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Fast charging the Kingsong 16X

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7 minutes ago, chrisjunlee said:

ideally we want to charge each cell individually, aka charging in parallel, with the assumption that cells are not perfectly balanced. Not sure why that's not the standard.

Because that's technically impossible. You can't wire a cell in series and in parallel at the same time, unless you start adding all kinds of switches in there. That would be a huge mess and extremely complicated to manage.

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6 minutes ago, ir_fuel said:

Because it does not work like that

Yes you are feeding 1A or 2A, but that doesn't say a thing about how "fast" or "slow" or "much" or "little" that is wrt to the cell/cells. To know that you need to take the capacity into account.

Imagine there exists such a thing as a 84V cell. If I feed that cell 1A and the cell has a capacity of 500mAh, that would be quite fast/heavy charging. If the cell has a capacity of 50000mAh then it would be very slow trickle charging.

Compare it to pouring water. If you pour water at certain rate in a small cup, it will splash and overflow. Now pour exactly the same rate in a huge bucket. You'll hardly notice it falling. 

I guess the confusion here is you're talking about cells in general - I'm strictly talking about 18650 cells, with let's say, a nominal capacity of 2200 mAh to 3100 mAh.

That variance isn't as extreme, as let's say, a 10180 cell with around 350 mAh.

If you want to split hairs, the *C charging guidelines are rough simplifications. It just happens that a larger capacity pack can scale to take in 1C because it gets split evenly across itself.

So what is the actual limiting factor? Internal resistance.

IIRC, an IMR 18650 has much lower internal resistance than standard 18650's, the tradeoff being much lower capacity. (900mAh vs 3100mAh). Yes, putting a 3C charge on an IMR puts the same amount of stress as 1C on a standard 18650, due to its lower internal resistance.

It's been years since I've looked into the finer points of this, so I may be wrong, but that's my current understanding. Feel free to correct or add to my understanding :)

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Just want to add, my understanding of batteries and C rating is consistent with what ir_fuel has written.

 

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Posted (edited)
4 hours ago, ir_fuel said:

Sorry man, but I can't explain it any simpler than I did. It doesn't matter if it's 18650 cells or LiPo pouches. The principles are the same. 

And I don't want to split hairs, it's you that doesn't understand the principles of charging battery packs and keeps on equating them to charging a single 18650 cell.

Fact of the matter is that 1A or 2A is nothing for our EUC battery packs, even 5A is nothing. You can "fast" charge your EUC every single time and your battery cells will not suffer from it, because true fast charging (wrt the what the cells are capable of) would be pushing 30A into them, but if you would do that a lot of stuff would melt before the current would even reach the batteries.

And again, the C rating is based on the capacity. Not the capacity of the cell, but the combined capacity of all cells in parallel. And this capacity is given in Ah. The more you have in parallel, the higher the amount of amps is that equates to 1C.

You are talking about an average capacity of around 2500mAh for your 18650 cells. Let's build a simple battery pack and see how it behaves.

Put 6 of those cells in parallel (as is the case on the KS16X 3P config times 2), that gives you a 2500*6 = 15000mAh or 15Ah battery pack.

Let's say you want to be safe, so you only charge at 0.5C as your simple 18650 charger does. 0.5C in this case equals 7.5A (15Ah --> 1C = 15A).

That's already more than your "fast charger" outputs. Your "fast charger" that "stresses" the batteries only outputs 0.5C, which isn't more than your charger at home for individual cells.

Now you want to be really on the safe side (because reasons) and you charge at 2A. Well, using the above number that's equivalent to 0.13C. That's very low and I would never call that "fast". 

To give you an idea: if I were to charge 1 of my drone batteries at 0.13C it would take 2.5 hours to charge it. I normally charge them in 20 minutes at 1C.

 

I hope it's clear now. I don't know how to explain it simpler :D 

 

 

Hmm, not sure why you’re saying I don’t understand when we’re saying the same thing. 

I have a solid background in physics, electronics and also come from an RC background, so not sure what the misunderstanding is 🤔.

From my perspective, this is the conversation this far:

Me: “1A is normal charging rate for 18650 cells”

You: “bullshit, 1A is meaningless. What if the battery is tiny or huge?”

Me: “I said it was 18650. For normal 18650 with X capacity 1A is a normal charging rate”

You: “that logic doesn’t apply to battery packs!”

Me: “if you have x cells in series, and you charge them at x*voltage_per_cell at 1A, each cell still gets 1A. If you have two packs in parallel and charge at 2A, each pack gets 1A”

You: “that’s not how it works. It’s all about C”

I’m not even sure what your disagreeing about since it seems like you’re changing points so often.

