Power Center problem

[Stereo]

I'm renovating an '80's circa slide-in, pop-top Skamper. With a lot of help from DWH, I've rewired the bus bar and other stuff. However, after having done all that, it doesn't appear the converter is working. The 12V items (lights, 12V accessory outlet, and water pump), only work when the battery is connected, i.e., when the power center switch is flipped to "Converter," rather than "Battery," the 12V stuff works IF the battery is connected but not when it isn't connected. The lights work off shore power or battery, being slightly brighter when running off shore power. Note that the 12V wiring for the lighting comes directly off the power center, whereas the other 12V stuff is connected through the bus bar that's connected to the converter by a wire adjacent to the 12V lighting and furnace power cables.

I'd appreciate help in figuring out how to identify the problem.

Here are photos of the original wiring mess, and the re-wired bus bar. From top to bottom, the wires from the bus bar go to the converter, a 12V water pump, and a 12V accessory outlet.


The front of the Power Center has a switch on the left side. Flipping the switch to the left is for shore power use and should engage the converter. Flipping it to the right is for battery power. Off is in the middle. There's a fuse on the left. On the right is a green indicator light that doesn't work (it appears to be physically broken) and a 120V outlet.


The back of the cover plate shows the wiring diagram for the power center.


Here are pictures of the 12V and 120V sides of the power center.


When I put a multimeter on the 12V terminals on the power center, it reads 12V only from the terminal on the far left which corresponds to the "converter" side of the switch. I get no reading on the middle terminal which connects to the fuse and corresponds to the off position of the switch, or the right-side terminal which corresponds to the "battery" side of the switch. I put in a new 30A fuse and still got no reading. There's no corrosion in evidence. Not surprisingly, when the battery's not connected, I get no reading off the bus bar. When it is connected to the battery, everything reads about 9V on both sides of the fuses and the bus bar.

And here's the back of the power center.
View attachment Power Center diagram.pdf

Could the problem just be a bad switch?

Thanks for any help you can give.

 

[dwh]

Okay, lemme see...

Starting on the 120v AC input side.

Looks like a black coming in and going to the gray wire nut, which then feeds into a 120v push-button breaker (above the 120v receptacle on the face plate).

The neutral (white) that goes with that incoming hot goes to a yellow wire nut. The bare goes to the ground bus bar.

Then, on the other side of the breaker, is one black feeding down to the receptacle, and another black that goes through the grommet in the dividing wall.

The incoming neutral goes to a yellow wire nut, then from there to the clear crimped on "hat" connector just next to the breaker. From the hat connector there is one neutral down to the receptacle, and another goes through the grommet in the dividing wall.


So, the original incoming connections TO the unit from shore power, are the black wire that is in the gray wire nut, and the white wire from the crimped on hat connector.


At some point (probably when the camper was built), someone tapped in to feed another 120v "something" (probably another receptacle). They piggy-backed that yellow wire onto the output side of the breaker. where it runs over to the yellow wire nut and connects to an outgoing black wire. When they did that, is also when they put all the neutrals under that one yellow wire nut. (Originally, there were probably two grey wire nuts - one to connect the incoming hot to the breaker, and one to connect the incoming neutral to the wire from the crimped hat connector.)


So, the 120v receptacle in the face plate of the unit and the black wire that feeds through the grommet - and the piggy-backed yellow - are all protected by that push-button 120v breaker.

Thus, if that breaker is tripped or non-functional, there will be no power to the face plate receptacle, or the 12v converter section - nor the other whatever it is that is fed by that yellow wire.

I see no problem with the 120v side of things - it all looks to be wired properly.


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Now, going to the other side of the dividing wall to the converter section, we see a black and white coming through the grommet. I can't see where the white goes, but the black obviously goes into a crimped on hat connector. I'll assume the white does as well.

Those are the 120v that feeds IN to the transformer in the converter section.

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Coming out of the transformer, we've got a blue that goes through a metal wall and feeds one side of the switch.

The other side of the switch is fed by a red wire which comes from the fuse block (and battery).

From the center of the switch, we've got an output that goes through the fuse holder and feeds the lights and furnace.

When the switch is one way, the lights and furnace (loads - center of switch) are connected to the fuse block / battery. When the switch is the other way, they are connected to the transformer. When the switch is centered, the lights and furnace are connected to nothing.

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Okay, so here's the problem...

Flip the switch one way and the output from the transformer (switch set to "converter") is connected to the lights and furnace. Flip the switch the other way, and the fuse block / battery is connected to the lights and furnace.

But at no time, is the output from the transformer connected to the fuse block / battery.

So that unit can draw 12v FROM the fuse block bus bar, through a fuse and can then connect that incoming 12v from the fuse block to the lights/furnace with the switch.

