Jump to content
Smoother

Bought Charge Doctor. Now What Do I Do?

Recommended Posts

3 minutes ago, Smoother said:

So, let me get this straight.  We use batteries that are fully charged at 4.2V but are effectively dead at 3.4V, ---0.8V less?  That almost sounds like a failed product, other than for all the successful devices using them.

There is enough energy available throughout this range. But Less voltage drop until empty would still be better.

3 minutes ago, Smoother said:

A second question.  Why does a battery with 3.4V/3.2V have no useful energy left in it when a brand new AA or AAA or C or D conventional battery starts around 1.5V?

The have a different chemistry.

  • Like 2
  • Upvote 1

Share this post


Link to post
Share on other sites
2 minutes ago, Smoother said:

So, let me get this straight.  We use batteries that are fully charged at 4.2V but are effectively dead at 3.4V, ---0.8V less?  That almost sounds like a failed product, other than for all the successful devices using them.

A second question.  Why does a battery with 3.4V/3.2V have no useful energy left in it when a brand new AA or AAA or C or D conventional battery starts around 1.5V?

Thats not EUC related, that are standard values for ALL lithium Ion batterys...

nominal 3,6 or 3,7

Full loaded 4,2-4,25

Empty at 3,3-3,4 while some of them have no problem to go down technically to 2,5!

But from 3,3 to 2,5 the voltage drop is immense and normaly the cells are not meant to be used under 3,3 Volt!

Thats just what the actual cells are capable off. Not an EUC related thing!

  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites

Well, it obviously works, when packaged properly for the application.  It just sounds like a business presentation that would not be funded, based on the numbers.  "Alive now, dead 0.8V later, How many millions do you want to invest?"

Come to think of it, its par for the course across the battery industry.  12V car batteries are fully charged at a resting Voltage of ~12.7V and effectively dead at ~11.9V.  That's about the same drop.

Share this post


Link to post
Share on other sites
1 hour ago, Chriull said:

As a 100% charge at 25°C does just 4% degratation over a year i would also not worry too much about full charges...

I think you misread the table, the degradation is 4% at 40% charge and 20% at 100% charge (Table 3). That is indeed the main reason why I use the charge doctor. I would be very interested in the degradation number at 75% charge tough. 

Edited by Mono
  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites
1 hour ago, Mono said:

As @Keith suggested a little while ago, the lower value is more like 3.4V. While the cell can go down to 3.0V, there is only little capacity left below 3.4V.

I pick 3.0v as that is what BU generally uses as empty and so is what they base their percent of charge figures on. My V8 considers 3.4v to be empty but how the cells are used and what it is used in is irrelevant for charging.

Share this post


Link to post
Share on other sites
49 minutes ago, Smoother said:

Alive now, dead 0.8V later, How many millions do you want to invest?

Dead 0.01V later, everything else being equal, would probably be worth around a billion or ten.

Edited by Mono
  • Like 2
  • Upvote 1

Share this post


Link to post
Share on other sites
4 minutes ago, WARPed1701D said:

I pick 3.0v as that is what BU generally uses as empty and so is what they base their percent of charge figures on.

I know, I did the same mistake before Keith corrected me.

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Chriull said:

As they are talking in table 3 from 100% charge this 4,2 peak voltage/peak charge voltage is for "saturation" charges (where one does not cut iff at a certain voltage threshold but continue with the normal liion charging with this max voltage).

Your cells "recover" from the almost 4,2V quite immedeately - the degratation figures in table three are over one year!

As a 100% charge at 25°C does just 4% degratation over a year i would also not worry too much about full charges...

Sorry. I only referred to table 3 as a reference to find the following paragraph about peak charge voltage. The relevant table to this discussion is table 4 and the discussion of cell stress due to high charge voltages. 

Share this post


Link to post
Share on other sites
15 minutes ago, WARPed1701D said:

I pick 3.0v as that is what BU generally uses as empty and so is what they base their percent of charge figures on. My V8 considers 3.4v to be empty but how the cells are used and what it is used in is irrelevant for charging.

