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Proper Li-Ion Battery Care

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Ben333

Folding for Team 32!
Joined
Feb 18, 2007
I know I myself am curious about what's best for my laptops' batteries and I'm sure many others are too. I've got two laptops that still have working batteries, a Compaq Presario 2100 that I got new in 2004, and an Acer Aspire One that I got last year. Both of those sit plugged in all the time, and I figure that should give the batteries a top off if they ever need it. Now to the questions...

Laptop that isn't in use: Leave it plugged in? Cycle the battery for maintenance every now and again or just let it sit?

Laptop using the battery: Try and use as little battery as possible and recharge when possible or drain all the way before recharging?

My trusty old thinkpad was left in a bag for over a year back around 2005 when I stopped using it. (Before that it used to sit plugged in all the time) The next time I used it the battery wouldn't hold a charge for a second :( Don't want this to happen to my Compaq.

I'm also considering buying new batteries. One for the thinkpad, one for an old gateway solo and one for a sony vaio. Guessing the one on ebay with the highest MAH rating and the word NEW in the sale would win?
 

nd4spdbh2

Member
Joined
Nov 15, 2005
Location
Camarillo, CA!
when im on my netbook at home i keep the battery out of it and charge the battery up only when its not in use so as not to heat the battery up more than need be. and i only charge when i need the battery otherwise i will store the batt at a less than 60% charge. goes along with just about everything you should do with a li ion batt. served me very well... my netbook bat has shown no signs of wear, has always given me the same runtime.

Ben if you follow that guide ull have batts that last for quite some time.

one thing i have noticed espically with my mini 9. is that you dont wanna just use say 5% of the bat then stick it back on the charger as the internal circuitry to calculate how much storage the battery has can get a lil screwy. it would be better to say use the laptop down to 80% to make sure the batt knows where its at before recharging.
 
OP
Ben333

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
I have to disagree with you on a couple things Ben, it can't be good to leave the batteries sitting in a less than fully charged state, can it? I thought if you left a battery totally dead for a certain amount of time it would become junk - I figure that's what happened with my thinkpad. I'd imagine if I left my thinkpad plugged in (with the battery in) then the battery would still work somewhat today.

EDIT: Hmm, that article has some good information. So I guess I should drain my compaq's battery down to 40% and leave it out of the machine if I don't plan on using it? And my netbook that I use on AC power a lot I suppose I should do the same?
 

nd4spdbh2

Member
Joined
Nov 15, 2005
Location
Camarillo, CA!
ya its been known for some time that 40% charge is the magic number for storage of lithium ion bats, i have no clue why but it is why i never leave my batts at more than a 60 to 70% max charge if im going to store the battery for longer than a coupla days. It is why when you get a laptop you will generally see the charge level upon the first boot very close to 40%.

Ya get it close to 40% say ~ 45% then take it out if your going to be using the laptop for an extensive time just on ac power.
 

tricknasty

Member
Joined
Aug 2, 2004
Location
Los Angeles
thanks for the link to the article. I never knew to keep the laptop batteries stored at 40% charge. also interesting that the heat of the laptop itself degrades the battery. ~~
 
OP
Ben333

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
Ok, so being bored while waiting for my new batteries to arrive, I decided to crack open the Vaio's battery. Inside were three cells... so I got out my multimeter and not one had even a tenth of a volt. I started rummaging through my future recycling / proper disposal box and began testing some cells with my DMM. I found three matching ones that read over 2 volts, so I figured it was worth a shot. I stuck them in the places of the others and did a clean and tight wrap with electrical tape. Then, I had to modify the old battery case a little, but things did go together (with tape around the battery case :D). I booted and saw that it had began charging. In about an hour, I was full and unplugged from AC power and it stayed on! Now though, it doesn't want to power on from the battery. If I press the switch without it plugged into the power brick, it won't boot. But if I boot it plugged in and then switch to battery it works fine. Any ideas? Something else weird, while running on the battery it says "Charging" in windows.
 

Mpegger

Member
Joined
Nov 28, 2001
I believe those types of Li-Ion batteries start at 3.0V. Anything lower and the battery is pretty much toast, as its been discharged below its minimum voltage and will no longer hold a charge.
 
OP
Ben333

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
^ Well, I just used the three best matching cells I had... all a little under 2.5V.

@nd4, I don't think nicad cells would be charging on a laptop setup for lithium ion lol
 

cyberfish

Member
Joined
May 23, 2008
Location
London, England
Open cell voltage doesn't mean much. For many battery chemistries (not sure about Lithium ion), even when fully discharged, you can still measure significant voltage. But it will drop to ~0 once you put any load to it (very high internal resistance).

And if they are different chemistry... run for cover. Different chemistries have very different charging/discharging behaviours, with different charge termination techniques and so on. They are NOT compatible (eg, Li-ion is usually terminated by voltage, where NiMH is by temperature or dV/dt. If you charge a NiMH in a Li-ion charger, it will explode before it reaches 3.7V).