Portabl charging solution for electric skateboard

Batteries, Chargers, and Battery Management Systems.

Portabl charging solution for electric skateboard

Postby noahsw » Mon Apr 17, 2017 10:28 pm

Hey guys,

I have a Onewheel (www.onewheel.com) that requires a 58V 3A charge through an XLR plug (https://en.wikipedia.org/wiki/XLR_connector). I'm looking for a portable charging solution so I can charge up when I'm out riding trails. It's got to be lightweight (< 3lbs), safe, and hopefully not too expensive (< $300).

This 52V Mighty Mini (www.onewheel.com) seems to be the best I've come across but I'm not sure how to upconvert that to 58V 3A. Any pointers?

Thx in advance!
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Re: Portabl charging solution for electric skateboard

Postby amberwolf » Tue Apr 18, 2017 1:23 am

I'm not sure it meets your weight/size requirements, but the Cycle Satiator from http://ebikes.ca has an XLR connector and can be set for the voltage and current you want. (it can actually be setup for several different profiles for various batteries/EVs, with one as the default when it powers on, if you like).


While you could use a DC-DC converter to change the voltage, it will not act like a normal charger at that point, and may not do what you want (or what your battery needs).
Last edited by amberwolf on Tue Apr 18, 2017 1:27 am, edited 1 time in total. View post history.
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Tue Apr 18, 2017 11:51 pm

Thx for the suggestion! I'm not seeing the complete picture though. Is the Cycle Satiator to charge my board? Or to charge the battery that will then charge the board?

It seems to require an AC input. http://www.ebikes.ca/product-info/cycle-satiator.html

My understanding is I need to find some sort of portable battery along with something that can use that battery to charge my board.
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Re: Portabl charging solution for electric skateboard

Postby amberwolf » Wed Apr 19, 2017 2:03 am

Ah, I didn't catch that you wanted to charge from another battery--that makes everything much less compact, less efficient, more costly, more complicated, and more expensive.

It would be much simpler if the board has a removable battery, then you can just carry spares and swap them out.

Otherwise you need either a much bigger Wh battery than the one in the skateboard to be able to fully charge the board via a converter, depending on the efficiency of the converter.

If you had a way to just limit the current between them (I'm not sure what an easy reliable way would be that would also be efficient) you could jsut carry a second battery the same as the internal and plug it in to the charge port--but you can't do that without limiting the current to what the internal cna charge at, and what hte external can discharge at, or there will probably be quite a fire, depending on how high the current goes.
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Wed Apr 19, 2017 9:08 am

Yep - that's the problem. The board doesn't support swappable batteries :-(

Most guys use an AC battery pack like https://www.amazon.com/gp/product/B01MF ... UTF8&psc=1. It provides great capacity but it's 7lbs and you also have to carry around the AC charger. Too heavy to ride around with.

The more adventurous guys are using lighter battery packs and then upconverting to the required 58VDC 3.5A with a solar power booster like https://www.amazon.com/gp/product/B01HC ... 7P1BBKCZM8. Apparently, it can control the output voltage and amps like you were mentioning. The sketchy part seems to be the battery packs they use. Some are buying random ones off eBay, typically 36V 4.4ah. Others are buying LiPos which need too much care than what I'm looking for.

The board's battery holds about 130Wh but I don't necessarily need a full charge per battery, as long as I could carry around a few. I also don't care about maximum efficiency as long as it's decent. My biggest priorities are weight and safety so I can sleep at night without worrying that my house will burn down ;-)

Your advice is much appreciated!
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Re: Portabl charging solution for electric skateboard

Postby Punx0r » Thu Apr 20, 2017 3:29 am

The real answer is swappable batteries for the board, but if the manufacturer won't support that you'll have to do the best you can with a mobile charging solution.

Is the standard charger suitable? I.e. does it charge quickly enough and is it small/light enough to carry around?

If so, many will work directly from a DC input rather than AC mains. That eliminates the size/weight/cost of the AC inverter, you just buy a suitable battery to directly power the charger and using the original charger means the onboard battery is being charged as the manufacturer intended and the conditions of the warranty should be satisfied.

Otherwise you can use a DC-DC solution and skip the standard AC charger: like the solar chargers you mentioned, but there are also many voltage and current-limited dc-dc converters on ebay that will charge a li-ion battery. It's a bit more Heath Robinson and you will need to take some care, but it's potentially a lighter/small/faster solution than using the board's standard charger. Unfortunately the voltage of your board's battery is a bit too high for most RC model chargers - they take a 12VDC input.

For a battery to charge your board's onboard battery the top two choices would be li-ion RC pouch cells, like Multistars from Hobbyking which are cheap and light but require careful looking after and aren't all that safe. Then there's a ready-built pack made from li-ion 18650 can cells, like used in laptops, power-tools etc. They're more expensive but safe and reliable. You'd pick up a ready-made pack for an ebike or similar. As long as the pack is from a reputable manufacturer it should provide safe, reliable operation for years.
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Thu Apr 20, 2017 10:04 am

The standard charger is suitable but it doesn't look like it supports DC input. Figuring that out would be ideal though because as you say, it would keep me within warranty. Here's the label:
IMG_6104.JPG
charger
IMG_6104.JPG (143.12 KiB) Viewed 248 times


The LiPos are out of scope for me given their safety issues.