Naaah....3,0 is a bit to empty, in my view.

Like said, a lot of cells alow the tecnical minimum voltage to be 2,5 to 3,0 Volts...but under 3,3 Volt every 18650 Li-ion cell gets a ridiculous volt drop!

You can ask Flashlight forums, E-bike, Vaping Forums and battery gurus....Not that good to discharge a cell to 3,0 Volt on a regular basis.

Edited by KingSong69
  • Like 3

Share this post


Link to post
Share on other sites
58 minutes ago, Mono said:

Kind-of the opposite. The less voltage drop a battery has during discharge, the better. That is, a 4.2V battery which delivers the last drop of current at 4.1V would be (much) better than the Lithium-ion batteries that we use right now. 

Except for one little thing: how do you measure when the battery is full or empty, if the voltage change across the charge state is very small (maybe smaller than voltage drop caused by high current draw over the internal resistance)? ;) 

  • Like 1
  • Upvote 2

Share this post


Link to post
Share on other sites
3 minutes ago, KingSong69 said:

Naaah....3,0 is a bit to empty, in my view.

Like said, a lot of cells alow the tecnical minimum voltage to be 2,5 to 3,0 Volts...but under 3,3 Volt every 18650 Li-ion cell gets a ridiculous volt drop!

You can ask Flashlight forums, E-bike, Vaping Forums and battery gurus....Not that good to discharge a cell to 3,0 Volt on a regular basis.

For EUC use I agree that 3.4v is a good stopping point for discharge. Our demands vary and a cell with a high voltage that has only had a slow trickle of power demanded from it for some time would suffer a huge voltage drop if suddenly loaded up with little capacity left to offer. However setting 3.4v as a cut off for something with a high constant load would leave you only able to access a small amount of the battery's potential capacity.

Tests of the LG MH1's (V8 Cells) which you can see here

http://lygte-info.dk/review/batteries2012/LG 18650 MH1 3200mAh (Cyan) UK.html

show that at a constant 5A load the cell has only used about 60% of capacity at 3.4v. At a trickle discharge of 0.5A 3.4v would however signal the beginning of the sudden voltage drop and next to no capacity left.

How a cell is discharged has no bearing on how it should be charged however and we are in agreement at what should be considered empty for an EUC during discharge (3.4v). I use 3.0v as my 0% charge value and as the basis of voltage % calculations as that is what BU use in all their charging observations and at that point it is just another LiIon cell being charged regardless of what device it is installed in.

Share this post


Link to post
Share on other sites
20 minutes ago, esaj said:

Except for one little thing: how do you measure when the battery is full or empty, if the voltage change across the charge state is very small (maybe smaller than voltage drop caused by high current draw over the internal resistance)? ;) 

To derive the charge status from voltage, we have to measure the current anyways. Otherwise we get values all over the place while driving, as it seems to be the case for the current Gotway wheels.

For a constant-voltage battery we have to integrate the current over time to know the charge status, like the CD does. I see your point though, if it is impossible or unreliable to predict when the battery runs out of juice it is a relevant disadvantage in particular for the usage with EUCs.

Share this post


Link to post
Share on other sites

@meepmeepmayer --- you have proven that you are quite knowledgeable on this subject matter and so I was wondering if you could answer this quick question re: Charge Doctor.

I am trying to set an 80% cap on a battery I just purchased but was informed by the battery manufacturer that the charger has a negative and positive port that aligns with my machine. Is there a certain way I have to plug in the charge doctor to the machine so that the negative and positive align properly? I don't want to cause any damage to the battery or machine because of improper plug-in. (Relevant pics attached)

 

EDIT: Note, I realize that I mixed up the positive/negative labels but the question remains.

1. Charge Port Connections (underside).jpg

2. Charge Port Input.jpg

3. Charger Connector (postive and negative).jpg

Edited by Justin Zamora
  • Upvote 1

Share this post


Link to post
Share on other sites
4 hours ago, Justin Zamora said:

@meepmeepmayer --- you have proven that you are quite knowledgeable on this subject matter and so I was wondering if you could answer this quick question re: Charge Doctor.

