Electrical Question: Auto Switch Converter

[lespnd]

I wired my trailer up with a new converter/charger. This unit comes with an external module that switches from shore 110V to generator automatically. However, My question is, can I plug inverted 110V into the same circuit as generator? Obviously as along as they both aren't connected at the same time. Right now the Converter is only powering the 12V circuit while on battery. I would like 110V powered as well. Here is a rough drawing of my proposal. Is this possible? Thanks for your input.

[Thomas G.]

I don't see why not, unless you are powering some devices that don't like the output of the inverter (I'm assuming modified sine wave output).

[lespnd]

Hi Tom

I agree, sine wave issue aside, its a logical connection, just don't know about the charge return circuit and how that is affected. I was thinking of just making this connection in those rare moments when I need 110V for a short period while boon docking with no tug. I have a single 12V marine battery 120 AH. Wouldn't be able to run a large draw for very long but I think it would work in a pinch.

[Thomas G.]

Originally Posted by lespnd

Hi Tom

I agree, sine wave issue aside, its a logical connection, just don't know about the charge return circuit and how that is affected. I was thinking of just making this connection in those rare moments when I need 110V for a short period while boon docking with no tug. I have a single 12V marine battery 120 AH. Wouldn't be able to run a large draw for very long but I think it would work in a pinch.

Gotcha - the battery would be trying to recharge itself via the inverter. I guess you could add an additional 110v Normally Open relay between the charger and the battery. That way when you had shore power, the relay would close and allow the charger to power the battery and when you had no shore power the relay would open.

[dylanear]

I've thought about this, I think you'll want to somehow cut off the AC to DC portion of your box, you don't want to go DC from your battery to the inverter, then AC from the inverter to your converter which will then send DC back to the battery etc. A loop. Sounds bad to me.

I have no experience with this, but I'm planning my solar system and while I'd like to have an inverter that outputs to my standard plugs, I'm thinking I'll want to have some heavy duty toggle to switch one AC circuit and associated 110 plugs from the converter/breaker box to the inverter.

I think in the perfect world there all these boxes would be networked and would talk to each other saying what they are doing, converter, charge controller, generator, inverter, it would be nice if it was easier to integrate them and have them work together as a perfect system.

[dylanear]

Looking at your diagram, is the switch labeled Generator/Inverter? Or just generator and you're assuming/hoping to put an inverter on there?

The connection from the converter that charges the battery will need to be disconnected when the inverter is connected at the very least, I think also you do not want to power up the AC to DC circuits from the inverter even if they don't get connected back to the battery, because you already have DC from the battery, converting it to AC and back to DC or even just having juice to those circuits will waste battery power. So unless your converter is made to take inverter power in and adjust itself accordingly I think you'll need to make a switching system or use separate AC plugs from your inverter.

What kind do you have? Because I'll consider replacing mine if there's one that will properly adjust to the inverter like you hope to do.

[dylanear]

Originally Posted by Thomas G.

Gotcha - the battery would be trying to recharge itself via the inverter. I guess you could add an additional 110v Normally Open relay between the charger and the battery. That way when you had shore power, the relay would close and allow the charger to power the battery and when you had no shore power the relay would open.

Somehow I missed this comment.

Sounds like you were already on the right track before my blabbing.

[ericw]

As drawn I would not do it. The currents are going to get high really quick as it charges the battery from the same battery. It might work for a short time but I would not recommend it even that.

Fundamentally, I think the goal you are trying to achieve is feasible. For example, with more relays/switches you could make it work by getting the battery charger out of the loop. My first thought was to have a switch disconnect the input power to the battery charger.

[Thomas G.]

Originally Posted by dylanear

I've thought about this, I think you'll want to somehow cut off the AC to DC portion of your box, you don't want to go DC from your battery to the inverter, then AC from the inverter to your converter which will then send DC back to the battery etc. A loop. Sounds bad to me.

The relay would be installed in the blue wire between the converter/charger and the battery, breaking the loop when there is no shore power.

I have no experience with this, but I'm planning my solar system and while I'd like to have an inverter that outputs to my standard plugs, I'm thinking I'll want to have some heavy duty toggle to switch one AC circuit and associated 110 plugs from the converter/breaker box to the inverter.

You can do this with a DPDT switch. At 110 volts it doesn't need to be especially large or heavy duty

I think in the perfect world there all these boxes would be networked and would talk to each other saying what they are doing, converter, charge controller, generator, inverter, it would be nice if it was easier to integrate them and have them work together as a perfect system.

Perfect business opportunity for you.

