Summary of Open Source 12V Power Bank
The author built a custom 12V power bank because commercial options for high-end tablets are either too expensive, underpowered, or incompatible. Existing solutions include Quick Charge models that lack generic 12V support, expensive proprietary units, and mid-range banks with insufficient current. Car jumpstarters were also rejected due to unstable voltage ranges.
Parts used in the Open Source 12V Powerbank:
- Li-ion cells
- Charging circuit board
- Output connector compatible with 12V +/- 5%
- Cube i7 Stylus tablet (for testing compatibility)
- Microsoft Surface series (as reference for input requirements)
Why did I build a power bank?
Why would anyone even try to build a power bank – i.e. an external battery for charging mobile devices – these days? These things are commodity, it’s impossible to compete. Right? Well, that is until you find out that the type of power bank for your application, namely charging a higher-end tablet with 12V input, does not exist cheaply. Looking around for 12V power banks yields a lot of li-ion car jumpstarters (*) and very few actual power banks. Those that exist are pretty expensive and often don’t even perform that well. Let’s run down the list:
(*) Car jumpstarters will not work, because they have a 3S pack of li-ion cells directly connected to the output, meaning the output actually varies from about 10-12.6V. My tablet (Cube i7 Stylus) and the Microsoft Surface series only accept 12V +/- 5%
Prices exclude shipping. I tried my best to include an example of every ‘category’ of available power bank in this list, but there are obviously hundreds. They fall into four general categories:
- QC2.0 chargers, which use the new Quick Charge protocol to deliver 5-12V at up to 18W to supported mobile devices. These are the only ‘cheap’ 12V power banks, but unfortunately also woefully underpowered as well as using a communication protocol on the charging port. That makes it very hard to use as a generic 12V charger for a tablet.
- Ridiculously expensive chargers. There are a bunch, and they all retail for between 100-400 dollars. Some are specifically marketed towards high-end laptop/audio/photographic gear. They do have really good specs (often up to 4-6A outputs and variable output voltage), but are also generally heavy and very proprietary in their connections.
- ‘Almost there’ power banks. There are a lot of 12V/1.5A and 12V/2A power banks in the $60-100 price range. Unfortunately, I need 2.5A to be able to charge AND use my tablet and $60 is a bit on the high side, especially with more than $15 shipping (to Europe). Locally, these tend to retail for €100+.
- Weird application-specific stuff. I put in a solar charger. Often without satisfactory documentation
So, how do we fix this? Well, build your own.
Read more: Open source 12V powerbank
- Why did the author build their own power bank?
Commercial 12V power banks are either non-existent, very expensive, or do not perform well enough for high-end tablets. - Can car jumpstarters be used to charge a Cube i7 Stylus?
No, because they have a 3S pack directly connected to the output, causing voltage to vary from about 10-12.6V instead of the required 12V +/- 5%. - What is the main limitation of QC2.0 chargers mentioned in the text?
They use a communication protocol on the charging port and are woefully underpowered, making them hard to use as a generic 12V charger. - How much do the expensive high-end power banks typically cost?
They retail for between 100-400 dollars. - Why were the almost there power banks considered unsuitable?
The author needed 2.5A to charge and use the tablet simultaneously, but these banks often only provide 1.5A or 2A. - What issue was found with solar chargers listed in the market?
They often come without satisfactory documentation. - What specific voltage requirement does the Cube i7 Stylus have?
It requires a stable 12V input with a tolerance of plus or minus 5 percent. - Are cheap 12V power banks widely available according to the article?
No, while QC2.0 chargers are cheap, they are not suitable for generic 12V tablet charging applications.
