drsteve wrote:
RoyB wrote:
What do you do when the battery gets hit with your 14 PLUS VDC and wants to draw around 20AMPS of DC current. There may not be that much DC current available in your 7-way connector wiring.
I wondered that myself.
To the OP, have you used it yet to see how well it charges your batteries?
Short driveway testing only so far. In 40%F weather.
My initial testing showed 20+ Amps to my pair of Group 24 Marine batteries when I dropped them to about 75% SOC. In fact, they were cranking too much current when they were both running in parallel and I set the output voltage high (14.8V) and blew a fuse in my truck. I need to lower the voltage output to reduce the current draw on the truck.
The little voltage boosters are designed for laptop power supplies that can plug into 12V cigar lighter outlets in cars. They are designed as constant voltage output (variable voltage). With no apparent limit to the current. They will burn out quickly if allowed to pass lots of current - thus the fan to cool them in the summertime. Max power is 150W per device.
Other things to do for testing/refining/playing:
1. reduce output voltage to reduce current draw from truck 7-pin. I'll probably try 13.6V when camping to see how that goes.
2. bring lots of fuses for the truck so I can have fun experimenting with this when camping :-)
3. hook up jumber cables from truck alternator to input side of these converters eliminating the 7-pin from the circuit. Then I have to worry about letting the smoke out of these voltage boosters with too much current / power.
rough power estimates below:
150W x 2 voltage boosters = 300 Watts max power before component failure and smoke let out. When current is flowing, the 7-pin will have reduced voltage due to the high current.
Output (charging side): 300W/14V = 21.4Amps
If Input side (7-pin) is @12V: 300W/12V = 25 Amps
If Input side (7-pin) is @11V: 300W/11V = 27.2 Amps
If Input side (jumper cables) @13V, 300W/13V = 23.1 Amp
EDIT: I did the testing a month or two ago. And actually, now that I think about it, the truck fuse would blow only when I had both voltage boosters operating. With only one wired in I would get half the amps and it wouldn't blow the truck fuse. And what is disturbing is I just found this:
Dodge Trailer Battery Charging Wirewhere someone states Dodge uses 14 gauge wiring for the trailer battery charge wire! While Ford and Chevy use 10 gauge. 15 Amp max on 14 gauge wire.
It looks like I'll use jumper cables to power this thing or use just a single booster and drop the voltage to keep the current under 15 Amps from the 7-pin.
Ed
