DIY "mobile supercharger"

5 June 2016, 18:48 UTC

@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.

17 June 2016, 05:23 UTC

Awesome info here.
Where do I order the plug that goes into OW charging port?

17 June 2016, 05:29 UTC

Never mind, found it.
Sorry

http://www.ebay.com/sch/i.html?_odkw=DC-DC+booster+up+converter&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR12.TRC2.A0.H0.TRS0&_nkw=XLR+connector&_sacat=0

17 February 2017, 12:28 UTC

@cr4p said in 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 (https://archive.owforum.co.uk/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!!

McGyver!? ;)

22 June 2017, 15:16 UTC

So, I built one of these, thanks to this thread (thanks @cr4p ) and this great instruction guide: http://onewheel.wiki/Charging_on-the-go

I've attached a few pictures below.
I've tried two methods:

12v/10Ah (120Wh) LifePo4 battery + 300Watt power inverter + Onewheel supercharger
Total Weight (including Onewheel charger): 5lbs, 8oz
Results: Charge Onewheel 65% in 30min
12v/10Ah (120Wh) LifePo4 battery + 58v up-converter
Total Weight (no Onewheel charger needed): 3lbs, 15oz
Results: Charge Onewheel 72% in 90min

Needless to say, I'm disappointed with my results using setup #2 (basically the setup described in this thread) both in terms of the minimal charge improvement over the 120v inverter method but also/mostly in terms of the 90min charge time.

The thing I don't understand (which is probably why the charge time was so long) is that I programmed the up-converter to deliver 58v and 3.5a but it only actually was delivering at 1.1a. Did I do something wrong? Do I need a different kind of battery? Any suggestions would be appreciated.

Method 1:

Method 2:

Charging display during 90min/72% charge session, showing only 1.1a draw:

22 June 2017, 17:33 UTC

@kbern Your battery is only 12V. I think you will need at least 24V.

22 June 2017, 18:08 UTC

@kbern

https://www.quora.com/What-charges-a-battery-faster-more-current-or-more-voltage

23 June 2017, 02:13 UTC

@JacoNZ Thanks. Yeah, I think so too, though I'm still confused about why the 12V battery can't output 3.5A, but I will try a higher voltage battery and see what happens.

23 June 2017, 04:25 UTC

@kbern and @cr4p

The my volt meter is reading power supply xlr jack as: pin 1 as negative, and ping 2 and 3 are positive. Do you wire this the same? or just use pin 2 as positive and pin 3 blank?

23 June 2017, 04:27 UTC

@SkyPilot 2 and 3 need +

23 June 2017, 04:42 UTC

@SkyPilot @wr420 yup, pin 2 & 3 are both "+", per the instruction page (though that tidbit is easy to miss):
http://onewheel.wiki/Charging_on-the-go
and I tested both + pins with a voltmeter to make sure they both had good connections.
Thanks for brainstorming. Let me know if you can think of any other potential issues.

23 June 2017, 06:48 UTC

since the question with the pins is already answered I just like to add another thing:
if you guys are using the (very comfortable) MPT-7210A, I THINK that you it would be a good idea to use a battery pack/configuration with a higher voltage. altough the spec/user manual of the solar charger says it´s capable of 12 to 60V, it seems like on the lower voltage side it limits the current output which leads to longer charging times. so if this theory is correct, the more towards the 58.4V you go, the better (also the efficiency would improve I guess). As an alternative you might find a better step-up-converter which is really capable of delivering the required output current with 12V inputs.

as mentioned, that´s just a guess - has yet to be confirmed;-)

24 June 2017, 05:38 UTC

@kbern have you attempted to hook this up via power supply, and did you get the same results? If the power supply was faster, then it maybe related to the battery's discharge rate. The inverter combined with the output rate may be exceeding the max discharge rate of the battery.

I'm thinking the MPT-7210a may have more overhead than everyone thinks when up converting 12v to 58v. I suggest increasing the battery voltage to 24 or 48 volts and see if there's an improvement (adjustable voltage power supply is ideal for testing.)