Edit: Ok, the only way I can make sense of this from your side: maybe you don’t realize our EUC battery packs are literally made out of 18650 cells?

Edited by chrisjunlee

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5 hours ago, ir_fuel said:

You are talking about an average capacity of around 2500mAh for your 18650 cells. Let's build a simple battery pack and see how it behaves.

Put 6 of those cells in parallel (as is the case on the KS16X 3P config times 2), that gives you a 2500*6 = 15000mAh or 15Ah battery pack.

Let's say you want to be safe, so you only charge at 0.5C as your simple 18650 charger does. 0.5C in this case equals 7.5A (15Ah --> 1C = 15A).

That's already more than your "fast charger" outputs. Your "fast charger" that "stresses" the batteries only outputs 0.5C, which isn't more than your charger at home for individual cells.

Let's use this as an example of where you seem to be misinterpreting my post.

If we have a 6P battery pack, my fast charging rate is 2.0 A per cell => 12.0 A total for the pack.

5 hours ago, ir_fuel said:

Let's say you want to be safe, so you only charge at 0.5C as your simple 18650 charger does. 0.5C in this case equals 7.5A (15Ah --> 1C = 15A).

That's already more than your "fast charger" outputs. Your "fast charger" that "stresses" the batteries only outputs 0.5C, which isn't more than your charger at home for individual cells.

7.5 A is less than 12.0 A, thus it is not more than the fast charger output. There is no contradiction with my guidelines.

 

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Let's go by example 84V mean 20 cells in series 

So one string has capacity of 50Ah

Now the final capacity depends how many of those are in parallel.

So if 1A is safe charging level for one series, then for 10 series (500Ah) safe limit would be 10A... 

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23 hours ago, US69 said:

KS has amp limits, that protect battery and board, in worst case by fuses. GW has no amp limit.

It does actually. I’m not sure where it’s at exactly, but I’d assume somewhere around 220 degrees Celsius... 

:roflmao:

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Posted (edited)

I'm going to play with fast charging my 16X with two of these Meanwell HLG-600H-48A LED power supplies in series. This will allow me to charge the wheel between 6.2A-12.5A, adjustable via the onboard pots. The nice thing about these is they are fanless and nearly silent :) This is rather overkill but I already use these power supplies for charging my electric skateboards so its worth using them on other applications.

 

https://www.meanwell.com/Upload/PDF/HLG-600H/HLG-600H-SPEC.PDF

20190524_135537.jpg

Edited by BleepBloopBlop

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17 hours ago, chrisjunlee said:

Let's use this as an example of where you seem to be misinterpreting my post.

If we have a 6P battery pack, my fast charging rate is 2.0 A per cell => 12.0 A total for the pack.

7.5 A is less than 12.0 A, thus it is not more than the fast charger output. There is no contradiction with my guidelines.

 

Well in that case, case closed since we agree, but judging from the reactions of others here it wasn't very clear for them either what you were saying :)

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28 minutes ago, BleepBloopBlop said:

I'm going to play with fast charging my 16X with two of these Meanwell HLG-600H-48A LED power supplies in series. This will allow me to charge the wheel between 6.2A-12.5A, adjustable via the onboard pots. The nice thing about these is they are fanless and nearly silent :) This is rather overkill but I already use these power supplies for charging my electric skateboards so its worth using them on other applications.

 

https://www.meanwell.com/Upload/PDF/HLG-600H/HLG-600H-SPEC.PDF

20190524_135537.jpg

That's a power supply that you can regulate manually for CV or CC. I don't know if it's a good idea to use that to charge LiPos.

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I've been thinking about just opening up the eWheels charger and replacing the fan with a quieter fan. ¯\_(ツ)_/¯

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2 hours ago, ir_fuel said:

That's a power supply that you can regulate manually for CV or CC. I don't know if it's a good idea to use that to charge LiPos.

For starters the batteries in the 16X aren't Lithium Polymer. These power supplies are widely used as chargers for all sorts of PEVs. There is no issue with the voltage adjustment on these for setting the finish charge voltage. No issues as these do CC/CV charging out of the box.

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3 hours ago, magicrobots said:

I've been thinking about just opening up the eWheels charger and replacing the fan with a quieter fan. ¯\_(ツ)_/¯

Let us know how that works out. I might have to do it as well. :) 

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On 8/7/2019 at 11:29 PM, BleepBloopBlop said:

This is rather overkill but I already use these power supplies for charging my electric skateboards so its worth using them on other applications.

