*@Mr.Retroplayer*:

You kind of confused me there. If i understood correctly, you are basically saying that by knowing the voltage you provide to the battery through the series resistor and the voltage drop across the resistor in series with the battery you can calculate the EMF of the battery ?? (ie EMF of the battery = voltage supplied to the resistor and battery - Voltage across the series resistor)

>Wouldn't this equation give me the voltage that is used to charge the battery?

>Would it give me the actual EMF of the battery in order for me to log the data down and be abple to determine the -deltaV?

> Wouldn't i have to stop the charging process, measure the open circuit voltage of the battery and the continue with the charging process in order to measure the EMF of the battery?

>By the way, i know that for lipos, its mostly the cell voltage that changes (drops) while the battery is drained (increase in internal resistance has a smaller effect). Does this not apply for NiCads and NiMhs? Does internal resistance vary greatly while the EMF of the battery remains more or less constant?

No. Well, yes.... lol.

I am talking about understanding the relationship between voltage, current, and resistance in a circuit series and parallel circuit properties, and Thevenin's thereom. But you don't need to have an engineering understanding of all that. Just know that your charger is providing a voltage. And in a series circuit, all components will drop a portion of that voltage and that will always add up to the total voltage.

So let's say you have 2 resistors and a 9V battery. Measuring the voltage across one resistor reads 3V. Wtihout even measuring the voltage across the other resistor, we already know it is 6V because all the drops must equal the total voltage.

So we put a small resistor in series with the battery and measure the voltage drop across the resistor. We subtract that from the charger voltage and we know the voltage across the battery. We incidently also know the current through the circuit doing this. Ohm's law.

I think you are overcomplicating it and getting hung up on dVt.

To summarize, you are measuring the volage across the added, known-value, resistor. You subtract that voltage from the known charging voltage.

A great resource is The Battery Handbook