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DIY battery setup help Answered

Hi, I'm a first time DIY-er and would like to build a useful, long lasting battery pack for my *new* laptop (late summer). I'm 17, and this would be a perfect project for me to finish in the next few months. I'll be working with my dad and asking my physics teacher, who seems very all-knowing, for advice. My teacher understands electricity and batteries better than anyone else locally and is leading our STEM team, of which I am a member and need this experience. Keep in mind that I'm not just doing this to have a (much needed) battery pack for my laptop.

I got most of my information from here and will most likely be purchasing new batteries.

As far as the housing of the components, I have a hard plastic, 10+ year old lightly used blue lego container in the shape of a kid-sized briefcase. 

Old blue lego carrying case, 11” x 7.5”(9 including curved  front) x 3.5”

Insulation tape

Batteries: (x4)

Battery holders: (x4)

PCB: (protected voltage is higher, balance charger required)

Balance Charger:

Fuel Gauge:

DC port:

Wire terminals (for organization)

Balance charge cords:

Optional inverter:
I heard about these being inefficient, so I'm not sure about it.

Please inform me if there are any other parts that I'll need or if I've left out any information.

Also Inform me if everything I'll need for a lithium battery pack is on this list.

P.S. The case was chosen based on the fact that it will fit in my backpack with my books and looks much less alarming and more like a DIY battery than a black box or briefcase. especially with the fuel gauge and plugged in laptop.


It looks like a nice project but you need to consider if at the end your project is cost effective. Did you compare the cost of all your materials with the price of a replacement battery for your laptop?

Cost of all materials = 130-160, assuming minimal defective batteries

This is partially based on the irreplaceability of ultrabook batteries. This is based on multiple factors that led me to want this as a project (before I buy the laptop)

I'd like to use 4s6p for more AH, but the pcb only supports 4p.

That makes 14.8 volts, 12 amp hours, and 177.6 watt hours. Taking with a grain of salt, probably 140 watt hours, double an ultrabook's battery.

By cost effective I mean if at the end your project will bring you same or better results than with the conventional way. Say that you spent US$160 in your project, the last battery that I bought for my laptop was US$170, you saved ten dollars in your project. If you count the time and effort that you put on this project 10 dollars is not much of a saving. Even if you create a better way to power your laptop, your laptop's use of that power will be limited by its design. I don't mean to discourage you but it seems, at least to me, a waste of time and resources. Would you put a Lamborghini's engine in a small American car? Probably you could but, the frame of the car is not designed to run at the potential speed of the engine.

The time put in to building this pays off with time spent with my dad, bragging rights, and experience to be used towards next years' stem competition involving solar powered go-cart. I was not expecting any cost savings. Most manufacturers do not or will not make room for replacement or addon batteries for their ultrabooks.

Correct me if I'm wrong, I've only seen one ultrabook with an expandable battery.

The use of this is almost a plus to the bragging rights. This thread is mostly for "will this work with these materials and if not, what do I need to add or change?"

Edit: fixed typo

For your info, I plugged the words "ultrabook battery replacement" in Google and I got videos that show how to replace the battery. You seem excited about your project and I don't want to discourage you but I am more practical about things. My son is your age and he finds electronics a boring subject so have fun with your Dad!

my bad, I've only been looking at the flagship "convertible" ultrabooks, which often make it difficult to change a battery quickly.

Assuming that wattage would be equal on both ends of the laptop power adapter, I'd need a higher amperage to charge a laptop. Would either of the previously stated PCB or any other PCB work better for this battery pack?

To answer some of these questions I recommend that you PM (private message) Steveastrouk, Iceng or Frollard whom are knowledgeable in electronics.

I'm not sue the max amperage of the PCB (4-6) is enough to charge a laptop, can you confirm whether it would be enough through a DC charging cord? if not, where should I look for a better PCB?