So, I recently threw out a bag of random chargers I didn't think I was using anymore. Later I found that my Dremel charger was part of these. I did however save all the connectors and just threw out the adapters, incase this would happen.
From what I can identify on images of the 7750, it is using a 5v 1650mA adapter, where the outer shell of the barrel is negative and the core is postive. Well I thought this would actually be quite nice, as I could wire it to a USB-A and just use one of my many AC-DC adapters, powerbanks, USBhubs... to charge it. (I have tried it using an old 5.2v 2.4a ipad charger, and 5v 2a oneplus charger)
So I did this and the light on the Dremel does light up red as an indication of it charging, but it never reaches max capacity (usually indicated by a green light if my memory is correct, and just turns off after a while). Once the light disappears I can turn off the power and turn it on again and the red light appears and seemingly keeps charging. After 10 minutes the Dremel is able to turn on and I can use it for a minute or so before it dying out. Leaving it for a longer period does not change the time.
I have attempted to use a cheap USB current reader, but it does not show any information, as if the current drawn is too low or something. I'm a novice in the field and would appreciate any explanation to why this is happening (: