I just returned from a 56km Boosted Board ride. I toured the bike trails along the Upper/Lower Crystal Springs Reservoirs and San Andreas Lake here in the San Francisco Bay Area. This is a new record for me. My previous range record was 27km on a single charge.
|Boosted Board with external battery in my backpack :]|
This battery pack is designed to attach to a custom designed board that I have been working on but is not ready for prime time yet. Below is a sneak preview of the board I am working on. I have decided to name it Voyager as one of the design goals has been to prioritize range.
|10S6P battery mounted to Voyager with custom charging cable attached|
Before diving into the details of this battery pack, here is a screenshot of the route that I took. This was captured by MapMyRide.
|Boosted Board Route|
I will likely add a 120A fuse in the remaining cavity, just in case a short occurs.
|The aircraft-style multi-pin charge connector|
|iCharger 4010 Duo showing a discharged, but highly balanced pack :]|
|Unboxing 60 LG MJ1 cells|
The Voyager pack has 60 cells mounted inside a 3D-printed enclosure. There are cutouts for the high-current primary load connector and a multi-pin aircraft-style connector for charging. There are also wings on the ends for attaching the battery pack to mount points on the Voyager board. We can just ignore those when using this battery in my backpack.
You might think that this battery pack is quite large and I fully agree. The idea with having known mount points is that different battery packs can be designed and installed depending on the requirements of the trip/day. I have considered building a 10S3P pack with higher-discharge cells which sacrifices range for weight.
|Prototype enclosure: verifying board mount points and experimenting with cell arrangements :]|
The cells are connected to one another using nickel battery tabs. This is a significant step up over the soldered battery packs that I have experimented with previously. I am investing more time and money into Voyager so I decided to opt for the right tools for the job.
|My workbench showing candidate cells and battery welder. Let the games begin!|
|An individual 1S6P pack|
|A fully-assembled, but folded battery pack|
Once the cells were arranged into the complete 10S6P configuration the pack was flattened and wrapped entirely in Kapton tape to improve strength. The pack is nearly ready to be installed in the final enclosure.
|A fully assembled and unfolded battery pack|
|A terminated 19-pin aircraft-style connector|
A balancing charger requires a wire for each of the individual cells in a pack in order to ensure that all individual cell voltages are equal to one another. I selected a 19-pin aircraft-style connector. There are 11 pins reserved for the balance leads (system ground and 10 leads, one for each cell). I then split the remaining 8 pins into 4 positive/4 negative for the main charging current. I can also charge the pack through the main connector but this has the benefit of simplifying the charging cable. It also allows leaving the board powered while charging and accessories could be powered through the charge connector as well.
When dealing with batteries I like to think of them as a heavy-duty power supply that cannot be shut off. Batteries can be quite dangerous to work with especially if a short-circuit is created. To ease the installation of the aircraft connector, I soldered pigtails to each of the pins and then attached one wire at a time. This ensures that I only ever have one wire exposed at a time and removes the chances of an accidental short circuit.
|Fully assembled with dust gasket and heated-inset screws|
The battery is sealed by a lid that attaches via 9 M5 screws into brass heated-insets. A 2mm rubber o-ring is used to prevent dust from creeping into the pack. Prior to sealing the box I applied some outdoor window silicone to any port holes (ie: the primary load cable) to prevent dust from breaching the case. I also used grommets where possible.
|Primary load cable grommet|
|Just a few lose screws :]|
Next a charge cable was created to match the pinout of the charge connector. This allows a quick connection to an external charger. There is one caveat with this design in that the charger must be connected to the cable before the battery. The risk is that the banana leads could short together. I may consider replacing them with an XT60 connector in the future.
|Voyager battery charging cable|
Here are a few more glamor shots of Voyager. The major outstanding TODOs are a remote with more precision and improvements to software, namely to speed regulation. I need to invest some time in writing tests before putting my life on the line with a long trip on Voyager.
|Voyager Side Shot|
|Voyager lighting system (it has turn signals!)|
If you made it this far, thanks for reading! Feel free to drop me a line if you are interested in what you see here.