Opening a battery pack and connecting an external power source, such as a 12 volt

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MisterBill2

Joined Jan 23, 2018
7,029
With some models of HP laptops, including those that I have, the power connector has a skinny center pin that is used to communicate between the charger and the bios. That pin is very fragile and if it breaks off then the bios will refuse to allow battery charging. This leads to a stone dead battery and no way to recover. And in many laptops the fragile solder connection of the power connector to the motherboard will break and no charging at all, but the computer will work if the battery can be charged in another computer. Re soldering would not be hard but the 23 pages of instructions for dis-assembly discouraged me.
I have been wondering about opening the battery pack and instead of replacing the cells, add connections to run it from external DC power, such as 12 volts in my car. Then I could use the free WiFi at fast food places from my car and not need to stay inside and run on battery power because of no AC outlets available. Regulating 12 volts down to 10.73 volts should not be so very hard, I don't think.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
Has anybody done that? Opening a battery pack and connecting an external power source, such as a 12 volt automotive battery system connection? If the pack is a nominal 12 volt stack of lithium cells it seems reasonable, but I am hoping to learn about what others may have discovered.

(Perhaps I should post this as a new thread???)
 

ian field

Joined Oct 27, 2012
6,539
Has anybody done that? Opening a battery pack and connecting an external power source, such as a 12 volt automotive battery system connection? If the pack is a nominal 12 volt stack of lithium cells it seems reasonable, but I am hoping to learn about what others may have discovered.

(Perhaps I should post this as a new thread???)
There's a blog somewhere from a guy who hacks apple stuff.

AFAIK: most packs have power management MOSFETs that only enable the pack if it gets the expected key code from the device. you probably have to cut a hole each end to get at the cell terminals without going through the PCB - I have no idea how the charge balancing system will react to that.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
There's a blog somewhere from a guy who hacks apple stuff.

AFAIK: most packs have power management MOSFETs that only enable the pack if it gets the expected key code from the device. you probably have to cut a hole each end to get at the cell terminals without going through the PCB - I have no idea how the charge balancing system will react to that.
Actually, I do have some stone dead battery packs for my HP probook 6450b machines. I had presumed that the cells were dead, but they might not be. Interesting indeed. But presently there is nothing to lose because of the pack not working at all. I have recharged lithium cells with a low current regulated supply. Not a fast process by any stretch, but that was not the goal.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
The problem with the computer battery packs is that they are solidly welded closed, obviously intended to never be serviced. Perhaps it would be effective to start referencing them as "products not worth repairing", which would hopefully be perceived as a negative remark about the quality. Much of the "design for manufacturing" mantra winds up producing products that are difficult or impossible to open without damaging them. But a $120 battery pack is a big part of the computer price and so it really should be made to be serviced. Mostly, the computers are made so that they can be serviced, although repairing the broken surface mount solder connections at the power connector is a tedious and painful ordeal on most computers. It is appalling that HP and Dell have produced such fragile assemblies.
 

ian field

Joined Oct 27, 2012
6,539
Actually, I do have some stone dead battery packs for my HP probook 6450b machines. I had presumed that the cells were dead, but they might not be. Interesting indeed. But presently there is nothing to lose because of the pack not working at all. I have recharged lithium cells with a low current regulated supply. Not a fast process by any stretch, but that was not the goal.
There's a minimum spec for terminal voltage - the charge management chip probably blocks any further activity on dead cells.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
There's a minimum spec for terminal voltage - the charge management chip probably blocks any further activity on dead cells.
So I need to open the pack and recharge each cell individually. That sounds very tedious indeed.
But it would completely explain why one of my computers has suddenly refused to acknowledge or charge it's battery pack, which seemed to be OK a couple months earlier. Thanks for the information.
 
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ian field

Joined Oct 27, 2012
6,539
So I need to open the pack and recharge each cell individually. That sounds very tedious indeed.
But it would completely explain why one of my computers has suddenly refused to acknowledge or charge it's battery pack, which seemed to be OK a couple months earlier. Thanks for the information.
Charging individually is the safe option as charge balancing probably shouldn't activate.

I used my brute force & ignorance charger (not allowed on this forum) to charge a whole pack just to see what happened.

Its risky unless you know the device ratings in the balancing system.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
What I would hope to do is find out what pins on the battery connector are the output. Since the whole string of batteries is about 12 volts, or maybe less, it should not be very hard to run the whole computer from a car;s 12 volt system. Lots of filtering and a bit of circuitry to limit the voltage, which should not be really difficult. And for the Dell computer, I just want to get the battery pack working again.
 

ian field

Joined Oct 27, 2012
6,539
What I would hope to do is find out what pins on the battery connector are the output. Since the whole string of batteries is about 12 volts, or maybe less, it should not be very hard to run the whole computer from a car;s 12 volt system. Lots of filtering and a bit of circuitry to limit the voltage, which should not be really difficult. And for the Dell computer, I just want to get the battery pack working again.
There may not be any point - some interrogate the device for a key code before enabling main power.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
7,029
There may not be any point - some interrogate the device for a key code before enabling main power.
Thanks for the bad news, I.F. But I suppose the only way to find out is to try. Sharing one good battery between two laptops is tedious, and the other one does not even acknowledge when I apply the power. That one is an HP Pavillion dv6000, the tag claims it will run on 18 volts, drawing 3.5 amps. So since I don't have the original supply I attached a correct sized plug to an 18 volt 5 amp supply, and nothing happens, it does not draw any current nor does the ring around the connector, which is supposed to light up, illuminate. I would disassemble the computer to see if the poer connection has broken, but I don't see any way to take it apart.And since the condition, at least physically, is "very good" I don't want to start hacking away just yet.
 
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