Keeping laptop battery healthy

[David]

Hi there,

I recently got a new laptop an my Dad is telling me I should let the battery completely drain before charging it every time, is this true?

Oh and the laptop is an Apple Macbook

Cheers

[The Natural Philosopher]

No, its bollocks.

Its an urban myth that arose out of one incident once with nickel batteries. Everyone today uses Lithium polymer and its completely irrelevant to that chemistry.

Place it along side teh 'moblie -phones set petrol on dfir when filling you r car' myth.

Again, concidentally, someone's petrol caught fire about the same time they took a call. Some bright spark suggested it must have caused a spark. Every car that drives in has a bonnet full of sparks. On a hot or very dry day you get far bigger ones between the car and the grounded metal filler anyway.,

[David]

Thanks, so what is the correct way to keep it healthy?

[Bob Minchin]

Just don't let any spare ones go flat/uncharged for long periods. I just swap mine around every month or so.

Bob

[gazz]

Take it to the gym twice a week, make sure it gets a good portion of fruit n veg daily, avoid junk food etc :)

Honnestly, just use it as you want to, it'll take care of it's self,

my current laptop is coming upto 3 years old, battery still lasts the 1 hour

45 mins it did when new, and it spends 3/4 of it's life on the charger, only thing i do that others may not is take the battery out when i'm in the motorhome and run it directly off the power supply/charger, as it's a 12 volt charger i use, and doing this saves me 2 amp hours from the motorhomes batteries not charging the lappy whilst powering it on a night, i'll charge it turned off during the day when the suns out and working me solar panels.

But modern li-po batteries are amazing compared to the old nickel cadmium batteries use a few years ago, the laptop has built in protection so it wont let you over discharge them... which is what will kill a li-po battery, but unless you deliberately remove the protection circuitry from the machine, you dont even need to think about that.

other thing that dammages li-po's is over working them, i.e. pulling more power than they are rated for, but modern batteries have very good C ratings, 30C is pretty common now, that means for a 1 AH li-po battery, you can pull 30 amps from it safely, but in a laptop this is is irrelivent, i fly electric model aircraft, where very light small batteries are used to give performances that almost rival engine powered craft.

so really, just use the laptop how you want, yes in 2, 3, 5, 10 years time the battery will fail, but you'll have had your moneys worth out of it, and you wont even think about getting a new battery, as it'd be cheaper to get a new laptop as your current one will be well out of date and aproaching obsolete.

[andrew]

I don't believe it is, the problem related to nicads under very specific circumstances and the myth has spread from that.

In general a battery has a life which is a function of time and the cycles of discharges and charges, the integral of all the amps flowing.

I have a firend who always disconnects his laptop battery if he is using it from the mains for this reason plus he says the chargers overheat the batterry when it is being used. I'm still not sure about this one but I have managed to kill my laptop battery in 3 years and I seldom used it away from the mains.

AJH

[Adrian C]

Plenty of the manufacturer's advice on

particular

[Clive George]

Rather spoils one of the great advantages of a laptop if you unplug the battery - built in UPS.

Mine is seldom used away from the mains and seems happy enough - HP business laptop, so may be better quality than some of the cheaper kit.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember David saying something like:

I know from experience what to avoid - leaving it on charge as standby for weeks on end. It kills batteries. Since I stopped doing that, the replacement batteries have lasted years.

[js.b1]

L-Ion batteries comprise multiple cells and a management chip. If a cell within a L-Ion battery goes sufficiently out of spec then charging could result in an overheat hazard. The purpose of the management chip is to identify this risk amongst others and prevent the battery from charging, rendering it dead but safe.

Some people think that L-Ion batteries have a management chip which "counts N charge cycles then dies" having experienced several failures around the same time (usually just out of warranty). It is possible that a management chip could work on a charge cycle count, but more likely it operates on overly stringent charge criteria (same thing, just more difficult for a class-action suit to win!). Basically it comes down to battery cell quality and matching cell voltages (thereby achieving a better battery than a production population distribution of cell voltages would indicate).

With a laptop permanently on mains AC (eg, desktop replacement usage) the L-Ion battery may be sitting on standby charge for extended periods - which is known to diminish its capacity. It comes down to the particular charger design and the controlling software. Thinkpads for example use a battery conditioner program to extend battery life.

The best solution is to remove the battery and recharge periodically - unfortunately that loses the "integral UPS" a battery provides during AC failure and a known charged battery should the laptop be moved off AC. It comes down to the particular laptop in some cases - I think HPQ were hard on batteries once, others better (check the relevant forums for experience).

[Rod]

As is mine. At the moment it says '98% available (plugged in, not charging)' - which rather suggests that the charging mechanism avoids doing any charging when the battery is close to full. And the charger itself is usually fairly cool - only really warming up when it definitely is charging and being used at the same time.

My previous machine (a Toshiba) suffered only slowly reducing battery capacity despite being abused. After a few years, I did get a higher capacity replacement which has so far lasted a couple of years.

[js.b1]

Indeed, you should still have >50% capacity after 2.5yrs. For some laptops that may mean only 1hr 15min runtime, others still "a good few hours".

[David]

Thanks for all the useful input guys, might show my Dad this!

[The Natural Philosopher]

Cool, half charged.

[D.M.Chapman]

As it's a mac,

might be of interest (as well as reading Apples own advice that someone linked to earlier).

Cheers,

Darren

[Jules]

Yep, pretty much the same with my Dell - the battery's about the only good thing about it :-) Must be about 4 years old now, and I still get about 2 hours out of the battery off-charger, and normally run it from the mains PSU for maybe 95% of the time.

[Mark]

Don't use it ;-)

Seriously though these batteries have a finite number of charge/discharge cycles so it is better to disconnect the battery when you can (i.e. when using on the mains).