May 7, 2016

Voltage Balancing

"Why is balancing voltage on each battery in the string important?"

"What can it do to help prolong my battery life and increase battery reliability?"

   In an ideal scenario each battery would be charged at the exact voltage that is recommended by the manufacturer. Charging a battery at a high voltage leads to gassing and therefore a shortened service life. Charging at a low voltage leads to sulfation and, again, early retirement for your battery. It is common knowledge that when batteries are put into strings it is nearly impossible to ensure that string charge voltage is divided exactly evenly, without the proper tool of course. A properly installed Generex BACS System on your batteries can evenly distribute charge voltage within a hundredth of a volt over each battery in a string. That means if your total charge voltage was 540 VDC over 40 batteries in a string each battery would read exactly 13.50. The first advantage of this is obvious. With all batteries evenly sharing charge voltage we can essentially eliminate gassing and sulfation of batteries while on a float charge therefore eliminating two of the most common reasons for premature failure in a battery.

"That means if your total charge voltage was 540 VDC over 40 batteries in a string each battery would read exactly 13.50."


Here is an example of typical variation in battery voltages before and after BACS has balanced the voltages. The batteries with the highest voltages are removed from the dry out region and the lowest batteries are brought to a proper charging voltage and removed from the sulfation region. Below is a screenshot of real data being analyzed in BACS Viewer.

Screenshot 2015-09-22 13.44.42

"How will I know if a battery has gone bad or is going to soon?"

"The BACS System will log the individual battery voltages during a discharge as well as time on discharge."

The Generex BACS System automatically logs individual battery voltage, impedance, and temperature for the life of the battery. This information can either be viewed live via a web-based interface built into the Generex Webmanager or it can be downloaded into the provided program BACS Viewer for trending analysis. In combination with historical data you will also be able to see battery voltages and current during any battery discharge that occurs in a automatically prepared report by the BACS Viewer software. Using both of these tools can make identifying a bad battery much easier. Critical Power Experts also offers professional data review and battery assessment. The best way to get an accurate measure of how your battery will perform during an outage is to complete a battery or UPS load bank. The BACS System will log the individual battery voltages during a discharge as well as time on discharge. From here the health of each battery as well as the string's overall voltage can be assessed. Please contact CPEX for more information on battery discharge testing.


Here are a couple doctored screenshots of real data captured by the BACS System during a discharge with an example line of what a bad battery might look like. On the left, an open cell. On the right a weak battery with reduced capacity. Below is a passing discharge graph and the automatically prepared report in BACS Viewer.

Discharge graph Lake Mary Verizon 4-7-14

"Can I replace a single bad battery in a string? What affect does this have on the other batteries?"

The other major advantage is the ability to replace a single battery in a string and know that the variation in charge levels will not lead to over/under charging of the other batteries in the string. In my opinion, this is the second best reason to balance the voltages of your individual batteries. When a battery in a string goes bad it is common practice.

When a battery in a string goes bad it is common practice to either replace the individual battery if the battery string is still relatively new OR replace every single battery in the string if the battery string is over 4 years old. When a single battery or multiple batteries are replaced in a string the charge differences in the new batteries and existing batteries can cause major voltage variation problems. This immediately causes both dry out and sulfation issues on all of the batteries. You've gone from a bad situation with one or a few batteries to a worse situation with ALL of your batteries. This is why it is customary to replace the entire string. With the Generex BACS System a single battery can be replaced in a string without the worry of setting off a chain reaction that will damage all of the other batteries in the string. The existing batteries and new battery voltages will all be match by the BACS System. Below is an example of real data collected when 4 completely discharged batteries were placed in a string of fully charged batteries.

Please note, this is NOT the intended use for the BACS System, simply a test.

slow charge

The BACS System is gradually allowing additional charging current the 4 dead batteries while limiting charging current to the other 36 batteries. This is how the BACS System can accommodate a new battery(s) into a string, on a much smaller scale of course.

"How can the BACS System accomplish voltage balancing with such precision over battery strings up to and over 240 batteries?"

The BACS System utilizes a complex algorithm that has been developed and tested over many years. Using collected data from test installations on many different platforms to finely tune this process has resulted in a process that appears to work magically. The truth is very small and precise adjustments to each individual BACS Module can harmonize an entire string of batteries.

Below is a short 25 slide presentation for a more in-depth look at how Generex BACS System is able to accomplish what others can't.