Choosing A Solar Wire For Your Battery Bank
Generally, the battery bank usually has the thickest wires in a solar energy system. The battery bank needs thicker wires because the power inverter sometimes pulls more current than the solar system can supply by itself.
Typically, the batteries of a solar battery bank are connected and the power inverter with 1/0 wires, which have a capacity rating of up to 150 amps.
As with the wire for the solar panel or combiner, length matters when choosing a wire for your battery bank. Ensure you match the AWG of your battery bank wires with their lengths to avoid safety issues and ensure the batteries last longer.
Can I Use Acsr Wire For Solar Panels
No. The ACSR wire has aluminum conductors, but those conductors are much thicker to make up for the lack of electrical current flow from an aluminum conductor compared to copper.
You can do calculations as you would for THHN wire to make sure your wires have enough wattage capacity for your application .
The cables also have different insulation, usually a colored sheet to identify the wires voltage and wattage.
Manually Calculating Wire Gauge For A 100 Watt Solar Panel
As an example, we will calculate the wire gauge needed for the wire that runs between a single 100-watt solar panel and a 12V battery bank.
We will be working with the Inergy Linx 100 Watt Flexible Solar Panel, available from Shop Solar Kits. This solar panel has a voltage at the maximum power of 17.6V, and a current at the maximum power of 5.68A.
To work out the target resistance, we will use ohms law which states that V = IR. This means that 17.6/5.68 = 3.09 ohms, which is the resistance that will occur for this solar panel.
We are going to assume that the cable you are purchasing is made out of copper, as that is the most common material for solar panel wiring.
Copper has a resistivity of 1.724 x 10^-8 ohm meters at room temperature, and you will have to multiply this by the meters that the wire needs to be. In this case, we will say that it has to be at least 50 meters long.
50 x 1.724 x 10^-8 = 8.62 x 10^-7 ohm square meters.
Next, we get the wires cross-sectional area by dividing our answer by our target resistance.
8.62 x 10^-7/3.09 = 2.79^-7.
To find the wires radius in meters, we will first have to divide our above answer by pi.
2.79^-7/3.142 = 8.88^-8 meters.
We then need to find the square root of this answer, which will be 0.000297. To get this radius into inches, we will multiply it by 39.37.
0.000297 x 39.37 = 0.012 inches.
For the same 100-watt solar panel, we know that it has a maximum current of 5.68 A.
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How Do You Protect Solar Panel Wires
If youre wiring together your solar panel system, then its best to use junction boxes for all of the connections that need to be made.
Youll probably want to use some conduit if you plan on running wires inside the walls/attic of your house, etc. Conduit is just tubing with openings at each end so you can feed wires through it and seal up both ends with plastic/metal caps.
It might also be advisable to use thermal insulation to wrap around the actual solar panels themselves if you live in a really hot climate.
Key Points About Solar Wire Size
- The standardized scale of solar wire sizes is called American Wire Gauge, or AWG. There are different capacities and different wire gauge sizes. The gauge number will influence the operation.
- In general, the high the gauge number, the more resistance the solar wire has, and the lower current it can deal with securely.
- Also, different using purposes require different wire sizes. For instance, the wire used to connect battery banks may require different sizes from that used to connect charger controllers.
- It can vary according to the types of your solar systems. Residential solar systems and commercials systems demand different wire sizes.
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How Should I Route Wires From My Roof
With the majority of our installations, cables go from the solar panels to a combiner box on the RV roof. Depending on your rig, these combiner boxes may be installed near existing roof penetrations, like vents, or a new roof penetration will have to be made underneath the combiner box. The placement of these combiner boxes and cable routes is always planned very carefully before any holes are made. An installer will want to keep cables as short as possible while maintaining structural integrity and preserving the vehicles aesthetics.
What Size Gauge Wire Do I Need For A 1500 Watt Inverter
The inverter with a capacity of 1500 watts would require 4 AWG cables to power the device. Keep the length of the wire short as possible.
The low range will increase the power efficiency and less loss while transmitting the power from the cable. The material uses in the AWG gauge is dense copper that provides the better transmission of electricity.
When you pass the energy from point A to Point B, there will be friction between the electrons and the material used in the making of the wires.
This friction makes the wire heat. If you connect the wrong cable, the overheating will burn the protective layer of the wire.
It is prone to catch fire and damage the entire system and things around the inverter. Ensure safety with the selection of the right type of wires for the inverter.
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Why Ground Solar Panels
Grounding solar panels is necessary because:
- It reduces built up charge, making your system less attractive to lightning.
- If a charge builds or lightning hits, the discharge will go into the earth instead of your cable. Without grounding this will not happen.
