Where power systems are concerned, reliability means profitability, and that reliability is often dependent on quality battery backup systems. Most businesses dependent on these batteries have often had to juggle between high maintenance costs and good service. Keeping track of hundreds or thousands of these batteries can be a very expensive proposition, so in many cases managing these batteries has given way to simply replacing them on a preset schedule, whether or not they need replacing. In other cases, unmonitored batteries may fail before they are scheduled for maintenance, leaving no reliable backup solution in place.

Drawing on our substantial battery design experience, Encell Technology has developed a total battery management solution called The Sentinel Smart Power System™ that is designed to accomplish four very simple but important goals:

1. Reduce or remove the harmful effects of high battery temperatures caused by float charging;
2. Increase the visibility into battery backup systems so that maintenance visits, battery replacement costs, and failure-related outages can be reduced;
3. Decrease environmental impact, capex and opex costs, and safety issues associated with lead-acid battery deployments;
4. Increase the availability and reliability of network systems that depend on battery backup.

The Challenge: Battery Degradation

Where power systems are concerned, reliability means profitability, and that reliability is often dependent on quality battery backup systems. Most businesses dependent on these batteries have often had to juggle between high maintenance costs and good service. Keeping track of hundreds or thousands of these batteries can be a very expensive proposition, so in many cases managing these batteries has given way to simply replacing them on a preset schedule, whether or not they need replacing. In other cases, unmonitored batteries may fail before they are scheduled for maintenance, leaving no reliable backup solution in place.

The typical backup system uses lead-acid battery stacks to supply power. These may be effective initially, but they quickly lose performance when they are used for even short periods of time. Continuous charging current takes years of life off these batteries; their temperature is raised by constant overcharging which causes grid corrosion, dehydration and positive active material degradation. These effects reduce capacity and power further. There is also the risk that high temperatures from overcharging can cause thermal runaway, resulting in battery rupture, gassing or even an explosion.

Battery performance is also strongly affected by environmental temperatures. Every 20°F increase from the ideal operating temperature of 68°F reduces the life of a battery by 50%. So at 120°F, a battery that should last 10 years can last as few as 2.5 years. This drives up replacement costs and severely increases the impact on the environment.

The Solution: The Sentinel SPS™ Battery Management System

The Sentinel SPS is designed to work in harmony with your current backup batteries and power systems (both 24V and 48V) to protect them from damage due to constant overcharge and its consequent heat, grid corrosion, gassing and active material degradation, WITHOUT the need for expensive cabinets and active refrigeration units. It is a game-changing approach to monitoring and maintaining lead-acid batteries that can drastically reduce downtime as well as the cost and frequency of onerous maintenance.

With 12-volt batteries, only the complete battery can be checked, not each individual cell. The inability to check a 12-volt battery on a cell-by-cell level can create a higher potential for future battery problems such as early failure due to under-performing cells. The Sentinel SPS works with existing batteries and rectifiers, so special investments or initial battery replacements are not required. Our dynamic load voltage testing and trending algorithm predicts remaining life in each cell more accurately than other methods, enabling better maintenance planning. Batteries that have failed are identified and isolated from charging so they don’t negatively affect stronger batteries in the bank. Battery status is delivered in real time via IP-based monitoring tools so that weaker batteries can be identified and replaced before they can fail unpredictably.

There are a number of advantages our remote monitoring platform has above and beyond simple DC plant battery monitoring:

Actual State-of-Health Measurement:  The Sentinel puts a micro-DC load on the batteries to determine true-state-of-health EVERY DAY by comparing the open-circuit (no-load) voltage vs. the loaded voltage.  A DC plant typically measures state-of-health through planned deep discharge cycles.  With a DC plant solution, batteries need to be discharged to 80% depth to get any real understanding of capacity.  They then need to be recharged following this activity, which can take up to 8 hours depending on battery configuration. Additionally, this test can only be done about twice a year without killing the batteries in the field.

Avoiding Temperature-controlled Float Charging: This is effective in theory but is poorly executed in the field.  Because the charger or plant is in a different location from the batteries, this methodology does not support longer battery life or better charging.  As an example: the DC plant cannot measure either ambient temperature or the battery temperature well enough to sense how to properly account for fluctuations in temperature.  For the DC plant to utilize this method properly, remote temperature sensors need to be deployed.  Additionally, utilizing this sort of method without truly understanding ambient and battery temperature greatly increases the risk of over/under-charging the batteries.  To account for this, the DC plant typically incorporates an equalization charge that DOES overcharge the batteries.  This equalization charge temporarily elevates the charging voltage of the entire battery string above the normal float voltage.  This lowers the electrolyte level of the batteries and permanently damages the cells. The Sentinel’s charging methodology only charges the batteries when needed.  This creates a much more simplistic but smart way to connect the batteries to the bus and reduces the risk of overcharging batteries in the field.

The Sentinel SPS delivers meaningful and measurable benefits in four strategically important areas:

Safety and Community Relations. The Sentinel SPS protects batteries from abuse, damage and potentially dangerous situations by maintaining them in an optimal, benign state. These are areas of substantial concern for communities, so mitigating them can enhance your reputation in the communities you serve.

Service Reliability and Availability. Using The Sentinel SPS’s remote monitoring software, plant engineers can get instant insight into the state of health of backup systems at all their locations from their desktop, which allows for better maintenance planning, fewer site visits, more reliable backup systems, and more confidence.

Environmental Stewardship. Lower battery temperatures and remote monitoring capabilities mean longer battery life, fewer replacements, less recycling, lower leakage and fire risk, fewer maintenance visits, less community disruption, and lower energy consumption. When spread over many locations, these benefits really have a positive impact on your carbon footprint and reputation.

Reduced Cost. The Sentinel™ is designed to have a reductive impact on many costs, particularly backup system capital and maintenance operating expenses. Fewer network outages, better insights into maintenance planning, lower energy bills—these add up to real savings across an entire network, and these savings can accrue directly to the bottom line.

Download the Encell Sentinel SPS™ Datasheet