Charging laptop battery?

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Hey guys and gals,

I figured I'd start here since the signal to noise ratio is quite good here ;) I have a laptop battery pack that I want to use for another project. It's currently had its case removed and is being used outside of the laptop. But to charge it I have to return it to the laptop at least overnight. I'd like to be able to charge it externally, using a 3rd party charging circuit. It's 11.1v, and has 12 cells, so I guess that's 3s4p. If so, is this the thing I'm looking for?

https://www.banggood.com/4S-40A-Li-ion-Lithium-Battery-18650-Charger-PCB-BMS-Protection-Board-with-Balance-p-1405559.html

It seems all too easy if that is. I'm concerned that I'm missing some factor that I haven't taken into account. I don't know what I don't know, you know? Thanks a lot :)
 

Radical Brad

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I am not sure this is what you want, unless you have actually cracked open the pack to determine what kind of ballancing and internal charge monitoring circuitry it has with it (if any). The charger you linked to looks like it was made for balanced 18650 cells that do not have active balancing circuitry with them. That is just my guess though, and this site has a lot more info...


If the lithium bomb factor is a concern, try LifePo (Lithium Iron), I have used that style battery it a lot when burning down a house is a concern. All assistive devices have also moved to LifePo, it is only slightly less power dense than ION, but 4 times as dense as SLA.

Brad
 
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Thanks Brad. It looks like I may have the right thing, then. I'm trying to replace the board on this:



You can see it's a set of 18650's. That board is the BMS that's made to integrate with the laptop, but I want to replace it with something that I can power with something other than the laptop itself. I'm not concerned with burning anything down really, although being careful with implementation is key to such things. I've also already got the battery, which is a bit of a deciding factor. I purchased this battery for a laptop, but the BMS is defective. It doesn't report the charge to the laptop correctly. The seller sent me another battery and told me to keep this one, hence its availability. I currently use it to power small ham radio projects, and who knows... it may do so on 3 wheels too ;-)
 
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Thanks Brad. It looks like I may have the right thing, then. I'm trying to replace the board on this:



You can see it's a set of 18650's. That board is the BMS that's made to integrate with the laptop, but I want to replace it with something that I can power with something other than the laptop itself. I'm not concerned with burning anything down really, although being careful with implementation is key to such things. I've also already got the battery, which is a bit of a deciding factor. I purchased this battery for a laptop, but the BMS is defective. It doesn't report the charge to the laptop correctly. The seller sent me another battery and told me to keep this one, hence its availability. I currently use it to power small ham radio projects, and who knows... it may do so on 3 wheels too ;-)
This isn't my area of expertise really so I may be talking very much out of turn.
What voltage and current does the Laptop's charger kick out? My one here says that its output is 20V @2.5A (say 50 .. 60Watts?).
Can you not just use any DC source higher than this and a couple of balanced buck-converters to supply the required volts and amperage?
I did this to power a wide range of electronics from my e-assist 20AH battery. I had 2 x 12V cooling fans (to keep the buck converters cool - if required) and a 25Watt per channel 12v motorbike MP3 player.
It worked very well and brought both smiles & frowns to those who heard opera and classical music as we bowled along. :D:eek:😢
I must confess that it was rather intrusive, and I won't do it again.
 

Twinkle

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Look at model radio control lipo chargers they use a simpler system to monitor and charge .about 18GBP and they have 12v or mains powered versions


regards emma
 
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Look at model radio control lipo chargers they use a simpler system to monitor and charge .about 18GBP and they have 12v or mains powered versions


regards emma
Thanks for the ideas, all! I'll check out the RC stuff too :)
 
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My thoughts as well. I would have thought that a measure of current and voltage supplied to the battery pack from the laptop would tell you what sort of DC supply to use. That would have been the way I would tackle it. The BMS ensures that each cell is balanced, controlling the charge and shutting it off when no longer required. Using the BMS that already exists would save some work/expense.

Amateurs usually have more than one DC supply. You mentioned it is 11.1V so I would expect a 12V battery could do with the current BMS doing its job.
 

Twinkle

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a 3s pack will reach 3 x4.2v ( 12.6 v ) When fully charged . The model lipo charger is probably the better route to take if eventually you find more cells to configure for more power packs.
cell voltage monitors are also available for a few dollars each .

regards Emma
 
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I wanted to thank everyone for their input. I looked at the module that is on the battery and it is quite small. I suspect that it can only provide a small amount of amperage before self-destructing. I will be powering a headlamp and possibly rear lighting as well as a 5-volt USB charger and maybe at some point will need to draw a couple of amps for a radio. I went ahead and ordered the part that I linked to in my opening post.

I also ordered the missing link: the charging circuit! It turns out that the part I linked to is only for protecting the battery from me overdrawn but it is not a charger. They are two separate pieces. I also ordered the USB charging circuit which also has a voltage monitor on it.

Burning down the house is of course a concern. The initial testing will be done in an ammo can away from the house enough that if it does catch on fire it won't destroy anything.

Once all the parts arrive I will try to get set up and report back.
 
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