Storage Batteries are a key component in backup and off-grid systems, often serving as the only energy storage device.Storing electricity for use at a later time, they also provide a reserve of available energy to run loads that require more power than that provided by the charging source. To guarantee that they function properly it is important that your batteries are maintained. A chief part of this maintenance is proper charging. Your batteries should always be maintained above a 50% level of charge and receive a complete recharge once a month to ensure operation at peak performance. Prolonged use of the battery below a 50% state of charge will adversely affect the long-term health of the battery and can result in premature failure.

Batteries wear out and must eventually be replaced. Regular monitoring and maintenance will extend the life span of your battery bank and save you money. The deeper they are discharged, the shorter their life span will be. Batteries contain toxic materials and should be disposed of properly.

There are many types of batteries available. Many are unsuitable for an independent power system. Choosing the right type of battery is the first step in designing a reliable renewable energy system.

Motive Power Batteries
Motive batteries are deep-cycle batteries used to provide energy for electric vehicles such as golf carts and forklifts. They have thick plates that will withstand many deep discharge cycles. These are used for most independent power systems as they are durable, have good storage capacity and are cost effective. These are usually in a 2V, 6V or 12V casing. Typically, the golf cart batteries will last four to seven years, while the Global-Yuasa forklift batteries will last 10 to 20 years.

Stationary Batteries
These cells, common known as utility backup cells are used by telephone companies for back-up power supply systems. They are often designed with calcium alloy plates which are not for deep cycling, so they are poor batteries for a most renewable energy systems. However, they may be suitable for use in systems where there is no requirement for autonomy such as a micro hydro installation. When batteries are used this way, also referred to as 'float service', they are storing reserve energy for peak load demands. Stationary 2V cells frequently come in a clear casing.

Battery Charging

The multistage charging process uses several regulation stages to allow fast recharging of the battery energy storage system while ensuring a long battery life, high performance and efficient operation of the overall system. The charging process begins with the BULK stage, where maximum current is sent to the batteries until the target "absorb" voltage is reached and the absorb stage of the charge begins. During ABSORB , the charger provides the batteries with the just enough current to hold at the set voltage for a preset amount of time. Following this cycle, the charging system changes between available OutBack charging products. Using the MX-60, the batteries enter the FLOAT stage where they are given a maintenance charge until there is no excess renewable energy. The FX or VFX inverter/charger will go into SILENT mode where the charger turns off until the battery voltage drops to the "re-float" setting. At this point the inverter/charger initiates the maintenance FLOAT charge. This method reduces fuel and utility consumption.

It should be noted that the temperature of your batteries has an impact on the charging process. The OutBack RTS should be used to monitor this. In higher ambient temperatures, the battery charging regulation settings will be reduced to prevent overcharging of the batteries. Conversely, in lower ambient temperature conditions, the regulation settings will be increased to ensure complete recharging of the batteries.

Batteries are composed of a group of individual cells. Through normal use, the charge of each individual cell will not be equal to the other cells. To address this, your batteries should be EQUALIZED either once each month or once every few months depending on usage. During the equalization charge the electrolyte in the battery is stirred up by gas bubbles, which help to create an equal mixture of water and acid. Simultaneously the full cells are overcharged which allows the low cells to "catch up" and all of the active material in the battery to be reconverted to its charged state. Depending on usage, the hardened battery plate material that is no longer active in the battery- sulfation can also be reduced by an equalization charge.

Preventive Maintenance

When a battery is first received the cell acid levels should be checked and the battery should be put on charge. After removing from charge the specific gravity readings of each cell should be recorded and kept for the life of the battery.. If the electrolyte levels are low before the battery is put into service do not add water but contact your dealer or Surrette Battery Company Limited. Only add water as it is consumed.

Preventive maintenance involves, at a minimum, checking the cell electrolyte level for correct acid volume once a month and equalizing once every six months. The cells should be watered back to the original acid level which is 1/4 - 1/2" below the bottom of the vent well (tube inside the battery cell with slots on each side). Distilled water is preferred but water not chlorinatedmaybe acceptable if it is not "hard" or does not contain high iron levels. Use of non-distilled water can cause mineral build-up in the battery cell.

Battery Venting

Batteries can produce hydrogen gas which can biuld up and be hazardous if not vented. The battery enclosure needs to be ventilated to discharge this gas to the outside of the building. Your system should include a battery vent fan.

The battery vent can be controlled to operate only when the batteries are in a charging condition likely to produce hydrogen or can operate continuously , modern inverters include relays to allow operation of remote equipment based upon battery voltage. We use one of these relays to control the fan. If the system does not include an inverter with relays, then a separate voltage controlled relay can be installed. This vent should be included in any system design and installation.