DC circuitry in an RV

[noplace2]

OK, I know I'm a rube. Cut me some slack. 🙂

To the battery, ya' got your white wire and your black wire. If my logic is correct, as opposed to AC, the white wire connects to positive and the black wire to neg. So far so good?

My further problem is that yesterday morning, in the midst of a thunderstorm, shore power was lost. That's when I discovered that I have no DC. I have 2 batteries that I maintain regularly, but only one connected to the rig at a time. They measure respectively 12.84 and 13.11 DCV. I connected both in turn. Zip, zero, zilch coming in. And yes, I pulled every single fuse and cycled every breaker. Continuity checks out across the board. With AC connected, everything works.

What am I missing? Thanks in advance for any help

[noplace2]

wa8yxm wrote:
I have seen that described as Ring terminals

Now why didn't I think of that?

That description shall ever reign in the future. Thanks.

[wa8yxm]

I see several re-posts of possible issues after the O/P said it was fixed.

And to the O/P.. Terminal or Lug or Connector all fit the description of what you described

Terminal is usually used to describe the battery post but to be honest it is anything that is at the end of something (End of the plates on teh battery, or in this case end of a wire)

I have seen that described (on a box of them in my spares cabinet) as {size} Ring terminals, also as lugs.

They are also described as connectors since they connect.

Several terms. all apply equally.

[RoyB]

Now that was easy huh!!!! Always easy after you spot the problem... Give the $200 service charge to a homeless person...

Glad you got it fixed up...

Just keep in mind both the battery and the shore power setup fed the same point on the 12VDC Distribution Panel. With Shore Power not connected you very first test is turn on the trailer ceiling lights and they should light up telling you all of the in-line fuses including the REVERSE POLARITY fuses and all battery connections are good between you battery and the 12VDC Power Distribution Panel where all of you 12VDC fuses are located.

If you don't have you ceiling lights burning then you have a bad connections of some sort or the battery is dead. We always just read the battery DC VOLATGE at the terminals 12.6-7VDC for fully charged battery and when we connect up to shore power this reading will jump to 13.6VDC telling me that on board converter is working.

Glad you back up and running now...

Roy Ken

[ken_burke]

opnspaces wrote:
Don't call the professional yet. Since you have a meter do a few things. They're all easy and quick so what have you got to lose? 🙂

Disconnect shore power.

Check across your battery for battery voltage (write the voltage down). If you have voltage then continue.

Grab your negative battery cable right at the post. BTW it should be white :). Using your hand follow the wire until it goes to the frame. If the wire on the negative terminal does not go to the frame you're hooked up incorrectly. Find the wire that does go to the frame and put it on the negative terminal.

Any wire that does not go to the frame is probably positive. Follow each wire until it goes into the trailer. If there are any bumps or rectangles in the wires you have probably found a circuit breaker.


Check for battery current from each post of the circuit breaker (CB) to the negative battery post. If you don't have voltage on each side, the breaker is tripped or bad. Anything less than battery voltage on either side is bad. Check for a small reset button on the side of the breaker.



If you find a fuse careful inspection will reveal that there are two holes on the back of the fuse, one on each side of the amperage rating. (silver dots on either side of the 10 in the picture below).


These holes allow you to probe the fuse for voltage without disconnecting it from the holder. As with the CB above check for current from each hole in the fuse to the negative post of the battery. Anything less than battery voltage on either side is bad (either fuse or holder).


If everything checks out fine then temporarily plug into shore power. Now go into the trailer with your meter and find a good ground. You're looking for a place in the fuse panel where you can put your positive meter probe into the back of a working fuse and touch the black (negative) probe to ground. If you get 13+ volts you have found a good ground.

Okay now go unplug the shore power cord and go back into the trailer and check each reverse polarity fuse (green 40 amp fuses) to ground. Check both holes on the fuse to ground. You should get battery voltage on each hole on the fuse to ground. If your battery is connected you will get battery voltage on at least one of the two holes in each 40A fuse. If you get voltage on only one of the two holes then your fuse is bad.

If you get no voltage at the green 40A fuses take a digital picture of your fuse box. Look at the picture and make sure you can see where every fuse goes.

Go verify that you are not connected to shore power.

Now pull all the fuses out and remove the panel that covers the wiring behind the fuses.

Look for a thick black and white wire near the fuses and connected to the circuit board that the fuses are plugged into. You will probably see markings on the board for + or POS and - or NEG. Use your meter to verify that you have battery voltage. these are the wires coming from the battery.

If you do not get voltage there is a problem with the connection to the battery. At this point you'll probably either want to call in a professional or go check at the battery one more time.

thanks . . . . good info

[noplace2]

opnspaces wrote:
Can I ask what terminal was corroded?

Terminal may be the wrong term. It was the round connector at the end of the ground cable held to the battery with a wing nut.

[opnspaces]

Glad it worked out and a big thank you for coming back to report the outcome to us all.

