Solar How-to Tips: Mounting and Wiring PV Modules

This article explains how to make your own PV mounting rack, how to install it, and how to wire up the whole works. This is in response to many requests for this info.

Face It SOUTH
The critical consideration in mounting PV modules is the yearly path of the Sun. The PV modules must receive maximum sunlight. Consider shading from trees and buildings. The decision of where to mount should be made only after careful consideration of all your options. The PV modules, in most nontracking situations, should face South. The closer the plane of the rack is to facing true South, the better overall performance the PVs will deliver. Only consider mounting surfaces that are within 15° of facing true South (within 10° is much better). Any surface further off will require more complex, asymmetrical mounting racks. If you don't have a roof or wall that is suitable consider ground mounting. Since PVs produce low voltage DC current, keep the wire lengths to the battery as short as practical.

Where you are going to put your PVs determines the type of rack you need. Roof mounting (on either pitched or flat roofs), wall mounting, and ground mounting are all possibilities. So consider the variables and pick the best for your situation. These racks can be used in all three types of mountings.

So Which Way is South?
Determine South with a good compass and someone who knows how to use it. Be sure to allow for the difference between magnetic North and true North. This difference is called magnetic declination. In California for example magnetic North is some 19° East of true North. If you don't know your magnetic declination, then go to the library and look it up.

Mounting Racks-- your PVs hold on the World
The obvious purpose of the rack is to attach the panels to a fixed surface. At first glance this seems simple enough, but consider wind, snow, falling ice and temperature variations, not to mention possible leaks in the roof!

We are going to talk about a simple to build rack that can hold up to four panels. This rack uses inexpensive hardware store parts. It mounts on roofs, walls, or on the ground with the appropriate foundation. In all mounts, the rack is adjustable for panel elevation, and allows seasonal optimization of the racks tilt. This rack approach was developed by Electron Connection Ltd. for its customers. Its design and application are so simple that I'm sure many others are using just about the same technique.

The Rack Materials
The rack is constructed out of slotted, galvanized, steel angle stock. This stock is available at most hardware stores. Our local store sells National Slotted Steel Angle (stock #180-109) for about $7.00 each retail. This stuff is 6 feet long, with two perpendicular sides each 1.5 inches wide. The stock is about 1/8 inch thick, with a heavy galvanized coating. Its entire length is covered with holes and slots that will accept 5/16 inch bolts. We have had no problems with corrosion or electrolysis with this galvanized stock after three years in the weather. We haven't yet tried this material on a seacoast, and would welcome feedback from anyone who has. To the left is a drawing of a typical length of this steel angle.

You can shop around locally, and may encounter different sizes and lengths. Six foot lengths are long enough to mount 4 of just about any type of module. We use this angle on Kyocera, Sharp and Canadian Solar modules without having to drill any holes in either the angle or the PV modules. Working with this stock is like playing with a giant erector set.

The only tools you really need are:

1. Wrenches
2. Hacksaw to cut the angle
3. Drill for making holes in the surface holding the rack

The amount of steel angle stock you need depends on:

1. Size of modules
2. Number of modules
3. Mounting location
4. Environment of mounting location

Let's consider the rack shown in the photo on the next page as an example. This rack holds four 85 Watt Kyocera PV modules and is bolted to the almost horizontal metal roof of a mobile home. Each PV module is 25.7 inches wide and 39.1 inches long. The mounting holes on the bottoms of the PV modules match the hole cadence in the slotted angle. This particular rack used 9 of the 6 foot lengths of the steel angle. Four lengths comprise the framework for the modules. Three lengths make up the legs and bracing, while two more lengths are used as skids on the roof. Strictly speaking, the skids are not essential, but do add rigidity and relieve stress on the mounting points on the sheet metal roof. We don't want any leaks.

A rack could be built with the about half the materials. The top and bottom pieces of the rack holding the panels, the brace on the legs, and the skids could all be deleted. If this were done
then the rack would be roughly equivalent to most commercial models. In our opinion, PV modules should be mounted as securely as possible. Many commercial racks use the PV
modules' frames as a structural members in the whole module/rack assembly. This rack does not do this. Many commercial racks use 1/8 inch aluminum angle. This rack uses steel of the same thickness; it is much stronger.

This rack lives in snow country, with lots of high winds. Consider that the rack holds some $2,000. 00 worth of PV modules. We figured that the additional $35. the extra bracing costs to be worth it in terms of security. It's comforting to be inside during a howling snow storm and know that when its all over the PVs will still be there. Don't skimp on materials for your rack. Use extra bracing to make it as strong as possible. Remember that it holds over a thousand dollars worth of PV modules. The 9 pieces of slotted angle cost us about $65., and are well worth it.

