Ok.
First you state that you are using a USB port to charge the device.
Then you say that you are using a 3½A charger to charge the device. yes i use the usb port on the device to charge the device and the poser supply is a 3.5 amp charger
There is a big difference, as USB is a slow charge. Very slow. i would think 3.5 amps is plenty of power to charge most any device
So slow, in fact, that my crummy 1GB device will slowly discharge while plugged into a USB port if I leave Wi-Fi on.
If the battery is shot, then that is your issue. battery could be bad but it does actually charge up to full power according to the device's own battery monitor.
Check the power cord, even if that cord works o other devices. i have use 3 cords now i have on i got the says itis able to handle 3.4 amps and one that is for tablets from the mfg. and another one that has been charging other tablets just fine.
If there is no way to monitor the milliamps that your charger is providing (settings, battery), then get an app that will do so.
CPU Float
CPU Info
Ampere i will try all of these to see what one may be better for my tastes
This will allow you to compare the charging rate between different cords.
I bet you will be surprised at what you find.
Make sure that the charging port is clean, on both the charger and device ends. can't speak for the device as i got it from ebay but the power supply is new and the cord is new and rated for 3.5 amps
Last but not least, it may be of some use to go through the system apps and any user apps (you did say that it was used, right?) and disable whatever you don't need.
Dim the screen, turn the automatic dimmer off, and force stop any app that you don't use that you can't disable. all i have installed after a factory reset is tinycam monitor and radar and speed test. and yes i went into the system and turned off everything that did not say android or google for systems or deleted all not necessary
Hopefully all this will save enough power and increase the charge rate to a point where it can maintain function for you.
so it charged all night and got up to 80% and this morning i turned it on to view the cameras at 5am and now at 9am it is down to 40%
so that is why i asked if anyone knows if all the battery wires were needed to run this device. my other tablets will run with no battery but this is a verizon phone that is 10" and like most phones seems to not like turning on without the battery. but i'm betting it can run without actually have the battery connect to the point of charging it. i think the battery is bad but they want 50$ for a new battery and for what i use this for that is not o happen. but it does a good job for showing the cameras so if it is fixable i will give it a go if not i will toss in out. as the seller gave me a refund. thanks