Nickel battery monitoring goes digital

The latest digital sensors and diagnostic systems are overcoming a longstanding barrier to online monitoring of nickel batteries. Remote digital monitoring offers the potential to improve visibility of assets in the field, reduce operational expenditure (OPEX) and make better decisions. 

The challenge when applying this to nickel batteries is that digital technology fits perfectly with digital control but these batteries are based on analogue electrochemistry. However, it is now possible to add digital sensors to monitor key performance indicators, carry out diagnostics to develop deeper insight. 

Once connected to the cloud, operators can log in to view the data for near-real time monitoring of battery performance. It is possible to establish alerts so that operators can take action if a battery is not performing as expected. They can also review and analyse long-term performance or share data with maintenance partners if they need external troubleshooting.

Such sensors monitor operating factors such as temperature, current, voltage, electrolyte level and hydrogen level in almost real time. They can be integrated into a new battery system in the factory and can also be supplied as a kit for retrofit installation into existing assets in the field. 

State of Charge and State of Health

An additional benefit is possible for operators that are applying Saft’s Intelli-Connect system to Saft’s own batteries. The system has an algorithm that integrates knowledge and data from decades of experience of our batteries in the field around the world. 

Combining this algorithm with the data from the sensors enables the system to estimate the state of charge (SOC) and state of health (SOH) of their batteries. 

SOC is important for short-term peace of mind. It shows at a glance how much charge is available in a battery system to support mission-critical loads at a moment’s notice. 

In contrast, SOH is a measure of a system’s remaining calendar life. SOH insight could tell an operator with a 17-year-old battery that they need to replace it within three years as expected. Alternatively, it might say that the battery has enough capacity left to prolong its lifetime, enabling the operator to defer battery replacement and making the most of their assets. 

Ideally, operators of mission critical sites want reassurance of both SOC and SOH. 

To accurately estimate these requires knowledge and insight into the many factors that can influence battery performance. These include temperature, charge and discharge frequency and depth, maintenance and testing.

Year-long trials

Knowing that there’s a huge variety of applications and environments for nickel batteries, we carried out a year-long set of field trials starting in 2020. We selected eight operational batteries at customer sites. 

What they have in common is that they all support mission-critical loads and are locations that are remote or difficult to access for maintenance engineers. 

We also wanted to reflect a wide range of operating factors within the trial therefore chose batteries with differing ages, electrical profiles, applications and environments. 

For example, one of the trial batteries provides high cranking power to start up backup diesel generators in the event of a mains power outage. Another ensures safe shut-down of valves at a refinery, and others provide backup to reconfigure electrical switchgear on utility power distribution networks. Elsewhere, one trial battery provides backup to industrial SCADA system, another support railway signaling and one supports continuity for a fire alarm system. 

The trial sites represent different energy storage capacity and system voltages from 24 – 360V. This covers power requirements ranging from injecting high current over a few minutes to supporting a trace current over several days. 

We also wanted to ensure that different climates were covered by the trial sites. Ambient temperature influences the speed of the electrochemical reactions inside batteries and affects power performance, as well as calendar life. Therefore, we selected customer locations to reflect a wide variety of climatic conditions. The trial covered batteries in Sweden, France, Belgium, Spain, Brazil and South Africa. 

Lastly, we wanted to confirm performance with batteries of different ages so chose batteries ranging from new to 15 years old. 

An unexpected outcome of the trial was that it also evaluated the system’s ease of installation. We had originally planned to install these first trial systems ourselves in early 2020. This coincided with travel restrictions under the COVID-19 pandemic. However, with a little phone support, our customers were able to install the sensors and connect them to our secure cloud-based platform.

All batteries connected successfully over the year and the system shows how operators can review performance, for example by geographic location, as a dashboard with KPIs, or by drilling down to check detailed performance logs.

Return on investment

After a year of gathering data, the most important finding is that all cases achieved a return on investment, with the payback being unique to each site. 

 For example, we were able to help one of the trial customers save energy. Its data showed that it was heating its battery room. This is not necessary for nickel batteries as they can withstand a wide operating temperature range, therefore it was able to save energy bills and emissions. 

Another operator’s batteries were found to have more remaining capacity than expected. Therefore, we were able to suggest that the customer could increase their discharge time to get more backup duration out of the existing asset. This could have significant benefits for some sites. 

The data at another site identified a fault on a battery charger. This prompted the customer to carry out a repair they wouldn’t have done otherwise and therefore protect their asset and ensure safe continuity of their services. 

Another one of the trial customers was able to save itself engineering development time. It had been considering developing its own nickel battery monitoring system, therefore our technology saved their development costs and provided the additional benefit of SOC and SOH monitoring. 

Without digital monitoring data, it would have been difficult for any of the operators of the trial sites to identify these issues and take action. 

When it comes to return on investment, the payback depends on the typical factors that are used in a total cost of ownership (TCO) or life cycle cost (LCC) analysis. This includes the criticality of the installation, which influences its risk profile. The calculation should also consider how remote a site is, which influences the time and cost of sending a technician, as well as the local cost of labor. 

Ready for roll-out

Today’s industrial operators are under intense pressure to control costs and make the most of their assets with remote digital monitoring. 

Until now, it’s been tricky to apply digital monitoring to analoguebatteries but this is now possible with the latest type of system. 

With the experience from the trial customers under our belt, the indications are clear that digital nickel battery monitoring will play a key role in increasing system availability and reducing maintenance costs for nickel battery systems. 

It’s likely that the early adopters of such systems will be operators of sites that are both remote and mission-critical, where technicians cannot easily visit and where the value of data is highest. 

Erick Lopes is Saft’s nickel battery product manager
www.saftbatteries.com