Making a external battery for a laptop

[patrick4525]

so i wanted to have a external battery for my laptop

the charger for my dell vostro 5568 provides 19.5V to the laptop

i took a dewalt 18v drill battery and connected it (i know the 18650 lithium cells makes the fully charged battery go to 21.25V but i read somewhere that electronics could operate in between 10% so im thinking that is fine)

but there was a 3rd wire in the laptop cable. 

i measured it and it was 3.4V DC and also 3.4V AC for some reason

i took and connected one of the cells of the dewalt battery and it gave it 4.25V that is a litte high

which comes to my problem when i plug in the dewalt battery it says plugged in not charging (in windows)

[AvocadosGuac]

dont fucking do this...

 

You're gonna kill the damn laptop and the expensive battery

[patrick4525]

5 minutes ago, Jrock said:

dont fucking do this...

 

You're gonna kill the damn laptop and the expensive battery

well i have already plugged it in and the laptop still works and charges with the original charger

[tikker]

So basically you want a powerbank? Why not just get this from Dell themselves then instead of risking destroying your battery and potentially your laptop with it. Yours is on the compatability list on the bottom of the page.

[flextrex]

I guess its for communication with the charger... maybe using IC2 or something propietary. I guess this will becom difficult for you. I would try to give in the 18650 power into in attached battery directly. So you connect them up in parallel and therefor have more capacity. It's worth a try but don't blame me if you destroy you battery.

[patrick4525]

4 minutes ago, tikker said:

So basically you want a powerbank? Why not just get this from Dell themselves then instead of risking destroying your battery and potentially your laptop with it.

well i dident know it existed

[tikker]

1 minute ago, patrick4525 said:

well i dident know it existed

Well now you have a safer alternative  

[patrick4525]

1 minute ago, flextrex said:

I guess its for communication with the charger... maybe using IC2 or something propietary. I guess this will becom difficult for you. I would try to give in the 18650 power into in attached battery directly. So you connect them up in parallel and therefor have more capacity. It's worth a try but don't blame me if you destroy you battery.

well i was hoping it was more simple

[patrick4525]

Just now, tikker said:

Well now you have a safer alternative  

correct. its a little expensive but its better than frying my laptop

 

[tikker]

1 minute ago, patrick4525 said:

correct. its a little expensive but its better than frying my laptop

 

Yeah. Almost a second *insert certain fruity company here* with their accesories  

[patrick4525]

i was hoping a custom bios could do something

am i correct in that?

[manikyath]

10 minutes ago, patrick4525 said:

correct. its a little expensive but its better than frying my laptop

 

its expensive because its a pretty high power device

 

also, the third wire is a "sense" line that communicates the charger's capabilities to the laptop in a really vague way.

[manikyath]

1 minute ago, patrick4525 said:

i was hoping a custom bios could do something

am i correct in that?

you want to break stuff? because thats how you break stuff.

 

and no, custom bios would do more bad than good, also good freaking luck getting said custom bios written

[Catsrules]

There are a lot of external battery packs.

Here is an example
https://www.amazon.com/MAXOAK-50000mAh-Portable-External-Notebook-Most/dp/B00YP823NA/ref=sr_1_1?ie=UTF8&qid=1506630370&sr=8-1&keywords=battery+backup+laptop