Laying Out the Rack
You could design the entire rack on paper after first making all measurements of the critical dimensions on the modules. This takes time, and is subject to measurement inaccuracies. We have a simpler idea, with no measuring required. Let's treat the entire project like an erector set. We assemble the entire rack on the ground first, even if it must be disassembled to be finally installed. This assures no surprises upon final installation.

Lay a thick blanket or sleeping bag on a flat, smooth surface. Place all the modules, face down on the blanket and lay on the side angle pieces that connect the panels. See the diagram. Note that no measurement is required. Simply align the mounting holes in the module frames with the holes on the angle. We usually leave any extra angle on these pieces, rather than trimming it off. It comes in handy. On this particular rack the 4 Kyocera modules mounted perfectly, with no trimming of the 6 foot side rails necessary. The distance between the mounting holes on the modules determines the width of the rack.

Cut two pieces of angle to form the top and bottom rack rails. These should be trimmed exactly to fit inside the framework created by the side rails. The net result is all four panels are encased by a perimeter of steel angle. Use 1/4 inch bolts about 1 inch long, washers, lockwashers, and nuts to secure the modules to the framework. The bolts on the corners of the framework go through the module, the side rail, and the top (or bottom) rail. The result is very strong.

If you don't have four panels to put on the rack right now, you can use several pieces of angle stock in place of the missing panels. We strongly recommend building the four panel version. If you don't, then system expansion is going to be harder. Also building a smaller rack costs about as much when the waste on the 6 foot lengths of angle is considered. So build for the future, and see how easy it is to add a panel or two once their rack is already in place.

The Skids
We usually leave the skids uncut six foot lengths. The skids form the base for roof, wall or ground mounting. If the rack is to be wall mounted the situation is much the same except the skids are vertical instead of horizontal. In all cases, one end of the skid is connected directly to the module frame rails by bolts. This forms a rotating hinged point for rack elevation adjustment. This hinge line points East and West (so the rack faces South) in horizontal applications, and up in vertical the Fall increase the PV output by about 5 to 8%. This is really not a very great increase in performance, but the success or failure of an AE system depends on attention to detail. We personally consider that a 5% increase in our PVs performance is well worth the twice yearly expenditure of 15 minutes of our time to adjust the rack.

On roofs that are not horizontal (and most aren't), the legs get shorter as the roof gets steeper. A good overall, nonadjustable, mounting angle is your latitude. If you live at 40° latitude, then mount the rack so that the angle between the rack's face and horizontal is 40°.

The table shows the proper leg lengths for South facing roofs and a variety of latitudes. This table assumes the use of 6 foot rack rails and skids. The top of the table contains roof angles from 0 degrees (flat) to 60 degrees from the horizontal. The left side to the table shows latitude in 5 degree increments. The actual leg lengths in feet are in the body of the table.


Consider someone living at 38° latitude with a 25° slant on his roof. The table shows a leg length of 1.36 feet. Note that this table shows leg length decreasing as the roof's angle approaches the latitude. Once the roof's angle becomes greater than the latitude, the legs are attached to the bottom of the rack rather than the top. Instead of raising the top of the rack to face the Sun, we raise it's bottom.

If you're into math, the formula used to generate this table is based on the Cosine Law. Here is a solved and generalized equation that will give leg lengths for all situations regardless of rack or skid dimensions, latitude or roof angle.

L= length of the Leg in feet
R= length of the Rack in feet
S= length of the Skid in feet
P= the angle of the roof's plane to the horizontal in degrees
A= your latitude in degrees

The geometry is much the same for wall mounting, but the skids are vertical. In any case, don't be afraid to mount the skids however you must, adjust the rack's elevation, and cut the legs to fit. This approach while, low tech, gets the job done applications.

The Legs
The actual length of the legs varies depending on:

1. 1. Where the rack is mounted
   2. Your latitude
2. 3. Whether or not you want adjustability
   4. The slant or pitch of a roof
   
3. Let's consider the simplest case, that of mounting on a flat roof or on the ground. In this case, the skids are horizontal and level with the ground. Figure 4 illustrates the geometry of this situation for adjustable racks for latitudes around 40°.
   