It can also draw 12v from the transformer and connect that to the lights/furnace with the switch.

BUT, the output from the transformer (converter) NEVER gets connected TO THE FUSE BLOCK / BATTERY! It only pulls from the fuse block, it does not push toward it. It sucks, but it doesn't blow! D'oh!

So the transformer will never power the loads connected to the fuse block - NOR will it charge the battery of course, since the battery is connected to the fuse block.

That unit was never designed to charge a battery at all.

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But maybe we can fix it.

What we want to accomplish, is to have the output from the transformer connected both to the lights and furnace as they are now, and ALSO connected to the fuse block / battery.

The simplest way to achieve that, would be to use a doohickey. Doohickeys rock - they are far superior to widgets and gizmos. We could use one that looks like this:

We could stick the doohickey on the center terminal of the switch, put the blue wire to the loads on the doohickey, then pull the red wire off the end of the switch and double it up on the doohickey with the outbound loads wire.

So we'd have the wire from the transformer feeding into the switch, and the output would go out the center as it does now - where it would feed the blue wire to the furnace/lights, and ALSO feed the red wire to the fuse block.

Thus ALL the loads - the fuse block as well as the lights/furnace will be fed continuously from the battery (though the lights/furnace would still go through the fuse on the front panel).

AND when the converter is powered up by shore power, it will supply up to 9a to the "12v system". If your running loads are less than 9a, then it will trickle some power to the battery until the battery reaches 12.5v.

If the switch were in the off or battery position, then the only result would be that the TRANSFORMER is no longer connected to the "12v system". The feed from the fuse block / battery to the lights/furnace would always be active.

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HOWEVER! That doohickey setup might be a VERY BAD IDEA!!

There might be an actual reason - other than blatant nincompoopery - why they built the unit the way they did. The only reason I can think of is that the transformer is not protected from backfeed from the battery.

It might be a very bad idea to connect that transformer to the battery...the battery might do something horrible to the transformer. If so, then they way they did it - with a switch so that the transformer and battery can never connect to each other - would be the correct solution.

And that's almost certainly why that switch is there...

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So now what?


Well...the "proper" way to wire that thing up, would be to connect the fuse block to the same place as the lights/furnace (output from center of switch through fuse to lights/furnace/fuse block) and then instead of running the battery to the fuse block, run it to the red wire off the switch.

Then, ALL the loads would be powered EITHER by the transformer, OR the battery, but "never the twain shall meet".


That would be proper - but the converter is JUST a "converter" it is not a "converter/charger". In that configuration...it will not charge the battery.

Which is was never designed to do in the first place.


But you can pick up a battery charger and feed it from the incoming shore power, so when connected to shore power you'll be running the loads (up to 9a) from the converter, and charging the battery.

But...

If you do that, then you don't need the antique converter anyway. Just connect the battery to the fuse block as you have it now, move the lights/furnace loads over to the fuse block, and then connect the battery charger to the battery.

Then, all the loads run from the battery all the time, but when you've got shore power to the battery charger, it will supply up to X amps (whatever size the charger is) to the "12v system".


That is what I'd do.*

I would also add a switch (simple SPST on-off switch) between the battery breaker and the fuse block. That way, I could just kill all the loads by flipping the switch, but still have the battery able to charge when there is shore power.

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(*Well...not really. What I'd actually do is try the doohickey hack first. IF that results in letting all the magic blue smoke out of the transformer - THEN I'd rip out the converter and go to the battery charger setup.

But of course, no one should never do what I would do. M'kay? <insert rapidly spoken legal mumbo-jumbo about liability and fire and hazardous to life and limb and why oh why didn't I take the RED pill>. I'm a lunatic, m'kay? Don't do what I do, m'kay?)

 

[Stereo]

Well...the "proper" way to wire that thing up, would be to connect the fuse block to the same place as the lights/furnace (output from center of switch through fuse to lights/furnace/fuse block) and then instead of running the battery to the fuse block, run it to the red wire off the switch.

YOU ARE A WONDERFUL TEACHER! Once again, a million thanks for not just answering my question, but teaching me how and why stuff works so I'm better equipped to solve problems on my own down the road.

Because I already purchased a charger after our discussions about the low output of the converter - when we didn't realize it wasn't even designed to charge the battery - I'm going to avoid the potential blue smoke for now (though I'm not averse to experimentation :sombrero. I think I'd like to power stuff directly through the transformer when tied to shore power 'cause I'm thinking that always running off the battery might shorten the battery's life. No?

P.S. I'm not sure that contraption on the 120V side is a push-button breaker 'cause I don't see any amperage rating on it. I think it's just an indicator light which is non-functional. The outlets all work.

 

[dwh]

YOU ARE A WONDERFUL TEACHER! Once again, a million thanks for not just answering my question, but teaching me how and why stuff works so I'm better equipped to solve problems on my own down the road.

