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Practical considerations when designing a battery room

Practical considerations when designing a battery room
27 Jul 2018

A battery room is a constructive element that must have not only design considerations and a logic of use, but also must comply with specific safety regulations. Logical,isn`t it? And even so, throughout my professional career, on many occasions I have witnessed many curiosities, to call them in some way, that undermined any principle of design, logic and regulation. In this post I will gather in a succinct way some recommendations on these three aspects. I even encourage you to use it as a basic checklist (not to replace for a professional duly accredited) to take into account if you need, or already have, a battery room at your workplace.

Accessibility: When dealing with a large-scale battery installation, we need to anticipate the delivery of pallets using vehicles and/or fork-lifts.  Thus, it makes no sense to house the batteries at height or in areas with narrow access corridors. At least, allow for the easy positioning of a standard euro pallet, paying particular attention to steps, corners and in the case of lifts, door width and weight limitations.  

Location of battery room:  When considering accessibility, remember that as batteries work at low voltages, a voltage may necessitate the use of expensive cables to provide a solution and compensate for the .  

Ventilation:  In any electrochemical combination where there is water decomposition, there will be hydrogen release (https://goo.gl/vrdvR3).  This includes breakdowns (over-charging) in sealed batteries, causing high internal overpressure which then releases H2 into the atmosphere.  By natural (ventilation size) or mechanical means, it is important to ensure adequate ventilation so that the H2 concentration in the room never exceeds 4%.  Clean air should enter through an inlet in a low position and exit through an outlet positioned at the highest possible point.  This practice recommends the use of forced induction rather than natural aspiration, so that whenever possible, the fan motor works with clean air.  Be aware that both the switches for timers of motors and lighting should be situated outside the room.

Roof Shape:   As H2 tends to rise if there is an escape of gas, a flat roof may cause the gas to form pockets with concentrations that may be higher than 4%.  Therefore, it is important to have air vents at the highest point possible to avoid these pockets of gas. Keep in mind that the battery room is usually closed with little air circulation and not much traffic.  

Safety:  It would appear evident that doors should open outwards to facilitate the escape of gas in the event of an explosion, and also to ensure easy access and sufficient room for both the safety shower/eye wash station and a helper in case of accidents.  Due to the low cost involved, we always recommend the installation of explosion-proof lighting which should be positioned away from the highest point in the room.

Occupational Health and Safety Regulations offer ample recommendations for ATEX rooms which should be followed.  Especially important is the positioning of posters at entrances prohibiting access with open flames, sparks etc.

Even nowadays with wide cell coverage, a landline telephone should be installed outside the battery room door along with a poster providing information for emergency services.  

Maximum temperature:  With the exception of batteries specifically designed for high temperatures (https://goo.gl/pnGa3d), all sealed and vented batteries are designed to work at 20ºC, and while they can tolerate higher temperatures, it is usually detrimental to the working life of the battery.  Therefore, it is important to keep the temperature as low as possible by not locating battery rooms near power transformers, boilers, turbines or any other exothermic/heat-releasing industrial equipment or process.  Also take into account sunny facades etc.

Air conditioning: To avoid the above-mentioned problem, it’s usual to calculate and install an air-conditioning system to prevent temperatures rising above the desired level.  However, it needs to be remembered that the system cannot work in a closed cycle, as the H2 concentrations would exceed 4%.  A system that allows air renewal (even partial) is therefore, an important consideration.  

Minimum temperature:   Generally, all types of batteries will tolerate very low temperatures if they are charged, however, low temperatures will cause lead acid batteries to lose density if discharged.  In the discharged state, the electrolyte becomes more water-like and will freeze (below 0ºC). In a flooded lead acid battery, this will increase the volume and cause cracking (and leaks) in the battery cases.  When low temperatures are expected, a cut-off circuit at minimum voltage (normally 15% of nominal voltage) should be installed, in order to prevent a deep discharge and the electrolyte freezing.

Minimum dimensions:  Depending on the type of rack or cabinet chosen (https://goo.gl/1wUk3B - Practical considerations for choosing racks – Sizing examples), there will need to be access through halls/corridors. The minimum width of the corridor would need to be 75cm, but 1m is recommended. Door openings should be at least 2 x 80cm wide with the possibility of opening both at the same time.  Where possible, leave at least 1.5m free on each side of the eye wash station.

Without question, the room height must be the maximum permitted by the highest point of exit ventilation, to increase the volume of the room as much as possible and therefore, decrease the concentrations of H2.  

It is recommended to provide a cupboard or shelving for the storage of maintenance material.  

N.B.  The legislation of each country or the company’s own internal regulations may impose further restrictions or minimum requirements, thus our recommendations are only a guide based on our experience.  

For installation in Spain or under Spanish legislation, please see:

  • RD 337/2014 (high voltage) and especially ITC-RAT-11 Accumulator installations (https://goo.gl/4EnsY5).
  • RD 842/2002 and s (low voltage) and especially ITC-BT-29 Premises with risk of fire or explosion and ITC-BT-30 Premises with special characteristics (https://goo.gl/x7qeN).

Anti-corrosive and Insulating Coatings:  Traditionally, it was common to use such coatings, however, with the proliferation of sealed batteries and the voltage stability of modern electronics, electrolyte spills have become negligible and therefore, nowadays their use is not so vital.  Of course, the legislation for each country and individual company regulations must be taken into account.

For example, in Spain, ITC-BT-30 Point 7, requires the installation of insulated flooring if the battery voltage is greater than 75 VDC and there are accessible conductive points.  

Fuse Box and Breaker Points:  Some national legislation and electrical company regulations will demand a voltage cut-off breaker next to the battery.  If no other option is available, it may be installed in an ATEX box in the battery room, being accessible without the need to open the box and clearly labeled showing the operating direction of the shut-off switch.  Where possible, it is usual to place a standard wall cabinet outside the battery room next to the door, so in the case of an emergency, the voltage may be cut BEFORE entering the room.

The most serious type of battery room emergency occurs when battery electrolyte levels fall too low and cause a chemical fire with smoke generated from the plastic casing materials – we have an electrolyte spill which is acidic and highly corrosive – voltage sources where there is spilled electrolyte (a conductor) – plus, there are usually sizeable metal racks or cabinets adding further voltage sources.  

It would appear sensible to be able to at least, cut rectifier voltage before entering the room, rather than having to search for the voltage cut-off in a smoke-filled and dangerous environment.  

Amplification/Expansion:  We have learned from experience that a battery room can never be too big!  It’s always possible that battery numbers may need to be increased at a future date.  If your original plans have considered this prospect by allowing for greater dimensions and ventilation points, it will prove priceless when the time comes to upgrade the installation.  

While it would appear obvious, we must avoid, under all circumstances, the battery room being transformed into a storeroom/warehouse/cleaning room as has often been seen in various facilities.  (Recently I encountered a bottle full of cigarette butts indicating a secret smokers’ room – no comment necessary!!!)

Notice Board/Poster:  given the potential risks in any battery room, we would like to stress our recommendation regarding the positioning of safety/emergency action plan posters outside the room which should include: possible dangers, a pictorial representation of order of actions to be taken, as well as any important maintenance advice.

Rodrigo Suárez Cueto

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