Redarc DC-DC Battery Charger
I’m in the process of installing a Redarc BCDC1225D battery charger in my truck camper. I got it installed enough yesterday to give it an initial test, and was pleased to see that with the truck idlin...
Forum Discussion
NRALIFR wrote:
The length of the circuit from the truck batteries to the Redarc charger is about 25 feet, and according to the wire sizing recommendation in the install guide, the 25 amp charger required 6 gauge wires minimum for that length, and the 40 amp charger required 4 gauge minimum. I wanted to over size the wires if possible, so I stuck with the 25 amp model. Plus, it was about $60 more for the 40 amp charger.
There are 2 issues related to current carrying capacity of a (copper) wire :
- Power lost to heating of the wire
- Voltage at the end of the wire
Both are related to the actual resistance of that given length of wire. We all know that long/undersized wire will loose more voltage, but this should not be an issue with a DC-DC charger. They are designed to accept lower input voltage (the spec on this model is 9V). The other issue is heating (which is where the voltage is lost to). If this is excessive the insulation will melt causing a short circuit.
The temperature rating for wire insulation varies quite a bit. 175F is pretty common and you can get wire rated at 220F for not much more. Some insulation is rated as high as 400F but it is expensive.
I think the manufacturer of your product is being overly cautious. If the distance is 25', you should double that (for the round trip). At 50' I would say the heating of an 8 gauge wire would NOT exceed the rating of "typical" insulation. Yes, it would be warm to the touch.
