Trouble hooking up battery.

[tommymsw]

First let me start by saying I have done my work and know how to hook up house batteries.
Second, let me say that I just have an old tiny RV. It is not much, but it is mine.

So I just bought it this winter and have been fixing it up. Now it is summer and I want to put a new house battery in. But I have no idea what wires go where.

I am not overly worried as I may blow a fuse or two figuring it out, but just wanted some experienced advice...

I am guessing that the 2 white and the red wire would connect to the POSITIVE terminal and the black wires that attach to the side and come down go to the NEGATIVE.

But there is ONE more black wire (lowest wire in the picture) that is not connected to the others. I am assuming it is STILL a negative, and that all 3 black wires are negative and the red and 2 white are positive. That would mean 3 negative and 3 positive.. so my math works out. 🙂

Maybe the red wire and the FREE black wire are the charging wires?

Does anybody think I am wrong?

[tommymsw]

OK! So I have some more news...

The lone red and black go to the LP sensor.

The 2 black wires that combine on the side PUSH 12v when I am plugged into shore. So the power box must be sending change to the battery. They push NOTHING when I unplug shore.

Then... If I start the RV (still unplugged from shore) and check the 2 black wires.. I get .5v but then it keeps going up slowly.. .51, .52, .53.. I waited until .81 and got bored of holding the meter. It took probably 45 seconds or so.

So... I can now hook up the wires with no threat of crossing them (thank you all again).

My guess now is that ONE black and ONE white are the CHARGE wires and the OTHER black and white power the converter from the battery when I am not plugged in. (Does that sound right?)

Or maybe, the one set of black/white both PUSH and PULL depending on the need, and the OTHER set go to the engine alternator.

[MrWizard]

when it comes to RVs
white for grd/negative has been the 'common' way of wiring since mfg first started putting in batteries

they had 110v house lights and fridge in trailers, before batteries and 12v were added on, when they started adding 12v items, like water pump and a few lights
they just used blk and white, made blk postive, because positive is 'considered' the hot wire, and made white neg/grd/common

its backwards verus 'cars'
but its 100yrs of 'standard' concerning trailers/RVs

[tommymsw]

Again... No way I can trace them. I would have to tear the entire floor out and the couch. For now, I will assume that the all the whites are ground and all the other colors are power. And just assume that the missing grounds are chassis.

I will assume nobody made the mistake of using opposite color wires.

That's the best I have to go with so far! 🙂

[wa8yxm]

When working on an RV I would NEVER make an assumption as to color of wire indicating anything... Many are wired by House electricians and they often get ;em backwards by Autotive/Electronics standards

THis is why I recommend paint, nail polish or colored tape/wire looms on all wires BEFORE you disconnect.

Wish I could be of more help but METER METER METER.

[mike-s]

MrWizard wrote:
As RJ has pointed out
It's possible one black is a negative
The loose one
The one going to thermal reset is most certainly a positive
The red is most likey positive
The factory whites are negative
That leaves the loose black as ?

That's the premise i would start with

Yep.

Black to breaker is +.
Whites are GND.

The thin red and black which are separate could be going to the "vehicle" side, and use the common (non-RV) DC convention of black ground and red +.

When it gets figured out, label them.

[MrWizard]

As RJ has pointed out
It's possible one black is a negative
The loose one
The one going to thermal reset is most certainly a positive
The red is most likey positive
The factory whites are negative
That leaves the loose black as ?

That's the premise i would start with

[RJsfishin]

In a house black is always hot.
In auto/RV, black is not ALWAYS pos/hot !!
If you have a red positive/hot wire, there is most likely a black negative wire completing that red circuit.
So, anytime you have a red and black in the same circuit, black is ALWAYS neg !

Anytime you are unsure, temporarly hold a fuse or CB between it, then it won't smoke.

[mvas]

tommymsw wrote:
First let me start by saying I have done my work and know how to hook up house batteries.
Second, let me say that I just have an old tiny RV. It is not much, but it is mine.

So I just bought it this winter and have been fixing it up. Now it is summer and I want to put a new house battery in. But I have no idea what wires go where.

I am not overly worried as I may blow a fuse or two figuring it out, but just wanted some experienced advice...

I am guessing that the 2 white and the red wire would connect to the POSITIVE terminal and the black wires that attach to the side and come down go to the NEGATIVE.

But there is ONE more black wire (lowest wire in the picture) that is not connected to the others. I am assuming it is STILL a negative, and that all 3 black wires are negative and the red and 2 white are positive. That would mean 3 negative and 3 positive.. so my math works out. 🙂

Maybe the red wire and the FREE black wire are the charging wires?

Does anybody think I am wrong?

ASSUME nothing.
You must trace each wire back to the source and then attach labels.
Then you will have facts.
You need to KNOW.

Can you follow any wires back to a Charge Controller?
What about frame ground?

I would be very worried about "blowing a fuse or two".
Reverse polarity may damage the device on the other end before the fuse blows - not a good idea.

[Fubeca]

It is very possible that negative wires from the system are using the frame for ground rather than wire all the way to the battery.

[tommymsw]

MrWizard wrote:
my best guess
with out being there and ringing it out with a meter

is red is positive both blacks are positive
and the white is negative

RED is NOT negative

forget automotive wiring, think house wiring
house or commercial wiring black and reds are always the HOT wire

That is how I am figuring it... But I am short TWO negative wires that way. I have then 4 positive (3 black and one red) and two negative (the two white wires).

Is it POSSIBLE that the negative from the converter that charges the battery and the negative from the alternator are BOTH connected to the chassis and then do NOT have the negatives going to the house battery? (That is my best guess so far)

[MrWizard]

my best guess
with out being there and ringing it out with a meter

is red is positive both blacks are positive
and the white is negative

RED is NOT negative

forget automotive wiring, think house wiring
house or commercial wiring black and reds are always the HOT wire

[beemerphile1]

Some only use one white/negative/ground wire and all other systems use the frame as a ground.

Sometimes though, a smaller white wire goes to the converter and a larger white wire goes to the frame/tongue near the battery.

[tommymsw]

Yea... I know the white is negative... I am an idiot and wasn't thinking. I just replaced the power system and connected the black wires to positive.

See? I thought the wires connected to the side were to GROUND it... Didn't realize it was a circuit breaker! 🙂 I now think the lone black cable is the charging wire. There was a lone black and white wire (not connected to one another) at the power box, so those have to be the charging wires.

But now I have an ODD number of wires.. 2 white negative and 3 black positive and a red wire I have ZERO idea about. There was no red wire at the box and I don't see the white "charging wire" in the battery box. Maybe somewhere it turns into the red wire?

You all have helped a LOT. I think I have most of it now. All I have left is just the red wire and where the white ground from the charging line went to.

If the alternator in the engine also charges the house battery (and it should right?)... I should also expect wires from the alternator coming to the house battery. Maybe THAT is the RED? But then I am missing TWO grounds! lol

I can find a LOT of stuff about how to connect the batteries, but nothing on how the internal wiring all works... Like from the house to the alternator and so on.

[Cameo_Phil]

Can you look at your battery posts? The battery posts should be marked with a + positive mark and a - negative mark. That should show you which wires are positive and which wires are negative. Once you determine this then mark the wires on each terminal so you will know where they go on the new battery.

You can use red tape for positive cables and black for negative cables.