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Ask HN: Should I unplug my laptop charger at 100%?

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Re: Ask HN: Should I unplug my laptop charger at 100%?

#71

Post by jotm »

DominikR wrote: post #55

My personal experience with a Lenovo W520 having the battery needlessly inserted for two years (40 hours per week) while connected to the charger: The battery lost 50% of its capacity. The laptop was almost exclusively used while connected to the charger. So if there hasn't been a big change in how laptop batteries work in the last few years I'd recommend removing the battery whenever the charger is connected if poss…

I found that fully discharging and recharging such a battery 3-4 times will bring it back to (near) its original levels.

I've always had laptops plugged in all the time (desktop replacements) for months at end, with the battery acting as a UPS.

When first disconnecting the power adapter, the batteries always discharged much faster than they should. After a few cycles, they went back to normal.

I believe that leaving a laptop plugged in all the time is better for the battery than doing complete discharge-recharge cycles (5-100%).

Re: Ask HN: Should I unplug my laptop charger at 100%?

#72

Post by Someone1234 »

hvjackson wrote: post #63
paulannesley wrote: post #18

> For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for…

The fact that Apple no longer has this statements on their website makes me think it's no longer true for their batteries (if it ever was).

Indeed. From my understanding, while this is still technically true, they have replaced the need for users to do anything with chips in the batteries themselves which shut off recharging when they're near 100%.

That's why if you pay attention you'll often see your battery % go from 97%-100% and then back down to 97%. It is reporting as "charging" but in reality it goes idle to let the battery de-charge a little.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#73

Post by revelation »

bkanber wrote: post #58

Source: I have a master's degree in mechanical engineering in hybrid vehicle powertrains, and a big part of my research was battery technology. I spent some time working with the folks at National Semiconductor learning this, so I have several primary sources. Disclaimer: my knowledge of the field is from ca 2010. 1) Lots of deep discharge cycles do negatively affect battery life. Try not to jump between 0% and 100%…

This assumes the battery percentage displayed is the SOC. This might be the case for laptops or small appliances where manufacturers are happy to trade long battery longevity for a small gain in time to empty, but the Model S for example has gap of a kWh+ and will simply not charge or discharge the battery fully, to avoid these cases where a very low of very high SOC damages the battery.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#74

Post by robotcookies »

My experience has been that it depends on the laptop and how it handles the charging. Some will keep trickle charging at 99% so it keeps recharging the laptop frequently. That wears out the battery and usually in a couple years it won't hold much charge. Other laptops though wait longer until it falls to say 94% even when you leave it plugged in. This reduces the frequency of recharging and the battery lasts longer.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#75

Post by JimmaDaRustla »

A few things:

1. A lithium ion battery charger is smart, it will not overcharge or harm your battery in any way keeping it charged.

2. In terms of discharging a lithium ion battery - they are not susceptible to memory like ni-cd and ni-mh batteries, so regular discharging is not required.

3. Apple and other companies will suggest discharging your lithium ion battery fully. The reason being that a complete discharge followed by a full recharge will update an internal counter which records the capacity of the battery. The capacity decreases over time, so your battery charge indicator will need this full discharge/recharge regularly to stay accurate. Not important for actual capacity you get out of your battery.

4. There is a recommendation that in order to get the MOST NUMBER OF DISCHARGE CYCLES out of a lithium ion battery, you should only discharge it to 50%. I put MOST NUMBER OF DISCHARGE CYCLES in bold because it is important to know that this is the most important factor in the life of your battery - you do not need to discharge the battery to 50% in order to get a longer life, but if you do need to discharge it, 50% discharge is optimal to avoid any damage by over-discharging. If you discharge your battery EVERY day because you charged it to full, you are going to severely decrease the lifespan.

5. (Edited in) Laptops and phones use a State of Charge estimation model to decide how full the battery is. Depending on the device, the manufacturer may suggest fully discharging and fully recharging the battery so that the estimation model understands the capacity of the battery and avoids overcharging: http://chargedevs.com/features/the-challenges-of-battery-sta...

My recommendation: Don't discharge when it is full. Only discharge when you need to. Charge it at 50% if possible to avoid over discharging. KEEP IT COOL - heat kills batteries lifespan as well.

Battery technology has changed a lot since I worked in the industry - they're always advancing and changing. There are many resources to keep yourself well informed: http://batteryuniversity.com/learn/article/how_to_prolong_li...

Edit: All applications and devices are different. My recommendation might not be the best - some have suggested avoiding keeping your battery at 100% constantly, whereas my suggestion assumes that the charger won't harm the battery by overcharging. For example: battery is at 100% on the device, but in actuality it is sitting at 90% state of charge in the context of lithium ion technology.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#76

Post by thisispete »

yexponential wrote: post #23

Tesla e should know this.

Not sure if it's exactly pertinent, but If I remember correctly tesla recommends draining your battery to 20% then charging back up to 80% when driving on a road trip, but this if mostly for speed of charging. The car battery charges fastest in this half-full range, charging past 80% to 100% is a exponential rate like blowing air into an already full balloon, it gets harder as you reach 100%.. to their recommendation is not necessarily about battery health but more likely about reducing the speed of your mid-trip recharge.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#77

Post by tjohns »

tdkl wrote: post #20
cjbprime wrote: post #2

No. Your battery degrades each time there's a cycle of charge->use. If you're lucky, you can do that a few thousand times before you lose much of your battery's capacity. If you leave it plugged in, you aren't losing cycles, so you should do that.

> If you leave it plugged in, you aren't losing cycles Too bad that some batteries wear out even faster this way because of the heat.

Why would there be extra heat if the battery is fully charged? Shouldn't a well designed charge circuit disconnect once the battery hits 100%?

Re: Ask HN: Should I unplug my laptop charger at 100%?

#78

Post by jotm »

ars wrote: post #7
cjbprime wrote: post #2

No. Your battery degrades each time there's a cycle of charge->use. If you're lucky, you can do that a few thousand times before you lose much of your battery's capacity. If you leave it plugged in, you aren't losing cycles, so you should do that.

A cycle from say 70% to 80% doesn't wear it out much at all. The problem with leaving it at 100% is that just sitting at full charge wears it out, it's better to just keep it within 40%-80% than to leave it fully charged.

If the indicators are correct, HP's chargers keep the batteries at ~95% (varies between 95-100% all the time). So they're not keeping them fully charged or overcharged, but instead leave some breathing room.

Re: Ask HN: Should I unplug my laptop charger at 100%?

#79

Post by ignostic »

ars wrote: post #7
cjbprime wrote: post #2

No. Your battery degrades each time there's a cycle of charge->use. If you're lucky, you can do that a few thousand times before you lose much of your battery's capacity. If you leave it plugged in, you aren't losing cycles, so you should do that.

A cycle from say 70% to 80% doesn't wear it out much at all. The problem with leaving it at 100% is that just sitting at full charge wears it out, it's better to just keep it within 40%-80% than to leave it fully charged.

A 40% depth discharge is going to put way more wear than leaving it at 100%. Unless you want to plug and unplug constantly most users are probably best leaving it plugged while working.

If you really want to, you can do a little bit of good by letting it drop to 40=80% during periods of non-use.

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