. That's fact not presupposition.