yet another silly battery question

[bearsden]

While towing my 2000 Coleman Masa pop-up with my 1996 Ford Explorer, the battery dosn't seam to be taking a charge.
   I have charged the 1 year old battery for 24 hours pryor to our trip (which takes us about 4 hours on the road) and the battery dosn't seem to be holding a full charge, or it's losing part of the charge it had when we left home. I would think it should be fully charged by time we get there.
   I do run the fridge on DC while we are driving but I dont think that's enough to draw the power down like that.
 
please let me know whats going on with this situation
 
thanks Dennis:banghead:

[AustinBoston]

Depending on a number of factors, the fridge can and often will drain as much as 50% of the useful life of the camper battery.

Battery charging is highly dependent on voltage drop.  The more voltage drop, the less charge.  It turns out that the difference between a fully charged battery and one that is less than 50% charged is only about 0.5 volts.  The way to reduce voltage drop is to reduce electrical resistance.

Here are the key factors (in no particular order):
1) Have good, clean connectors on both the pop-up and the tow vehicle.  A little corrosion on the terminals can significantly add to voltage drop.
2) Have a quality ground connection through the electrical connector.  Using the ball for this is neither adequate nor reliable.  The wires for this ground should be at least 8 gauge. (smaller numbers are bugger & heavier wires, so #6 is better than #8, and #10 is not adequate).
3) Have a quality charge line connected to both batteries that is fused or breakered at both ends (see safety note below).  This should be at least 8 gauge.
4) Use quality connectors at every junction (at the battery, at the ground points, etc.) and it's a good idea to solder them.
5) Consider running the fridge on propane when towing, at least if you are going to be dry camping (see safety note below).  The fridge draws 10-12 amps - up to 45% of the available charge current.  If the total current goes over 25 amps, the circuit breaker will trip, and the fridge will then get it's entire 10 amps from the battery, making things worse.  Some time later (20 seconds?) the breaker will reset, and end up tripping again - and again and again.

Safety notes:
A) My charge line has a 30 amp fuse at the tow vehicle battery, and a 25 amp self-resetting circuit breaker at the camper battery.  It is vital that this particular wire be fused/breakered at both ends.  If a short develops, it will draw current from any available source, and you have big batteries at either end, either one of which is capable of melting a wire or starting a fire.

B) Use reasonable caution when fueling if you tow with the fridge on propane.  There's plenty enough exciting stuff without seeing your story on the evening news.

Austin