They look nice! Unfortionately not available piecewise for the needed voltages.

Did you ever try to put them in series already or heard positive reports about someone doing that?

In the block diagram in the datasheet one sees that the output -V is connected via a capacitor to ground(earth) level! 

Could be that they are not really indented to be put in series or this is just a non issue? Just some very small cap to prevent the output to lines level by parasitic capacitances, or filter hf disturbancies against earth/chassis or whatever...

Or they are big enough to burden the internal regulation once beeing put through this capacitor to ground level by beeing connected in series?

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On 8/7/2019 at 2:59 PM, ir_fuel said:

That's a power supply that you can regulate manually for CV or CC. I don't know if it's a good idea to use that to charge LiPos.

Hmm, I thought the BMS handles the current regulation? 

My understanding of chargers: they're DC supplies with an impedance that limits how much current they can deliver. 

So a 84V 10A charger is basically a battery with an internal resistance of 8.4 Ohms (ignoring the load completely).

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26 minutes ago, Chriull said:

In the block diagram in the datasheet one sees that the output -V is connected via a capacitor to ground(earth) level! 

Could be that they are not really indented to be put in series or this is just a non issue? Just some very small cap to prevent the output to lines level by parasitic capacitances, or filter hf disturbancies against earth/chassis or whatever...

IIRC the capacitor near the output serves to minimize ripple - it's to smooth out and buffer the voltage level.

 

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Just now, chrisjunlee said:

Hmm, I thought the BMS handles the current regulation? 

No. BMS just shuts off in case of cell overvoltage. And does some balancing.

Just now, chrisjunlee said:

My understanding of chargers: they're DC supplies with an impedance that limits how much current they can deliver. 

No. They regulate this constant current up to the max voltage. With lower current they are "normal" DC power supplies.

Just now, chrisjunlee said:

So a 84V 10A charger is basically a battery with an internal resistance of 8.4 Ohms (ignoring the load completely).

No. But this could work out. Just the efficiency is bad (power dissipation at the resistor!) and the current will drop continously instead of beeing constant.

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10 minutes ago, chrisjunlee said:

IIRC the capacitor near the output serves to minimize ripple - it's to smooth out and buffer the voltage level.

 

Such a ripple minimizing condensator would be a "big" (electrolytic) one between -V and +V. Not between -V and earth.

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Time to build a twin Lenovo connector harness to test out my 1000w Quiq charger on the 16X! It's bulky but is fanless and nearly silent. Should be a good test to see if the internal wiring can take a 12A charge. I won't use this charger often. Just for a quick recharge mid day when I want to ride more!

IMG_20190811_100823_620.jpg

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Posted (edited)
53 minutes ago, BleepBloopBlop said:

Time to build a twin Lenovo connector harness to test out my 1000w Quiq charger on the 16X! It's bulky but is fanless and nearly silent. Should be a good test to see if the internal wiring can take a 12A charge. I won't use this charger often. Just for a quick recharge mid day when I want to ride more!

Remember to triple check polarity! KS switches the Lenovo polarity.

Edited by chrisjunlee

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Posted (edited)

And to simplify things, you might be able to get away with a single connector: the two charger ports are connected in parallel.

I would double check by doing a connectivity test in the input ports (V+ to V+, ground to ground).

No clue what the max current rating is for the connector though.

Also, KS has stated 10A is fine. 12A might be pushing it (either the wiring or the BMS), but it might work out, you never know.

Edited by chrisjunlee

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Lenovo Slim Tip chargers are offered up to 11.5 amps @ 20 volts. I'd feel more comfortable using two connectors while I experiment. Worst case I roast the connectors and rig up an XT90 or similar charge port.

 

https://www.lenovo.com/us/en/accessories-and-monitors/chargers-and-batteries/chargers/PWR-ADP-BO-TP-230W-AC-Adapter-slim-tip/p/4X20E75111

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1 minute ago, BleepBloopBlop said:

Lenovo Slim Tip chargers are offered up to 11.5 amps @ 20 volts. I'd feel more comfortable using two connectors while I experiment. Worst case I roast the connectors and rig up an XT90 or similar charge port.

https://www.lenovo.com/us/en/accessories-and-monitors/chargers-and-batteries/chargers/PWR-ADP-BO-TP-230W-AC-Adapter-slim-tip/p/4X20E75111

11.5 A @20V implies ~2.7 A at 84V right? Twin is the way to go then :) 

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