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Charge Doctor


Nick R
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Does anyone have a link to a youtube clip on how to use the Charge Doctor to charge euc to 80% 
I tried to follow the screenshots on ewheels.com website and its confusing as hell.

I ordered one and expecting it in a day or so.. I sure hope there is a manual to explain it clearer. 

 

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5 minutes ago, Nick R said:

Does anyone have a link to a youtube clip on how to use the Charge Doctor to charge euc to 80% 
I tried to follow the screenshots on ewheels.com website and its confusing as hell.

I ordered one and expecting it in a day or so.. I sure hope there is a manual to explain it clearer. 

wow I thought it was just me... I can't figure this out either, the screenshot instructions are WAY confusing. 

Anyone, help?

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http://hobby16.neowp.fr/ is the official website. Instructions there.

How to do it:

  • You limit charging by cutting off at a certain voltage (it rises during charging) with the Charge Doctor (CD).
  • What the cut-off voltage is depends on the wheel (wheel voltage, e.g. 84V). You can also simply use experience values (what the CD shows when the wheel is at a certain percentage) because the calculations are never 100% exact anyways.
  • You set the CD to stop charging at a certain voltage and set that voltage. To do this, enter "adjustment mode" by plugging off the CD from the charger, plugging it in while holding down the side button, then you can do these things.
    Wait til it cycles to the third screen and set it to "up V", then in the first screen you can set the voltage.
    See the website for detailed instructions, looks complicated, but once you've done it a few times it's easy.
    (Also, don't forget to have auto cut-off enabled in the non-adjustment-mode 3rd screen of the CD. It's the default setting, but maybe check)
Edited by meepmeepmayer
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The official site has the same screen shots and confusing instruction as on ewheels.. I guess ewheels copied the informaton over.

It would be really nice if someone would put together a short youtube clip to show the step by step setup. 
 

Edited by Nick R
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Example voltage calculations:

Cells are empty at 3.2V and full at 4.2V for most wheels (not Rockwheel GT16 or the Inmotions, I believe).

For 84V (20 serial cells * 4.2V max per cell) wheels, this means empty is at 20*3.2 = 64V and full is at 20*4.2V = 84V. Every 1V is 5% on 84V wheels. So 80% would be 80V cut-off voltage on 84V wheels.

For 67.2V (16 serial cells * 4.2V max per cell) wheels, this means empty is at 16*3.2V = 51.2V and full is at 16*4.2V = 67.2V. So 80% is 64V cut-off voltage on 67.2V wheels.

You can compute any battery percentage by going the approximate amount between empty and full. In reality, this may differ by like 5% battery, so you have to try a bit what voltage gives you what battery percentage.

21 minutes ago, Nick R said:

The official site has the same screen shot and confusing instruction as on ewheels.. I guess ewheels copied the informaton over.

It would be really nice if someone would put together a short youtube clip to show the setup. 
 

Don't have a video or time to make one at the moment, but it's not that hard if you read the instructions and know the thing isn't going to explode or something:efee8319ab:

  • Hold the button (but not longer than 5s, just a bit) while plugging in the charger into the doctor.
  • Wait til it cycles to the third screen and press the button one or two times until you have "up V".
  • Wait til it cycles to the next (1st again) screen, or unplug and plug in while holding the button again to get to the first screen of "adjustment mode", and then press the button a few times (holding also works) to adjust the voltage to what you want.
  • Unplug, and then use it normally to charge the wheel.
  • Optional: unplug charge doctor, then plug it in again without holding the button (regular mode) and press the button twice to get to the third screen. If it does not show your voltage already, long-press the button for a moment until it does (it would show ---A or ---V if the auto shut down mode was off).
Edited by meepmeepmayer
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You don't start from 0.

Battery cells are "officially empty" at a certain voltage which is NOT 0V, but usually for us 3.2V and "officially full" when at 4.2V (you could over- or undercharge them, but then they die).

So only how far you are between 3.2V and 4.2V tells you how "full" your battery is.

Multiply that number by 20 (84V wheels) or 16 (67.2V wheels) and you know what your voltage corresponding to the charge state is.

E.g. 80% battery is 80% on the way from 3.2V to 4.2V, which is 3.2V+0.8*1V = 4V.

4V*20 = 80V which is 80% battery on 84V wheels. [Sorry, had a typo in the post above, it's 80V not 82V.]

