Possible charger voltage reading problem?

[poopers]

I’m using a Fusion LX61B Eclipse Pro charger (set to balance charge lipos at 1C or less) and a variety of 2 cell lipos from Turnigy & IP, and I’m finding my charger constantly seems to over read the cell voltages.

E.g. I charge to 4.2V per cell, disconnect the lipo from the charger and connect to my Etronix battery doctor, and it says around 4.15V per cell. I can then instantly reconnect the same battery back to my charger and it now reads around 4.15V per cell. Same thing when charging to store, I charge to 3.85V per cell then check with the battery doctor and it reads around 3.78v, connect back to charger and again it’s now reading .07V lower.

I was just wondering if anyone else had experienced this, and if it’s within a standard level of discrepancy?

[imull]

Yeah, that's not unheard of. You need to bear in mind that the electronics in the charger are as cheap as the manufacturers can get away with (for the most part) and we're all relying on them to perform pretty accurate measurements so there's bound to be a difference between units.

If I just get a bit technical for a second:

The most common processors in these chargers are Atmel AT Mega. The ADC (analogue to digital convertor) is 10 bit (1024 step) and they operate from 3.3 or 5V.

If we assume that it uses 5V reference then each bit is 5mV, i.e. the smallest change you could theoretically detect, so you can see that 50mV could be easy to lose.

I hope that makes sense!

Ian

[poopers]

Brilliant, thanks Ian, appreciate you going into detail

I was getting concerned my charger was on its last legs!