- Grounding minimizes power shock from high voltage components.
- The NEC requires grounding. Article 690 includes solar panels, whether it is high or low voltage. Not grounding your system is not only risky but also illegal.
- A grounded connection minimizes the hum produced by some solar inverters, lights and other electronic devices.
The most common mistake solar panel owners make is assuming that lightning must strike directly to cause damage. In fact, lightning can hit miles away but still generate high voltage in your solar panel cable. Solar panels with long wires are particularly susceptible to this.
When the voltage surges it can destroy your appliances and entire solar power system. This can be prevented by grounding solar panels. Grounding means electrically wiring parts of the solar system to the earth .
What Gauge Wire Should I Use
All of our SunRunnerTM System Cores come with an appropriately sized wire harness to minimize line losses and maximize value. We use 10 gauge cable from the solar panels to the combiner box. Since the panels in our systems are always connected in parallel you can assume about 6 amps per 100 watts of solar panels. For cable run lengths typical in RV applications, we recommend 10 gauge wire for 20 amp systems up to 4 gauge wire for 40 amps systems. If your system calls for more than 40 amps of charging current you will use multiple wire harnesses to multiple charge controllers. The cables going from the battery bank to the inverter have to be much thicker because they have much more current flowing through them . These cables are typically limited to 10 feet in length and a 2/0 cable is most commonly used.
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Calculate Charge Controller To Battery Wire Size
Solar cable wire sizes are based on standard AWG, so you should have no problem finding one. The following table lists the most widely used solar controllers and the corresponding wire sizes.
The figures on this table are for high quality copper cable. The wire size recommended for your charge controller may be different. Check your owners manual or contact the manufacturer.
| Charge Controller Capacity | |
|---|---|
| 100 amps | 6 AWG |
The rule for any type of solar cable is, use the thickest and shortest wire size available. The sizes given above are the optimum, though you can always go with a bigger cable. So if you have a 30A charge controller, you can use the Renogy 8 Ft 10 AWG cable for your setup.
Some more reminders:
- We emphasize bigger, thicker cable wire, not longer. The longer the wires, the more current is lost. So keep the wire between the controller and battery as short as possible. This also applies to the solar panel and battery cable.
- Always follow the cable size recommended in the controller manual. If the manufacturer says use a specific wire size, go with only that.
- Use only high quality cables. Look for those designed specifically for batteries and charge controllers. The more flexible the cable the better.
Determining Wire Gauge For Small
If you are looking to charge devices or a Voltaic battery from a solar panel positioned far away from your device, you need to think about the gauge of the wire you use to transfer the power. The issue is that the Voltage will drop based on three factors: 1) length of the wire, 2) thickness of the wire, and 3) amperage.
Why is this important?Devices have minimum charging Voltages and they often charge better above a certain minimum threshold. Lets say the output of your battery is 5.2 Volts and your Galaxy Tab stops charging at 4.76 Volts. You need to design your cable so that you have no more than a 0.44 Volt drop or your tablet wont charge.
How do I calculate the gauge I need?
1. Figure out the Voltage of your source and the minimum Voltage your load / device requires. Voltaic batteries typically output 5.2 to 5.3V for the broadest device compatibility, but you can measure yours with a multimeter to confirm.
3. Measure the maximum Amperage your device will draw from the source. You can look on the battery for Amperage, but better yet, measure the current flow using a multimeter.
4. Determine optimal and minimum current requirements for your device. This is a bit trickier. We use an adjustable Power Supply. If you dont have one of these do research online to determine the device requirements. You can also ask us.
5. Measure the amount of cable needed between your source and load / device.
6. Calculate Voltage Drop Using the Resistance Coefficients
| Wire Gauge |
|---|
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What Cable Should I Use For 12v
Unfortunately, knowing what cable you should get for your solar power requires more knowledge than just the voltage. Generally speaking, most residential solar systems are good with wires between 8 and 14 gauges, depending on the exact wattage and amperage.
To know which cable to get, you need to look at the amp. The amp tells you the minimum AWG you should get based on a 2% voltage drop.
The Importance Of Using Correctly Sized Wire In A Solar Panel Array
The wire you use in your solar panel system may seem like an unimportant, or nonurgent, afterthought.
However, figuring out the correct size of wire you need is just as important as finding the answers to questions like What size charge controller do I need for a 100-watt solar panel? and What size inverter do I need for a 100-watt solar panel?
When we refer to the size of the wire, we are referring to the length, as well as the gauge of the wire.
