Installation of the Photovoltaic Power Generation System Battery Bank
The installation quality of batteries directly affects the reliability of the battery pack's operation. The general principle for battery installation is: in small photovoltaic power systems, the battery should be installed as close as possible to the battery module and controller. In medium and large photovoltaic power systems, it is best to separate the battery from the controller, inverter, AC distribution cabinet, etc. The installation location of the battery must ensure good ventilation, convenient drainage, prevention of high temperatures, protection from direct sunlight, distance from heaters or other radiant heat sources, and the environmental temperature should be maintained at 10-25 degrees Celsius as much as possible, with a maximum range not exceeding 0-35 degrees Celsius.
Pre-installation Inspection
(1) Before installation, it is essential to first inspect the appearance of the battery to prevent damage to the battery casing and internal structure caused by improper handling during production and transportation. The inspection should include checking for any cracks or acid leakage. It is also necessary to check whether the terminal posts are bent or damaged; bent or damaged posts can make installation difficult or impossible, potentially leading to seal failure, creeping acid, acid seepage, high contact resistance, and even the risk of melting. During the inspection process, if there are suspicious wet spots on the casing, a multimeter can be used with one end connected to the battery post and the other touching the wet spot. If the voltage is zero, the casing is not damaged; if the voltage is above zero, it indicates the presence of acid, and further careful inspection is required.
(2) Before installation, it is important to check the manufacturing date of the battery, verify the time interval between production and installation use, and individually measure the open-circuit voltage of each battery to determine if charging is needed. New batteries should be put into use within three months. If left idle for an extended period, the open-circuit voltage will be very low, and such batteries cannot be installed directly but should be charged before installation.
Installation Precautions
(1) Insulation measures should be taken between the battery and the ground, generally by placing wooden boards or other insulating materials to avoid short circuiting and discharging of the battery with the ground. If there are many batteries, they can be installed on a dedicated battery rack, which must be reliably grounded.
Before installing connectors between multiple sets of batteries, individual batteries must be arranged neatly to ensure smooth installation of the connectors, and they should not be tightened forcefully to avoid stressing the battery posts and causing leakage at the seal.
(2) Batteries generate a certain amount of heat during the charging and discharging process, so the spacing between batteries should generally be greater than 50mm to ensure good heat dissipation. There should be good ventilation facilities between batteries to prevent combustible gases produced by battery damage from causing explosions and fires.
(3) Battery groups placed outdoors should have rainproof measures, and when the ambient temperature is below 0°C or above 35°C, the battery group should have anti-freeze, sun protection, and thermal insulation measures.
(4) The connection wires between batteries should meet the requirements for current flow. For parallel connected battery groups, the impedance of the connecting wires should be equal. The connection wires between the battery and the charging device and load should not be too thin or too long to avoid excessive voltage drop and heat generation due to energy loss during current transmission, posing hidden dangers to safe operation.
(5) Circuit groups with series-connected batteries should have a circuit breaker for maintenance purposes. It is best for each parallel group to have a circuit breaker to facilitate future maintenance.
(6) A battery group should not use a combination of new and old batteries, but should either use all new batteries or all old batteries originally from the same group, to avoid imbalances in the working states of new and old batteries, affecting the service life and efficiency of all batteries. Batteries with different capacities should never be used in series in the same group, as there are safety hazards during high current charging and discharging operations.
(7) The contact between the battery post and the wiring must be ensured to be tight. Before installation, use a copper wire brush to remove the oxide layer on the surface of the post, exposing the metal luster of the post's wiring part, and wipe the lead dust and dirt off the battery surface with a soft cloth. Apply a layer of Vaseline oil film to the post and connection point to prevent corrosion and rust leading to poor contact.
3. Installation of Battery Supports
(1) The battery cabinet or frame should be placed in a pre-determined position and leveled, with a horizontal error less than 1mm/m and a vertical error not greater than 1.5mm/m. Note that there should be a maintenance distance of 50-70cm between the battery cabinet and other cabinets, walls, and other equipment, and check whether the floor bearing capacity meets the requirements.
(2) First, place the support frame stably on the ground, then place the crossbeams on the side frames, align the mounting holes on both sides, and screw them in but do not tighten yet.
(3) Connect the left and right side beams to the side frames with connecting plates, screw in the fixing screws but do not tighten yet.
(4) Adjust the fit between all components, and if there is no misalignment, tighten all screws.
(5) If the battery support needs to be fixed to the ground, position the battery support, mark the fixing holes, move the support aside to drill holes at the marked locations, and clean up the site.
(6) Place expansion bolts into the holes, then move the support back into position and secure it.
4.Installation of Batteries
(1) When installing, it is necessary to manually lift the battery onto the bracket and arrange it neatly. Batteries in the same row and column should be placed consistently and orderly, in accordance with the connection sequence. The connection of the battery should refer to the design drawings and factory instructions.
(2) Use the special connectors or connecting wires provided with the battery, and connect the positive and negative poles of the battery according to the design requirements, forming a battery group through series or parallel connections. During connection, it is strictly forbidden to cause short circuits at the poles, and tools should also be insulated to prevent battery short circuits and personal injury.
(3) After the batteries are connected, the end caps of the poles should be fastened or coated with Vaseline oil or high-temperature grease to prevent the terminals from being corroded by acid.
(4) When the output voltage of the battery group is high, there is a risk of electric shock. Care should be taken when dismantling and connecting wires, and insulated tools should be used.
(5) When multiple batteries are used in parallel, arrange them according to the battery label's positive and negative polarity in sequence, and tighten the connection points to prevent sparks and poor contact.
(6) The installation distance between batteries is usually 10-15mm to facilitate convection cooling.
(7) Batteries should be placed away from heat sources and places prone to sparks (such as transformers, power switches, or fuses), with a safe distance of more than 0.5m. Smoking or using open flames near the battery system is prohibited.
(8) Before connecting the battery (group) to external equipment, ensure that the equipment is turned off, and check again whether the battery's connection polarity is correct. Then, connect the positive pole of the battery (group) to the positive terminal of the equipment, the negative pole of the battery (group) to the negative terminal of the equipment, and tighten the connecting wires securely.
(9) If batteries or battery groups need to be used in parallel, generally no more than 4 units (groups) should be connected in parallel.
(10) Do not individually increase the load on certain cells within the battery group, otherwise, it will cause an imbalance in capacity among individual cells.
(11) The connecting cables between batteries should be as short as possible. The selection of cable size should not only consider capacity output but also ensure that there is no excessive voltage drop.
(12) Special note: It is strictly forbidden to connect batteries of different capacities, manufacturers, or ages together.
(13) For larger photovoltaic power stations (sites) where conditions permit, it is best to equip the battery room with air conditioning and purification ventilation equipment to maintain an environmental temperature of 20-25 degrees Celsius.
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