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18650 diy Powerbank
#1
I’m sure this has been asked somewhere before but I’m looking to put all my lower cells to use. I want to make a 10-20 pack but am unsure how I could go about making it portable. I have several small battery banks and they all have the little circuit board. But would thoes boards designed to charge 3 cells work for 20? Is there a board out there I could buy that could support 20 cells in parallel with an output for usb 2.1a 5v that could charge all 20 cells
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#2
Yes they work, but be painfully slow.

What you want is something like this for output, 2/3 of them since you have 20 cells:
https://www.aliexpress.com/item/Single-C...23462.html

And for fast charging: https://www.aliexpress.com/item/5A-Lithi...97301.html

Set to say 4-5A output to the cells from say a laptop power supply.

Or if you want an AIO solution:
https://www.aliexpress.com/item/3-7V-Boo...87976.html

This will charge at a max continuous 18W, so shouldn't be a problem.
hbpowerwall likes this post
The power of lithium ion is in our hands!
We'll show them what we're made of!
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#3
That all in one solution. Is it saying I could charge it with a 5v 3a USB adapter? Or 9v 2a? Or 12v 1.5a? options and it will charge the same rate. And if that’s the case. Would 150ma be enough to charge the 20 cells at a decent rate?

Also side note do I need to worry about like capacities since all the cells will be in Parallel?
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#4
It's critically important that you learn how to calculate this for yourself. While we're always glad to help you can't come back over and over again to ask for the necessary calculations for your project. For example, 20 cells at 2Ah, 40Ah, 148Wh at 3.7V nominal. With that and the different charging options you know exactly how fast or slow the charging will be and you can decide whether this is a decent rate for you or not. The FAQ will teach you how the maths work.
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#5
(02-10-2019, 11:51 PM)DarkRaven Wrote: It's critically important that you learn how to calculate this for yourself. While we're always glad to help you can't come back over and over again to ask for the necessary calculations for your project. For example, 20 cells at 2Ah, 40Ah, 148Wh at 3.7V nominal. With that and the different charging options you know exactly how fast or slow the charging will be and you can decide whether this is a decent rate for you or not. The FAQ will teach you how the maths work.

That’s what I was trying to ask. The charger has 3 different inputs. I don’t know how the 3 difffrent options affect charge rate. I charge the cells individually I know what rate they charge at with 500ma. I’ve never use an aio before and don’t understand how different ones handle charging

Sorry if I still don’t follow I’m still new to 18650. So please bare with me

The 12v 1.5a option is 18w so to find how many hours I would just take the total wh and divide by 18w. So about 8h in the case of your example.

If that’s the case then I think I was thinking of it in the wrong way. I was trying to figure out per cell in my head not the hole pack
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#6
This QC3.0 board has QC3.0 outputs with QC offering higher voltages than standard USB but from the product listing, because of the near perfect english translation, I can't tell for sure if it also has a QC3.0 input Big Grin I think the last picture may show the 12V input.

Anyway, let's assume it does, but you always have to take voltage conversion into account. All cells in a powerbank are in parallel so the nominal voltage is only 3.7V. You were doing it right but there will be losses so assuming it supports 12V at 1.5A at its input means 18W input to the DC-DC converter which then converts the voltage down to charging voltage for the cell. Assuming there will be a 90% conversion efficiency the cells will be charged with 16.2W at up to 4.2V which gives rougly 3.85A charging current. I don't know what the current limit is, it probably won't charge at the maximum available current. Maybe it's limited to 3A as well. If so then the charging time for completely discharged cells will be probably like 16h.
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#7
Ok so no matter what power option I choose to use it won’t make a difference if 3a is the max charge rate
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#8
18W is the power that is going to reach the cells.

I've tested one of these modules(one from a dead RavPower QC 3.0 20Ah battery pack) rated at 24W input

With a powerful charger and a a very thick USB cable, I was able to get 23W input power.

However, in most cases, you aren't going to get 18W from the input since there are losses in the cable and DC converter itself.

@slayer200230, have you thought about using 2 of these units?

You'd be getting 4 USB outs, with 2 being QC 3.0 capable, and with 36W power input for charging at a decent speed.
The power of lithium ion is in our hands!
We'll show them what we're made of!
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#9
@BlueSwordM wow no I didn’t. It didn’t even cross my mind I could use 2 of these to charge the batteries. When using 2 would I need to do anything than just hook them both up to same terminals? I’ve only ever messed with single charging
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#10
(02-11-2019, 02:48 AM)slayer200230 Wrote: @BlueSwordM wow no I didn’t. It didn’t even cross my mind I could use 2 of these to charge the batteries. When using 2 would I need to do anything than just hook them both up to same terminals? I’ve only ever messed with single charging

That is correct. You would need two wall chargers too.

You could also just parallel a couple of tp4056 up. Beware, however to make sure you do not attach them to an undersize power supply, as you will overload it.

Another idea would be the tp5100. It is rated up to 16v. So you could connect it directly to your lighter socket in a car, and it would be able to charge.
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