Inverter Connection Question

[Captain Ron]

I posted this on 'another forum' and got mixed responses. What do you folks think?

I found the wiring diagram below on line and I have a question...

It shows the inverter connected directly to the batteries along with a battery charger. Is this OK to do or will the current draw of the inverter put a load on the batter charger instead of the battery?



In my case, the inverter will typically be providing approx. 100W to power two smokers. Max power would be 400W for about three minutes when each smoker is started initially. So, at peak, the DC current will be about 34A and typical about 8.5 amps. Would using a setup as shown in the drawing (with two 12V batteries for now) damage the converter/charger in my TH? If so, what would a better connection be? I am not opposed to have a separate battery just for the smokers and using an inverter/charger (that I already have), but it would be more convenient to have both batteries hooked to the TH and available in case we need them.

[Herk7769]

I see no reason that these hookups will not work as shown. My inverter is tied to the Positive terminal of the battery through a 100 amp fuse and I recommend you add a fuse to your setup. Your size will depend on your maximum planned draw and inverter size.

[Captain Ron]

Thanks, Lou... I already have the fuse, so that's taken care of.

I guess my concern was that the smokers were starting up and the current draw was highest that the converter could end up supplying the current instead of the batteries, and that may damage the converter. Is that a possibility?

[reinerka]

I don't have an inverter (yet). But the plan is to actually use a relay in between that switches between shore (generator) power and the inverter automatically.

That way if there is external power the outlet will use that power (and thus no draw on your battery during that time). Once external power fails it automatically switches over to the inverter. A bit more expensive (15A relay is about $50) but there will be no additional load on the charger once shore power is available and the full converter power goes to recharging the battery.

Reiner

[Herk7769]

Wait. I am confused.

Why would you use an inverter circuit to run your smoker(s) if shore power is available? Just plug it into your shore power or generator directly.

If you are running off the inverter, because you are using your battery bank, the AC to DC converter will not be providing any DC power because there is no AC to convert.

As to the auto switch, I am not sure of the benefit. I don't think the inverter can handle all AC in your camper and even if the inverter could the battery bank could not. I would rather individually manage what runs off the inverter circuit. I currently use extension cords off the inverter sockets to manage what gets hooked up to the inverter at any given time. When I get the belly cover off this summer to install the tank probes, I plan on running Romex back to a duplex convenient to the entertainment center and to a new exterior duplex outlet to be inverter only outlets.

That way if we forget to unplug the coffee maker, it won't destroy the battery charge making a single pot of coffee.

[Captain Ron]

Originally Posted by herk7769

Wait. I am confused.

Why would you use an inverter circuit to run your smoker(s) if shore power is available? Just plug it into your shore power or generator directly.

If you are running off the inverter, because you are using your battery bank, the AC to DC converter will not be providing any DC power because there is no AC to convert.

It's back-up in case the power provided by the competition fails (which happens all too often) (or the generator runs out of gas for those comps where no power is provided).

I can see two choices...

1. Have a separate battery and use in inverter/charger with an automatic transfer switch to manage that battery and power the smokers. This is fine, but I would have two separate batteries, one for the TH and one for the smokers, so the total capacity available to either would be lower. This is the easiest to implement since I have the inverter/charger/transfer switch but it is modified sine, not pure sine and I've heard of issues with RFI with these.

2. Have both batteries in parallel and connected to the TH and let the battery charger in the converter charge both batteries and have the inverter connected as well (per the above) providing power to the smokers. This way the capacity of both batteries is available to either the TH or the smokers. This would mean buying a new inverter (without the charger, but I can get an 800w pure sine wave inverter for around $150.

In either case the only things connected to the inverter would be the two smokers. If shore power fails and is not going to be restored in a timely manner I can get the generator out of the trunk and fire that up to run lights.

Hopefully that makes sense.

[reinerka]

I would go with option 2 by hooking the inverter up so that it powers the external outlets. That way you hook up your TH to external power or run the generator to provide that power. Once disconnected the relay would automatically switch over to the inverter for backup power.

That way you have power even when not in a competition and actually raise the resale value if you ever decide to upgrade the TH.

I would certainly go with a true sine wave - why spend the money only to find you should have done it anyways.....

Reiner

[Herk7769]

Why would a smoker need computer grade power?
It is a heating element right?

I use my outside outlets for an electric skillet, toaster, air compressor, and several other high draw items, but never would I do that on battery.

I only have a 150 amp hour bank (2 75 AH batteries) and a 34 amp draw (400 watts constant draw = 34 amps x 12 volts) is very high demand and amp hour capacity is reduced by about 50% at that discharge rate.

Wind Energy Explained: Theory ... - Google Books

See the graph on page 491. My bank would only last 2 hours.
ONE 75 AH battery would last about ONE hour.

