In principle is it possible to recharge AA/AAA/9v batteries in the device they are currently plugged in?
There are numerous smart chargers for AA/AAA and 9V batteries. The process requires taking all batteries out charging then putting back in. When you are potentially dealing with multiple such devices the experience can only be bettered by carefully modding any device to recharge batteries and skip on the in out routine.
Specifics to test this in my case is a 3V - 2xAA device(vacuum dust collector) and an "Intelligent" battery charger with 12V input and 4x AA/AAA charging slots.
So I am happy with modifications of any sort with the ultimate outcome of : 1)Allowing in device recharge 2)Allowing greater distance between where the device is resting and where the charger unit is. Think of USB charger + cable as a guide 3) Make the principle generic so it can be used on any device and any charger
Extras : If possible use a high capacity battery bank(26800mAh for examples sake) to power as many battery slots on the AA/AAA charger. Battery bank used in this example is a 3x USB with output DC 5V/5.5A(max) total and 2.4A individual USB total.
Please check photos for more clarity
The challenges I am aware of : 1) In the device AA/AAA batteries are connected in series with a simple metal piece spanning over both battery terminals. The 4x AA/AAA charger connects to each batteries +/- poles individually. So this might be a problem as the charger needs to adjust output to each individual battery's condition ...
How do you temporarily ( mechanically or electronically ) gain individual access to each battery given they are all connected in parallel inside the device? Modding/Reworking the insides of the device is fine... should be generic solution as most devices use the same Spring to metal plate hardware to raise input voltage from multiple AA/AAA batteries.
2) USB Cable length effect on the AA/AAA charger output. The charger expects batteries to be in the slot and not 1-2m away. Even if the charger might be capable of delivering whatever voltage is needed to offset the length etc. Being an "intelligent" charger means it may interpret the new circumstances wrong ...