Blue Box Batteries Ltd

We are suppliers of VRLA battery solutions and industrial batteries suitable for a range of applications. We offer proven product ranges from major manufacturers such as Yuasa, Fiamm and C&D Technologies including ancillary products and services.

Our industrial batteries range is expansive and includes a number of models in the following specifications:

  • Sealed lead acid (SLA)
  • High rate VRLA
  • Industrial battery system accessories
  1. How To Analyse Battery Open Circuit Voltage Data.
    11 May 2017

    Blue Box Batteries have now published our latest blog article ‘Battery Open Circuit Voltage Characteristics’ which can be found on the following link. This post looks at how to determine the integrity of a battery system using open circuit voltage data which includes how to obtain this information including methods and equipment required as well as how to process this information once properly received. Correct battery system assessment is essential in achieving the best standby battery autonomy and optimum service life from a battery backup system such as a UPS or emergency lighting system, open circuit voltage data will help in ensuring the system is properly monitored and allows for any possible issues to be dealt with efficiently.

    For many more articles regarding the technical aspects of industrial batteries, as well as helpful advice, then make sure you follow our blog for all previous posts as well as any new information. For direct assistance with a project then please contact us directly, our team will be glad to assist.

    Blue Box Batteries Ltd are approved supply partners for all major industrial battery manufacturers, and are established suppliers of Yuasa, Fiamm, Enersys, Exide GNB and many others. If you are looking for the best service and prices for VRLA batteries, then make sure you contact Blue Box Batteries for first time, on time service.

    How To Analyse Battery Open Circuit Voltage Data.
  2. Battery Room Design
    3 February 2017

    The latest blog article from Blue Box Batteries describes best practices for battery room and enclosure design including the need to consider accessibility, ventilation and security for purposes of ease of installation, on going maintenance and health & safety.

    It is essential to always follow manufacturers recommendations and our article is intended to explain further why these requirements are in place. A good battery room will ensure full optimisation of a system in terms of life span and performance. For help and advice for any specific project please do contact directly on 02381 789197 or enquiries@blueboxbatteries.co.uk. For the article please click on this link

    Battery Room Design
  3. VRLA Battery Internal Resistance & Short Circuit Current
    4 January 2017

    In the latest Blue Box Batteries blog article, we describe battery internal resistance and short circuit current looking at how these figures are calculated and the standards applied in compiling this data. All battery manufacturers, including Yuasa, Fiamm, Enersys, Exide and Wing will provide specific data in this respect with the intention of enabling on site analysis to establish the health of a battery system.

    Correct maintenance of back up batteries is an essential aspect of ensuring reliable power in the event of mains failure, understanding testing data is necessary to guarantee system integrity. The Battery Internal Resistance & Short Circuit Current article can be found here

    For any additional information please contact us directly.

     

    VRLA Battery Internal Resistance & Short Circuit Current
  4. Battery Testing Using Impedance Measurements
    2 June 2016

    This article considers ohmic measurements as a means of identifying rogue cells and monoblocs of VRLA AGM and GEL product installed on float standby systems. For batteries operated on cycling applications there are better ways of identifying rogue cells or the end of life for the complete battery. For vented product, the established method of visual inspection, float voltages, specific gravities and ultimately discharge testing are more reliable than predictions based on ohmic measurement.

    Searching the internet will show that there are many articles discussing battery ohmic measurements. Some will be written by operators such as telecommunication or UPS companies whilst others will be from instrument manufacturers and papers written by battery manufacturers are also available. Rarely is an article written with the intent of giving an overview of the subject and guidance for the interpretation of the results obtained and actual case examples. This article will show that whilst ohmic measurements may be used to identify rogue cells or monoblocs, the results can also be very misleading and may give the operator a false sense of security, or condemn product that is still fit for purpose.

    It has been shown that when ohmic values for a battery are compared over time, they can be used to predict the end of life. (See FIG 1 below). Care must be taken on drawing the wrong conclusions when comparing the results over time. Rogue cells can skew the results and it must be understood that the ohmic value of a cell will change in a none-linear way over time. Typically, the ohmic value will become better over the first years of service before falling away as the end of life approaches. This fall off may be steep and measurements taken on an annual basis may not be sufficient to identify imminent failure. It has also been shown that whilst the ohmic change is not linear with time, similarly the expected performance is also not linear with time and cannot be correlated with the change in ohmic value without detailed information of the instrument and product characteristics. If long term monitoring of cells is used to predict the end of life, the operator should consult with the equipment manufacturer and battery manufacturer to obtain the best possible predictions. Establishing the base ohmic value is essential and this should be done after an initial stabilising period of approximately six months in service.

