Well, I started to make a video of this thinking it was going to be a great new uninterruptable supply. I’d listened to others, I’d read the spec (or so I thought) and this was to be the new saviour of battery supplies.
The TOMO unit comes in different sizes, I chose the 3-battery solution. I bought mine from AliExpress. It has a USB input and 2 USB outputs and can power up to 2.1 amps in TOTAL (2.1 amps out of one output OR 1 amp out of the other – must use the same chip as everyone else).
It is nice looking and comes MINUS the batteries and hence is cheap. You can use one battery or more – either way it still acts as a power supply.
You can connect power and disconnect to your heart’s content, it will not interrupt the output. You can let the battery die (no input power) and then plug in power and it will recover gracefully, turning on the output.
Except for one tiny but vital detail… and I quote from the spec which I don’t think was in the advert but I might be wrong…. “when input and output at the same time, it will automatically charge the device first, then charge the battery”. I guess that’s what I get for not reading the instructions VERY carefully…
Do you see the problem? I must say it took me a little while to grasp this…. I noted when I put a meter inline with the incoming charge voltage to the unit – the current used was the same as the current used by the Raspberry Pi I had on test.
In short – when it is powering a computer like a Pi, it thinks it is CHARGING it – and hence continues to do this ad-infinitum and does NOT charge it’s own battery because the “Pi” never becomes “fully charged”.
Oh dear, another one bites the dust. I can’t even chuck it back at them as the function is fairly clear in the paperwork.
Even as a phone charger – why on earth they don’t show the state of the batteries when discharging into a load…. is beyond me.
But it gets worse. After fully charging the unit (according to the indicators) with 3 batteries, mid-afternoon yesterday, then last night I plugged my flat phone into the unit. This morning when I arose, the unit showed the batteries were less than half full (one being down to 25%) and yet the phone was only about 20% charged. Something seriously wrong there – I will try again.