I am trying to set an 80% cap on a battery I just purchased but was informed by the battery manufacturer that the charger has a negative and positive port that aligns with my machine. Is there a certain way I have to plug in the charge doctor to the machine so that the negative and positive align properly? I don't want to cause any damage to the battery or machine because of improper plug-in. (Relevant pics attached)

 

EDIT: Note, I realize that I mixed up the positive/negative labels but the question remains.

From a quick look at your pictures (just the connectors) it would seem that the polarities are what they're supposed to be. What is the make and model of your wheel? There's no standard per se for the pinout of the charge ports, but at least so far I've never heard of the Charge Doctor pinout being wrong for some wheel? If you really suspect this is the case, better ask from @hobby16 about the pinout of Charge Doctor and measure the polarity of your wheel and the Charge Doctor with a multimeter. Although, I'd suspect if the Charge Doctor turns on with your charger being connected to it (without connection to the actual wheel), it should be correct.

Edited by esaj
  • Like 1
  • Upvote 1

Share this post


Link to post
Share on other sites

@Justin Zamora Sorry I don't know with certainty. I merely managed to use my charge doctor. I'm no electrical expert. Also not quite sure what exactly your pictures show.

I'm with @esaj that it would be safest to measure both the wheel charge port and charge doctor to be sure. And everything else he says.

What 80% battery charge is depends on the battery voltage. For a 84V battery/wheel, that would be a charging cutoff at about 80V (this stuff is never exact, so check your wheel's battery % to see which cutoff voltage gives you 80% charge). For 67.2V, 80% battery should be about 64V. So set your charge doctor to switch off by voltage and then set the right voltage.

  • Upvote 1

Share this post


Link to post
Share on other sites

Thank you both for your replies! This actually is not for an EUC, it is for the no longer manufactured DualTron Man. MiniMotors OEM battery fried on me (it was li-polymer which apparently has a pretty high failure rate in these machines) and so I got a company to build me a li-ion battery to specs. They made sure to emphasize connecting the positive and negative terminals and to never reverse, which I knew... but there word of caution makes me hesitant to use anything but their supplied charger. I just fear that there is a small chance that the polarities could be reversed on the charge doctors and while not likely... that would be an expensive mistake. 

I am not very well versed with the technical aspect of how to measure the polarity with a voltmeter nor how to interpret the readings once I do. This is for a 60v, 19.2ah battery pack.

Share this post


Link to post
Share on other sites
2 hours ago, Justin Zamora said:

I am not very well versed with the technical aspect of how to measure the polarity with a voltmeter nor how to interpret the readings once I do. This is for a 60v, 19.2ah battery pack.

I'm sure there are loads of how to's on youtube.  But basically switch your multi meter to dc volts. now practice on a regular battery (see TV remote) place the red lead on the positive, black on negative, read result.  Now switch the leads (no damage will occur) notice how the voltage is the same but now there is a (sometimes tiny) negative sign in front of it.  THIS IS IMPORTANT IN YOUR CASE. WATCH FOR THIS NEGATIVE SIGN, it's easy to miss.  When measuring your wheel use good lighting and triple check that you have read the meter correctly as per this negative sign (and by that I mean it should not be there if the leads are hooked up the correct way).  Now label your wires. If you have electrical tape or masking tape.  Make sure your labeling system will make sense in the future if you take things apart again.

WHEN TESTING FOR VOLTAGE DO NOT LET THE METAL TIPS OF THE LEADS TOUCH EACH OTHER, OR ONE LEAD-TIP TOUCH BOTH TERMINALS AT THE SAME TIME, OR THERE WILL BE AN ALMIGHTY FLASH BANG AND THINGS WILL MELT INSTANTLY. This is the technical definition of a short circuit; you have shortened the circuit without it going through a load first. The multi meter simulates a load so the rules of electrical circuits are adhered to.

Edited by Smoother
  • Upvote 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×