Post by midland on Feb 5, 2020 19:16:01 GMT
I'm installing a new 20 A DC-DC charger in my slide-in camper. Since I have a 7-pin outlet at the truck's bumper already wired, I'm using that. (Note: up to now I've been using a simple & cheap buck/boost converter off of the 7-pin, but it doesn't have any regulation beyond putting out whatever I set it at, so I risk overcharging my house battery.)
I've verified that wiring is correct. The D+ sensor is in place. With the engine running and the charger off I get 14.4+ V at the charger input terminals, and ~1 A since there is no draw yet. (Since the camper is not mounted now I can only idle the engine, but it certainly puts out V and A into all the truck's accessories; turning on headlights keeps output above 14.4 V) As soon as I switch on power to the Charger the Input terminal drops to 2.5 V, and stays there. The green light on the Charger is on as if it's on standby, but there is not output.
I've also tried setting up the charger at the truck's engine bay and connecting input and output to batteries and engine ground, using my spare starter battery as a test output. (This battery's positive is switched off when the normal starting battery is on.) In this case the Charger seems to work - after waiting about 10 sec it turned on, the green light turned very bright, and went into float as measured by my MM, volts and amps. That's correct as my spare starter battery is fully charged already.
Next, I kept the previous setup except that I ran some longer Input wires back to the 7-pin outlet at the rear bumper. The charger also seemed to work in this case.
Finally, I put the charger back into the camper, where it sits in the rear at about 6 ft of wire from the 7-pin outlet at the bumper. It turned on and went immediately to 14.6 V and 10 A, a bit high since the house battery is almost fully charged. After about 30 seconds, however, the Charger turned off. I could not replicate this behavior. The Charger sits about 7 ft from the house battery where connecting wires are positive 8g, neg. 10g.
Questions:
0. Is this charger defective, or:
1. Do I have too long and/or too small wire runs from the engine to the charger? If so why did my engine-bay test work using the 7-pin, but the inside-the-camper test fail?
2. Is it not OK to use the truck's factory-installed 7-pin outlet (prob. 12g wires) with this charger? I can settle for reduced performance if it worked.
3. Even when I measure 14.4+ V at the charger Input terminals, there could still be too much resistance for the charger to work?
If answers 1-3 are yes, then I will have to install new, larger wiring from the engine back to the camper; but I'd like some opinions before I go the trouble and expense to do that.
Thanks,
Bob
I've verified that wiring is correct. The D+ sensor is in place. With the engine running and the charger off I get 14.4+ V at the charger input terminals, and ~1 A since there is no draw yet. (Since the camper is not mounted now I can only idle the engine, but it certainly puts out V and A into all the truck's accessories; turning on headlights keeps output above 14.4 V) As soon as I switch on power to the Charger the Input terminal drops to 2.5 V, and stays there. The green light on the Charger is on as if it's on standby, but there is not output.
I've also tried setting up the charger at the truck's engine bay and connecting input and output to batteries and engine ground, using my spare starter battery as a test output. (This battery's positive is switched off when the normal starting battery is on.) In this case the Charger seems to work - after waiting about 10 sec it turned on, the green light turned very bright, and went into float as measured by my MM, volts and amps. That's correct as my spare starter battery is fully charged already.
Next, I kept the previous setup except that I ran some longer Input wires back to the 7-pin outlet at the rear bumper. The charger also seemed to work in this case.
Finally, I put the charger back into the camper, where it sits in the rear at about 6 ft of wire from the 7-pin outlet at the bumper. It turned on and went immediately to 14.6 V and 10 A, a bit high since the house battery is almost fully charged. After about 30 seconds, however, the Charger turned off. I could not replicate this behavior. The Charger sits about 7 ft from the house battery where connecting wires are positive 8g, neg. 10g.
Questions:
0. Is this charger defective, or:
1. Do I have too long and/or too small wire runs from the engine to the charger? If so why did my engine-bay test work using the 7-pin, but the inside-the-camper test fail?
2. Is it not OK to use the truck's factory-installed 7-pin outlet (prob. 12g wires) with this charger? I can settle for reduced performance if it worked.
3. Even when I measure 14.4+ V at the charger Input terminals, there could still be too much resistance for the charger to work?
If answers 1-3 are yes, then I will have to install new, larger wiring from the engine back to the camper; but I'd like some opinions before I go the trouble and expense to do that.
Thanks,
Bob
