DIY "mobile supercharger"
together with a friend of mine, we developed a mobile supercharger for my personal use.
i have to admit that i have no intentions to make a product out of it and i won´t sell any of these. however, i just wanted to inspire you, since i know that some of you were thinking about doing something similar.
the reason why i did this was, that i needed something small and light-weight for the backcountry use, to extend my range to get more out of these perfect trails in my neighbourhood.
the technical setup is simmilar to what i mentioned in the other thread (http://community.onewheel.com/topic/1076/extra-battery-backpack/16):
therefore my friend has custom built a high power LIPO battery pack out of 24 high quality cells which are capable of delivering high current within a short time and are known for their stability. it wasn´t that easy to find some capable cells and they are a little bit expensive, but they work fine.
(it would have also been possible to use LIFEPO4 cells, but this would have costs about 4-5€ more per cell and for a charging device I did not really need those advantages)
he then added a circuit for overload- and undercharge-prevention and finished it.
after that, we were using an existing step-up converter to transform the 14V battery to stabilized 58V. some adjustments, measuring and testing and the thing was ready to go.
for a short-term solution i have added a 12V temperature controlled fan (to get rid of the heat when inside a housing) to it and put it all in a cheap plastic housing.
here are some technical details:
the batterypack is 14,8V and has (useable) 220Wh. since the OW has 130Wh, you can charge it 1.5 times
the (adjustable) step-up converter converts the 14,8V to 58,4V.
the overall weight ist 1.6kg (3.5pounds) including battery pack, circuit and the housing with the fan. due to its size you can easily carry it within a very small backpack, so you do not feel it when cruising those offroad trails.
since it already delivers those 58V you do not need the regular charger, but you can directly charge it and therefore get out more power of the battery (less energy waste)
well, just to give you an idea of how something like this can work ...
we are still trying to improve this thing. currently we are working on a custom circuit with improved power consumption and heat emmission and i will work on an aluminium housing with a smaller size. but for now, this allready works and i am using it on my rides!!
You my friend are a genius, I can't imagine anyone with a onewheel not buying one, gods speed on your development efforts...
@SeaP90d: thanks for the kind words, but in fact it´s not me that deserves it, the main work has all been done by a friend of mine.
also sorry to disappoint you but we won´t sell those things. i am not willing to deal with all the compliance bureaucracy about batteries, electronics and warranty stuff and also don´t have the time to do so - i am just one of you guys, i want to ride my onwheel all day long and get some extra juice when i am out in the wild;-)
but based on that information, you guys can probably build something simmilar on your own...
@cr4p I'll take six ;)
Very nice, I was looking to do something similar but I picked up this instead, weighs 7lbs, not including the charger.
@parrothd : Initially I was also looking for buying a finished product and stumbled over this thing from your picture. but for my purpose this was just too bulky and heavy. Allthough I searched a lot for a proper product, I couldn´t find any, that´s why I asked a friend to build it. I wish future motion would offer something like that, i have also commented it on their survey.
Nice work man! I wish I was a technical genius as you/your friend!
Hi cr4p, I don't mean to be a pest, but I think some would consider it cruel and unusual punishment to dangle this in front of us poor dead-onewheel packers without offering much hope to the non-electronic hardware folks among us. What if you posted a quick schematic along with a list of components by brand and item number and vendor. It would be a real life changer to not have to plan out every onewheel trip and still end up walking back a lot of the. Think about it, you would go down in history as the Steve Jobs of Onewheel mobility and peace of mind...
@cr4p Throw it inside a sombrero and I think you'll REALLY be onto something!
@thegreck : i will ;-)
@SeaP90d : i see your point...:-)
this was meant to be a information for those who are thinking of doing something simmilar and have some technical background.
I think someone with electronic background can already use this information to built his own mobile-supercharger, but i doubt a non-technician will built it even if i give you a detailed list of components.
however, of course I can post details for those who are interested.
~for the battery pack you basically need~
- as many high output current cells as you wish for the desired capacity (in my case: 24x SAMSUNG SDI ICR1865-26F 2F92; 3,7V per cell x 4 serial x 5 parallel )
- a suitable protection circuit for the battery capacity that you like to built (eg.: http://www.bestechpower.com/148v4spcmbmspcbforli-ionli-polymerbatterypack/BMS-D134.html)
- small parts like connectors & cables
- any universal charger which is suitable for the desired voltage (since I used LIPO cells i need a LIPO charger of course: http://shop.lipopower.de/230-V-Desktop-Lader-max-22A-fuer-3-4-Lipo-LiIon-Zellen)
of course you need a tool to assemble batteries (contact welding)
depending on the voltage you designed the battery pack for (depending on how many cells you put in parallel/serial), you need a step-up converter ("boost DC DC converter") which is suitable of converting the output voltage of the battery pack to the desired 58,4V of the onewheel.
