12/03/2024
The Risks of Incorrectly Sized Cables in Offroad Dual Battery Systems
Dual battery systems have become a staple for many offroad enthusiasts and campers alike, providing reliable power for extended journeys and off grid camps. However, a concerning trend has emerged in a few fitment centers (NOT ALL), where incorrectly sized 12v DC cables are being used, potentially putting both vehicles and adventurers at risk. Simply because it cuts costs, saving the company money while the client pays the same rate. In the last 2 weeks I've personally seen 3 installations with problems directly related to cable sizing. Let's discuss:
1. The Importance of Correct Cable Sizing
When it comes to dual battery installations, the size of the 12v DC cable cannot be underestimated. Using undersized cables with a thinner diameter than required can lead to a myriad of issues, including increased voltage drop over distance. This is NOT always evident until a load is applied, this is why understanding basic electrical properties is key.
2. Understanding Voltage Drop
Voltage drop occurs when there is a reduction in voltage as electricity travels through a conductor, such as a wire. This phenomenon becomes more pronounced over longer distances and with smaller diameter cables. The result? Reduced efficiency and power loss. Now, consider the average cable run for a rear mounted dual battery system is up to 7m.
3. The Dangers of Voltage Drop in Dual Battery Systems.
In offroad environments, where vehicles are subjected to intense vibrations and harsh conditions, the effects of voltage drop can be exacerbated. One of the most concerning side effects is heat buildup in the wiring. As the resistance increases due to voltage drop, more current is required to maintain the same power output. This increased current flow generates heat, potentially leading to melted wires and, in the worst-case scenario, a fire hazard. Like I mentioned earlier, that 8mm² or 10mm² wire the installer used for your dual battery that has a Amp rating of >40A will show 14.4v DC on a multimeter UNTIL you apply a load to it. Resistance matters. So now you add a 30A DcDc charger, then wonder why the charger won't charge the battery? Or why your 4x4 burnt out? It's because one shortcut leads to a ripple effect of issues. I've fixed charging issues where the user has had a brand new DCDC charger fitted but it continuously switches off, installer can't identify the issue either. It's simply that most units have a "low voltage" cutoff, once the incoming voltage drops below a preset value it turns off. This is often increased with voltage drop on cable runs, coupled with the regular running requirements of your vehicle (AC/lights etc) and you're now trying to send MORE amps down an already undersized cable pushing temperature up higher which results in further voltage drop. And the spiral continues until failure.
4. Ensuring Safety and Reliability
To mitigate these risks, it's essential to use appropriately sized cables for dual battery installations, in my opinion I recommend 16mm² as the bare minimum for a 30A DCDC charger, 25mm² for a 50A. When in doubt consult with experienced professionals. Additionally, regular inspections and maintenance checks can help identify any potential issues before they escalate.
In conclusion, while dual battery systems offer numerous benefits for offroad enthusiasts, cutting corners on cable sizing is never worth the risk.
These are my opinions, they may not align with yours and that is alright.
See the picture attached. Which cable would you want in your setup?
