Beware of normal-looking battery cables!

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ZuniJayne

Well-known member
Joined
Mar 5, 2005
Posts
334
Location
near Albuquerque, NM
Greetings, gang!

I am sharing an experience I had with hooking up my new batteries so someone else might learn from it.

I got the two new T-105 6 volt golf cart batteries installed in the box on the trailer tongue.  Diligently cleaned off all the battery cable terminals and replaced one obviously bad connection.  Put all the cables back on the same way they were before.  Checked the Link 10 meter - no 12 volt power in the TT.

I spent the next hour checking all the wiring from the batteries back into the TT.  Nothing, zip, zilch, nada.  Then I realize that the trailer is plugged into shore power, and still no lights.  Converter problem?  I check it.  No power to it, but all fuses are fine.  I thought converters mine is an iIntellipower 50 amp) were supposed to convert???

THEN I notice that the fridge, which was set to run on AC, is off.  Yet when I check the outlet in back of the fridge, there is good AC.  Now I am REALLY confused and thinking I fried the fridge somehow.  Dollar signs fly past my eyes.

So I went back out to the batteries.  Each had a 6.4 volt reading, but when I read across both batteries, I did NOT get 12 volts.  How can that be, I ask, as the foot-long cable connecting the two was 4 gauge, professionally made with shrink tubing and everything.  It still looks new!

A dim bulb lit up over my head.  I removed the cable in question and checked its resistance.  0.00.  then I wiggled it and checked again.  BAD!  I checked at various places along the cable and saw that it was bad in some places but not others.  Since it was the only one I had at the time, I bent it to a shape where it had no resistance and put it back on the batteries.  VOILA!!!  I had 12v in the TT.  To my surprise (and joy), when I turned the fridge back on to AC, it ran fine. 

I'm still confused about that.  Why wouldn't the fridge NOT run on AC if there was no 12V?  It's a Dometic two-way.  Is it made this way, or do I have another electrical problem to check out?  Why would the converter NOT run 12v items in the TT if it was hooked to shore power?  I saw in another thread that Bryan had finally found a grounding problem.  Could this be a similar thing in my rig?

The moral of the story is:  just because a battery cable or wire LOOKS fine, don't assume it is.  ;D
 
Jayne,

Even on 120 the frig needs 12 volt for the controls.
Like many coaches our Windsor had a 12 volt discontect switch at the front door. It ran to a solenoid in the back. The solenoid failed and shut off the 12 volt power. We weren't living in the coach at the time but it was parked next to the house, fortunately Sheila though it was strange that she didn't hear the frig running at all one day. I bypassed the solenoid to restore power. I called Monaco and told them the them solenoid should be ON it a failed state not off. We could have lost a lot of food and worse had a very smelly frig!

Ken


 
 
I called Monaco and told them the them solenoid should be ON it a failed state not off. We could have lost a lot of food and worse had a very smelly frig!

Ken, that's why most manufacturers use mechanically latching solenoids.  When the pick coil fails, the solenoid stays in the last selected condition, on or off. (actually they do it so voltage drain is not required to hold them activated) 

However, a more common mode of failure, for solenoids, is with the internal contacts.  If the contacts won't make electrical connection, then it doesn't matter whether the coil works or not.  The failure would appear as the solenoid (switch) being "off".
 
aka Porky,

My solution, just by bypass the solenoid. I am going to do this on my new motorhome. I never use the disconnect switch at the door anyway.

ken
 
What ever works for you.  I might bypass a bad solenoid, but not before.
 
I have seen any number of battery cables fail in the fashion you describe.  I like to replace battery cables whenever I replace batteries, unless there is a great deal of labor involved or the cables are of unimpeachable quality and condition.

I am currently of the opinion that the copper solder-cup type and the field-crimped type (made up in a special multifinger hydraulic press -- the local tractor and implement dealer has one) are better than any of the factory ones.  I tend not to trust solder in high current applications but the solder cup style seem to have enough contact area that neither resistive heating nor mechanical strength are a problem.
 
Another power cable that fails and looks perfect is the standard black or white grounded cable that is used on monitors and desktop computers. In sixteen years as a user support analyst I remember finding four or five such bad power cables. It cam from the practice of not crawling under/behind desks and putting in the new cable when an older cpu was replaced. I found dozens of new power cables in plastic bags in storage where the hardware geeks that installed the new units kept their stuff. That was five  computers we didn't have to bench and test and bring back not to work.

Kind of like saving $1950 for a new furnace by putting in s$30 thermostat
 
Ah, Bob!  You had to go and mention furnace.  That is next on my list of fixits.  Blower runs but it won't ignite.  I have to take thw whole thing out just to bench test it. :'(  But that will be a different thread.  ;D
 
before you remove the furnace you better check your LP detector, if it has tripped the fan will run but no ignition.  just a thought,  bob
 
I like to see at least a #2 AWG battery cable between the 6 volt GC batteries - #4 cables may be marginal...I try to be persuasive about using a new cable, and if a customer balks, I throw it in as part of the sale - Zuni's right - get a new cable and make sure your existing cables in the RV are bright and clean before reattaching - then use some gooey terminal protectant to coat the terminals against any corrosion!

I make our cables using cadmium plated solid copper eyes and clamps, crimped onto the stranded copper battery cable with an industrial type swage-crimper - and then using heavy, color coded heat shrink tubing with hot melt glue inside (for positive sealing of the components)...
Ray
 
Ray,  thanks for the comments.  I know that the current "serial" cable between the two 6 volts battery is a 6 gauge.  I have some 4 gauge that will replace it until I can get some larger diameter stuff.
 
This is a 9 year old post.  You may get better results with a new post.

In response to your question, I suggest getting pictures BEFORE removing any wires, then take off the ones you need to replace and go to your favorite auto supply store.  Make sure the wire gauge is at least as large as you are replacing.
 
ZuniJayne said:
Ah, Bob!  You had to go and mention furnace.  That is next on my list of fixits.  Blower runs but it won't ignite.  I have to take thw whole thing out just to bench test it. :'(  But that will be a different thread.  ;D

You might just accidently have fixed the furnace already.

You see.. (Very short version) When the T-Stat calls for heat the blower starts up
When the blower blows hard enough a device called a "SAIL SWITCH" closes
Then Ignition (in theory) Happens.

IF the battery cable is not passing enough current the blower can't blow hard enough and the sail switch never sails (Closes) .
 
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