    It has been suggested by some instrument manufacturers that a value more than 30% different in the negative direction from the base number represents a failure. This may or may not be correct depending on the instrument used and the product being evaluated.

    Ohmic measurements can be taken on large vented (wet) lead acid batteries but most of the instruments available are aimed at VRLA product of less than 500Ah. In this article, we look at a variety of VRLA AGM products. The principal can be extended to GEL product but it would not be practical to extend this to vented cells.  

    Although it is rather academic and mainly only for the interest of Chartered Engineers, it is worth looking at what is meant by ohmic value. There are three values for us to consider as follows: -

    DC RESISTANCE: R = V / I

    AC IMPEDANCE: Z = √ (XL2 + R2)

    AC CONDUCTANCE: S =1 / (√ (XL2 + R2))

    The internal ohmic value of lead acid batteries are made up of all three components listed above and can also be described as more complex because cells also have a capacitance and inductance which interact with each other to give an overall ohmic value. Understanding the overall value and using this to determine the health of the battery is what users search for, but is not easy to draw conclusions.

    There are many instruments available on the open market that claim to show the state of health and overall performance expectations. Most of these instruments will give an ohmic and will leave the interpretation to the discretion of the user. The user will often contact the battery manufacturer for “base numbers” for the battery being measured and from this some sort of conclusion can be reached. What is missing is that different instruments will give different results and some real results for different instruments are given below.

    Four different instruments were used to establish the ohmic value of a 12V 90Ah monobloc and the results are given below along with the manufacturers declared internal resistance. All four instruments claimed to measure the impedance but one actually measured the DC resistance. The manufacturers internal resistance was determined by the method described in IEC 60896 21-22 and not by using a measuring instrument.

    Instrument “1” - 2.72mΩ

    Instrument “2” - 3.39mΩ

    Instrument “3” - 3.80mΩ

    Instrument “4” - 6.49mΩ

    IEC 60896 21-22 Method - 5.20mΩ

    The inevitable question is “which is the correct value”? The answer is that all the readings are correct. Each instrument uses a different method to determine the “impedance” and it follows that each instrument will show different impedance. It follows that unless you have a “base number” for the specific product using a specific instrument, correlation cannot be made between the base value and readings obtained for batteries in service. It has also been shown that the actual method used can also affect the results. Specifically, the point on the cell or monobloc where the measurement is taken will, in many cases affect the result. Some instruments are more sensitive than others in this respect. A measurement taken on a bolt head can be significantly different to that taken next to the bolt on the connector. All measurements should be taken in the same way. Different values can be seen if the battery is on line or off line due to charger and load induced ripple.

    The most consistent values are obtained by using the IEC 60896 21-22 Method which involves discharging the cell or monobloc at two different currents and then calculating the resistance using a formula. It does not matter if the tests are carried out by an independent laboratory, user or manufacturer; the results will correlate well within experimental limits.

    Using the IEC 60896 21-22 method, the Internal Resistance is found by: Ri = (Ua – Ub) / (Ib – Ia) in ohms However, it is not practical to use the IEC 60896 21-22 Method on a battery in service. As a consequence, ohmic measuring test instruments have been developed which will measure the impedance, conductance or resistance of cells and monoblocs whilst in service. Some instrument manufacturers claim that the devices they offer are immune from ripple generated by the charger or load and will detect all types of battery failure from internal shorts to end of life.

    Some will argue that it is essential to have the base number for comparison purposes and this brings its own problems. The spread of ohmic values from a batch of lead acid cells or monoblocs can easily be ±10% or more within two standard deviation. With this type of spread in values, the process of identifying rouge cells or monoblocs becomes difficult. We also have to establish the value to consider for replacing a cell or monobloc. Even with the practical difficulties of establishing a base value, this should be done where ever possible. The best way of establishing a base number is on a new battery that has been in service for six months. During this time, the product will stabilise in both float voltage and ohmic value terms. The float voltage and ohmic values will have a lower spread as the product settles down. This assumes that no discharges have taken place. If the battery has been discharged, then a further 6 months stabilisation period should be applied. Then, using a selected instrument and test method, all cells or monobloc values should be measured and recorded for future reference. At that time it may be decided to consider failure as a given percentage from the mean value. Caution needs to be applied because stipulating too tight a tolerance will result in good product being rejected whilst a tolerance that is too wide may leave the installation exposed.

    Battery manufacturers and users have been using ohmic measurements for some years. In many cases these have been successful in finding weak cells or monoblocs before failure occurs when the float voltage has been within acceptable limits. However, in some cases the instruments used have either failed to identify weak product or have condemned product that was still serviceable. Below are real case examples of what has been found in the real world.

    Battery Testing Using Impedance Measurements

Buy from Blue Box Batteries Ltd

Request a Quote