Laptop battery has been fully discharged, any idea to wake it up?

[Willen]

I guessed my cells are not damaged, few days ago battery was fine. I think cells are discharged badly due to power short on laptop. So chip has been disconnected now. I thought i can create a link between battery n chip by charging cells manually (bypassing chips). Any considerations during testing n charging the cells?

 

[audioguru]

If you don't know about a dead Lithium battery then don't try to charge it.
Lithium is a very active dangerous metal. It can explode or catch on fire. An explosion splatters molten lithium all around. Its fire is extremely hot, something like a magnesium fire (used in white hot flares).
Water on a lithium fire makes it burn hotter.

 

[pebe]

The 'Battery University' states that charging an Li-Ion battery to a lower voltage than 4.2V can increase battery life, although the battery will have lower than normal capacity.

I want to leave a cell permanently connected to a voltage source clamped at 3.9V max (70% charged), Will it cause any problems? (Battery University does not give an answer).

 

[audioguru]

The battery in a laptop has about 4 cells of lithium. Each cell averages 3.7V and each cell is fully charged at 4.2V (16.8V for the entire battery. The battery has a "protection" circuit in it that disconnects it if its voltage drops to about 12.8V (3.2V per cell) so the battery is probably OK.

A Lithium battery must NEVER be continuously "trickle charged" and there is no reason to trickle charge because a charge lasts for years (if the battery is not used). This is what The Battery University says about it: "Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety". But I agree they do not talk about a lower than normal charging voltage.

 

[shafri]

"attended current limit" charging and periodically check if the cell is alive, every 5 minutes or so or every 10 seconds if you are paranoid. to be more on safe side, charge in a very spacious empty place with no combustible items around. how bad can it be? well, only as a last resort if all "approved" methods to resurrect the cell failed. if all failed, dig a hole put it in, buy new, eos.

 

[KeepItSimpleStupid]

The other "trick" is to reset the battery management system. You have to disable the ability to sleep, turn-off or whatever and let the laptop die on it's own and then re-charge.

 

[Willen]

The other "trick" is to reset the battery management system. You have to disable the ability to sleep, turn-off or whatever and let the laptop die on it's own and then re-charge.

Hi,
Is there any simple way to reset battery management system found inside of laptop battery?

 

[KeepItSimpleStupid]

That's the only way I know how. Capacity of the battery drops as the number of charges increases or the battery is abused. So, if the battery is 3-4 years old consider replacement.

 

[pebe]

.........A Lithium battery must NEVER be continuously "trickle charged" and there is no reason to trickle charge because a charge lasts for years (if the battery is not used). This is what The Battery University says about it: "Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety". But I agree they do not talk about a lower than normal charging voltage.

I consider this to be a float charge - not trickle charge. Normally, as the cell takes a charge, its voltage will rise until the maximum of 4.2V(?). If the charging voltage is clamped at 3.9V then, logically, charging will cease when that voltage is reached because the cell voltage cannot rise above the charging voltage.

My concern is whether there will be a small permanent leakage current that will prevent the charging voltage being reached, and if so will it be detrimental to the cell?

The intended use is a small piece of equipment that will be mains or battery operated. Batteries for portable use are 2 x 18650 Li-ion cells in series. I do not want to unscrew the case to remove the batteries for charging and I want to avoid switching if at all possible.

 

[audioguru]

I used an LM317 and a current-limiting resistor to charge two 18650 lithium-ion cells in series. I set it to 8.40V and let it charge for days. The battery stayed cool.

 

[pebe]

Thanks, you have reassured me.

 

[Willen]

I used an LM317 and a current-limiting resistor to charge two 18650 lithium-ion cells in series. I set it to 8.40V and let it charge for days. The battery stayed cool.

And what was the current level? 0.5Amp or less?

 

[audioguru]

And what was the current level? 0.5Amp or less?

I couldn't remember and couldn't find my schematic so I looked inside and saw NO current-limiting resistor. The LM317 is powered from a 9V/500mA wall wart and the LM317 set to 8.40V drops its output voltage (and therefore limits the charging current) when its input drops below about 10V. So the maximum charging current is about 250mA to 300mA.

 

[RCinFLA]

Single cell devices like cellphones and some tablets are much easier to manage the battery. Laptops have multiple Li-Ion cells in series to provide higher voltage. It creates a much more complicated battery management problem. Most laptops have a cell balancer management which is basically resistors that are placed across cells that achieve full charge before other cells.

Because laptop batteries have significant W/h capacity they also have the ability to create significant problems when things go wrong (like catch on fire). Many laptops have a eeprom or flash that tag the whole battery pack as bad if one cell drops below about 2 volts. This is not reversible unless you have access to software and hookup to reset the eeprom. Many have cut open a pack and replaced the individual cells only to find it still does not work due to the eeprom being tagged as bad.

All rechargeable Li-Ion devices should have a disconnect switch (Low Vds-On P-ch MOSFET switch) to prevent over discharge during usage. There is still cell self discharge and a few uA's for supervisor circuitry so even the disconnect switch will not save a battery that is left in the discharged state for months.

 

[Willen]

Single cell devices like cellphones and some tablets are much easier to manage the battery. Laptops have multiple Li-Ion cells in series to provide higher voltage. It creates a much more complicated battery management problem. Most laptops have a cell balancer management which is basically resistors that are placed across cells that achieve full charge before other cells.

Because laptop batteries have significant W/h capacity they also have the ability to create significant problems when things go wrong (like catch on fire). Many laptops have a eeprom or flash that tag the whole battery pack as bad if one cell drops below about 2 volts. This is not reversible unless you have access to software and hookup to reset the eeprom. Many have cut open a pack and replaced the individual cells only to find it still does not work due to the eeprom being tagged as bad.

All rechargeable Li-Ion devices should have a disconnect switch (Low Vds-On P-ch MOSFET switch) to prevent over discharge during usage. There is still cell self discharge and a few uA's for supervisor circuitry so even the disconnect switch will not save a battery that is left in the discharged state for months.

I am planning to cut pack and check the status of cells. If found good then will charge manually then will connect to system again to wake it up. But as you said if system already permanently locked then.....
Oh no... Do you or anybody know about HP laptop battery and its system?

 

[4pyros]

But as you said if system already permanently locked then.....

It battery controller may reset and unlock when disconnected from the cells.

 

[Willen]

It battery controller may reset and unlock when disconnected from the cells.

Wow nice! I hope HP battery system will reset/unlock after disconnect the cells. And I hope battery system will start to functioning after safe testing and charging.

 

[Willen]

And my last question is- Are there any device exist in market till now which will wake up fully discharged but well conditioned laptop battery?

I heared we can wake up cell phone battery and I heared there are various devices to wake up cell phones' fully discharged battery. Devices like trigger machine or drain or somthing....I forgot!

I am asking this because till now I didn't cut the battery pack because I don't want to cut if there are any devices which can repair without cutting pack. BUT if there are NO alternatives than cutting its pack then I won't wait more. More waiting might damage cells more badly. Tell me what to do?