As I type this I'm realizing the problem may be combined in both the loss in up converting and the max discharge of the battery.

Just some suggestions, getting late here please forgive my rambling.

27 June 2017, 18:31 UTC

This might work. ;)

https://www.amazon.com/Solar-Powered-Generator-Kilowatts-Trailer/dp/B01MDM8Q0J/ref=sr_1_1?s=hi&ie=UTF8&qid=1498588175&sr=1-1&keywords=generator

28 June 2017, 02:24 UTC

@crawcraw said in DIY "mobile supercharger":

This might work. ;)

https://www.amazon.com/Solar-Powered-Generator-Kilowatts-Trailer/dp/B01MDM8Q0J/ref=sr_1_1?s=hi&ie=UTF8&qid=1498588175&sr=1-1&keywords=generator

I was going to buy that one; have you tried it... does it do the job ? :P

28 June 2017, 17:10 UTC

@silvs yes! And at $130,000 it's a steal. Adding the trailer hitch to the Onewheel was a bit tricky.

29 June 2017, 02:01 UTC

@kbern said in DIY "mobile supercharger":

So, I built one of these, thanks to this thread (thanks @cr4p ) and this great instruction guide: http://onewheel.wiki/Charging_on-the-go

I've attached a few pictures below.
I've tried two methods:

12v/10Ah (120Wh) LifePo4 battery + 300Watt power inverter + Onewheel supercharger
Total Weight (including Onewheel charger): 5lbs, 8oz
Results: Charge Onewheel 65% in 30min

12v/10Ah (120Wh) LifePo4 battery + 58v up-converter
Total Weight (no Onewheel charger needed): 3lbs, 15oz
Results: Charge Onewheel 72% in 90min

Needless to say, I'm disappointed with my results using setup #2 (basically the setup described in this thread) both in terms of the minimal charge improvement over the 120v inverter method but also/mostly in terms of the 90min charge time.

The thing I don't understand (which is probably why the charge time was so long) is that I programmed the up-converter to deliver 58v and 3.5a but it only actually was delivering at 1.1a. Did I do something wrong? Do I need a different kind of battery? Any suggestions would be appreciated.

Might be the solar controller.
Anyone tried this method.. swapping out the capacitors to improve the performance:
https://youtu.be/LdunO-nFrGU

29 June 2017, 15:45 UTC

Question: Connecting 16 of 3.6V batteries in series gets 57.6V. Is this a possible solution so you don't need a converter? I wonder how many amp hours would be sufficient for a charge.

Ex:

http://www.batteryjunction.com/batteries-voltage-3v7.html

Edit: by my calculations a 3000 mA battery would give 171 Wh so you could get a full charge with it. It would be more efficient because with the step up converter from 14V to 58V, you lose 10 to 15% or so efficiency with the heat lost in conversion and cooling fan. If you attach another 16 batteries in parallel that gives 341 Wh. That would give 2.5 charges in theory. Also since it is the same specs, you may (?) be able to use the Onewheel charger to also charge the spare battery pack. This way you are spending all of your money on batteries and not on a up converters or chargers.

The two questions I have is is a battery of that voltage dangerous and would the small voltage difference 57.6 v 58.4 I've been reading and the batteries are key. Alot of these are Chinese rip offs that overstate the mAh.

5 July 2017, 22:59 UTC

Initial test. Just used the Chafon dc out (without the AC adapter - hooked two of the DC outs in parallel to get the amperage up) with an upconverter to get to 58.4 volts, i.e., not using the AC charger. It worked. I charged from 67% to 80% in 11 minutes. Chafon still reads 100%.

Since this is one conversion rather than two, it should be more efficient.
Chafon with stock adapter: 12 DC > 110 AC > 58.4 DC (2 conversions)
Chafon with DC up converter = 12V DC > 58.4 DC (1 conversion)

I have pics of all of the above. Will post more after more tests, but this looks good. I really think making a battery with higher voltage and upconverting DC to DC will give the best range for the lowest weight.

Edit: I don't think the Chafon has enough Amperage for this and the parallel connection didn't take. I think I need a better battery.