[Captain Ron]

Originally Posted by herk7769

Why would a smoker need computer grade power?
It is a heating element right?

I use my outside outlets for an electric skillet, toaster, air compressor, and several other high draw items, but never would I do that on battery.

I only have a 150 amp hour bank (2 75 AH batteries) and a 34 amp draw (400 watts constant draw = 34 amps x 12 volts) is very high demand and amp hour capacity is reduced by about 50% at that discharge rate.

Wind Energy Explained: Theory ... - Google Books

See the graph on page 491. My bank would only last 2 hours.
ONE 75 AH battery would last about ONE hour.

The smokers are computer controlled. They actually do fine on a MSW inverter, but I'm concerned about RFI on the TV and radio, but I may be worrying about nothing.

The 400W draw is for three minutes when each smoker starts up. The continuous draw for each is 50W (100W total) to power the electronics and the auger that feeds the pellets into the firebox. So, for 99% of the time the current draw is 8.5A, so two Group 24 batteries (probably the same as yours) would be enough to power the smokers for the competition (total cooking time of about 16 hours) (136 Ah).

But... My typical need is for battery backup for a short period just to bridge the power outage. If the provided power is really unreliable then I get the generator out of the truck and fire that up. If that's the case then I only need the backup if I forget to refill the generator tank (Honda 3000is Handi, about 7 hours run time at a load like this).

So, I'm back to my original question. Can I hook the inverter to the batteries at the same time as the converter while connected to shore power and not damage the converter? If not I'll keep the batteries separate and use one for the TH and one for the smokers and use my existing inverter/charger/transfer switch. Considering I don't need the inverter to provide power for extended periods I guess I'm talking myself into the latter

[Herk7769]

Originally Posted by Captain Ron

The smokers are computer controlled. They actually do fine on a MSW inverter, but I'm concerned about RFI on the TV and radio, but I may be worrying about nothing.

The 400W draw is for three minutes when each smoker starts up. The continuous draw for each is 50W (100W total) to power the electronics and the auger that feeds the pellets into the firebox. So, for 99% of the time the current draw is 8.5A, so two Group 24 batteries (probably the same as yours) would be enough to power the smokers for the competition (total cooking time of about 16 hours) (136 Ah).

But... My typical need is for battery backup for a short period just to bridge the power outage. If the provided power is really unreliable then I get the generator out of the truck and fire that up. If that's the case then I only need the backup if I forget to refill the generator tank (Honda 3000is Handi, about 7 hours run time at a load like this).

So, I'm back to my original question. Can I hook the inverter to the batteries at the same time as the converter while connected to shore power and not damage the converter? If not I'll keep the batteries separate and use one for the TH and one for the smokers and use my existing inverter/charger/transfer switch. Considering I don't need the inverter to provide power for extended periods I guess I'm talking myself into the latter

It might help to visualize what you are talking about if you link the smokers.

Having said that, I see no reason why you can't have the inverter tied directly to the positive terminal without any transfer switch.

I think the reason you are going this route is the computer timer right?
If the timer quits due to power failure you won't know when the BBQ is done.

Or will you have time to unplug from the camper and plug into the inverter without hurting anything?

As you can see from the photo, my inverter is tied directly to the battery positive terminal as you indicated in your drawing. The orange plug is an extension cord and the other thing is just an adapter plugged into a place where I can easily find it.

[reinerka]

To answer the original question.

Yes you can run the inverter while the charger is working.

The alternator (equivalent of the charger) is doing that in a car all the time (hopefully). Cars can have a huge draw as well (engine, heated seats, lights, etc). The same for any RV as nobody turns off all the 12V appliances when charging.

Reiner

[Captain Ron]

Here are the smokers...

Fast Eddy's by Cookshack Model FEC100
Memphis Pro

Both use food-grade wood pellets for fuel and a computer-controlled feed system to maintain temperature. I set the temperature (or a temp profile) that I want to cook and and the computer feeds the pellets into the firebox as a controlled rate to maintain temperature, so the power is essential. It's not needed for timing, but rather temperature control. If I lose power for more than 30 seconds or so I lose the temperature settings (not a big deal), but if I lose power for more than a few minutes there is no fuel feeding the fire and the fire goes out. That IS a big deal

I probably would have time to unplug from the camper and plug into the inverter, but, as Murphy would predict, the power outages seem to happen more frequently at night . I've been using a power failure alarm (typically some at the hardware store) that emits an annoying sound when power fails, and that wakes me up so i could move the extension cord fairly quickly, but if the power fails when we are away from our site (cooks meeting, visiting friends, etc.) then having the inverter permanently connected and always feeding the smokers, or using an automatic transfer switch would be essential.

Thanks for hanging in there with me. I could probably explain all of this in person with a drawing or two and it would take 5 minutes, but trying to do it in writing is more difficult.

