Interesting 'DIY Power Bank kit/shell' - bidirectional PD100W, 6x 21700 (in series, but balanced), no soldering required.

Wingman · August 7, 2025, 11:10am

I came across this high power/100w DIY power bank housing on Aliexpress, which looks interesting. Most of the high power/100w (or more) DIY power banks on Aliexpress, rely on at least 2 or more batteries to be placed in series, which could create some issues if the batteries aren’t properly balanced/charged by the power bank.

This one (most often shown as the ‘ZY-Q6’) stands out, because it doesn’t have the batteries in series (as far as I can tell), but visually they seem to be in parallel, but (as shown by a photo further down in this post) they seem to be individually managed/charged.

EDIT: It turns out that the batteries are in series, but should be individually balanced; see this post later in the topic.

The other thing that I find really interesting is that it can output up to 100w (20V/5A), but also can be charged with the same voltage! Combine that with 6 good quality 5000mAh 21700 and you seem to have powerfull power bank with (at least) known good quality cells!

The build quality looks quite sturdy/solid and the 21700 batteries seem be in proper holders/slots:

Besides the (remaining) percentage, it also shows the (active) in-/output voltage/current:

Apparantly it can also be (manually) put into ‘low current mode’:

One of the reviews I found was from someone having issues with it not working (due to a bad/lacking solder connection), but the possitive for us is that we can get a rough idea of how it (electronically) is designed:

I did found a somewhat more ‘extensive’ review from someone, listing a few ‘small’ issues. This review is auto translated by Aliexpress from Russian, I believe:

I take the second one, all charging protocols are present, it charges at 100 watts with a charger in 1 hour. 5 hours, the only thing that can be objected to is the incorrect percentage display. When charging, it reaches 70 percent and then stops charging. After a while, it updates to 100%, and the discharge occurs faster starting from 40 percent. . . You can consider it 10% remaining, otherwise everything is excellent, the battery will keep charging up to 4. 1 V discharges for about 3 minutes. 2V, enough to charge 3 phones with a 5000mAh battery, taking into account energy conversion and a slight overcharge, the battery will last longer and I consider the result excellent.

I expect that the "discharges for about 3 minutes. 2V is probably a translation error and must be ‘dicharges to 3,2V’

The only other downside that I’ve found so far: It is more expensive than I would like it to be.

It is mostly priced between 22 and 25 euro (including shipping), from what I could find.

But it certainly looks like an interesting and easy DIY power bank housing with a high (re)charge rate. If I can find it for just under 20 shipped, I might pick one up to check it out.

m03da · August 7, 2025, 11:21am

How fortunate, the other day i posted a thread looking for exactly this type of product, thanks!

Wingman · August 7, 2025, 12:34pm

I was thinking about that topic, but couldn’t remember who posted it or what the specific criteria were!

I’m glad that it might be of use to you and curious what your experience will be.

Oli · August 7, 2025, 12:37pm

It may be good for some people.
It probably would not be allowed on airplanes because you don’t have any clear markings as to the capacity. And no markings as to testing certifications.

Wingman · August 7, 2025, 12:52pm

Personally I wasn’t thinking of taking this with me on an airplane. I was purely thinking of using it my daily life as a powerbank that I can quickly grab and take with me or use in and around the house and can be quickly charged up again. Maybe not at the full 100w, but maybe at 65w or something like that, instead of a lot of the (cheap) ‘diy power bank shells’ on Aliexpress, that can only do 22,5w.

I personally also like the idea that I can choose my preferred batteries from a reliable vendor/store.

But as you said: this one is absolutely not for taking with you on an airplane!

Sirstinky · August 7, 2025, 6:15pm

That thing’s as sketchy as a fox in a henhouse. I have a few of those cheap 18650 power bank boxes from AE (one 6, one 8, one 21 cell). They’re all pretty much the same: somewhat okay, they work, but mostly cheap, low quality, inefficient charging/discharging performance.

This looks to have 6 individual channels like a buck/boost converter for each? I’m not an electronics expert or even a novice, but ive come across setups like that in the Nightwatch A15 with 4P 21700 that supported 100W charging. During charging at 20.5 v 5 amps, the head heated to 50 C and those poor batteries had to absorb over 5 amps each. 6P would be a bit better, but I can’t imagine it would last very long and the efficiency pf the circuit is probably poor. Plus the very inaccurate voltage of the charge state readout. I’d love to see someone test this thing.

