RooMiniPro

Portable universal charger

17 posts in this topic

Posted (edited)

This is a great idea @RooMiniPro.   RC LiPos and a buck-boost converter.  You could conceivably carry 10+Ah in a backpack, and quick charge whenever you got low.  One problem is finding the converters for 84v EUCs, as these are a bit rare (but I think you can find them on eBay ... I'll have to look).  Perhaps 2 x 42v in series (if that is possible).  I think I'd read somewhere on the forum that manufacturers were limited to 60v on a rail.

 

Edited by Chris Westland
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Cool idea :)

I wouldnt charge my EUC battery to 100% using constant current but you could probably charge up to about 4.1V per cell.

Lipo chargers charge in two different stages, constant current stage and constant voltage stage.

 

rcheli-diagram-charge_graph.png

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Posted (edited)

Or you could just carry 3 off 5S 5000mAh packs wired in series, plug them into the Ninebots charging socket when the wheel is fully charged (if the wheels voltage is lower when connected excessive current would flow) and gain the whole capacity without, usually quite significant, voltage conversion losses.

I've also seen people use a simple current limiting device such as a car light bulb in series with a 15S pack so it can be plugged in when the wheel battery is low without too high a charging current being generated. (Fully charged 15 cell pack 63V less than 30% capacity pack around 52V so there will never be more than 12V difference between packs).

Both of the above methods would also ensure the charging pack voltage did not get pulled too low and damage it as it can never be lower than the wheel pack which is protected by the wheels electronics.

Edited by Keith
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Great ideal.

 

It would be even better if someone can come up with off-board charge like those found on Segway 

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42 minutes ago, FULspeed said:

There are issues that would need to be addressed:

  • there appears to be no current limiter/ adjuster, only a voltage adjuster, it may, therefore, try to supply its maximum of 2Amps.
  • Stated max operating power is 100W with additional heat sinks and a fan. That is only just over 1Amp at 84V, possibly less if it is referring to input power rather than output power.
  • Adequate cooling may be a real challenge unless the current can be controlled to 1Amp or less.
  • Is a 1Amp charger actually worth the bother given that your ACM must have a battery of at least a15Ah capacity.
  • Indeed, assuming around 80% efficiency (seems unlikely with the heat it produces) is an extra 115Wh your 12V,12Ah battery is likely to be able to supply going to make much difference when the ACM battery is, presumably, at least 1300Wh?
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Posted (edited)

I have one of those too (CC/CV step up converter, not just constant voltage), bought it with similar use in mind, but then never actually used it :P 

https://www.aliexpress.com/item/High-Efficiency-95-DC-DC-600W-IN-12-60V-OUT-12-80V-Boost-Converter-Step-Up/32374850067.html

A word of warning: you need some load to set the voltage. I tried once setting the voltage unloaded (well, only load in the output was the multimeter, which has something like 10M ohm input impedance?), and the voltage shot closer to 100V (ie. the regulation becomes unstable with low current). I'm not sure, but I think this might cause a problem once the batteries are closer to full (low current). Also, the caps are rated 100V max, so it could blow those out with high voltage transients if the voltage starts to jump around? Adding a separate power resistor so the load stays at some minimum value at all times might help, but I'm still not really familiar with the intricacies of switching power supplies, so don't take my word for it.

The seller claims 600W maximum power, but it's probably much lower if the voltage difference is greater than in the "optimal" area...

Note: this need special instructions, our 600W refers to the module of nominal maximum power under certain conditions, under the condition of different input voltage, maximum output power by the input current limit has fallen.

Edited by esaj
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Posted (edited)

Thanks Keith for the remarks.

As I'm not an expert in the electrical field, I'm just trying to figure it out how it works...
(In fact I was wondering how to control the amps output)

Probably I would need a more complex converter, like that?

https://www.aliexpress.com/store/product/B900W-Input-8-60V-to-10-120V-900W-DC-Converter-High-Precise-LED-Control-Boost-Converter/808897_32690996337.html

And yes, I have a 1300 ACM, so probably the portable battery should be bigger to be really useful . (how big?)

Thanks

Edited by FULspeed
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Posted (edited)

1 hour ago, FULspeed said:

And yes, I have a 1300 ACM, so probably the portable battery should be bigger to be really useful . (how big?)

That depends on what sort of additional range you feel you need. This post below discusses energy consumption. Actually, it is a few years ago when wheels were slower, so our faster riding speeds are going to consume a fair bit more power than discussed here and higher rider weight will have a huge effect as well. It could be anything between, I guess, 12 and 25Wh/km a lot more if very heavy.