Can I ask what terminal was corroded? Was it a battery post, a circuit breaker, or a fuse?
Thanks

[noplace2]

Problem solved. Corroded terminal. Thanks to all.

[wa8yxm]

noplace2 wrote:

Dutch_12078 wrote:
Does your RV have a battery disconnect switch?

Not to my knowledge.

Your profile does not mention your RV's make and model or class
Motor homes: Nearly always (As far as I know always) have a battery disconnect sytem

Larger trailers.. Likewise
Some small trailers... Might or might not

(What is small.. A PUP or perhaps a 13' Scamp)

But odds are you have a battery shut off

ONE common location is just inside the door, may be marked ON/OFF may say AUX battery, may be marked USE/STORE (mine is)

May be on dash in a motor home

Ive seen them on a panel near the overhead cabinets, and in other places.

And not being an RV service tech.. I've not been in that many RV's but Ive seen the switches scattered.. USUALLY there are other switches (Like tank monitors and such) nearby if they are not at the door (like mine) or on dash.

[noplace2]

westend wrote:
Since there is a doubt as to main battery cable phasing, use your meter with continuity to frame from both cables. One should have continuity, one not.

As I tried to 'splain to you Lucy, I'm a rube! What you just wrote makes only a slight bit of sense but I get the gist and believe that I have correctly connected the battery(s).

Thanks for your help.

[westend]

Since there is a doubt as to main battery cable phasing, use your meter with continuity to frame from both cables. One should have continuity, one not. Mark the (+) phase cable with red tape, nail polish, or a marker. That is my color schedule and if I ever have to work on your rig, I'll know right away. :B

As was posted, you should have a circuit protector within a few feet of the batteries, either a circuit breaker or a fuse. The RV mfgs. like to hide these on the frame or inside a box.

if the protector faults when powered, check all your DC wiring and think if you have recently used a DC device. Disconnect it for testing. With two good batteries, the main problem should be easy to find.

Good luck in the morning.

[noplace2]

opnspaces wrote:
Don't call the professional yet. Since you have a meter do a few things. They're all easy and quick so what have you got to lose? 🙂

Thanks Matt, for your detailed and extensive advice. It is appreciated and will be followed through with in the morning.

.\\ark

[noplace2]

pianotuna wrote:
Hi,

Follow the positive cable from the battery. It will have some form of protection whether it be an in line fuse or a circuit breaker.

Thanks for the responses. It's 0 dark 30 here. I'll investigate further when it become 0 light 30.

[noplace2]

Dutch_12078 wrote:
Does your RV have a battery disconnect switch?

Not to my knowledge.

[opnspaces]

Don't call the professional yet. Since you have a meter do a few things. They're all easy and quick so what have you got to lose? 🙂

Disconnect shore power.

Check across your battery for battery voltage (write the voltage down). If you have voltage then continue.

Grab your negative battery cable right at the post. BTW it should be white :). Using your hand follow the wire until it goes to the frame. If the wire on the negative terminal does not go to the frame you're hooked up incorrectly. Find the wire that does go to the frame and put it on the negative terminal.

Any wire that does not go to the frame is probably positive. Follow each wire until it goes into the trailer. If there are any bumps or rectangles in the wires you have probably found a circuit breaker.


Check for battery current from each post of the circuit breaker (CB) to the negative battery post. If you don't have voltage on each side, the breaker is tripped or bad. Anything less than battery voltage on either side is bad. Check for a small reset button on the side of the breaker.



If you find a fuse careful inspection will reveal that there are two holes on the back of the fuse, one on each side of the amperage rating. (silver dots on either side of the 10 in the picture below).


These holes allow you to probe the fuse for voltage without disconnecting it from the holder. As with the CB above check for current from each hole in the fuse to the negative post of the battery. Anything less than battery voltage on either side is bad (either fuse or holder).


If everything checks out fine then temporarily plug into shore power. Now go into the trailer with your meter and find a good ground. You're looking for a place in the fuse panel where you can put your positive meter probe into the back of a working fuse and touch the black (negative) probe to ground. If you get 13+ volts you have found a good ground.

Okay now go unplug the shore power cord and go back into the trailer and check each reverse polarity fuse (green 40 amp fuses) to ground. Check both holes on the fuse to ground. You should get battery voltage on each hole on the fuse to ground. If your battery is connected you will get battery voltage on at least one of the two holes in each 40A fuse. If you get voltage on only one of the two holes then your fuse is bad.

If you get no voltage at the green 40A fuses take a digital picture of your fuse box. Look at the picture and make sure you can see where every fuse goes.

Go verify that you are not connected to shore power.

Now pull all the fuses out and remove the panel that covers the wiring behind the fuses.

Look for a thick black and white wire near the fuses and connected to the circuit board that the fuses are plugged into. You will probably see markings on the board for + or POS and - or NEG. Use your meter to verify that you have battery voltage. these are the wires coming from the battery.

If you do not get voltage there is a problem with the connection to the battery. At this point you'll probably either want to call in a professional or go check at the battery one more time.