Wingman · August 8, 2025, 6:14pm

I (believe?) I’ve never stated it was a ‘good’ (quality) or ‘reliable’ power bank, just that it’s an ‘interesting’ one!

This is what made me curious, since most of the other high power/100w (2-way) ‘DIY power banks’ on AE, have at least 2 or more cells in parallel/per ‘channel’. This one reminds me more of a ‘regular battery charger’ with 6 individual slots, but also with a 100W output. Taking into account some conversion losses from the input power to charging voltage of the cells, it could maybe/ ‘in theory’ charge 6 cells at 3A at the same time. Not sure if it actually achieves that, but there is only a limited offering of ‘regular 4 slot chargers’ that do that.

If I would buy/use one, I personally wouldn’t charge it at 100w, but maybe charge it with a 65/67w charger, just to limit the charge rate.
But I’m also curious which charging chip/controller it uses, how it functions/react with less than 6 cells, what the charging method/curve is, etc. etc.

Another reason that I’m curious about it, is that I have (bought) a bunch of 46950 batteries that I bought really cheap of which I had/have a ‘vague idea’ of using a couple of them for building a power bank with them myself, but I’m still looking inspiration/options for a way that is achievable with my (limited) technical skill set. I would prefer to put them in parallel (or individually charged), but so far all the standard/off the shelve charching boards (that are powerfull enough) have at least 2 or more in series.
Developing a custom charging solution is WAY above my knowledge.

Although is power bank kit isn’t powerful enough to charge 46950 at proper rate, it is one of the few power bank systems I’ve seen so that charge multiple single cells at a high(er) rate than (most) other powerbanks with such a setup that I’ve seen.

All in all, it’s mainly out of curiousity that I would want one and given that I’ve found a way to buy them for under 20 euro (via the ‘coins section’ in the AE app), I might buy one to get a better idea how it is constructed/works! (I’m in know way able to do a proper technical analyses, but I might be able to clear up some details.)

Mandrake50 · August 8, 2025, 7:05pm

Well I ordered one just to see how it works. When I get it I will run some tests. The concept is good, let’s see how the execution is.

m03da · August 8, 2025, 11:27pm

i would hope the readout is a bolt-on thing and the charge/discharge is controlled by an independent industry standard ASIC

we’ll see

Sirstinky · August 11, 2025, 7:31pm

I can’t say for sure, but i will say that those charge circuits on these cheap power banks arw generally rubbish across the board. Of the 5 I’ve used they have all been inconsistent and show inaccurate battery voltage. I had two that also show “0” when the batteries are still t 3.7-3.5 volts, add will shut down under load. It might be battery specific, but to me that’s unacceptable. I have a very high quality 8.4 volt (2s2p 21700) battery back from MagicShine that works fantastic as a power bank (but also cost 4x as much).

m03da · August 11, 2025, 9:28pm

could you share a link please?

Sirstinky · August 11, 2025, 9:55pm

I don’t think you can buy the battery separately anymore (you used to be able to). I gotnit in the MOH 55 Pro kit in 2020 or 2021.

Wingman · August 13, 2025, 10:10am

My Xtar PB2SL power bank/charger enclosure also isn’t super accurate in terms of %, even with 2 brand new, identical type/age and almost perfectly matched (in terms of ACIR) cells.

The only “DIY power bank” I have that is pretty accurate in terms of its %, are the 2 Lumintop Aurora that I have, but that has only 1 cell, which (most likely) is one of the main reasons that it is more accurate.

Wingman · August 13, 2025, 11:57am

Via the above mentioned ‘coins section’ and some coupons, I managed to get the price down to ~ € 16,- (incl. shipping) and for that price I’m willing to take a gamble to test it.

As soon as I have it, I will try to take some detailed photos, to get an idea of it’s internal design and specific partnumbers of components that have been used.

EDIT:
I also want to know if it can potentially function with only 1 cell and if the capacity % would be more accurate that way, compared to multiple cells.

I’m also planning on doing a capacity discharge test with my Atorch DL24 load tester. I’ve recently recieved my plug-in trigger board/adapter for it, giving me the option of manually selecting the discharge test voltage (5/9/12/15/20/28V). Should give a rough idea of what the efficiency is, compared to the Wh of the used cells.