The easiest way to understand how much you and your riding style, terrain, etc consumes is to go on a measured, typical, ride and when you return home use a Charge doctor (discussed in the above post link to see how many watt hours your charger puts back. Divide that by the Kilometres ridden. Let us say it is 20Wh/km, then if you feel you might, in an emergency (say) need an extra 10km, then you are going to need to carry an addition 200Wh plus a multiplication factor for the efficiency losses of any converter you use. Again let's say (wet finger in the air figures here) its 80% efficient then the battery would need to be 250Wh

Edited by Keith
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Posted (edited)

9 hours ago, esaj said:

I have one of those too (CC/CV step up converter, not just constant voltage), bought it with similar use in mind, but then never actually used it :P 

https://www.aliexpress.com/item/High-Efficiency-95-DC-DC-600W-IN-12-60V-OUT-12-80V-Boost-Converter-Step-Up/32374850067.html

A word of warning: you need some load to set the voltage. I tried once setting the voltage unloaded (well, only load in the output was the multimeter, which has something like 10M ohm input impedance?), and the voltage shot closer to 100V (ie. the regulation becomes unstable with low current). I'm not sure, but I think this might cause a problem once the batteries are closer to full (low current). Also, the caps are rated 100V max, so it could blow those out with high voltage transients if the voltage starts to jump around? Adding a separate power resistor so the load stays at some minimum value at all times might help, but I'm still not really familiar with the intricacies of switching power supplies, so don't take my word for it.

The seller claims 600W maximum power, but it's probably much lower if the voltage difference is greater than in the "optimal" area...

Note: this need special instructions, our 600W refers to the module of nominal maximum power under certain conditions, under the condition of different input voltage, maximum output power by the input current limit has fallen.

On the unit I have the current and voltage are adjustable. I set the max voltage with no load to 62.8v and when under load (charging the EUC) it does not shoot up, it drops to whatever voltage the cells are and gradually increases until they are fully charged. Once the max voltage of 62.8v is reached it does not go higher and the current gets lower and lower as the bms draws less and less as the pack reaches near full capacity. That is when I unplug it and carry on riding. I don't want to rely on this boost converter for a full balance charge, I can do that at home with the Ninebot charger.

This is working great for me :)

I have tested it to 350w on the watt meter and it supplies that just fine but the heat sink gets slightly warm, so I added the fan. However, when charging the EUC at 2.5 amps or less, the heat sink does not get warm at all and does not need the fan. 

For just $33 CAD ($24 USD) this is a very handy thing to have as it can charge any EUC or MiniPro under 80v.  It can be used as a car charger too with a cigarette plug. Or one of those 19v power banks for laptops. 

Last weekend I was on a ride and got stuck where a public event blocked my route back. I had to take a different route and I ran out of power and was stuck doing 5kph for a long time, then carrying the EUC part of the way. Now with this and a few Lipos in my backpack that will not happen again. A 30 minute charge at 3 amps (only 1.5x the stock charger's output and not at all too much for the 2P battery) provides a lot more kms of range in an emergency. Or taking a 20 minute break to rest my feet and top up the battery every hour significantly increases the range. I will soon try test riding slowly (to draw low current) while charging and see how viable that is. 

Edited by RooMiniPro
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I'm out on a ride right now and thought I'd add a photo of it in action.

 

FullSizeRender.jpg

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Some pics of the electronics in a semi-neat enclosure.

 

IMG_7502.JPG

IMG_7503.JPG

IMG_7504.JPG

IMG_7505.JPG

IMG_7506.JPG

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Here is a 900W step up module that is adjustable up to 120V.

I think this is the bigger brother of the one that @RooMiniPro uses:

https://www.amazon.com/gp/product/B01GFVI6R6/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=batter00-20&linkId=484a1902b5018199aa0604bc3078e670&th=1

Edit: This one also have CC/CV so it should be perfect for charging batteries :)

Edited by Lorents
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35 minutes ago, Lorents said:

Here is a 900W step up module that is adjustable up to 120V.

I think this is the bigger brother of the one that @RooMiniPro uses:

https://www.amazon.com/gp/product/B01GFVI6R6/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=batter00-20&linkId=484a1902b5018199aa0604bc3078e670&th=1

Edit: This one also have CC/CV so it should be perfect for charging batteries :)

Nice. This should work for the higher voltage EUCs.

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Here's my new slim battery setup for portable charging. A 6S and a 4S. Both use high quality 10Ah cells that I had left over from other projects. These slip into my backpack taking up hardly any space and should double my range. 

 

IMG_7559.JPG

IMG_7560.JPG

Edited by RooMiniPro
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