4V*16 = 64V which is 80% battery on 67.2V wheels.

Edited by meepmeepmayer
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8 minutes ago, Nick R said:

 

ok.. I see what you did..  extrapolation using 3.2V per cell as the 0% baseline and 4.2v as 100% 

16 x 80%  + 0% base line .  12.8 +  51.2 = 64V 

 

Yup, you saw what he did - shame it is completely wrong though isn’t it! A 64V cut off WHILST CHARGING will be less than 50% charged. Indeed not only that but the idea that the voltage drops linearly from 4.2v down to 3v is also complete nonsense so you cannot work out percentage capacity by simple voltage you need to use a discharge curve for the battery.

This has all been explained before and, actually if you are looking for around 80% you are better off cutting off on current not voltage as, depending on the charge rate you are using, you are likely to find that 80% charge will be once the battery has reached 67.2V and current is starting to drop. Rather than reinvent the wheel, please see the below post which explains all this:

 

Edited by Keith
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Works for me though:efeebb3acc: 82V should be 90% (84V Gotway) and it gives me 85% after the batteries have settled (ok, I don't immediately remove the charger when the cut-off happens, but some time later). Close enough. Cut-off by amperage does not work for bigger batteries afaik.

--

As said before, you can just charge your wheel, check the voltage on the Doctor, and then remove the charger, wait an hour, then you know what battery % that voltage gives you. So empiric values vs. calculated ones.

Edited by meepmeepmayer
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11 minutes ago, Nick R said:

So Keith .. what does your method says is 80% charge for the 67.2V battery ? 

It doesn’t, read the thread we already have on this that I linked to.

What capacity the battery is at if you cut it off at a given voltage entirely depends on the charge rate you are using. Cutting off when the current reaches a certain figure will pretty much give you the same state of charge regardless of charge current providing the charge current is high enough in the first place. However what percentage charge is in the battery at a given current cut off will depend on how many amp hours the battery is.

For example: Charging at 1C the battery will be at less than 50% charge when it reaches 67.2V at 1/3C it will be at something like 85% charge. 

Edited by Keith
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31 minutes ago, Keith said:

Indeed not only that but the idea that the voltage drops linearly from 4.2v down to 3v is also complete nonsense so you cannot work out percentage capacity by simple voltage you need to use a discharge curve for the battery.

I think you are exaggerating a little bit. A linear relationship is a simplification, but for some purposes it is a good enough model, in particular if we know and take into account that the graph flattens out on the extremes.

31 minutes ago, Keith said:

This has all been explained before and, actually if you are looking for around 80% you are better off cutting off on current not voltage as, depending on the charge rate you are using, you are likely to find that 80% charge will be once the battery has reached 67.2V and current is starting to drop.

That not only depends on the charge current but also on the battery capacity. For larger batteries (i.e. charging time >3h), 80% may not be achievable with current as trigger.

Edited by Mono
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12 minutes ago, Mono said:

I think you are exaggerating a little bit. A linear relationship is a simplification, but for some purposes it is a good enough model, in particular if we know and take into account that the graph flattens out on the extremes.

Yes it is so close to linear providing, of course that you treat empty as 3.6 Volts and not 3.0v per cell.

IMG_0358.JPG.f8e13c5b2278e88b7e8bff826578df2d.JPG

OCV = Open Circuit Voltage.  SOC = State Of Charge.

 

12 minutes ago, Mono said:

That not only depends on the charge current but also on the battery capacity. For larger batteries, 80% may not be achievable with current as trigger.

No, it depends on the C rating of the charge so battery capacity isn’t an issue, charge rate is - which is what I said in the first place.

Larger batteries tend to have lower charge rates which bring them nearer to 100% when current starts to drop.

Edited by Keith
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18 minutes ago, Keith said:

Yes it is so close to linear providing, of course that you treat empty as 3.6 Volts and not 3.0v per cell.

Good point, I didn't have in mind that below 3.6V OCV there is hardly 10% capacity left, but it fits well with my experiences with the wheels. I had in mind that the nominal 3.6V is also the median capacity, but this seems to be completely wrong then.

This link which I believe I haven't seen before gives also some related graphs, e.g. also under charge and discharge conditions

http://www.richtek.com/en/Design Support/Technical Document/AN024

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ok.. Getting back to the main question.. How to use the CD. 

