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While is important to select batteries that have the correct storage capacity and design, inverter-charger devices have the ability to can increase the efficiency of the system. Equally, an inverter-charger can damage a system if it is installed incorrectly, or of it is malfunctioning or poorly designed. The purpose of an inverter-charger is to transform current from AC to DC to charge batteries, and from DC to AC to discharge batteries. Inverter-chargers can do much more however – they can function as the “brain” of the electrical installation, coordinating the energy flows between the main source (generator or grid), batteries, and the end user. A proper inverter-charger can provide a far better quality of service than any other back-up systems, including:

  • Increased power: power Power available from the inverter can be as high as 4 times the maximum power of the main power supply.
  • Increased generator lifespan.
  • Regulated voltage and frequency.
  • Uninterrupted power supply.

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Battery Cable Connections

The cables that join the batteries together play an important part in the performance of the battery system. Choosing the correct size (diameter) and length of cable is important for overall system efficiency. Cables that are too small or unnecessarily long will result in power loss and increased resistance. When connecting batteries, the cables between each battery should be of equal length to ensure the same amount of cable resistance, allowing all batteries in the system working equally together.

Particular attention should also be paid to where the main system cables that are connected to the battery bank. All too often the system cables supplying the loads are connected to the first or “easiest” battery to get to, resulting in poor performance and service life reduction. These main system cables that run to the DC distribution (loads) should be connected across the whole battery bank. This ensures the whole battery bank is charged and discharged equally, providing optimal performance. The main system cables and the cables joining the batteries together should be of sufficient size (diameter) to handle the total system current. If there is a large battery charger or inverter it is important to be sure that the cables are capable of carrying the potentially large currents that are generated or consumed by these pieces of the connected equipment, as well as all the other loads.

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  • Isolate the battery system to decrease the risk of accident - such as acid leakage , or harmful gas emissions - and prevent non-authorised access.
  • Ensure good operating conditions: a battery room must protect electronics against water and dust, and be well ventilated.

Batteries used for power back up and distribution need a specific place to be located, and must be well planned. It is convenient to have the battery room close to the main power supply or the distribution board, however the batteries must not be installed in the same room as the generator. High or fluctuating temperatures considerably affect the service life and batteries performance. It , and it is recommended to have a separate well ventilated battery room with a temperature as close as possible to 20ºC.  If   A dry and ventilated a cellar or underground room is a perfect location, provided the underground storage location will not flood or collapse.

Under no circumstances should battery storage locations be located in living or working spaces. A fully charged battery is highly energetic, and can spark, give off fumes, combust, or even explode. A faulty charger or an overcharged battery may display signs of distress, including swelling and smoking. An However, an overcharged battery may also display no signs and provide no waringwarning. A ruptured battery can propel shrapnel and throw very toxic chemicals, while the fumes may be extremely harmful or even lethal if breathed. If a battery shows any signs of warping, distress or overheating, the entire system should be shut off, and the battery should be disconnected if and when it is safe to do so. Do no not attempt to reuse damaged batteries – they should be disposed of safely, and in accordance with local laws and regulations.

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To size a battery system, the following will be needed need to determinebe determined:

  • The maximum power the inverter has to be able to deliver to the installation.
  • The amount of energy that must be stored in the battery to cover your needs.
  • In some case, the power the charger can deliver to the batteries.

Please reference he the section on energy management on how to calculate the power and energy the system has to deliver.

To manually calculate manually the maximum power of the installation:

  1. List all electric appliances fed by the installation.
  2. Find the maximum power of each electrical appliance. For appliances including an electrical motor the maximum power is approximately three times the nominal power. For example, a 300W water pump will need around 1kW to start.
  3. Add all power together.

To manually calculate manually the energy consumption of the installation:

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Take into consideration the hours that the battery system is intended to deliver electricity and plan accordingly. A battery configuration won’t be the same if the system will deliver power only during night or be use used as a full day twenty-four-hour backup. If it is possible, plan to run a generator during peak energy consumption hours, decreasing the number of batteries required and reducing the full cost of the system.

The power of the battery charger will determine how long recharging will take. A high-power charger that can charge batteries rapidly are is useful if the main power supply is very expensive – a big generator with high consumption - or if the electricity from the main power supply is only available during short duration - public grid available only few hours per day.

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  • If 12V charger is used, the charge current must be: 2,150 / 12 = 180A..
  • If 48V charger is used, the charge current must be: 2,150 / 48 = 45A.

Additional considerations:

  • The minimum duration to charge battery is 4 hours. Faster charging may damage batteries, and some batteries may have limitations longer than 4 hours.
  • Even with a powerful battery charger powerful enough, the charge may be longer due to the limited power available from the main power supply - with 5kW generator, buying a 10kW charger is pointless.
  • For chargers that have advanced settings, the charge algorithm may extend charge duration to save battery life. Some chargers automatically decreases the charge power when the battery is close to 100%.

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Series Connection

Wiring batteries together in series will increase the voltage while keeping the amp hour capacity the same. In this configuration, batteries are coupled in series to gain higher voltage, for instance 24 or even 48 Volt. The positive pole of each battery is connected to the negative pole of the following one, with the negative pole of the first battery and the positive pole of the last battery connected to the system.

For example; 2 x 6V 150Ah batteries wired in series will give 12V, but only 150Ah capacity. 2 x 12V 150Ah batteries wired in series will give 24V, but still only 150Ah.

Parallel Connection

Wiring batteries together in parallel has the effect of doubling capacity while keeping the voltage the same. Parallel coupling involves connecting the positive poles and negative poles of multiple batteries to each other. The positive of the first battery and the negative of the last battery are then connected to the system.

For example; 2 x 12V 150Ah batteries wired in parallel will give only 12V, but increases capacity to 300Ah.

Series/Parallel Connection

A series/parallel connection is combines the combination of the above methods and is used for 2V, 6V or 12V batteries to achieve both a higher system voltage and capacity. A parallel connection is required if increased capacity is needed. The battery should then be cross-wired to the system using the positive pole of the first and the negative pole of the last battery.

For example; 4 x 6V 150Ah batteries wired in series/parallel will give 12V at 300Ah. 4 x 12V 150Ah batteries can be wired in series /parallel to give you 24V with 300Ah capacity.

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