No doubt you’ve seen ads for the little “Charger Doctor” gadget from China – well, my advice is to avoid it like the plague. I have two of them, I’ve used them in the past but never on a Raspberry Pi. It turns out that given a 5.2v input, one of them reduces the output voltage to 4.8v, the other to 4.6v as measured by a 5-digit meter on the Pi edge connector.
If I take the same load, the same charger and the same short lead with no “Charger Doctor” inline – I get the original 5.2v. i.e. same start up conditions, same meter, same everything – the only difference being the presence or absence of the “Charger Doctor”.
Spec for Charger Doctor is 3.5v-7v in, 0A-3A out. The loss is not specified – and in my book is WAY too high.
In the bin – both of them.