An undersized cable gauge is the most common cause of overheating and voltage drop on a parallel battery installation. Here is what to know before choosing.
Why cable gauge matters
The higher the current flowing through a cable, the larger the copper cross-section needed to carry it without excessive heating or a significant voltage drop. On a battery-to-battery link, current can spike during charge/discharge peaks, which makes cable sizing just as important as connector quality.
Sizing reference points
- 25mm² (roughly AWG 3-4): the standard gauge used on our parallel cables for the majority of residential lithium battery installations, in class 6 (extra-flexible) tinned copper to ease routing in tight spaces.
- Communication cables (RJ45): different logic - these carry a data signal, not power, so their build quality is about shielding and contact reliability rather than gauge.
- High-power installations or many parallel modules: in this case, check the battery manufacturer's maximum current rating rather than relying on a general rule of thumb.
If you are unsure about the right sizing for your installation (number of modules, maximum current), contact our support team before ordering, or use our custom cable configurator.
Length and gauge: a trade-off
For a given copper gauge, the longer the cable, the greater the voltage drop. For installations where batteries are placed apart (motorhome, boat, separate technical room), it is worth checking the length you actually need rather than always picking "longer just in case": measure the distance between connection points and add about 20% margin for routing curves.
