Hello ,

As suggested Andy in one of my previous posts I am trying to use a 4xAA 6V battery pack to power a microcontroller device and a peripheral scanning device (5V) and regulate it using a 7805 regulator IC .
The problem I am facing is that the 7805 is giving only a 3.6 V output. The batteries are brand new and show open ckt voltage of circa. 6.2 V.
Is this a right way of regulating the voltage , 7805 data sheets do not specify any minimal voltage input .
When I powered the micro and the peripheral directly without the regulator they work just fine . Is this safe to do it as 89c51RD2xx typically specify + 5.5 V max. I have seen that a new cell is 1.5V but it falls rapidly to 1.2~1.3 V and stabilises there.

An alternative I tried was to use a 9v alkaline battery . This solution works fine until I connect the peripheral and then the voltage crashes. The power consumption by putting an ammeter in series works out to ~100 mA idle mode and 270 mA while scanning. So it looks like this would not work out , even though 7805 is set for 1.5 Amp current.
Any good sites on batteries ?
Any forum member care to share some ideas ? Would be obliged .

Kind regards
Thomas