4. In the adjustable rack at 42° latitude, the legs are 3 feet, 425 inches long. Altitude adjustment is accomplished by unbolting the legs and repositioning them along the rack rails and mounting skids as shown in Figure 4. On a horizontal surface these 3+ foot legs allow adjustment of the angle between the rack and horizontal from 32° for Summer use, to 57° for Winter use. Twice yearly adjustments during the Spring and again in every time.
   

Mounting the Rack on a Roof
A roof is a difficult place to do a good job. The steeper the roof, the more difficult the installation. On steep roofs we prefer to assemble the whole rack, complete with PV modules (already wired together), legs and skids on the ground. Then transfer the whole assembly (about 50 pounds) to the roof for final mounting. We have successfully used the skid mounting technique on metal, composition shingle, composition roll, and shake roofs from 15° to 45° of pitch.

Don't mount the PV modules themselves directly on the roof's surface. PV modules require air circulation behind them to keep them cool. If you are blessed with a pitch that equals your latitude and a South facing roof, please resist the temptation to mount the modules directly on the roof. The high Summer temperatures underneath the modules will greatly reduce their performance and can cause the actual PV cells to fail. So leave at least 2 to 3 inches behind the modules for air circulation.

Use at least 4 bolts (5/16 inch diameter) to secure the skids to the roof. Use large fender washers inside the roof, and lockwashers on the outside. Liberally butter the entire bolt, washer and hole in the roof with copious quantities of clear silicone sealer. When everything is tightened down and the silicone sealer has set, we have yet to have any problems with leakage.

Ground Mounting
If you are ground mounting, take care to pour or bury a massive cement foundation for securing the skids. Ground mounting exposes the PV modules to all sorts abuse. They may be hit by everything from baseballs to motor vehicles. So pick your spot wisely, and provide lots of mass to hold the rack to the ground. Cement blocks, or poured cement strips are best.

Wiring the PV Modules Together
PV modules are usually set up for 12 volt operation. The module contains between 32 to 44 PV cells; each cell is wired to the next in series. Thus the voltage of all the cells is added to produce a nominal 14 to 20 volt output for recharging batteries in 12 VDC systems. Each PV module is a self-contained polarized power source. Each module has a Positive terminal and a Negative terminal, just like a battery.

The PV modules can be wired in parallel which adds their current, or in series which adds their voltage. Systems using 12 VDC will wire the modules in parallel, which systems using 24 VDC or higher will wire the modules in series. Figure 5 illustrates the basic idea of either series or parallel wiring of PV panels.

Use good quality heavy gauge copper wire (THHW or THHN insulation) to make series or parallel connections between the individual PV modules. Solder all possible connections. Most modules use mechanical ring type connectors to connect the wiring to the actual panel. If you use these connectors, solder the wire to them, don't just crimp the wires into the connector. Use shrink tubing instead of tape on all wire to wire connections. Be sure to use polarization indicators on all wires. We use red tape at the ends of all positive wiring.

Wiring the PV arrays to the battery is straight forward, using only two lines. These two wires carry the entire current of the array. Total wire length (consider both wires) and array current determine the wire gauge size necessary.

It is a very good idea to electrically ground the framework of your panels and rack. Make a good solid electrical connection with the rack with a bolt assembly through one of the rack's slots. Use at least 8 gauge wire connected to an 8 foot long, copper flashed, ground rod. Drive the ground rod at least six feet into the ground. Adequate grounding eliminates static build up on the panels during thunder storms and may reduce the possibility of actual lightening strikes on the panels. Figure 6 is a wiring schematic of the 12 VDC sample PV system shown in the photograph in Figure 2.

This wiring diagram does not contain any regulator for the PV system. Although many systems do not require a regulator for the PVs, we always recommend the use of a charge controller. A good rule of thumb is: IF your PVs don't charge the batteries at more than a C/20 rate, AND if the system is ALWAYS being used, then you do not need regulation. When in doubt, add a regulator. In other cases, wire the regulator into the system following the manufacturer's instructions.

This article gives you the basic information so you can figure out what to do for your own particular system. If after reading this, you don't feel comfortable the concepts involved, please seek the aid of someone to help. Proper positioning, mounting and wiring of your PVs is essential if they are deliver their maximum power.

Sizing an RV Solar System

Gone are the days of having to find a camp site with a power outlet to connect into. The world is there to be explored and solar can silently power all of your adventures. Often is all you need are a couple of solar modules, a couple of batteries, a charge controller and inverter to cover your energy needs when you’re away from the utility grid. How perfect to be harnessing the natural power of the sun while you enjoy the best sights nature has to offer!

