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External battery


adi

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  • 1 month later...
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o'right folks!

so I've been using my external battery 156wh for a month now. It is always connected to my unicycle and ac adapter goes to it. It exdended my range from 5-7 km to >18km with 3 long and quite steep hills - havent actually never fully drained it.

The best way to imagine this setup is 2 connected water columns for the 2 batteries. The ext one continously recharges and levels power with the internal one, so the time for ex btween 3 and 2 LEDs got lot longer.

Ext battery doesnt significantly affect my balance or foot position.

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How have you attached it and where? Have you had any unforseen "step offs" to see how it survives crashes?

The most vulnerable part I would think would be the cable plug as they can be easily shorted inside if pulled by the cable.

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I've had a few stepoffs, nothing major though.

Regarding pulling the ext battery cable, it's not possible. They were smart and the cable going from ext battery to unicycle also plugs into ext battery. So if pulled, it just unplugs and that's it.

See image bellow.

post-200-0-27598200-1428885548_thumb.jpg

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Hi Adi,

 

as you've already seen, i plan to build my own battery pack für the Airwheel.

The major issue of an external battery as you are using it at the moment, is the connection via charging port. Basically, you are draining the internal battery and recharging it with the external battery. Compared to loading the battery with the charger, the difference between the voltage of the internal and the external battery is much lower, so the charging current is very low.

An ideal solution would be a connection of both battery packs in parallel using a Schottky-rectifier. The Schottky-rectifier switches to the power source with the higher voltage within miliseconds, so teh batteries are discharged evenly. the only issue is the regenerative braking. Therefore, a circuit with current sensing amplifiers and MOSFETs has to be desingend.

Two battery packs connected in parallel without any balancing-cricuit would wear down much quicker, because one pack would charge the other and vice versa, depending on the battery voltage. For this setup, at least a fuse should be installed to protect the wiring and the battery packs

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@adi, where do you keep the external battery when you ride? Is it in your pocket, or maybe a backpack?

 

Since the internal battery is nearly always fully charged, are there any problems with regenerative braking overcharging the battery on long downhill runs? I'm not sure what happens when that occurs on most electric unicycles. The Solowheel has an overcharge warning shake that is really annoying, mentioned here: 

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@adi, where do you keep the external battery when you ride? Is it in your pocket, or maybe a backpack?

 

Since the internal battery is nearly always fully charged, are there any problems with regenerative braking overcharging the battery on long downhill runs? I'm not sure what happens when that occurs on most electric unicycles. The Solowheel has an overcharge warning shake that is really annoying, mentioned here: 

 

Wow that is a very good point I didn't think of.  Regenerative braking will definitely cause problems if you go downhill while the external is plugged in and keeping the main battery full, in theory.

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That's the thing, the internal battery is not kept full by the external, they both level each other out, so one could see the internal battery level (# of LEDs on unit) going down, but at a much slower rate than without the external battery.

The ext battery is attached to unicycle all the time, and now the a/c adapter goes to ext battery, I dont charge batteries separately but as a unit.

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That's the thing, the internal battery is not kept full by the external, they both level each other out, so one could see the internal battery level (# of LEDs on unit) going down, but at a much slower rate than without the external battery.

The ext battery is attached to unicycle all the time, and now the a/c adapter goes to ext battery, I dont charge batteries separately but as a unit.

Oh that's interesting.  I thought it's like those portable power banks you plug into your phone.  Those keep your phone 100% charged.

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That's the thing, the internal battery is not kept full by the external, they both level each other out, so one could see the internal battery level (# of LEDs on unit) going down, but at a much slower rate than without the external battery.

The ext battery is attached to unicycle all the time, and now the a/c adapter goes to ext battery, I dont charge batteries separately but as a unit.

The correlation should be as follows:

internal battery voltage          X

external battery voltage         Y, Y>X

regenerative braking voltage Z, Z>Y>X

 

Therefore the voltage difference between external and internal battery (IB) which is |Y-X| defines the discharge rate of the external battery (EB)/charge rate of the internal battery. A very low loading current is the result.

When the EU is slowed down by the motor (regenerative braking=RB), the motor is running in generator mode and feeding a charging current to the IB.

IMHO it is possible to overload the IB when doing RB, but as the charging current by the EB is not very high, there is little difference compared to the case where you only have the IB.

The IB can be charged via EB, which you seem to do. The other way around isn't possible because of the wiring. Both battery packs have BMS so the cells are evenly balanced. However I would load the IB and EB separately as all the energy supplied to the IB has to pass through the EB which puts more stress on it.

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yes ironfox, that's correct, regenerative braking only charges IB - the experimental observation is that the gain in number of LEDs obtained after long descends wears off just as fast as it used to before, without EB. A circuit as you described it above might solve pb.

And I agree that charging batteries independently would protect the EB. My concern in this scenario would be that the IB might be under more stress when both connected - overcharging? -due to larger capacity of EB. If I would chose btw them, I'd probably sacrifice EB as it easier to replace.

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Besides using charging port, which the external battery would always be kept at a higher voltage because of the electronics in between and would always be safe from over discharge, one could just as easily add a direct parallel battery port to internal batteries, just as long they are the same batteries and you can mount them safely in a protected box if you do not have room inside. Then charging both packs would be a snap, just will take twice as long to charge, obviously.

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  • 3 weeks later...

This is probably a noob electrical question but can I use a lipo battery to top off a liion battery.  My thoughts are "Yes you can" but always better to ask.

 

Basically I want to connect a Lipo battery to where I would charge my EU with a mains charger to extend the range of my EU.  Given that I have hooked up the Lipo battery with the same plug.

