I bought from China, quite neat looking powerbank on up to four 18650 cells. It has all the needed features (almost) and even more – what could go wrong?

It has:

• Output Overcurrent Protection
• Input Overvoltage Protection
• Electro-Static Discharge Protection
• Overheat Safety Protection
• Output Overvoltage Protection
• Battery Overcurrent Protection
• Input Overcurrent Protection
• Prevent Current Reverse

Nice! It can charge and discharge each cell individually, has two USB output ports with 1A and 2A output current.

You can read many other nice things about this powerbank on Internet. But the big problem is, it’s a crap! Why?

Well, despite this all nice features it simply drains cells during poweroff mode (energy leakage during standby mode). Yes, you will leave it for a week and bam! No energy in your powerbank. I was quite surprise when after a weekend, completely charged 4 cells, shows only 3 bars each. I thought I’ve missed something, that maybe cells are damaged etc. I did test with different cells and it became obvious that there is something wrong with device itself.

So I took my bench power supply and measured how much current M4 draw from cells, just to make it work.

Like you can see, when “simulating” one cell 3,8V, lightened up Tomo M4 will drawn 90mA of current. It’s ok.

This is the same situation, but the back light for LCD is turned off – If you will take a closer look, you can see bars for “battery” on display. M4 draw 70mA – still noting suspicious.

And now “grande finale”, M4 powered off…

Yes, you can see correctly – still drawing 70mA. I’ve waited for a while – perhaps some internal processes are still going on – it supposed to be “intelligent”, but not. M4 all the time is eating 70mA – this is the reason why, my cells where discharging by “just” staying in this powerbank.

This seems to be much over reasonable threshold. Competition like Soshine E3S claims it will discharge 2,4mAh per day. So I guess, I should read it as 2,4mAh/24h = 0,1mA – well it’s 700 times less then Tomo.

So I’ve tried contact Tomopowerbank company. On contact form page, they have nice looking description “We will reply within one business day.”. Well… NOT. Not a single reply (I’ve even check my mail server if it did not deny any mail from them) and I only wanted to know if it’s a problem of entire M4 line or just that I own is faulty.

I’ve even tried to leave a comment on the product page (so perhaps somebody will contact me) – guess what – they did not publish it. So if you would like to buy this device, be warned – it may by unusable (and probably is).