When sizing a solar system for your RV, the general rule of thumb is: for every 2-6 Volt golf cart batteries you use for your house batteries, you need approximately 100 watts solar power to maintain those batteries. If you have 4-6 Volt golf batteries, your system should have 2-100 watt solar modules. One 80-120 Watt solar module allows you to operate your lights, TV, radio and other basic appliances for a few hours each night without having to turn on your noisy and expensive generator. The following day, the solar module will recharge the batteries the next day.

While this general rule of thumb works for most RV owners, there are however, exceptions to this rule. Some of these exceptions include:

• Battery Voltage, 6 Volt vs. 12 Volt Batteries. Let's face it, trailers and RVs are extremely limited in space. Sometimes, there is only room for a single 12 Volt battery. In this case, a 50-80 Watt solar module will keep that house battery nicely topped off.
• Extended Dry Camping. If you typically dry camp for an extended period of time, 3-4+ days, you live in your RV or you simply prefer not to rely on your generator or shore power, you may find a solar system consisting of 200-400 watts will better accomodate your power needs.
• Short, Quick Dry Camping Adventures or Reliable Access to Shore Power. If you dry camp periodically, 2 days once every two to four weeks, a 100-watt module will keep your house battery(ies) maintained.
• RV Storage and Battery Storage Maintenance. There is nothing worse than getting ready for a new season of fun and adventure in your RV, you turn the ingnition and find out that your batteries are dead. A simple and effective way to maintain your starter battery during the off-season is to add a 10 to 80 watt solar module directly to your starter battery. For most RVs, a 10-20 watt "trickle-charge" module is the perfect size to maintain your battery, however, today's RVs more often than not, have more phantom loads than ever before. If your RV has a lot of these phantom loads, a larger solar module may be required to keep that battery maintained. Phantam loads come from electrical devices that continue to draw power even when they are in the "off" position. Things like GPS systems, TVs, DVD players and other items should be unplugged when not in use. Even being as thorough as you can, there may be additional items that are drawing power that you may miss, requiring a larger module.

One thing to keep in mind when sizing your solar system, is that the solar modules charge your batteries. The amount of power you have depends on how many and the type of batteries you have. The more solar modules you have, the quicker the modules will recharge your batteries the next day. The fewer the modules you have, the longer it will take to recharge your batteries.

Additional items that you want to include in your solar system:

Charge Controller. Don't forget the charge controller... Charge controllers are an inexpensive way to help protect your batteries from overcharging. And because overcharging your batteries can kill them, charge controllers are an essential part for your RV's solar system.

Power Inverter. And finally, the inverter allows you to operate your standard 110 Volt appliances including lamps, radio, TV and even a microwave. Not all RVs need an inverter. If you are hooked up to shore power or if all of your appliance are 12 Volt DC, an inverter isn't needed, but most people find that an inverter is a convenient component to add to your system. If you use a microwave, a 1500 watt inverter is the smallest inverter you want to use.

Generator. Its always a good idea to have a generator when you own a solar system. You may never use it or you may not use it very often, but its an item that compliments any system and can help during an emergency or during those times of extended cloud coverage. Depending on the inverter you have selected, an Automatic Generator Start Module (GSM) can be added. For many RVers, the GSM is a great convenience. When the batteries are low, the generator automatically turns on, charing the batteries and then automatically shuts off when the batteries are charged.

Additional information about proper charge controller, inverter and generator sizing for your RV can be found in future blog entries. If you need immediate assistance, contact us toll free at 1-800-842-5678 or 1-307-635-9205 or email us at solarelectric@gosunsolar.com.

Solar Discovery: How to Take Advantage of the Federal Stimulus Funding

Solar Discovery: How to Take Advantage of the Federal Stimulus Funding

Battery Charger Selection

Most deep cycle applications have some sort of charging system already installed for battery charging (e.g. solar panels, inverter, golf car charger, alternator, etc.). However, there are still systems with deep cycle batteries where an individual charger must be selected. The following will help in making a proper selection.

There are many types of chargers available today. They are usually rated by their start rate, the rate in amperes that the charger will supply at the beginning of the charge cycle. When selecting a charger, the charge rate should be between 10% and 13% of the battery's 20-hour AH capacity. For example, a battery with a 20-hour capacity rating of 225 AH will use a charger rated between approximately 23 and 30 amps (for multiple battery charging use the AH rating of the entire bank). Chargers with lower ratings can be used but the charging time will be increased.

Trojan recommends using a 3-stage charger. Also called "automatic", "smart" or "IEI" chargers, these chargers prolong battery life with their well programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float.

