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Author Topic: My New Favorite Battery Pack  (Read 1629 times)

cockpitbob

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My New Favorite Battery Pack
« on: August 25, 2017, 12:07:02 PM »
$11.29 shipped without 18650 batteries.
http://www.ebay.com/itm/5-12V-Mobile-Power-Bank-DIY-Box-Case-USB-3-x-18650-Battery-Charger-Adapter/152065079139?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649



It holds 3 18650 batteries IN SERIES.  It has "12V" output(5.5x2.1mm), 5V USB output and a protection board.  The "12V" output is the 3 batteries through a switch on the protection board.  4 LEDs indicate its charge status and it turns off when the batteries get too low. 

This is just what I've wanted since when I'm out in the field the 2 things I want power for is a QRP radio and keeping my phone alive.  I've got 3,000mAh batteries in it.  That should last a long time in the field.

You can charge it through the 12V output with a current limited source.  I'm just experimenting with charging it now.  I don't know if it balances the 3 batteries(I doubt it) or if it will shut off at an appropriate voltage(I think it will).  I think the safest thing is to charge the batteries outside of the box in a dedicated Li-Ion charger.  More later.

I'm just educating myself on the Li-ion battery protection boards.  I'll update this when I know more about how this thing's board protects it from over charging and discharging.


caulktel

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Re: My New Favorite Battery Pack
« Reply #1 on: August 25, 2017, 05:10:46 PM »
Hi Bob,

I think it does balance charge them, because looking at the circuit board traces in the Ebay pictures it shows a tap at all of the battery junctions and it has the shunt resistors and all the Mosfets on board, also a charge controller. I ordered one and will check it out when it arrives. I also ordered some 3S protection balance boards that should be here at any time to build my own. I salvage old laptop batteries, (18650's), by the hundreds. Might as well use them for something.

Joel
N6ALT

gil

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Re: My New Favorite Battery Pack
« Reply #2 on: August 26, 2017, 07:02:25 AM »
Awesome, thanks!

Gil.

cockpitbob

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Re: My New Favorite Battery Pack
« Reply #3 on: August 26, 2017, 12:05:50 PM »
I spent some time tinkering with it yesterday.  Here's what I've found:

It does not balance the batteries.  There's 5 I.C.s on the board.  Most I couldn't find data sheets for, but I was able to figure most of it out anyway.
* Two 8-pin devices are power FETS in series for turning it On and Off.
* One 8-pin device is the 5V DC/DC for the USB output.
* The big 14-pin device is a quad opamp used as a comparator for turning the charge indicating LEDs on and off.
* The fine pitch 16 pin device is the battery management chip.  It will disconnect the batteries if the voltage gets too high, too low or if the current is too high.

The charge indicating LEDs switch at 7.1V, 10.0V, 10.9V and 11.9V.

I had forgotten that I have protected 3,000mAh batteries in it, but it's nice that the board protects them too.  I figure every once in a while I'll take them out and charge them in my charger to re-balance them, but for topping off in the field, I'm not worried about it not balancing the batteries.

The one thing I was hoping for was that I could re-charge it from a USB port.  I'm fixing that problem with one of these: https://www.amazon.com/gp/product/B008HMETBE/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
$5 step-up DC/DC converters.  I tested it and it's $10 brother with a display (https://www.amazon.com/gp/product/B00J03PBW0/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
last year and they work really well.  They limit the input current to about 2A so the output current is limited to around 5/12 of that (0.8A) which is safe for the batteries.  I'll set the output voltage to 12.6V which is the max you want to charge 3 Li-ion batteries.  Efficiency of these is well above 85% so there isn't much lost in the transfer.

« Last Edit: August 26, 2017, 12:10:41 PM by cockpitbob »

caulktel

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Re: My New Favorite Battery Pack
« Reply #4 on: August 26, 2017, 05:34:57 PM »
Bob,

Thanks for reverse engineering it. I do the same thing as you, I have a balance charger and periodically balance them then stick them back in pack, it seems to work fine for me. My protection boards arrived today, so now I can build a few more packs. I still look forward to the pack I ordered, its so nice and compact. Hope it's blue like yours, it will probably be pink.

Joel
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cockpitbob

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Re: My New Favorite Battery Pack
« Reply #5 on: August 26, 2017, 11:31:03 PM »
Hi Joel, what protection boards did you get?  Are the shematics available.  I'm new to Li-ion batteries and protection boards and am still learning.

caulktel

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Re: My New Favorite Battery Pack
« Reply #6 on: August 27, 2017, 05:44:47 PM »
Hi Bob,

 I got them from, https://www.banggood.com/Seiko-Protection-IC-10A-Protection-Board-For-3S-11_1V-12V-12_6V-18650-Lipo-Battery-p-1107660.html?rmmds=search

The schematic is on this page.
The pictures in the BanGGood ad say V 1.01, but mine actually have V 2.0 printed on them.

Joel
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« Last Edit: August 27, 2017, 05:55:32 PM by caulktel »

caulktel

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Re: My New Favorite Battery Pack
« Reply #7 on: September 11, 2017, 06:54:13 PM »
Hi Bob,

I received my power bank today and I really like it, except the ON switch  fell apart when I took it apart to install the batteries. Other than that it works great. I ordered  20 of the little switches from HK, it will take a month or more, (slow boat). Meanwhile, it works well if I short the contacts with a small screw driver. Oh, and it's blue like yours, YaY! Thanks for the tip.

Joel
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cockpitbob

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Re: My New Favorite Battery Pack
« Reply #8 on: September 11, 2017, 07:29:24 PM »
I'm almost done tinkering with a step-up converter so I can re-charge the pack from a standard USB port or USB charger.  None of the step-up converters have current limits on their outputs and the ones I linked in post #3 above put out enough current into a discharged bank of batteries they get too warm and will easily pull down a 1A USB port.  So, I'm adding a transistor, 2 resistors and a capacitor to add limiting to the output.  Naturally my first attempt oscillated so I calculated new loop values but haven't had the time to test it.

When I'm done I'll be able to plug the USB-12V charger's input into my battery pack's USB output and I'll plug the charger's output into the same battery pack's 12V port and the pack can charge itself :o ;D

gil

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Re: My New Favorite Battery Pack
« Reply #9 on: September 12, 2017, 02:55:56 PM »
Darn, I thought it had a built-in USB charger. I have one on order and will buy more.

Genasun has solar chargers for these batteries, so it might be time to order one  and a lead/acid model..

Gil

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cockpitbob

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Re: My New Favorite Battery Pack
« Reply #10 on: September 12, 2017, 04:00:39 PM »
Darn, I thought it had a built-in USB charger. I have one on order and will buy more.

Genasun has solar chargers for these batteries, so it might be time to order one  and a lead/acid model..

Gil

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At least it has a protection board (non-balancing) so you don't need a smart charger, though I think it would be a little better to have one.

gil

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Re: My New Favorite Battery Pack
« Reply #11 on: September 12, 2017, 04:03:43 PM »
Quote
At least it has a protection board (non-balancing) so you don't need a smart charger, though I think it would be a little better to have one.

That's especially good for discharging, using radios with no built-in voltmeter...

Gil.

Ding Bat

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Re: My New Favorite Battery Pack
« Reply #12 on: September 20, 2017, 06:50:00 AM »
Thanks, CockpitBob. I just ordered one. It is a great find.

Oh how I love eBay.

DingBat