Adhesive problems for batteries
with polypropylene, flame-retardant plastics

The BACS module housing is made of flame retardant ABS plastic, the same material as the housings of most batteries on the market. The Velcro tape used to position the BACS module therefore uses an adhesive that is "safe" and does not pose any risk to the surface to which it is glued (no solvents that could possibly remove the plasticizer from plastics). The adhesive and Velcro combination that BACS uses as standard is the 3M Type 3550 with "DUAL LOCK"; it’s been used for more than 15 years on millions of battery cases worldwide.

The bonding process on ABS battery cases is simple: ensure sure that the battery bonding surface is clean and dry and that there are no remnants of silicones or other "gloss" coatings or acid residues, and if needed, "neutralizers" (e.g. NEUTRALON) can be used to clean the battery surface of acid residues. In the case of silicone, however, it becomes difficult. Since generally speaking a silicone remover ought not be used, only mechanical cleaning (eraser) is possible. With some porous battery case surfaces even this will not help - once contaminated with silicone, only the use of silicone glue can provide a firm hold for the BACS module.

But even if no silicone is found to complicate the bonding process, customers sometimes complain that the glue we use does not hold.

Because we here in Hamburg often do not know if the surface was cleaned during the gluing process or if the glue was not allowed to adequately dry, we have left the troubleshooting of such problems to the technician on site, who has found a solution in all cases.

However, since the introduction of the new halogen-free BACS measuring cables, there have been an increasing number of reports that the adhesive would not hold.

At first we thought that the cable's stiffness (mentioned elsewhere in this Newsletter!) resulted in a condition in which more pressure had been placed on the adhesive, causing it to peel off. But even after we’d made the cable more flexible, we continued to receive complaints about the adhesive strength, and so we investigated further:

It is not the stiffness of the halogen-free measuring cable that causes the modules to detach, but the plastic material used for the battery housings!

The adhesive supplied with the BACS modules is developed for ABS plastics, but also sticks to polypropylene and all other "smooth" surfaces – the key word being “smooth” because in such cases the natural adhesion force is added to the adhesive force. For this reason, our ABS Velcro tapes also adhere to the majority of Wetcells that are usually made of PP. Generally speaking Wetcell surfaces are transparent and therefore very smooth, which is sufficient for the ABS adhesive from BACS.

But polypropylene plastics for VRLA batteries often have a "rough" surface. With rough surfaces, less than half of the surface is available for adhesion force, which means that most of the bonding surface is "in the air". This is not enough to hold the BACS module in position, and adhesives so applied will eventually peel off because the air exchange causes the adhesive material to dry out. Even a replacement with new stickers - available as spare part  under the article name "BACS_STRIP5" will not solve the problem permanently:

For this very reason we’ve come up with a new solution:
For polypropylene (PP) battery cases, we now offer "BACS _STRIP6".

These Velcro strips are offered as a spare part (Per pack 20 pieces), already cut for BACS modules and compatible with the "Dual Lock" for ABS on the BACS module. The “BACS_STRIP6” battery adhesive side has much more adhesion on polypropylene surfaces. The combination of adhesive and Velcro also comes from the manufacturer 3M and has the article designation 3M3540.  

NEW
BACSSTRIP6 - Self-adhesive strips for BACS modules V3 on Polypropylene plastic battery housing. Velcro side „DUAL LOCK“ is compatible to BACSSTRIP5.

You will find the new BACS_STRIP6 with 3M3540 in the upcoming Price List 7/2023, available for order now under this article name.

Together with the new more flexible halogen-free measuring cables, the new adhesive of the BACS_STRIP6 3M3540 ensures a secure connection, even with porous PP housings, when used correctly.