BACS - The safest Battery Management System on the market has gotten even safer

12 April 2021

NEW: Halogen-free materials standard for all BACS cables

A recent major fire in Europe's largest data center has dramatically illustrated the vital importance of a secure power supply: at the French cloud provider OVH over 10,000 servers were destroyed, some with complete data loss. Efforts at investigating the precise cause of the fire are still ongoing, but there are increasingly signs that the cause of the fire was the UPS systems implemented on-site, and their batteries.

Subsequent to these signs is the sobering realization that the provision of monitoring services to the power supply systems within high availability applications is not sufficient if there is not also a system in place which can automatically initiate adequate countermeasures in the event of a fire:

Simple monitoring—and nothing else—of the UPS and batteries is not sufficient; it is imperative that an automation of these systems be introduced which counteracts in the event of a fire hazard without the user having to intervene.

Customers ought therefore not simply trust the monitoring measures as apply to a given UPS, but also as apply to the batteries themselves. When conditions deteriorate to the point that a UPS “notices” that its batteries have begun to overheat, the critical period for counteractive measures has already elapsed. Especially in the case of critical applications, it is imperative that the batteries also be actively monitored; better yet, there must be automated counter-reactive measures provided in order to actively prevent the escalation of fire at its source. This very approach has been followed in US-based datacenters for years and has led to the subsequent development of UPS-specific “US Fire Codes”, which instruct that given UPS batteries be automatically disconnected from the rest of the system in the event of overheating in order to prevent such escalation. In Europe such measures have not yet become the norm owing to the relative rarity of such devastating fire events; as such, adequate BMS implementations are currently more the exception than the rule. Following the recent events in France this situation will likely be forced into change, and certainly the rise of lithium batteries in such critical applications will further lead to similar industry regulatory requirements as concerns the management of such battery arrays.

In any case, investment in a battery management system complete with automatic battery disconnection functionality is an important feature of any safe power supply.

A simplistic BMS lacking such functionality is insufficient for critical applications; what use is it to the user if, following the occurrence of a fire, it is explained to them that the fire might have been "recognized" earlier through use of a BMS? In the event of a fire, many providers of competing BMS systems fall back upon a version of the following statement: “... the BMS was purchased to provide warning before a fire breaks out. If the BMS had also been used for consistently active monitoring, then it would not have burned ... "

This type of response  is unsatisfactory for the end customer because it not only succinctly deflects responsibility and subliminally conceals the inferior BMS’s lack of safety-relevant functions, but also because it argues a point ignorant to the operational reality—in the field, BMS systems are rarely “actively” observed. In practice, only automatically generated alarm messages are given the attention necessary. When it comes to thermal alarms, there is usually very little time available to effectively prevent a fire.

If one delves still deeper into the matter they will find that indeed the monitoring of a given battery is in and of itself not sufficient, as the BMS inevitably has to be physically connected to the batteries in order to integrate the electrical components of the BMS into the battery system. In the event of defective components and short circuits, the BMS itself can become a hazard if it is not immediately disconnected from the electrical circuit. GENEREX has recognized and solved this problem; unlike our BACS, the competitors’ battery monitoring systems do not use high-voltage fuses to carry out this vital disconnection in an emergency, but rather utilize a cheaper, direct-cable connection to the battery for their products. They offset the implied risk incurred by such lack of preventative care by labelling the risk potential as a "fundamental residual risk". However, it is precisely this fuse—a part of GENEREX’s BMS, and no other! —that is critical in the event of a fault, as lacking this feature, the affected BMS modules cannot separate themselves from the afflicted battery. As a consequence, the BMS module can overheat first and subsequently endanger the battery itself with a short circuit. The electrical fault can thus continue to build up until the fault current discharges in an arc, which ultimately triggers the actual fire. It is not for nothing that professional fire investigators very often find the electronics in the battery room as a trigger for fires. The prevention of fault currents through the use of high-voltage fuses, such as those used by BACS, is an important safety feature that ought not be missing in any BMS!

Each BACS measuring cable has 2 high-voltage fuses built directly into the cable structure, protected by fleece and welded far enough away from any given electronic component to prevent an electric arc - which can occur with high currents and voltages. Because of these fuses, each BACS module is effectively self-isolating in case of a short circuit or electrical fault on the battery to which it is assigned. In case of such a fault, any electrical surge which would otherwise reach the module and potentially cause a catastrophic event instead shorts the fuse, thus cutting the affected module off from the rest of the array. BACS senses this event and alerts the system engineer accordingly.

This unique BACS solution is very complex and costly, but our implementation of such technology has resulted in BACS becoming a total nonfactor as a potential source or amplifier of fire within the battery room!

The competition shies away from such an effort because the installation of a high-voltage fuse is very expensive and every single measuring cable has to be specifically calibrated in order not to falsify the internal resistance measurement by integration of the fuse. An enormous effort, indeed - but with the result that BACS is the safest BMS in the industry and is therefore accepted by all safety-critical users; in fact, in many cases (airports) our BACS has become a mandatory inclusion!

That BACS remains the only provider on the market in which 2 x 1000 V-Fuses are included within each individual measuring cable is a troubling fact. The argument given by the competition that halogen-free cables and fire-retardant materials alone make a fire less likely and thus less dangerous is itself a sign of troubling dereliction of responsibility, and is in no way a complete solution.

Halogen-free Cables: 

In the event of a fire, halogens contained within electrical components pose a safety risk as they form highly toxic gases when released into the atmosphere as a result of ignition. For this reason, many BMS tenders insist on the provision of halogen-free cables in order to exclude the development of such gases from the outset in the event of a fire.

The use of expensive halogen-free cables would actually not be necessary with BACS, since, as discussed above, a correctly installed BACS can precisely prevent the fire from occurring. However, since many end customers have had negative fire experiences with other BMS, "halogen-free cables" are repeatedly called for in many tenders.

We have therefore reacted accordingly, and now offer ALL BACS bus and measurement cables in exclusively halogen-free versions!

With the standardization of halogen-free measuring and data cables, GENEREX has once again raised the bar for the physical operational safety of BMS systems and, with BACS, are now delivering the safest battery management system on the market for stationary applications.