My CD just came in the mail.. I am using it for the first time. 

So I held down the button while powering it on... Then I cycle to find Up V or Down V depending on the current setting .. right ? 
I mean without holding down the button.. it powers up to 67.2 V now. which means if I do nothing to adjust.. it will charge it up to 67.2.

So if I want it to charge to 64 .. I would have to cycle it to Down V .. in this case... then click it DOWN to 64V... 

Then once I powered it off. Next time it comes up it reads 64V (not 67.2) and I can simply plug in my EUC and from now on, it will only charge up to 64V 
Am I right ?  

Edited by Nick R
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  • Hold the button while plugging it into the power source (the charger).
  • Let go of the button after 2-3 seconds (longer than 5 seconds, you're in calibration mode and may fuck up your calibration, don't do that!)
  • It cycles through the 3 screens. The third allows you to change to "up V" (NOT "dn V") from "dn A" (default) by short pressing the button there. If it cycles too long without input, it switches to regular mode.
  • After changing to "up V", In the first screen, set your voltage (it will start cycling through the screens a few moments after setting "up V", first is next after the 3rd), or just unplug and plug-in-while-holding-the-button again to get to the first screen.

That's it for adjustment mode (setting to cut-off by voltage [default is current] and setting the cut-off voltage). Wait til it automatically goes back to normal mode (no input while cycling through the screens too often), or unplug and replug without holding the button then it starts in normal mode.

  • You can check by short-pressing twice in normal mode, it should show the cut-off voltage. If not (it shows ---V), long press to change.

Note: the wheel is never part of any of this. Just afterwards, you plug the CD on the charger into the wheel to charge.

--

But seriously, just read the instructions, with these descriptions, they should be doable:) I'm not responsible if something goes wrong if you follow my description :-)

Edited by meepmeepmayer
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9 minutes ago, Nick R said:

ok.. Getting back to the main question.. How to use the CD. 

My CD just came in the mail.. I am using it for the first time. 

So I held down the button while powering it on... Then I cycle to find Up V or Down V depending on the current setting .. right ? 
I mean without holding down the button.. it powers up to 67.2 V now. which means if I do nothing to adjust.. it will charge it up to 67.2.

So if I want it to charge to 64 .. I would have to cycle it to Down V .. in this case... then click it DOWN to 64V... 

Then once I powered it off. Next time it comes up it reads 64V (not 67.2) and I can simply plug in my EUC and from now on, it will only charge up to 64V 
Am I right ?  

Please, read the instructions on the website again and be carefully! Dont hold the button to long after powering on, as you then go into the main settings, where you might even do something not so good for the wheel....

If you hold to long you dont adjust the cutoff you want, you adjust the main power source....meep meep explained it perfectly!

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ok.. It was confusing.. but I think I got it. 

I held more than 5 Secs to put it back to calibration mode and reset the initial voltage back to 67.2
then power it off. Restarted it again.. now it comes up 67.2 ... 

then power it on again.  held this time less than 5 S. 
let it go into PR2 mode and UP V .... This is where you say to wait until it goes back to screen 1 where I can set my cut off voltage. 
I was confused at first because pressing it takes up the voltage.. not down ( I want to go to 64V). But keep pressing it .. it went off the scale then restarted it at 0 so I was able to get it to 64V.  Then I unplugged. 

Now I think I have the cutoff set at 64V. 

With the quick check via the app.. my wheel is now at 93% and 64.7V 
So when I plug in the charger now, the CD shows  OFF .. 
I assume it is not charging since my wheel battery is currently already greater than my cut off 64V mark. 

 


 

bat.jpg

Edited by Nick R
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2 minutes ago, Nick R said:

I also got this usb connector with the charge doctor... 
For what purpose do I need to connect my charge doctor to my computer ? 

 

You do not need to but you may want to if you want to transfer charge data.

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11 minutes ago, Nick R said:


With the quick check via the app.. my wheel is now at 93% and 64.7V 
So when I plug in the charger now, the CD shows  OFF .. 
I assume it is not charging since my wheel battery is currently already greater than my cut off 64V mark. 
 

So look like if my wheel is showing I am at 93% and battery is at 64.7V 
May be my auto cut off should be set lower than 64V in order for me to hit 80% mark. May be at 62V ?

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