Xiaomi Mi 2 Powerbank 20,000mAh Review - New 20Ah King?

1. Yes this is normal. This is done because of the resistance of the cable, so the charger bumps the voltage to 5,2V so the phone/powerbank receives 5,0V.

2. It has 2,4A max output, but the device decides what current it is charging at. In this case, it is 2A. So, perfectly normal.

Cool, thanks for the answer. :slight_smile:

This powerbank will “boost” the output voltage when the current exceeds 1.5A, it is programmed to always do it because it has no way to detect cable resistance (for that you need feedback on the other end of the cable). but in your case the spikes are due to drops in the current draw.

Some manufacturers claim their powerbank being smart and will detect voltage drop across the cable/connectors and compensate for that, but they’re just being programmed to ramp up the voltage according to the current.

The Micro USB has an maximum rated current of 2.1A, and the 2.4A rating was designed for Apple which implemented 12W charging for their iPads. So even if your charger has a higher amp rating, no device with Micro-USB input should exceed 2.1A on the input side (in theory)

Thanks for that explanation, I have also been wondering how “powerbanks” can really detect voltage drop since the drop is on the other end…

I do notice several such behaviors, USB voltage increases a bit when current increases, different chargers/powerbanks implement them slightly in diffferent ways at different voltage thresholds (I use EBD-USB+ to do a current load sweep and notice the voltage changes).

For smartphones (mostly I’ve only checked a few older Samsung phones, and they typically charge to 1.8A max current at USB 5v. It’s only some powerbanks that I’ve noticed charging at 2.0A or sometimes spiking over 2.0A charging current)…

The Xiaomi powerbank in particular, seems to continuously “test” the charge current and voltage every now and then, at least that’s my understanding of the “spikes/dips” when I try to graph the Mi powerbank when it is getting charged…

Looks like Banggood pulled the ol’ switcharoo. The link in the OP takes you to the old version. 3.7v (74wh) instead of the 3.85 (77wh). Didn’t notice it till I got mine today. Not a major deal for me but you all should be aware if you are looking for the one in the review.

Anyone know a place that will ship this to Canada?

I would NOT want a lipo cell inside a power bank. This is not an upgrade to the design.

Also, the voltage spec is non-sense. The nominal voltage was listed as being higher to bump up the claimed capacity. Don’t fall for the obvious marketing.

Well, thats very disappointing but very observant of you to catch. I wonder how old the cells are in the old pack they pawned off on you? Do you have a link for the new model?

Bangood also did the same blatant switcharoo on me with a cell phone I ordered from them. Of course, they tried to deny the claim and then ignored me… until I filed a PayPal dispute and kicked their crooked asses. Now I have a free phone, but turns out it was used and broken by someone before me! Yeah, they sent me a used broken phone and claimed it was new, then tried to stick me with it!

I think they fixed it now because it does indeed link to the new (2C) version. Or they just decided to send you the old one?

About Lithium Polymer it’s all about preference, if safety if your primary concern then definitely stick with 18650 versions, which are marketed 10,050 and 20,100mAh respectively and have sightly lower energy rating. They have light blue LG F1 cells inside which according to discharge tests yield approx 3,200mAh.

Xiaomi has now released a Mi powerbank 3, same capacity same form factor, but now supports Power Delivery output up to 45W and costs about $12 more.

Both banggood or gearbest pricing are not so worth it for me now that a official Xiaomi store has opened in my town. The updated 10,000mAh version with 2 USB ports sells for $16 and the 2C goes for $25. And all of the other accessories are also much cheaper by a considerable margin.

I have also found that many “Xiaomi” branded accessories are also sold under the ZMI name, some of them being just 1/3rd of the price of banggood. Search zmi on amazon or go directly to their homepage and you’ll find some great deals.

30-4-2019 Update

Almost 2 years after my initial review and regular use of about 100 full cycles my unit started to show signs of swelling. My power bank is fully charged and ready to go most of the time, which is not optimal for Li-Ion storage but otherwise defeats the purpose of a power bank. And that’s how most people who are not into batteries will use them anyways, so “real world results” nonetheless.

A bit of swelling in pouch batteries is not always dangerous but there is a chance it continues expanding, in which case I must dispose it. One more reason to go with 18650, they also degrade quicker when stored fully charged, but at least won’t became dangerous.

Spins on its belly

Vs flat surface

By god.

This isn’t safe.

Due to how pouch cells are constructed, they tend to release much more gases during bad conditions compared to cylindrical cells.

This is also why powerbanks OEMs should implement an 80-90% storage charge and design it so it consumes as little power as possible.

My RavPower QC 3.0 20Ah has a standby drain of about 14,2uA, which is excellent, but some are 100uA, or even in the mA range in the worst of cases.

Therefore, a lithium-ion cell stored at say 60-80%+ with very little standby drain should have no problem not losing much power at all for a year, and not degrading.

Agreed!

@will34, a puffed/swollen Lipo of any extent is dangerous, you need to dispose of that pack immediately!

I’ve used Lipos for many years mainly for RC hobby, Lithium polymer cells are not as stable as Lithium Ion and even a Lipo cell that is only slightly puffed can unexpectedly blow its load and with yours being contained in a hard case would make that more likely and more explosive if it did.

Just curious, how do you test the standby drain of a powerbank?

That swelling is troubling, stay safe.

It’s april 2020 now and the latest model seems to be the PLM18ZM, which has 4 ports: 1x micro USB as input, 1x USB C as in/output, and 2x USB A as output. There are also 2 other similar looking models from Xiaomi related brands:

- Redmi PB200LZM

  • ZMI QB821

Does anyone know how these compare? Or is it essentially just the same device, but with different names?

Here they show the internals of the ZMI. It has the two flat cells, just like the Xiaomi. But how about the Redmi?

Time to revive this thread.
My powerbank seem to be swollen too.
Anyone rebuild it? What cells are inside?
Mike

Lithium-ion polymer battery.

Rebuilding not worth it IMO, plenty of nice portable chargers currently on the market with improved input and output options, many of them also features Lithium polymer cells but with newer tech they don’t swell as easily. I had my Xiaomi 20,000 pro 45W for the same amount of time and it has been stored full for months, no sign of swelling.

However I still much prefer cylindrical cell powerbanks, my first gen Xiaomi died long time ago but the pulled LG 18650F1 cells still run fine.

my 20000mah 2C has started to bulge too, less than the OP and it’s only noticable because it spins on a desk and doesn’t sit flat, you can see it against a straight edge. it’s old but I’ve barely used it!

is this expected from all pouch cell power banks eventually?

Yes.

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