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How to Solder- the basics

Richard Perez

oldering insures permanent, low loss, electrical connections. A soldered electrical connection is not Sdifficult to make, it only requires a little practice and the right tools. If you're making your own power, then your system's wiring and its maintenance are critical. Without good electrical connections, even the finest system will perform poorly or not at all. Here's what you need to know to make effective

soldered connections for your system.

Interconnection- the electric pipeline

In order to use the electricity we make, we need wiring. Wiring transfers power from its source (PVs, Hydro, Wind or what have you), to the batteries for storage, and from the batteries to

the appliances which consume the power. The chain of wires and connections that eventually leads to say turning on a light, must remain intact if the light is to operate. It only takes one weak or bad link in this chain to render the entire circuit inoperative.

Electrical wiring is made of

copper and aluminum

because both metals have

low resistance to electron flow

(electric current). The major

problem with mechanical

connections is the formation of

oxides on the copper or aluminum.

These oxides are poor conductors of

electricity and increases the resistance of

the mechanical connection. The pure copper

or aluminum on the surface of the wire gradually changes to copper oxide or aluminum oxide by chemical reaction with the oxygen in the air and in the water.

I shudder to think of what acid rain does...

Why Solder?

Mechanical connections are made by twisting the bare wires together or by compressing a wire into a connector or terminal. Wire nuts make mechanical connections that, while better than twisted wire connections, still don't prevent oxidation within the electrical connection. As the wires that make up the mechanical connection oxidize, the electrical resistance of the connection increases. This results in a voltage loss across the connection. This voltage loss is directly proportional to the amount of current flowing. The loss of voltage (and thereby power) across the connection manifests itself as heat- the oxidized mechanical connection gets hot. On the other hand, a well made soldered connection will have about half the resistance of a new mechanical connection and will not oxidize with time. Years down the road, the soldered connection will have many times less resistance than the oxidized mechanical connection.

In 120 Volt wiring, the voltage loss due to oxidized mechanical connections is negligible because the input voltage is so high- 120 vac and thereby the current flow is low. Here, mechanical connections are standard and perfectly acceptable. In 12 Volt systems, however, the voltage loss is appreciable. For example, consider a 120 Watt load being powered via a mechanical connection with a resistance of 0.2 Ω ( a fairly typical funky connection's resistance). At 120 vac, the 120 Watt load will consume 1.0 Amperes of current (I=P/E, I=120 Watts / 120 Volts, I=1.0 Amperes). At 12 VDC, the 120 Watt load will consume 10 Amperes of current (I=P/E, I=120 Watts / 12 Volts, I=10.0 Amperes). In order to transfer 120 Watts of power, we must move ten times the current in a 12 Volt circuit as in a 120 Volt circuit. Increased current produces increased voltage loss across a bad connection. The voltage losses and power losses for this scenario are in the spreadsheet below (calculated at a variety of voltages and using

Basic Electric

Power Resistance

12 Volts 24 Volts 36 Volts 48 Volts

120 Volts 240 Volts

120 Watts

0.2 Ohms (Ω)

Current Voltage Amps. Loss

Voltage Loss %

Voltage Power Loss Thru Watts

Power Loss %

Ohm's Law).

10.0

2.0

16.7%

10.0

20.0

16.7%

5.0

1.0

4.2%

23.0

5.0

4.2%

3.3

0.7

1.9%

35.3

2.2

1.9%

2.5

0.5

1.0%

47.5

1.3

1.0%

1.0

0.2

0.2%

119.8

0.2

0.2%

0.5

0.1

0.0%

239.9

0.1

0.0%

Note that the voltage loss for the 120 Watt load is only 0.2 Volts at 120 Volts input. However the voltage loss for the same 120 Watt

Home Power #18 • August/September 1990

35

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