Watering Flooded Batteries

Flooded batteries need water. More importantly, watering must be done at the right time and in the right amount or else the battery's performance and longevity suffers.

Water should always be added after fully charging the battery. Prior to charging, there should be enough water to cover the plates. If the battery has been discharged (partially or fully), the water level should also be above the plates. Keeping the water at the correct level after a full charge will prevent having to worry about the water level at a different state of charge.
Depending on the local climate, charging methods, application, etc. Trojan recommends that batteries be checked once a month until you get a feel for how thirsty your batteries are.
Important things to remember:

1. Do not let the plates get exposed to air. This will damage (corrode) the plates.


2. Do not fill the water level in the filling well to the cap. This most likely will cause the battery to overflow acid, consequently losing capacity and causing a corrosive mess.


3. Do not use water with a high mineral content. Use distilled or deionized water only.

CAUTION: The electrolyte is a solution of acid and water so skin contact should be avoided.

Step by step watering procedure:

1. Open the vent caps and look inside the fill wells.


2. Check electrolyte level; the minimum level is at the top of the plates.


3. If necessary add just enough water to cover the plates at this time.


4. Put batteries on a complete charge before adding any additional water (refer to the Charging section).


5. Once charging is completed, open the vent caps and look inside the fill wells.


6. Add water until the electrolyte level is 1/8" below the bottom of the fill well.


7. A piece of rubber can be used safely as a dipstick to help determine this level.


8. Clean, replace, and tighten all vent caps.

WARNING: Never add acid to a battery.

Battery Discharging

Discharging batteries is entirely a function of your particular application. However, below is list of helpful items:

1. Shallow discharges will result in a longer battery life.
2. 50% (or less) discharges are recommended.
3. 80% discharge is the maximum safe discharge.
4. Do not fully discharge flooded batteries (80% or more). This will damage (or kill) the battery.
5. Many experts recommend operating batteries only between the 50% to 85% of full charge range. A periodic equalization charge is a must when using this practice.
6. Do not leave batteries deeply discharged for any length of time.
7. lead acid batteries do not develop a memory and need not be fully discharged before recharging.
8. Batteries should be charged after each period of use.
9. Batteries that charge up but cannot support a load are most likely bad and should be tested. Refer to the Testing section for proper procedure.
   

% Discharged
100
80
60
40
20
0
0
20
40
60
80
100
% Charged

What Happened to UniSolar's US64 Modules?

Over the past 15+ years, we have sold and installed thousands of UniSolar's US64 modules. They are probably one of the best modules available on the market. They are:

• Unbreakable
• Shadow Tolerant
• Tolerant of Extreme High/Low Temperatures
• Triple Junction Technology (in simple language, the 64 watt module is comparable in daily output to an 80 watt glass module)

The biggest drawback is their size. And depending on the available area for the installation and overall power requirements, polycrystalline and monocrystalline modules are more often used.

For most of our customers, I don't need to sell them on the benefits of UniSolar. Once you have used them, you know exactly what I'm talking about. But it does lead to the question,

What happened to the US64s? Where are they?

UniSolar stopped manufacturing their framed modules about two years ago and their flexible modules in 2005. Why? The solar market has shifted away from small, low voltage applications with an emphasis, first on residential installations and currently, on large scale commercial installations. The module hasn't disappeared... it has simply taken on a new form... a flexible unframed module.

UniSolar's BIPV modules are available in a 68 watt 9 ft version and a 136 watt 18ft version. Architecturally, they are great. They blend into the roofline, allow complete design freedom with ridge to eave coverage possible. They have a "sticky back" that just peels off, making installation easy and cost effective.

They come in rolls that you roll onto your roof or other mounting structure and feature all the benefits of the US64 and a few more:

• Theft resistant!
• No back-ventilation of solar panels necessary (lightweight laminates are easy to handle and can be field applied directly on metal)
• No support structures needed
• UL Listed as prepared roofing cover
• Wind and water-tight roof
• Suitable both for renovation and for new construction
• 20-year power output
• Standard junction box or weather-tight quick connect system
• “Peel & stick” adhesive backing capable of withstanding 160 mph wind loads

The 68 watt version is great for carports and RV roofs. We found the installation to be really simple. But I do have to tell you, once you have taken the backing off and have applied them, they are not coming off again. So you really need to make sure they are going down straight because you only get one try.

If you are a fan of the US64, try the PVL-68. You'll really like it once you've seen it.

Battery Q&A :: What is the Difference Between Marine and Deep Cycle Batteries? And When is the Best Time to Use Each?