Docendo discimus.

I think I'd like to power stuff directly through the transformer when tied to shore power 'cause I'm thinking that always running off the battery might shorten the battery's life. No?

Well...no.

Okay, first of all you get the idea of the bus bar. That bar is actually just a small part of the entire "12v bus" (what I referred to as the "12v system" in my previous post).

The "12v bus" is the system that moves 12v power around. Think of it like a manifold in a compressed air system. You can hook up various things to the manifold, such as an air storage tank (battery), a compressor (converter or charger) and some air tools (loads - lights, furnace, whatever).


So what happens when the compressor is running? It keeps the storage tank topped off, and also supplies air to the air tools. If you hook up enough air tools to draw more from the system (bus) than the compressor can supply, then the air tools will consume all that the compressor puts out, and will begin to draw down the reserves in the air tank.

Same thing happens on the 12v bus.

You can think of the voltage as PSI (pressure), and the amperage as CFM (flow rate).


So let's say you are hooked up to shore power, and you've got a 10a battery charger hooked up. The charger will "push" the bus voltage up to 12.6v (or whatever the charger's voltage is set at) and hold it there. It can hold that pressure up to 10 cfm (10a).

When loads are running, up to 10a can be supplied to the bus by the charger. If the loads are less than 10a, say 7a - then there will be 3a of extra available to flow toward the battery.

That will happen until the battery "pressure" (voltage) equalizes with the pressure of the rest of the system. I.e., if the charger is putting out 12.6v, then the battery will absorb power until it reaches 12.6v.

Now, if the loads total up to more than 10a (or whatever the charger is rated for) - let's say 13a - then the loads will consume the full 10a coming from the charger, and since the charger cannot hold the bus voltage up, the additional 3a will begin to flow from the battery to the bus...and from there to the loads.


If you don't have shore power, then it will be the battery supplying power to the bus, and when any loads pull power from the bus, power will flow from the battery to try and hold the bus voltage up.


So as long as there is shore power, and the loads are less than the charger's rated output, you aren't using the battery anyway - you are actually keeping it topped off by allowing the charger to push it up and hold it at the bus voltage.

If there is no shore power, then you are drawing the battery down.


So no... the battery doesn't wear out quicker by having the loads connected to it permanently. (Unless of course your loads are bigger than what the charger can supply.)


There actually is an advantage to the way you are talking about doing it...

If you have all the loads running off the transformer in the power center, and also have say a 10a battery charger. Then when the loads are running from the transformer, the full 10a of the charger is available to flow to the battery. So the battery will charge quicker.

The disadvantage is that the power center transformer cannot provide more than 9a to the loads - whereas the battery, with the #10 wire and 30a breaker could supply up to 30a to the loads.


In either case, you need to get all the loads together. If you use the power center, then you pretty much MUST feed the fuse block from the blue wire that feeds the lights/furnace.

Since that is fuse protected by the fuse holder mounted in the power center face plate, you should run from the 30a breaker to the red wire which feeds the battery input on the switch. But...if the red wire is less than #10, and the switch is rated at less than 30a...then you really should use a breaker sized to protect them.

If I were doing it, I would run a #10 from the battery, through the Bussman breaker directly to the battery input on the switch, and try to figure out what the switch rating is (probably around 15a), and then use a Bussman breaker sized to protect the switch (probably 15a).


(Though not really. I would try to feed the fuse block from the power center's transformer. If that worked, then I'd move the lights/furnace over to the fuse block. Then, with 9a from the transformer, and say 10a from the charger, I would have up to 19a supplied to the bus to run loads and charge the battery. Sweet.)

P.S. I'm not sure that contraption on the 120V side is a push-button breaker 'cause I don't see any amperage rating on it. I think it's just an indicator light which is non-functional. The outlets all work.

Could be, but I kinda doubt it. It wouldn't make much sense to feed all the 120v loads *through* the filament in a little incandescent lamp (electrician's call those things lamps - a "bulb" is the glass part that protects the filament in the lamp). If they did that, then the filament would be acting like a fuse.

 

[Stereo]

I would try to feed the fuse block from the power center's transformer. If that worked, then I'd move the lights/furnace over to the fuse block. Then, with 9a from the transformer, and say 10a from the charger, I would have up to 19a supplied to the bus to run loads and charge the battery.

Thank you for clarifying. In essence, the battery is just a conduit unless the load exceeds the 9A provided through the transformer, and if the battery's below 12.5V, it gets recharged as long as it's not needed to provide additional power. I'll give your set-up a try, fire extinguisher in hand :snorkel:. And I'll take the duhickey (most likely a push-button breaker) in to Saunders Electric and see if they've got a replacement.

Thank you again.