Monitoring the UPS batteries must be independent from controlling

Safety above all, what about Batscan – the battery monitoring system? Batscan does not control the battery, the charger or the load. This is not a limitation, it is an essential requirement for a true monitoring system, that by definition it should be allowed to observe only, without any means of influencing the result. Any technical system can fail, and most do – sooner or later. When this happens with a device that controls the battery, an independent monitoring system will prove its value.

Of all the requirements that can be placed on a battery monitoring system, the requirement for this protective resistance should be the foremost. This is far more important than the rest of the system working. After all, monitoring the batteries is a secondary function that should not be able to jeopardize the plant’s primary function or safety.

So the main requirement for a battery monitoring system is that it must be completely safe both for people who can come into contact with any part of the measuring system (touch safe) and for the system itself, ie short-circuit safe without heat generation or risk of spark formation and thereby risk of explosion. Batscan meets these requirements by making all connections to the battery via high-ohmic resistors that limit any short-circuit current to less than 1mA.

There are many additional reasons why protective resistors must be used.
Rules and good engineering practice state that all power lines must be dimensioned so that they can withstand the maximum short-circuit current of the power source.
The environment in a battery room is corrosive, this affects the metal in the measuring cable, who knows what the measuring cable looks like after 10 years?
It is unreasonable to assume that the system would be ’locked’ forever. It should never be life-threatening to touch any part of the measuring system.
There is always a risk that a measuring line will come into contact with a coupling plate with a different potential at some point during the life of the system. With the protection resistor, it is completely harmless. Without the resistance, there will be a short circuit and the wire will burn up, the result may be an explosion or the automatic fire protection tripping.

All batteries comprise a number of interconnected cells. The battery voltage increases with the number of cells that are connected in series, but the number of cells in series also increases two risk factors:

• High voltage implies increased risk for personal injury and flash-over that can cause explosion or other damage to the battery.
• Large cell count increases the risk for an open-cell condition and thereby power failure.

The only possibility to detect a fault in the battery before it can cause a power outage is by continuously monitoring each battery cell (or group of cells). However, this must be done without introducing any additional risk factors.

Batscan measures all channels simultaneously at short intervals, which means that we do not have to do long discharge tests to get data that is sufficient to analyze all cells / blocks in the battery, even short power outages and the battery tests that the UPS itself does every month are enough for Batscan to find fault.

As one of the largest UPS manufacturers writes: “A good battery maintenance program will serve as a valuable aid in maximizing battery life, preventing avoidable failures, and reducing premature replacement.”*¹

*¹https://www.eaton.com/content/dam/eaton/markets/data-center/Not-so-shocking-truths-about-UPS-safety.pdf