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I would imagine the most important thing would be to check that they were both charged up to the same voltage, otherwise any potential difference between the batteries could cause the lower voltage one to charge much too quickly and be ruined.

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  • 3 weeks later...

Has anyone successfully attached an additional battery to an ips unicycle? I have heard that via the charging port IPS have designed it so that you can't.  Any one confirm this? 

Additionally has any one been able to attach an extra battery direct into the innards bypassing the charge port?

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The problem with the IPS is that it won't turn on with the charger attached so as it sees the external battery as a charger it won't turn on.

There is a simple work around in that if you plug the battery in after you turn the wheel on, obviously after making sure that they are both charged to the same voltage, it will work.

This would be a bit of a pain whenever you step off or drop the wheel as you would have to unplug, turn of and on to reset and then plug in again.

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Hello

I have an X3 airwheel for one year now and more that happy about this purchase. I bought like you from passiongadget the external battery.

I plug as recommended the external battery to the Charger plug but i cannot see any improvement regarding my range . I did some test many time and it looks like my external battery is still fully charged.

I need your advise regarding this issue.

-Both should be  charged i guess and this is what i did.

-do i need to switch On first the airwheel and then plug the external battery ?

-In your description , do you have the charger connected all the time even while riding the Airwheel ?  not sure i picked up this.

Cheers

 

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I am trying to find a way to have more backup power. I have this powerbbank for my phone  http://www.amazon.com/gp/aw/d/B00RJQB4IU/ref=mp_s_a_1_1?qid=1432583671&sr=8-1&pi=AC_SY200_QL40&keywords=aukey+20000&dpPl=1&dpID=31kF1yiCUvL&ref=plSrch

I cant find a usb cord that charges an eu. Do you think it is possible to take a eu charger, cut the cord, combine it with a usb and then charge using the above usb powerbbank? I know very little about electricity so this may be a stupid question, I just feel like there has to be a way.  ​haha I don't know.

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I am trying to find a way to have more backup power. I have this powerbbank for my phone  http://www.amazon.com/gp/aw/d/B00RJQB4IU/ref=mp_s_a_1_1?qid=1432583671&sr=8-1&pi=AC_SY200_QL40&keywords=aukey+20000&dpPl=1&dpID=31kF1yiCUvL&ref=plSrch

I cant find a usb cord that charges an eu. Do you think it is possible to take a eu charger, cut the cord, combine it with a usb and then charge using the above usb powerbbank? I know very little about electricity so this may be a stupid question, I just feel like there has to be a way.  ​haha I don't know.

As far as I know, USB-chargers actually have a handshake where they agree on the charging current with the device, so I don't think it's going to work if you just change the USB-plug into EUC-plug, but could be wrong. Also I think USB uses far lower voltage than EUC-chargers (something like 5V on USB vs. around 60V with EUCs), so that could be a problem too. Probably another "real" EUC-battery in parallel with the current internal battery is the way to go.

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No chance. As esaj  says USB is 5volts  and eucs charge at 67volts . 

The eucs that have USB sockets built in also have step down transformers to get 5volts  out if the high voltage euc battery.

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  • 2 months later...

Could somebody disassemble external battery and make pictures with comments please? I have plenty of 18650 and i want to make my own external battery but I understand that it should be something else inside except batteries.

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  • 1 month later...

Hiya, I have just finished building an external battery pack 2p16s, so thats 32x 18650s paired with 16 in series. I bought a balancing circuit from aliexpress.
I will post photos of the build in the next 24 hours.. maybe tonite.. I used old laptop batteries that I got for free from the local recycling centre. Im really lucky that I can get as many as I need only 5 mins drive from home. Ive learned quite a bit about the different types that come in the laptop packs. Ive settled with just two types. They are the metallic green and blue ones. They seem to be the newest, are all 2200mah and hold a good charge. Any battery with faded red, pink, or yellow I have returned as these are generally of lower capacity and from older laptops. I will do a new post for this build shortly. I have decided to use an external plug and socket so I can fully remove it when needed. The socket is parallel with the internal battery wiring.

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On 2015/8/13 at 4:11 PM, PAV said:

Could somebody disassemble external battery and make pictures with comments please? I have plenty of 18650 and i want to make my own external battery but I understand that it should be something else inside except batteries.

Pics below are one of the Gotway MSuper batteries, Cells are Panasonic NCR18650PF*32, 340Wh for the pack.
There is no discharge protection(therefore no BMS cut-off), the thick discharge wire is soldered directly to the battery terminal.

Charging is protected though, both for over voltage and over current.
Charge balancing circuitry is also provided with two 151 resistors in parallel for each cell group so that the balancing current would be 4.2/75=56mA.
Should be the same for external battery, only the arrangement is different for portable reason.

 

 

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Off the shell external battery for EUC, 32*18650 2.2Ah cells.
The reason I cut it open is because of the very small discharge current. Discharge is protected by a 2A recoverable fuse(yellow) which gives only about 1.5A continues current. Later I replace it with a 10A normal fuse. This pack is for IPS EUC with direct internal battery connection.
Internally nearly the same with Gotway battery.

 

 

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so I've been using my external battery 156wh for a month now. It is always connected to my unicycle and ac adapter goes to it.

Some months later...

Are you still happy with your external battery, and with the very simple way you use it (= always connected each other, so,charging both IB+EB together throught the EB connector) ?

 

Edit: is there a risk using it this another way: the EB considered just an emergency battery, that we plug to the EUC charging connector only on demand, and doing that at the right time (which need to be defined...)

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