I do have 2 sets/types of 6 new 21700 batteries for it, which should be good for consistency in testing, but the downside is they are low drain (and therefore also low charge current), which would limit the possibility of using the high power functionality of the charger. I’m thinking of ordering 6 ‘tabless’/full tab batteries for it (EVE 50PL), which should heat up (substancially) less, also when charging, but if I do so, that won’t be here until the end of september.

Wingman · August 13, 2025, 1:03pm

By the way, an Important Notice in the description on AE, about these power banks:

Battery Reset: After removing and reinserting batteries, the power display will reset to 0%. Please fully charge to recalibrate.

Important to be aware of this, because this can obviously create confusion when you first start using this.

It also does suggest that the capacity % is a completely seperate function from the individual charge controller(s), given that regardless of that 0% reading when inserting batteries for the first time, it still would be able to identify the correct (termination) voltage anyway.

This would be in line with what @m03da stated earlier in this topic (and I am also hoping/expecting):

But we are going to find out anyway.

Wingman · August 20, 2025, 11:58am

Recieved my ‘Q6 DIY power bank’ today. Fortunately the housing is build really solid, because packaging by the seller was ‘mediocre’, to put it mildly.

First of all: the batteries are NOT connected in pararrel, but are in series. I was ‘fooled’ by the orientation of the batteries and didn’t look good enough to the photo to really notice how it was designed. The batteries seem to be being balanced though, but more on that later.

I have taken some QUICK photos with my phone, which are not of the highest quality, but they give an initial impression!

Photo of the text on the casing, confirming the series connection (22.2V):

Here are some photos of the backside of the PCB, giving a better view of its design:

The SW6306 chipset (seen below) is the (100W) Fast Charging chipset used, which according to a website I found via Google, is described as: “It is a highly integrated four port multi protocol buck boost mobile power bank SOC.” (More elaborate details on that website I mentioned.)

Between all batteries, and placed besides the inductors, is an ETA3006 ‘Inductive Cell Balancer’. The description in the (official) datasheet says:
“ETA3006 is an inductive cell balancer. Unlike conventional passive balancing technique, ETA3006 utilizes a control scheme with an inductor to shuffle currents between two cells until the cells are balanced. Due to the switching nature, the heat and power dissipation generated in conventional linear balance technique are greatly reduced. The balance time is also significantly reduced due to higher balancing current not being limited by package thermal dissipation.”

The ICM CM1361 is a battery management/protection chip. The website Chargerlab(.com) describes it in this article (although that is the ‘-DAT’ variant, not the ‘-CAT’ shown on my photo) as follows:
" The iCM CM1361 is a battery protection chip designed for applications with 6-cell battery packs and supports battery balancing functionality. It features high-precision voltage and current detection circuits built into the chip, allowing it to monitor the voltage, current, and temperature of each cell in a series-connected battery pack. The chip provides multiple protection features, including overcharge, over-discharge, charging overcurrent, discharging overcurrent, overheating, and battery pack disconnection protection."

If anyone wants more (detailed) photos of certain components or specific parts of the PCB, let me know.

Wingman · August 20, 2025, 12:16pm

By the way: it only came with a chinese ‘manual’, but through the magic of the Google translate app, something I could read came out:

Mandrake50 · August 20, 2025, 4:57pm

Thanks for the information. I too got mine. I haven’t played with it much. I loaded it up with 21700s, It turned on and “super” fast charged my Galaxy phone. I am in the middle of a few other projects right now, but at some point I will do some comprehensive testing.

m03da · August 20, 2025, 6:55pm

Thanks for the awesome overview! Cool to see them in series, with dedicated balancing circuitry it’s good for efficiency, downside is the inability to function without all cells installed, that could be a way to make it arbitrarily lighter for backpacking, or air-compliant. No idea how it could be tested safely but i wonder what’s there in a way of reverse polarity protection- i assume the bank will just not operate because the relevant protection IC will block the current but i wonder if possibly that slot’s fusible resistor (great seeing those as well!) might blow making reverse polarity installation a thing that kills the bank.

ebastler · August 20, 2025, 7:21pm

Ooh, active balancing. Fancy. Usually those things only have passive balancing, which means (super) slow charging towards the end of the charge cycle.