General wiring misunderstanding on Nash22H

DrewE wrote:

pickjare wrote:
For my voltage drop concern: The converter went into normal mode this morning only pushing about 2 amps and 13.7 volts. The voltage and amperage was exactly the same at battery terminals as at converter connection. Strange how when charging at 21 Amps my amp measurement was exactly the same at the battery terminal as at converter connection, yet voltage was .7V lower. There has to be some electrical law that says no, if voltage is lost in a circuit somewhere, so will current, therefore current flow should have been lower. Ill have to try this again. I am going to assume for now that the .7 volt drop I saw when charging at 21 Amps is because its a long cable, perhaps it should have been made with larger gage.

But, I will continue checking connections and have plans to eliminate crimp on butt connectors. The connections I made use solder on type copper lugs. I did check voltage drop across the switch and through my 6 V battery connector cable, and the cable had 7 MV and the switch had 26MV--wouldn't both be considered acceptable? Connector cable being the 2 foot cable I made to connect 6V batteries in series. I have not done voltage drop across the entire positive and negative circuits from batteries to converter, just checked those 2 things since it is so easy.

There are a few basic electrical laws that come into play here. The first is Ohm's law, which defines the relationship between voltage and current in purely resistive circuit elements (such as wires). It states that E = I x R, where E is the voltage ("electromotive force"), I is the current, and R is the resistance. Since the resistance here is constant, the voltage drop when 2A is flowing is one-tenth that when 20A is flowing.

The second basic electrical law is Kirchhoff's current law. This states that at any junction in a circuit, the signed sum of all the currents is zero--or, put another way, the current flowing into any junction is equal to the current flowing out. Current doesn't pile up. If your circuit is a simple loop, this implies that the current is the same throughout the circuit, no matter where it's measured, as the current doesn't have any differing routes to flow through.

The third basic electrical law is Kirchhoff's voltage law. This states that, for any closed loop in a circuit, the signed sum of all the voltages around the loop is zero. If the converter is supplying 14.4 volts, then the voltage at the battery plus the voltage drop on the positive leg plus the voltage drop on the negative leg is also 14.4 volts.

Armed with these three laws, you can (at least in theory) analyze any DC circuit built up out of voltage or current sources and resistances and determine the voltage at any point and the current through any device or wire. As I recall, these laws plus opamps formed pretty much the whole of Circuits I in college.

Thanks DrewE. I understand that current will be the same no matter where it is measured in a circuit (before or after load, positive or negative side). So when 21A are flowing, I can measure that anywhere in circuit and see meter say 21 A.

What I found real puzzling is that while converter was charging at 14.4 V and pushing 21 A, but up at batteries I measured LESS voltage, 13.7v. Now, Im trying to wrap my head around this. I don't understand how according to ohms law for my circuit to still measure 21 A at batteries, but have lower volts 13.7v, only way that is possible is if resistance was lower 10 feet from converter at batteries. For ohms law math to work, (21*.685=14.4 at converter vs. 21*.653=13.7 at battery), resistance must be lower near batteries since voltage is less to still have 21 A. But that is not the case since the longer the wire the higher the resistance. And finally, if resistance was lower I would expect to see less drop so higher voltage would be measured near battery.

These laws you mention are 100% true fact , and you've got them right. And they work every time. I'm not arguing or doubting. But I'm sure confused. It's alright though, truth is I don't need my batteries to charge extra fast, more like just charge properly so they last long. Chargemaster changed to storage mode, now there is only 90MA flowing at 13.2v. So in 3 days they must be charged.

I do find this interesting, thanks for the help.