We received a question from G. Holmes regarding the difference between a marine deep cycle battery and true deep cycle battery. And which battery type would we recommend using for a system using a wind generator.

Generally, a marine deep cycle and a true deep cycle battery are the same. However, there are differences that do make one type of battery better suited for certain applications and environments than others. The primary differences between the battery types are 1) exposure to environmental conditions and 2) size of the battery's plates.

Corrosion Resistant. Marine batteries have been designed to withstand the harsher environments often associated with a marine environment that often speed the corrosion process including:

• exposure to water
• exposure to salt

Battery Plates. Another difference between these battery types are the sizes of the plates. A marine battery has a thinner plate for higher cranking amps--or in other words--the thinner plate is better for the rigors of starting a battery. Deep cycle batteries have a thicker plate for slower discharge.

Applications. These differences in plate size allows you to use a marine deep cycle battery as a house and starter battery for boats and RVs whereas a deep cycle battery is better suited to be used as a house battery or as energy storage for battery based, stand-alone, solar and renewable energy systems.

Wind Generator Recommendaton. For a wind generator, we'd recommend using a true deep cycle battery, such as a golf cart battery. However, if your wind generator is located on a boat or near the coast with exposure to marine conditions, you may consider the marine version.

Equalizing Flooded Batteries

Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged. It reverses the buildup of negative chemical effects like stratification, a condition where acid concentration is greater at the bottom of the battery than at the top. Equalizing also helps to remove sulfate crystals that might have built up on the plates. If left unchecked, this condition, called sulfation, will reduce the overall capacity of the battery.

Many experts recommend that batteries be equalized periodically, ranging anywhere from once a month to once or twice per year. However, Trojan only recommends equalizing when low or wide ranging specific gravity (+/- .015) are detected after fully charging a battery.

Step by Step Equalizing:

1. Verify the battery(s) are flooded type.
2. Remove all loads from the batteries.
3. Connect battery charger.
4. Set charger for the equalizing voltage (See Table 2 in the Charging section).
5. Start charging batteries.
6. Batteries will begin gassing and bubbling vigorously.
7. Take specific gravity readings every hour.
8. Equalization is complete when specific gravity values no longer rise during the gassing stage.

NOTE: Many chargers do not have an equalization setting so this procedure can't be carried out.

Battery Charging

Charging batteries properly requires administering the right amount of current at the right voltage. Most charging equipment automatically regulates these values. Some chargers allow the user to set these values. Both automatic and manual equipment can present difficulties in charging. Tables 2 & 3 list most of the necessary voltage settings one might need to program a charger. In either case the original instructions for your charging equipment should also be referenced for proper charging.

Here is list of helpful items to remember when charging.

1. Become familiar with and follow the instructions issued by the charger manufacturer.
2. Batteries should be charged after each period of use.
3. Lead acid batteries do not develop a memory and need not be fully discharged before recharging.
4. Charge only in well-ventilated area. Keep sparks or flames away from a charging battery.
5. Verify charger voltage settings are correct (Table 2).
6. Correct the charging voltage to compensate for temperatures above and below 80o F. (Add .028 volt per cell for every 10o below 80o F and subtract .028 volt per cell for every 10o above 80o F)

Table 2. Charger Voltage Settings for Flooded Batteries

System Voltage
Charger Voltage Setting
6V
12V
24V
36V
48V
Daily Charge
7.4
14.8
29.6
44.4
59.2
Float
6.6
13.2
26.4
39.6
52.8
Equalize
7.8
15.5
31.0
46.5
62.0

Table 3. Charger Voltage Settings for VRLA Batteries
Charger Voltage Setting
System Voltage
12V
24V
36V
48V
Daily Charge
13.8 - 14.1
27.6 - 28.2
41.4 - 42.3
55.2 - 56.4
Float
13.5
26.4
39.6
52.8

1. Check water level (see the Watering section).
2. Tighten all vent caps before charging.
3. Prevent overcharging the batteries. Overcharging causes excessive gassing (water breakdown), heat buildup, and battery aging.
4. Prevent undercharging the batteries. Undercharging causes stratification.
5. Do not charge a frozen battery.
6. Avoid charging at temperatures above 120o F.
   

Additional VRLA Charging Instructions:

1. Become familiar with and follow the instructions issued by the charger manufacturer.
2. Verify charger has necessary VRLA setting.
3. Set charger to VRLA voltage settings (Table 3).
4. Do not overcharge VRLA batteries. Overcharging will dry out the electrolyte and damage battery.