[dylanear]

Originally Posted by Thomas G.

Perfect business opportunity for you.

If I had a few million in start up funds I'd love to create an advanced RV/off grid home technology company. I'm not an EE, or any kind of engineer, but I could hire them! Oversee overall product design!

Integrated, high efficiency systems. I wanted to be a car designer as a teen, I'd love to design high tech trailers! Dream job.

[lespnd]

I'm running an Parallaxx 7345 with auto switch ATS (ATS301) like this one. Apparent this switch is inverter friendly. See Here

RV Power Products from Parallax Power Supply

You all have some very good points. I wondered while on inverted 110V if the rate at which the converter tries to recharge the battery is significant enough to effect the circuits at all. I'm thinking it would insignificant but that would depend on the recharge stage, however in light of some of your comments, one must err on the side of caution, hence the reason I pose the initial question. Has anyone tested or done this with success?

[Thomas G.]

Originally Posted by lespnd

...... I wondered while on inverted 110V if the rate at which the converter tries to recharge the battery is significant enough to effect the circuits at all...........

My guess is that it would be an added drain on your battery. A switch or a relay would be a simple fix.

[dylanear]

Originally Posted by lespnd

I'm running an Parallaxx 7345 with auto switch ATS (ATS301) like this one. Apparent this switch is inverter friendly. See Here

RV Power Products from Parallax Power Supply

You all have some very good points. I wondered while on inverted 110V if the rate at which the converter tries to recharge the battery is significant enough to effect the circuits at all. I'm thinking it would insignificant but that would depend on the recharge stage, however in light of some of your comments, one must err on the side of caution, hence the reason I pose the initial question. Has anyone tested or done this with success?

Perhaps contact the manufacturer, seems the inverter friendly means that the AC to DC will work nicely with less than perfect sine wave AC, that doesn't mean it's meant to be powered by an inverter that's also charging the battery it's running from. Which may be an insignificant waste of power, but also may be a serious wiring problem. I'd kind of expect the later more than the former, unless that box was designed for that sort of hookup. Seems someone should make an integrated AC/DC converter, battery charger, solar controler, inverter. Because they all need to work together closely.

Let us know how it goes, I'll probably be in a similar spot soon. But I'm trying to deimphasize the AC/inverter side of my set up and emphasize the DC 12V side. May only run the TV and a few random items off AC while on battery. All lighting, laptop charging, most things will be native 12V.

[dylanear]

Originally Posted by Thomas G.

My guess is that it would be an added drain on your battery. A switch or a relay would be a simple fix.

Switching off the battery from the charger would be the first step, but I'd personally avoid letting power get to the AC/DC converter at all. Even with no/low load I'd expect there to be some loss.

[lespnd]

I totally agree Tom. I would be inclined to totally isolate the recharge circuit. It wouldn't take long to drain a battery this way but would work in a pinch. I do have a master battery switch on the side of the battery box. This would be an easy test. FYI: I do have a small 2 stroke Gen but hate to use it. This is food for thought and I appreciate the input and forethought. Its a bit of a mind twister. We haven't even discussed adding 7 pin charge line from the tug.

[Thomas G.]

Originally Posted by dylanear

Switching off the battery from the charger would be the first step, but I'd personally avoid letting power get to the AC/DC converter at all. Even with no/low load I'd expect there to be some loss.

Right, I was trying to keep it simple.

[dylanear]

Really seems like converters should be made to handle this issue. Perhaps this one is, still unclear about the "inverter friendly" thing.

[lespnd]

dylanear
Yes this is still unclear. Perhaps some others have yet to weigh in on this topic before I call parallax.

[lespnd]

I spoke with Parallax today. Using the generator outlet is not the recommended configuration. I have updated the drawing to reflect an acceptable configuration. There are a lot of ways people can get into trouble when doing this type of thing. For instance, they recommend turning off the DC converter breaker to eliminate the draw on the battery to recreate 12V current. The problem is that there is no way to prevent someone from providing dual 110V service to this unit from an inverter and shore power at the same time. Obviously a big no no. So, the way to keep things straight is to use the shore power cord/outlet for both the Inverter or shore power. ONE AT A TIME. As far as the Generator outlet is concerned, it is strictly reserved for the use of a Generator only. I hope this clears things up a little.

[cpaharley2008]

according to my math
50 amp from battery X 12v=600 watts/120v= 5 amp
there is not enough juice after 20% efficiency drop from 12v to 120v back to 12v
even if you plugged in a charger to your inverter, a trickle charger, you would still lose 20%