Prevent Issues With BMPRO BatteryPlus35
BatteryPlus35 is a battery management system designed to support transition of caravans to lithium batteries.
Question: We recently sent a BMPRO BP35 35 unit back to your team under warranty as it appeared damaged — the +Ve terminal on the battery connection looked sort of rusted out, but apparently it was damaged on the inside. I didn’t really understand the issue as explained. Can you please look up my repair ticket and clarify? (from Raphael Moreau)
Answer (David Bayliss): Hi Raphael. We have looked up the ticket created when you sent your unit back, and I’m very happy to explain further so that yourself and others can prevent this issue from happening in the future. The very basic version is that you had a loose connection on the positive terminal of the BP35 unit where it wires down to the battery. This loose connection caused an electrical condition of higher resistance. The rust colour you describe is the oxidation process that occurs during an electrical brownout due to poor connection. Heat has drawn up inside the unit from this poor connection point and caused damage inside to other components.
When an electrical connection becomes loose, the load that is connected — the battery, in this case —is still drawing power from the source provided. However, the poor connection causes an increased resistance, and the power that is drawn through this point arcs from one surface to the other (in your scenario, from the wire to the screw terminal or the spade connector). This arcing creates heat, which is our worst enemy in these situations. Over time with continual vibration as the connection is broken and remade multiple times, the heat continues to build up, gradually melting the wire, the connector, and/or the insulation. It depends on the amount of current being drawn through this connection and the severity of the loose connection as to how quickly or severe this process will actually be.
As the heat builds up and the wires and insulation around begin to disintegrate, this causes the heat to look for other avenues in which to dissipate and spread. In the most severe cases, this could be in the form of creating a combustion event or further damage to other electrical componentry in the path. Heat also increases the oxidation on the metal surfaces, and this in turn increases the resistance between the wire and the terminal, making it worse.
There are many things which you can check to ensure you have high functioning electrical connections. Firstly, a simple tug test will ensure that your connections are properly secured to the terminal to which they're being attached. Turn off all sources of known power (solar, A/C vehicle AUX) and remove all jewellery, watches, and so on to prevent electrical shorting, then use your thumb and forefinger gently pull the wires from their connected point to ensure a stable connection. There is no need to yank the wires as this does not replicate the real-world scenario — we are merely trying to replicate vibration during normal use of the RV. If you find a wire that is relatively easily removed from its connection, you should immediately resecure it properly.
Secondly, if you are using screw terminals, ensure that the wire wrapped around the screw is secured in a clockwise manner. This will be the same direction as tightening the screw and will therefore prevent inadvertent loosening.
Third, check that the insulation leading into the connection does not have excessive bare wire exposed, which could cause a short. Also check that the insulation outside the wire is not impeding the connection.
Overall, at BMPRO we would recommend as part of the general maintenance of your caravan that you would regularly check the terminal connections between the various components of your system. Just as you check your driving lights or your coupling, it is very important from a safety perspective to check these electrical connections — not only to ensure you and your family's safety, but also to ensure the integrity of your system. Most systems are installed by highly qualified 12V electrical experts, but after you have taken several trips, the road conditions and general use can have an impact on your system. So, regular checking is advisable.