Battery Storage

Periods of inactivity can be extremely harmful to lead acid batteries. When placing a battery into storage, follow the recommendations below to insure that the battery remains healthy and ready for use.

NOTE: Storing, charging or operating batteries on concrete is perfectly OK.

The most important things to avoid:

1. Freezing. Avoid locations where freezing temperature is expected. Keeping a battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to a battery's plates and container.
2. Heat. Avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 80° F accelerate the battery's self-discharge characteristics.
   

Step by step storage procedure:

1. Completely charge the battery before storing.
2. Store the battery in a cool, dry location, protected from the elements.
3. During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less. See Table 1 in the Testing Section.
4. Completely charge the battery before re-activating.
5. For optimum performance, equalize the batteries (flooded) before putting them back into service. Refer to the Equalizing section for this procedure.

Cleaning Your Batteries

Batteries seem to attract dust, dirt, and grime. Keeping them clean will help one spot trouble signs if they appear and avoid problems associated with grime.

1. Check that all vent caps are tightly in place.
2. Clean the battery top with a cloth or brush and a solution of baking soda and water.
   When cleaning, do not allow any cleaning solution, or other foreign matter to get inside the battery.
3. Rinse with water and dry with a clean cloth.
4. Clean battery terminals and the inside of cable clamps using a post and clamp cleaner.
   Clean terminals will have a bright metallic shine.
5. Reconnect the clamps to the terminals and thinly coat them with petroleum jelly (Vaseline) to prevent corrosion.
6. Keep the area around batteries clean and dry.

Flooded Battery Watering

Flooded batteries need water. More importantly, watering must be done at the right time and in the right amount or else the battery's performance and longevity suffers.


Water should always be added after fully charging the battery. Prior to charging, there should be enough water to cover the plates. If the battery has been discharged (partially or fully), the water level should also be above the plates. Keeping the water at the correct level after a full charge will prevent having to worry about the water level at a different state of charge.


Depending on the local climate, charging methods, application, etc. Trojan recommends that batteries be checked once a month until you get a feel for how thirsty your batteries are.
Important things to remember:
1. Do not let the plates get exposed to air. This will damage (corrode) the plates.
2. Do not fill the water level in the filling well to the cap. This most likely will cause the battery to overflow acid, consequently losing capacity and causing a corrosive mess.
3. Do not use water with a high mineral content. Use distilled or deionized water only.


CAUTION: The electrolyte is a solution of acid and water so skin contact should be avoided.


Step by step watering procedure:
1. Open the vent caps and look inside the fill wells.
2. Check electrolyte level; the minimum level is at the top of the plates.
3. If necessary add just enough water to cover the plates at this time.
4. Put batteries on a complete charge before adding any additional water (refer to the Charging section).
5. Once charging is completed, open the vent caps and look inside the fill wells.
6. Add water until the electrolyte level is 1/8" below the bottom of the fill well.
7. A piece of rubber can be used safely as a dipstick to help determine this level.
8. Clean, replace, and tighten all vent caps.


WARNING: Never add acid to a battery.

Battery Testing

Visual inspection alone is not sufficient to determine the overall health of the battery. Both open-circuit voltage and specific gravity readings can give a good indication of the battery's charge level, age, and health. Routine voltage and gravity checks will not only show the state of charge but also help spot signs of improper care, such as undercharging and over-watering, and possibly even locate a bad or weak battery. The following steps outline how to properly perform routine voltage and specific gravity testing on batteries.

I. Specific Gravity Test(Flooded batteries only)

1. Do not add water at this time.
2. Fill and drain the hydrometer 2 to 4 times before pulling out a sample.
3. There should be enough sample electrolyte in the hydrometer to completely support the float.
4. Take a reading, record it, and return the electrolyte back to the cell.
5. To check another cell, repeat the 3 steps above.
6. Check all cells in the battery.
7. Replace the vent caps and wipe off any electrolyte that might have been spilled.
8. Correct the readings to 80o F: Add .004 to readings for every 10o above 80o F /
   Subtract .004 for every 10o below 80o F.
9. Compare the readings.
10. Check the state of charge using Table 1.

The readings should be at or above the factory specification of 1.277 +/- .007. If any specific gravity readings register low, then follow the steps below.

1. Check and record voltage level(s).
2. Put battery(s) on a complete charge.
3. Take specific gravity readings again.

If any specific gravity readings still register low then follow the steps below.

1. Check voltage level(s).
2. Perform equalization charge. Refer to the Equalizing section for the proper procedure.
3. Take specific gravity readings again.