[Captain Ron]

Originally Posted by reinerka

To answer the original question.

Yes you can run the inverter while the charger is working.

The alternator (equivalent of the charger) is doing that in a car all the time (hopefully). Cars can have a huge draw as well (engine, heated seats, lights, etc). The same for any RV as nobody turns off all the 12V appliances when charging.

Reiner

Good point. I didn't even think of that

[reinerka]

That is some interesting hardware you have there. Would love to try one of those things out one day.

30 seconds is a long time for a failover relay but a blink for a human to realize what is going on and run to unplug and plug it in somewhere else. I wouldn't try to go the manual route at that point. Especially if that happened at night I doubt anybody is going to do that in such a short time.

What I would view as the optimum setup is:

- Outlets power from the TH
- Inverter for backup in case external power fails
- Remote Control Panel that can automatically start the generator if batteries get low

Expensive but you could sleep all night without ANY worry. As it that setup failed (i.e. no more gas for the generator) there would be no option left.....

The original drawing you had will be fine for what you describe. Just don't expect to run the TV all night (or even a few hours) on the same inverter ;-)

Reiner

[Herk7769]

Well, I did read 5 amps at 120 VAC.
That is 600 watts PER UNIT last I checked.
Are you sure that is the model you are using?

How did you come up with 400 watts total for two?

[Captain Ron]

Originally Posted by herk7769

Well, I did read 5 amps at 120 VAC.
That is 600 watts PER UNIT last I checked.
Are you sure that is the model you are using?

How did you come up with 400 watts total for two?

Two ways... Actual measured power consumption during use (with a Kil-a-watt) and also talking extensively with Eddy Maurin, the guy who designed the FEC-100 and the engineering team at Hearthland products. The ignitor that both products use is the same and draws 400W when on, and the ignitor in both is turned on for the first three minutes after starting the smoker to ignite the pellets. They both use similar auger motors, fans and controllers and both consume approx. 50W once the ignitor is turned off (the FEC-100 is actually about 46W and the Memphis Pro is about 53W, so I rounded to get a total of 100W.

I've been running the FEC-100 off of a group 27 battery for the past three years when we were using our cargo trailer. It didn't have a converter/charger so I used the inverter/charger/transfer switch combo unit with out issues. Now that we have the TH I'm trying to figure out the best way to do things.

[Captain Ron]

Originally Posted by reinerka

That is some interesting hardware you have there. Would love to try one of those things out one day.

30 seconds is a long time for a failover relay but a blink for a human to realize what is going on and run to unplug and plug it in somewhere else. I wouldn't try to go the manual route at that point. Especially if that happened at night I doubt anybody is going to do that in such a short time.

What I would view as the optimum setup is:

- Outlets power from the TH
- Inverter for backup in case external power fails
- Remote Control Panel that can automatically start the generator if batteries get low

Expensive but you could sleep all night without ANY worry. As it that setup failed (i.e. no more gas for the generator) there would be no option left.....

The original drawing you had will be fine for what you describe. Just don't expect to run the TV all night (or even a few hours) on the same inverter ;-)

Reiner

Thanks... The only thing that would run on the inverter would be the smokers. They are more important than the TV or just about anything else.

I don't think there is a way to start my generator automatically. The Honda 3000is Handi is a pull start only. But, as long as i have a way to keep things powered for the time it takes me to get the generator running I'm fine.

[Herk7769]

Ron, you have certainly done your homework. Now that I am up to speed on your equipment and your needs, I think you would have absolutely no problem running the smokers completely off the inverter ALL the time.

Your converter is most likely a 55 amp converter, so it can supply 55 amps DC to your entire rig at a higher voltage than the battery.

Plug the smokers into the inverter, the inverter into the battery bank and leave the battery bank hooked up to the camper's converter.

When on shore power, the converter will run your smokers through the inverter since it will be supplying the higher DC voltage. When the shore power quits, the batteries will take over powering the inverter without a hiccough since the inverter has been doing it all along.

My computer does not even reboot when the generator runs out of gas because that extension cord off the inverter runs the computer, monitor and TV when we dry camp.

[Herk7769]

Another thought by doing it this way is that if the power does go out in the field, the batteries will hold the settings and keep on cooking until you get the generator out of the truck and get it fueled and started. Then unplug the shore power cord from the campground and plug it into the generator. Then the generator will be powering the converter.

When the lights come on next door; reverse the procedure.

The smokers will never see a power outage through all of that.

[Captain Ron]

Sounds perfect Thanks!

I'm a habitual over-researcher You should see my competition schedule. I have a spreadsheet that includes everything that I have to do from the meat inspection when we get on site up to popping a beer after the last turn in Friday afternoon and evening is pretty calm, but we get pretty focus come Saturday morning up until 1:30pm when the last entry is in the hands of the judges.