It is important that it can deliver as much power as the Onewheel consumes while charging (3.5 A * 58,4V = 204 Watt).
There are ready to use step-up converters available on amazon. the one i am currently using (but NOT satisfied with, as i have written in the initial post) is the following:
but again, i think this thing is chinese crap, thats why we are trying to build another (it still delivers a little bit to less current on the output side and gets a little bit too hot)
now after you have assembled the battery pack, all you have to do is connect the battery pack to the step-up converter, use the screw to adjust the volatage to exactly 58,4V do some measuring and then connect it to the Onewheel.
since the step-up converter will heat up with the huge ammount of power the onewheel consumes in a short time while charging, you have to cool it down. you can use a regular pc-temperatur controlled fan (12V), this will work (depending on the voltage of your battery pack of course). something simmilar to this:
all you have to do is place the temperature sensor between the circuit and the heatsink and connect the fans power cable to the input of the step-up-converter.
basically that´s it, but of course you need someone with some technical knowledge to support you.
@cr4p Eezy peezy!
@thegreck: ;-) well, i would not have been able to do it myself neither, that´s why i asked this guy to do it. once it has been figured out it is not too hard to do, but anyhow you should have some knowledge about it, because you do not want to destroy your onewheel or burn your house down.
@cr4p Yeah I know, I was just messing with you. That shit is way out of my ballpark, so I'll let the smarter people try it.
@cr4p can you ask your friend, how are the pins outs on the 3-pin xlr wired.
And also did you discuss forgetting about the step up transformer and just putting more batteries series. Couldn't you connect the backup battery unregulated - I'm guessing the charging circuitry is in the onewheel right?
@cr4p that is really innovative! Smaller and lighter than commercial batteries and doesn't need the ultra charger. Maybe fm can get inspired by your schematic and offer something for the rest of us. Even better, fm can hire your friend to make it for them. Congrats.
@jasont : i will have a look at the wiring to tell you.
about the other questions. of course you could do the battery pack with a higher voltage - maybe this is a good idea, i am also open for suggestions on improvement, which i can also benefit from;-)
but either you get the battery pack to exactly 58,4 V (or something very close too), or you will still need the step-up converter.
it has been done like that, because we do not know how the OW exactly works inside and whats their battery and charging design looks like, so we wanted to stay on the safe side and make sure that the output voltage of the mobile supercharger is perfectly stabilized to avoid damaging of the onweheel.
but of course you could design it to any voltage between - lets say 10 and 50 V, as long as it multiplies with 3,7V from the cells.
but you have to keep the battery design in mind (required space and format, required wiring for serial/parallel, ...).
yes the, charging circuit is in the onewheel. i can´t tell you if you really need the circuit on the battery, but we wanted to be on the safe side. the circuit on the battery pack prevents the battery from beeing damaged (undercharging, overpower, short circuit)...220Wh is a lot of power and the OW cunsumes a lot of power while charging in a short time, therefore the battery pack and the step-up converter do have some challenges while charging. we also didn´t want to risk anything here. if something goes wrong i don´t want the battery to explode or be damaged, so i am happy to have that circuit...
@cr4p it's interesting because the sticker on the Ultracharger claims to only put out 3.5amps per hour which at 60V is only 210W. So in a 20minute charge it's only putting around 70W/hr into it.
I noticed that on the step-up transformer you bought, you can set the output amps. Do you know how many amps you have it set to?
@jasont I'm going to try building something similar. I think you could shed some weight and size by using flat packs of Lipo or LiFePo4 batteries instead of the round cells. Maybe one like this http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=74096
@jasont did u figure out the pinout for the XLR connector? I have my boosted converter outputting 58.4v but it won't initiate the charging. It won't draw more than .15A
@jasont Those packs are just over 3 pounds, significantly less than the 7 pound backup for sale on Amazon. Any idea how many charges you'd be able to get out of that?
Be great if one of the electrical geniuses on here would produce one of these things and sell it. Not sure if I'd be able to make one without electrocuting myself.