If any specific gravity reading still registers lower than the factory specification of 1.277+/- .007 then one or more of the following conditions may exist:

1. The battery is old and approaching the end of its life.
2. The battery was left in a state of discharge too long.
3. Electrolyte was lost due to spillage or overflow.
4. A weak or bad cell is developing.
5. Battery was watered excessively previous to testing.

Batteries in conditions 1 - 4 should be taken to a specialist for further evaluation or retired from service.

II. Open-Circuit Voltage Test

For accurate voltage readings, batteries must remain idle (no charging, no discharging) for at least 6 hrs, preferably 24 hrs.

1. Disconnect all loads from the batteries.
2. Measure the voltage using a DC voltmeter.
3. Check the state of charge with Table 1.4. Charge the battery if it registers 0% to 70% charged.

If battery registers below the Table 1 values, the following conditions may exist:

1. The battery was left in a state of discharge too long.
2. The battery has a bad cell.Batteries in these conditions should be taken to a specialist for further evaluation or retired from service.

TABLE 1. State of charge as related to specific gravity and open circuit voltage

Battery Inspection

There are many tools that may help in properly caring for and maintaining batteries. Below is a list of basic items that Trojan recommends for this task:

Recommended Equipment:

• Wrench
• Distilled Water
• Voltmeter
• Hydrometer
• Post Cleaner
• Baking Soda
• Vaseline
• Goggles & Gloves

CAUTION: Always wear protective clothing, gloves, and goggles when handling batteries, electrolyte, and charging your battery.

Batteries should be carefully inspected on a regular basis in order to detect and correct potential problems before they can do harm. It is a great idea to start this routine when the batteries are first received.

Inspection Guildlines:

1. Examine the outside appearance of the battery.
   Look for cracks in the container.
   The top of the battery, posts, and connections should be clean, free of dirt, fluids, and corrosion. If batteries are dirty, refer to the Cleaning section for the proper cleaning procedure.
   Repair or replace any damaged batteries.
2. Any fluids on or around the battery may be an indication that electrolyte is spilling, leaching, or leaking out.
   Leaking batteries must be repaired or replaced.
3. Check all battery cables and their connections.
   Look closely for loose or damaged parts.
   Battery cables should be intact; broken or frayed cables can be extremely hazardous.
   Replace any cable that looks suspicious.
4. Tighten all wiring connections to the proper specification (see below). Make certain there is good contact with the terminals.
   

Proper Torque Values for Connection Hardware:
Flooded

• Automotive 50-70 in-lbs
• Side 70-90 in-lbs
• Wingnut 95-105 in-lbs
• LPT 95-105 in-lbs
• Stud 120-180 in-lbs
• LT 100-120 in-lbs
  

VRLA

• Button 90 to 100 in-lbs
• LT 100-120 in-lbs

WARNING: Do not overtighten terminals. Doing so can result in post breakage, post meltdown, or fire.

Definition of Battery Types

Lead acid batteries are generally classified by application (what they are used for) and by construction (how they are made). The primary application is automotive in which the battery is used for starting and lighting. Deep cycle is another major application but is usually broken down into more specific applications such as RV, golf cars, renewable energy, and marine.

There are two popular construction types: flooded batteries (wet) and VRLA batteries (Valve Regulated Lead Acid). In the flooded types, the electrolyte is a solution of sulfuric acid and water that can spill out if the battery is tipped over. In VRLA batteries, the electrolyte is suspended in a gel or a fiberglass-mat (AGM technology), allowing these batteries to be mounted in a variety of positions.

Before getting started, be sure to identify the type of battery involved.

Simple Module Installation Tips and Tricks

Working with MC Connectors
on a Solar Module
In Low Voltage Solar Applications

Most 12 Volt solar modules come with a Junction Box (JBox) to make easy connections. A JBox is shown to the right. MC Connectors are the next generation connector and are used most often in high voltage residential and commercial applications. MC Connectors are shown below to the left. But some manufacturers are now using MC Connectors in place of Junction Boxes.

If you have a 12 Volt system and a low voltage module with an MC Connector and you want to connect your module in parallet, just cut the MC Connectors off. Before you cut the ends, make note of which connector is postive and which is negative. We usually mark with a piece of tape (red for positive). To verify, or if you cut the ends before marking the cables, use your volt meter. Set the meter to "Volts." The meter will tell you the polarity of the cable (either positive or negative). Once you've cut the cables, use a butt connector to hook the panels in parallel for a 12 Volt system.