Do you have specific recommendations on 18650 packs? The best one I've found is https://lunacycle.com/52v-mighty-mini-c ... ffordable/ (300Wh!) but the solar booster charger I've been looking at doesn't support 52V as an input. Another option is https://jet.com/product/detail/9483763f ... c12294c362 (36V 154Wh). I suppose I could use something like https://lunacycle.com/36v-4amp-luna-mini-charger/ to charge the battery, and then the solar booster charger to charge the board.

Some of the other eBike ones are simply too heavy. I'd like one in the 1-3lbs range. Laptop or power tool batteries would be interesting but I'd have to worry about their proprietary connectors, no?

Thx so much! This forum is great!
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Re: Portabl charging solution for electric skateboard

Postby amberwolf » Thu Apr 20, 2017 1:46 pm

noahsw wrote:The standard charger is suitable but it doesn't look like it supports DC input. Figuring that out would be ideal though because as you say, it would keep me within warranty. Here's the label:
IMG_6104.JPG

They won't say that they take DC, it's just that the design of most of this type of SMPS accepts it, as long as it is within the voltage range listed there.

Some of them will accept much lower voltages--I've used quite a few "wallwart" power adapters and such that have wide-range AC inputs 100-240vac, that also work down to 60vdc or less. Some will keep working even lower, but may not startup below that.

If you have a 60vdc battery you could try it on the two flat prongs of the wall plug of your charger. It's unlikely to damage anything, even if it won't start it up.

The LiPos are out of scope for me given their safety issues.

While RC Lipos are a special case, often dangerous due to little or no QC (to keep costs down) in both batteries and the chargers commonly used for them, keep in mind that no battery is "safe", especially in the case of a physical damage situation (like a crash/impact), and so you'd want to box any battery you carry around into a hard impact-resistant casing, with internal padding sufficient to keep the battery from moving around in there. Unfortunately it will make it quite a bit larger and at least a little heavier. :(


Regarding the mightmini pack, I've not personally had one of those, but I do have an older version that's similar:
viewtopic.php?f=14&t=81108
and I've had duct-tape-wrapped 18650 LiFePO4 packs, too.

If the MM is also a "loose" pack like mine have been, you'd need to put it into a hard case that can protect it in case of being dropped, or if you fell while carrying it on a ride, and landed on it, etc. If it's not protected, then like any other battery, it could be damaged in a way that either leaves it unsafe or nonfunctional, or less than fully functional (like if one of the parallel groups gets a cell interconnect broken so it is lower capacity/capability).


Note that the cases many batteries come in are not sufficient; like the Shark, Dolphin, etc etc; there have been some that were destroyed even in shipping, due to insufficient packing materials, because the cases simply aren't sturdy enough.

Pelican cases would work, but aren't cheap and aren't small. :/


I'm not sure how sturdy they are in impact situations, but the Grin Tech LiGo packs at http://ebikes.ca/ligo are designed to be handled and shipped, etc, individually, and might be an option if your converter has that voltage as an input option.
Last edited by amberwolf on Thu Apr 20, 2017 1:49 pm, edited 1 time in total. View post history.
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Re: Portabl charging solution for electric skateboard

Postby Punx0r » Thu Apr 20, 2017 4:56 pm

AmberWolf covered it nicely :)
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Fri Apr 21, 2017 12:05 am

I like the sound of those LiGo packs! Reasonable weight, size, and price. Looks legit and safe as well! Capacity ain't stellar but it might be worth the trade-offs.

The solar booster handles 36V no problem - https://www.amazon.com/gp/product/B01HC ... 7P1BBKCZM8.

Good call on the hard case too!
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Fri Apr 21, 2017 12:17 am

Any reason I wouldn't be able to use this LunaCycle charger (https://lunacycle.com/36v-4amp-luna-mini-charger/) to charge either the LiGo or this hoverboard battery (https://jet.com/product/detail/9483763f ... c12294c362)?
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Re: Portabl charging solution for electric skateboard

Postby flat tire » Fri Apr 21, 2017 1:02 am

Your board uses lifepo4 so first step is convert to a better format like high discharge 18650 or better yet lipo. Lipo isn't that big of a deal especially when you're not paralleling a bunch of packs which you wouldn't be. You just need to be sure not to overcharge or over discharge any of your cells or physically damage them by using a balance charger and constantly monitoring your cell conditions. The biggest advantages of lipo are 1) quick charging, you can fully charge some packs in like 15 minutes with enough power 2) low and I mean really low voltage sag under load compared to any other chemistry it also doesn't drop as much voltage as it discharges so your performance is more consistent throughout the pack. 3) way better power density per volume and weight compared to the lifepo4.

A good high discharge 18650 pack will have all these advantages but to a lesser extent and without the fast charging. Also, once you convert it to accept your own packs you can swap them on the go which gives you the range you need.
Last edited by flat tire on Fri Apr 21, 2017 1:03 am, edited 1 time in total. View post history.
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Re: Portabl charging solution for electric skateboard

Postby noahsw » Fri Apr 21, 2017 8:33 am

Thx! I just don't have the willpower to monitor the Lipos so closely.

Can you recommend a specific 18650 pack? Or teach me how to tell if one has the right discharge?
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