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Final Thoughts: Safety Considerations When Selecting Wire For Your Solar Array
The biggest consideration one should think about when selecting solar array wire is safety.
If an electric wire cannot safely handle the current fed through it a fire can happen, which is dangerous to both your camper van and yourself.
In order to get your solar array wiring right and safe, we encourage you to read our other two solar wiring posts:
What Wires Should You Use For Solar Panels
MC4 connectors are the most commonly used wires for solar panels because they dont need to be in conduit, and you can use any old house wire for them.
Other MC4 cables are available, but theyre usually more expensive than standard insulated house wires like THHN, THWN, etc.
You can also use non-insulated MC4s if you want to install the wires by themselves without having anything else surrounding them except air, like on top of your roof where there would be nothing nearby that could catch fire even if the insulation were to get knocked off.
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Windynation One Pair Solar Connectors
The WindyNation One Pair Solar Connectors is our top pick for good reasons. For one, it has an ampacity of up to 40 amps in dry and wet conditions. This means you get stable performance since the power loss over wide temperature ranges is low.
The WindyNation One Pair Solar Connectors are available in two gauge numbers: 10 AWG and 12 AWG. The 10-AWG comes in 13 different lengths, while the 12-AWG is available in 14 lengths. This means you get more options than you will get with the BougeRV Solar Extension Cable.
WindyNation One Pair Solar Connectors operate in the same temperature range as the BougeRV Solar Extension Cable . It is insulated with chemically cross-linked polyethylene. While polyethylene offers marked resistance to water and dust, it does not match the effectiveness of PVC.
The polyethylene used in crafting the WindyNation One Pair Solar Connectors offers some UV resistance. But over time, it may succumb to UV degradation.
The price difference between the WindyNation One Pair Solar Connectors and the BougeRV Solar Extension Cable is insignificant and non-uniform. So, except you are getting a very long one, you would not have to bother about their prices.
While this product might be okay for connecting a solar panel to the charge controller, it may not work for the batteries. It may also be unsuitable for use as a combiner.
Watt Solar Panel Wiring Diagram
Theres a few points worth clarifying about this wiring diagram before you get into the detail:
- The wiring diagram shows only the supply side installation of a 200 watt solar panel system. It goes as far as charging the battery. For the load side detail, check out our post on campervan wiring.
- It excludes charging the battery from shore power or the alternator.
- For information on how to fit the battery, see our post on campervan batteries.
- The diagram also excludes wiring a power inverter it sits on the load side of the battery.
- The 200 watt solar panel wiring diagram assumes 2 x 100w panels are being fitted. If you happen to be fitting 1 x 200w panel instead, see our 100 watt solar panel wiring diagram.
- Weve included 2 diagrams below. The first shows a 200w solar panel set up wired in series. In the 2nd diagram, theyre wired in parallel.
- Read our complete guide to wiring your solar panels in series or parallel if youre not sure how best to wire your array. It covers mixed panels too and includes an interactive calculator to find the most efficient setup for your panels.
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Can I Use Regular Cables For Solar Panels
Dont use standard cables. They wont handle the high currents associated with solar panel systems because theyre not rated for outdoor installation and direct sunlight exposure.
Use cables that are specifically made for outdoor installation, such as MC4 connectors or copper grounding lugs, so you can guarantee they will last a long time.
If you have access to a welder, then you might also want to consider sealing all of your connections together with some metal-to-metal adhesive because itll prevent corrosion from forming over time .
That being said, many people dont bother to seal their wires together, and sometimes it doesnt matter as much as you would expect because stainless steel wire is already corrosion-resistant.
Variables And Parameters To Focus On When Calculating Wire Gauge
Three main variables need to be considered when calculating the wire gauge required for your solar array.
These variables include the voltage of the system, the maximum amperage that will be produced by your solar panel, and the distance between the batteries and the solar panels, or between the batteries and charge controller.
Different wire gauges can only handle a certain amount of voltage and amperage, which is why it is important to look at the specifications of your solar panel as your starting point.
If you look at the Inergy Linx 100 Watt Flexible Solar Panel, available from Shop Solar Kits, you will see that the voltage at maximum power is 17.6V, and the current at maximum power is 5.68A.
This means that our gauge wire needs to be big enough to safely handle these two measurements.
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Do You Need A Fuse Between A Charge Controller And Battery
A fuse is not required and neither is a circuit breaker. But it doesnt hurt the system and for safety reasons you should install one. Although solar panels are safe, accidents can happen and it is better to have a fuse to minimize the risk.
The charge controller and fuse amps have to match. Place the fuse about 8 inches from the battery and it should work fine. Once installed, the fuse will safeguard the connection.
