Icarus Ligths Di2 Battery Circuit Board

Pat Gerke is know for Icarus Lights.  He has designed a bike light that can be totally customized to your riding style.  His next project is just as cool.  When FairWheel bikes came to Pat with a new challenge he was excited.  That challenge was to build a better Di2 battery that could be mounted internally.  His solution is what we have pictured above.  The cylinder fits 31.6 seat posts, but custom cases can be made.  While the case on this pre-production model is clear plastic, I am told the production models will use a thin walled aluminum.

Past the break you will find the tech details, and a photo of a pretty slick custom install.

Icarus Ligths Di2 Battery Pack

The Technical Details:

  • Retail price is $150.00
  • Available with both External USB port or Internal USB port (for affixing in Seat Post)
  • Charge via a Micro USB port (Cable with the battery) So you can charge it with the same cable as your smart phone, etc.
  • They have a capacity of 900mAh, which is 150% more than the stock Di2 batteries.  Good for up to 6 months battery life.
  • The weight of the prototypes is 88grams, including the cells, casing and charger. Final production weight should be similar.
  • Charge time from a complete drain is approximately 4 hours
  • Designed to fit inside all standard 31.6 Seat posts. Custom casings can be worked out as well.

At this time, Pat does not have the information up on his website.  However, if you would like to inquire about, or purchase the battery pack you can contact him at orders@icaruslights.com.

Icarus Ligths Di2 Battery Internal USB Port
Rob English of English Cycles put this new battery pack to good use in one of his latest builds. Just park your bike near an outlet, and use your cell phone charger.




  1. @Leon The port on the English bike has a rubber plug in it. Others that have used this setup tuck the entire assembly in the seat post. Being that it rarely needs to charge, it’s not so bad, but it does require the removal of the seat post.

  2. @Norcom – I wouldn’t say trustfire are cheap in terms of quality. I looked into Japanese and Korean cells, but couldn’t find a good source without paying large middle-men fees.. If you know of a good source I would appreciate it.. For the time being, Trustfire are readily available, and they’re just what I’ve always used (and apparently so do you).

    It should be noted that the batteries are not the determining factor in the price point; it’s the cost of the circuitry, the cost of developing said circuitry, the casings, and, of course, my time. And 6 months isn’t such a dubious claim when you take into account riders in the le Tour did the entire race on a single charge with batteries much lower in capacity to mine…

  3. @Icarus Lights: I don’t doubt that the design and the cost for making the circuitry wasn’t cheap.

    From the pictures it looks like you’re using the protected cells. Most of the Japanese made 18650 cells I’ve seen aren’t protected. I’ve seen some Panasonic based protected cells but they were over 3x as much for each cell. I wish I knew where to get those at a good price.

    I have over 40 18650 cells of all types. Bought from DX, ebay and other online shops. They were all cheap but some were reviewed better in the CandlePowerForums. I have the exact cells you’re using and I got them after reading the reviews on CPF. My biggest issue with ALL the cheap cells is that some don’t hold a charge as well as the others. Best bet is to stock up and use the cells that keep holding the charge.

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