The 'myth' of overcharging....

Hello,

I've been reading that keeping the laptop connected to AC while the battery is full will 'overcharge' the battery. It sounds strange to me because doesn't the laptop switch from battery power to AC power when the battery is fully recharged. Also, isn't overcharging when something gets a higher than normal voltage ?

Comments/confirmations/information are welcome....

Thanks

 

Read the battery guide.

 

My question is that doesn't the battery get switched off when the laptop is fully charged and that its connected to AC power ? My Pocket PC when it is completely charged shuts-off the battery and run on AC power. I touch the battery and its pretty cool... Don't laptops have a similar feature.... ?

 

Yes unless there is a malfunction you should not be able to overcharge.

 

Overcharging a battery will produce highly flammable hydrogen so it must be protected against for safety reasons.
However, holding a battery in float charge really isn't that good for it. It increases the moisture loss, which reduces efficiency over time.

 

That's the answer I was looking for... so basically, keeping the battery in while the laptop is on AC is not a problem. I guess the degradation at that point is pretty negligible....

 

don't overcomplicate things. as long as there isn't a malfunction in the circuitry, the laptop will keep the battery trickle-charging and switch over to AC power.

 

they have circuits now using simple ic's that will prevent any kind of major overcharging same as cell phones... they drop to a trickle state once they are fully charged. i have a cell phone on my desk that stays plugged in 24/7 for over a year now and i can still umplu and use the battery just fine with no issues. the older ni-cad's and some others yes but the newest li-ion or nickel metal's should be just fine..

 

are you an EE?

 

star will be one someday.

But star a float charge seems to be more of an issue with lead acid batterys and float charge reduces the loss of moisture vs Rapid charge. They sell "Float Chargers" because they help. And does not apply here.

Link

 

So should i keep my battery charged in or removed while using it for a long time?

 

I keep mine in because the minimal loss of battery life that the higher temps and top offs will cause make no diff to me. Storing your battery at 40% to 50% charge in a fridge will maximize it's lifespan but of course makes it hard to use. If you want to take it out it might add a very little amount of lifespan. It is a Choice.

 

Some guy told me when theres a surge, the battery will absorb the extra shock, dont know how true is it.

 

Some guy told me that if I stand outside in a thunderstorm and get hit with lightning, the soles of my shoes will take extra shock because they are made of rubber and everyone knows that rubber doesn't conduct electricity. Don't know how true it is.

 

Lithus that is not true.

 

If you have a thunderstorm, the shock will go through anything that conducts electricity.... A battery follows that function... so you better unplug your laptop if you find yourself in an area where thunder strikes are a great risk....

I guess the Electric Engineer can give more information on such... But I'm guessing that rubber shoes act an sort of insulator... prevent a complete circuit. But maybe... the voltage/amperage of the lightning can be strong enough to 'circumvent' the resistance of the rubber.......

 

Or buy a surge protector.

 

I think we are a little off topic but oh well

I don't think he was referring to a thunderstorm. Thunder striking ok lightning bad . Great risk? I wouldn't go that far.

Considering it travels through the air I am thinking that's a good guess.

 

correct me if im wrong, but i'm fairly certain lightning travels from the earth upwards to the sky, not the other way around

 

Way beyound my expertise but. Lightning tends to hit the highest object in the area, say the golfer on the golfcourse or the tree they hide under.

I believe that most lightning is from cloud to ground. Many types and much is not not known.

Lightning is so much voltage that sneakers are unlikely to stop it.

 

"Let's take a look at the process through which lightning is known to be formed. Lightning occurs because of a difference in charge between a storm cloud and the ground.

First, the base of a cloud sends down a little electric discharge, called a stepped leader. It descends to the ground in steps, each about 50 yards (about 46 meters) in length. This process is extremely fast and impossible to see with the naked eye. Each step is less than a millionth of a second long. The interval between steps works out to about fifty-millionths of a second. This process can only be observed with the assistance of extremely quick-exposure cameras.

The stepped leader generally moves at about 75 miles per second (120 km/s) towards the ground. A typical trip duration is 20 milliseconds. Atoms pass along electrical charge much more quickly than sound vibrations.

The stepped leader carries tons of negative charge. As it nears the ground, it induces enormous quantities of positive charge in the earth, especially at the tips of tall objects. Because opposites attract, the stepped leader and the negative charge at the ground reach towards each other and quickly meet. The path from storm cloud to the surface is complete and "the floodgates are open", so to speak.

Because the cloud is filled with negative charge, it has a lot of current to offer to the newly created discharge path. This charge quickly moves from being distributed throughout the cloud to being concentrated at the point where the stepped leader first dropped from the cloud, into the ground or an elevated object. This discharge is called the return stroke, and is what we think of when we hear the word "lightning".

The return stroke takes around 100 millionths of a second to reach the ground. The immense flash generated is enough to leave an afterimage in our eyes for seconds at a time, giving us the illusion that the lightning flash is longer than it really is. In reality, our eyes cannot resolve any of the steps involved. We only see the final product - a lightning bolt.

So, to answer the original question - put roughly, lightning does move from cloud to ground - if you consider only the return stroke. The whole process begins in the cloud, goes to the ground, then goes back to the cloud, then goes from the entire cloud to the ground. That's how lightning works." - http://www.wisegeek.com/does-lightning-travel-up-or-down.htm

what we see is the return stroke which travels from the ground up, but it essentially does both.

 

Reread 2nd to last paragraph.

Also there is positive lightning, the article in Wikipedia is far superior. It acknowledges that there is much we do not know. It describes many different kinds of lightning. Some lightning does come from the ground but most does not. Your source sounds like you misread what they are saying reread the last three paragraphs.

This article is just too broad but it does say cloud to ground.

 

Jeez this thread has degenerated. I was using the shoe example of how futile a battery is to stop a surge - just as powerless as your rubber soles will save your life.

 

Yes, let's cut that electricity mumbo-jumbo off right here, guys.

Whaddya think this is supposed to be... a discussion forum?!?

I thought that the catch with leaving the battery (for an extended period of time) in while on AC power was that the battery would be fully charged and then cutoff by the circuitry; but then over time, it would lose a bit of its charge, causing the charger to kick in again. Therefore, since batteries only have a certain number of practical discharge/recharge cycles, it would wear down the battery faster than taking out and storing the battery would. I'm pretty sure I read that in the battery guide but I might be wrong; I read it a while ago and might not be remembering it right.

edit: if a surge caused by lightning hit an outlet with a laptop plugged in, wouldn't only the AC adapter just be fried, leaving the laptop itself intact?

 

As far is "practical discharge/recharge cycles" think of those as "full" practical discharge/recharge cycles, so you are fine on that. Topping off is OK. The benifit of from removing the battery is minimal, the heat is likely a greater threat to longevity than topping off. Two charges when Battery is at 50% equal one full charge.

As to your Edit, Lightning is a phenomenon we do not completely understand. It appears all is possible. I believe people have died talking on the phone during a storm. The phone line is incapable of conducting that much current but it does, it is beyond any normal rules ergo a phenomenon.