Powerbank has only 60% capacity

tonyrulez · April 22

Hi,

I've bought a powerbank (AlzaPower Parade) which is a 30000mAh 60W one (111Wh s rated on the case). First thing I did was charge it to 100%a nd then charge with it my phone from 60% to 95%, which has a 5000mAh battery, and the powerbank went down to 75%. With these numbers it comes to at max 2 phone charges, which doesn't seem right.

Next I took a USB-C tester, and did two 0-to-100% charge and 100-to-0% discharge tests. When charging the powerbank it reaches 50W and trickles down to 10W and then 5W. When charging a laptop with it, it managed to put out 55W-58W. So the power rating is legit. However, charging the powerbank only took 65Wh and 74Wh. Discharging it totally until it shuts off, took once 61Wh and then 67Wh

My laptop has a 46Wh battery, and while running (idle) it charged it from 4,6Wh to 33,5Wh, USB tester was reading 67Wh, based on idle power usage experience tester seems to work ok.

Now I know that I wont get the full rated capacity, deliberately miscalculated by the BMS to keep the battery healthy, and watching reviews you get 85%-90% of rated cap. In this case, it was more like 55%-60% Is this normal? I just sent it back, they replaced it, and I'm reading the same low capacity from my tester.

TL;DR: 111Wh powerbank only outputs 67W = 60% of rated capacity.

Needfuldoer · April 22

Every step in that chain has at least a little efficiency loss. Charge added to the phone won't perfectly match the charge that left the battery pack, but the difference shouldn't have been that huge.

I think they just lied about the true capacity of that battery pack. That's all too common with off-brand batteries.

Bitter · April 22

Likely lied or listed the theoretical max capacity of the cells. I have a 10,000mah Samsung bank that if you read the fine print is only 6,000mah usable. You can't drain every last wh from a cell otherwise you'd damage it. So yes but actually no, deceptive but not an actual lie possibly.

tonyrulez · April 22

Here is the back side of the powerbank. No "actual capacity" rating.

Biohazard777 · April 22

@tonyrulez

What @Needfuldoer said, you probably have a power bank with lower than rated capacity...

That being said, take a look at this:

So yeah, getting 60% efficiency isn't unheared of, even for well known brands.
There is a lot of variables... higher battery internal resistance = more heat = less efficiency, these can have a lot varience between batches.
Unoptimized electronic circuits can also contribute, etc.
So maybe the manufacturer didn't lie, you just got two of their shittiest runs in terms of efficiency.