Electrical people, tinkerers, handypeople, renaissance people, puzzlemeisters, and hornswogglers...

[Ralphie ★]

Why would a laptop battery suddenly start to only charge to 73%?  The battery is just a couple of years old but already shows a full charge of only 3460 mAh, versus design of 7800.  That latter part sounds like the way a battery would wear, but not charging fully seems odd.

[groupw]

I’m not an expert on current battery tech, but sounds like a cell went bad. 

[Ralphie ★]

Just now, groupw said:

I’m not an expert on current battery tech, but sounds like a cell went bad. 

Works for me - thanks!  And sorry I left oot computer people.

[maddmaxx ★]

Well, now that you asked computer people, a cell failed.

It would appear that your "battery" was 2 cells in parallel to boost the capacity and is now just one.  Same power, just half the time.  

It's probably time to start hunting for a new battery.

[Ralphie ★]

5 minutes ago, maddmaxx said:

Well, now that you asked computer people, a cell failed.

It would appear that your "battery" was 2 cells in parallel to boost the capacity and is now just one.  Same power, just half the time.  

It's probably time to start hunting for a new battery.

My money was really on a hornswoggler.

 

 

[2Far ★]

Prolly oughta call a chemical engineer to esplain why batteries lose their mojo. 

[Kirby]

Sorry, I can only help you with closets.

[JerrySTL ★]

2 hours ago, maddmaxx said:

Well, now that you asked computer people, a cell failed.

It would appear that your "battery" was 2 cells in parallel to boost the capacity and is now just one.  Same power, just half the time.  

It's probably time to start hunting for a new battery.

Maybe someone broke the tab between the two cells. 

[maddmaxx ★]

26 minutes ago, JerrySTL said:

Maybe someone broke the tab between the two cells. 

Go ahead, kick me.

[Ralphie ★]

2 hours ago, 2Far said:

Prolly oughta call a chemical engineer to esplain why batteries lose their mojo. 

I did come across an article saying a li-ion cell is only good for 300-500 cycles.  I hope that was old info and they are better now!  

[Kzoo]

Hornswoggler here.  I got nothing.  A bad cell is a good WAG.

Never trust a hornswoggler.

[Ralphie ★]

5 hours ago, Philander Seabury said:

I did come across an article saying a li-ion cell is only good for 300-500 cycles.  I hope that was old info and they are better now!  

I also read that the voltage it gets charged to makes a big difference and lower voltages can bring the the cycle life up to 2-3000. 

[maddmaxx ★]

Battery charge current is expressed in "C" rate.  For a 1000mah battery (1 amp hour or 1000 milliamp hours) a 1 c rate would be a 1 amp charge current which would charge the battery in a little over 1 hour.  This is a "safe" rate.  Many batteries can be charged at higher rates but still "like" that 1 C rate best.  The c rating also helps to describe the ability of a battery to discharge as well.  This is why you see batteries designated with a cell count, mah size and c rate.  For example, in my drag car I use a 2S (2 lipo cells for 8.4 volts) 8000 mah (capacity)  100C rated battery.  One recent run logged an 80 amp peak current and I'd like to get more, perhaps as much as 140 amps.  I still charge it at much less than a 1c rate (about 3 amps)

Next.  Your modern batteries, unlike NiCad's of old do better if they are not discharged to the bottom of their capacity.  They do  better if they are charged more often, say when they hit 50% or so.