Question: Truck Battery Bank for Shore Power

[Dave_in_Central]

Based on some back-and-forth with my original post, I've redefined my problem.

1. Situation: I'm trying to use the battery bank on my truck for shore power for my travel trailer. I want to be able to use the battery bank on my truck to run low-draw AC appliances while dry camping.

1.1. Battery Bank: On the truck I have three deep cycle batteries in parallel connected to an inverter. These are not tied into the truck's alternator. I use a Schumacher battery charger to keep them topped off.

1.2. Wiring from Camper to Inverter: First, the camper's shore power cable plugs into a 30Amp RV to 15/20Amp pigtail adapter. Second, a 20-amp 10-gauge generator cord plugs into the pigtail adapter and goes to the back of the truck. Third, the generator cord plugs into a 15A to 20A adapter, and then is plugged into the inverter.

1.3. Inverter Information: My set up works with an 800W inverter that outputs 120 volts. My set up does not work with my 2000W inverter that outputs 115 volts.

2. Problem: I want to use my 2000W inverter to provide shore power to my camper. Seeing that the 800W inverter that outputs 120V works and the 2000W inverter that outputs 115V does not, is there anything I can do to get the 2000W inverter to work?

2.1. The inverter I'm asking about is a Whistler Pro-2000, it outputs 115 volts (modified sine wave). When I connect the shore power cable to it, the RV gets power for a second, then the inverter goes into alarm mode (audible alarm, light blinking red-green-red-green, and power from inverter cuts off).

2.2. Last night, I was asked whether my inverter outputs 120 volts. I looked and the labeling on the inverter clearly states it outputs 115V (the Whistler Pro-2000). I also have an 800W inverter in the house that outputs 120V. When I tried using this inverter for shore power, I was successful in using truck's battery bank to provide power to the RV.

Thanks,
Dave

[pauldub]

Somewhere I think you have a short between the neutral and ground. Try plugging the RV cord into the inverter with only a single adapter or just use a meter and check for a short between neutral and ground. Forget about 120V versus 115V, that's just a red herring and doesn't matter.

[BFL13]

Probably in all those adapters. You should be able to just put a 30/15 on the shore cord and plug that into the inverter. As it is, perhaps the 2000w has a protection that the 800 does not have, explaining the differt results.

[road-runner]

Dave in Central NC wrote:

The cheater plug gets the 2,000w inverter working.

I think you have a real safety hazard here. I don't know all the details and it's slightly complicated, so I could be making some wrong assumptions, one of which is that the inverter is in the truck. The result of the cheater plug working says that something goes wrong when the inverter's case is connected to the RV's grounding system.
That leads me to three conclusions:
(1) The RV's neutral and ground are bonded, not a good thing.
(2) There's likely a shock hazard if the RV chassis and truck are touched at the same time.
(3) The RV's skin might be "hot".

I'm surprised that such a large inverter would use the hot neutral design described by Tom M. It does reduce manufacturing cost. If the statement in the owner's manual about the internal voltage being 145 is correct, it's likely not the hot neutral design, but there's no assurance that statement is correct. Another possibility is that the inverter is actively detecting a downstream ground-neutral fault as is done with GFCI devices.

Bottom line: The cheater plug result shows that something is wrong with the RV's wiring. Running with the cheater plug might create a serious shock hazard.

[Dave_in_Central]

Ding Ding Ding...we have a winner!

The cheater plug gets the 2,000w inverter working.

The inverter turned on without going into alarm mode. Lamp came on, then I started the microwave, then I turned on the AC (fan mode). 1,300 watts +/- in total being consumed.

Thank you, Tom_M.

Tom_M wrote:
From the Samlex website FAQ page:

"In some inverters designed for portable use, the two current carrying conductors connected to the "Line/Live/Hot" slot and the "Neutral / Return / Cold" slot of the receptacle ( for example, 15 A NEMA5-15R) are isolated from the metal chassis of the inverter. In these inverters, none of the two poles can be called Neutral as both these poles are isolated from the chassis of the inverter. Both the Line and Neutral slots of the receptacle will be at an elevated voltage with respect to the chassis - normally around 60 VAC (Half of the voltage between the two current carrying conductors). Hence, do not touch the neutral slot of the receptacle!

These types of inverters are designed to be connected directly to the AC loads. These are not designed to be permanently installed into household or recreational vehicle AC distribution wiring. As this type of connection / installation can not be classified as a permanent installation, the NEC requirement of grounded distribution system doesn't strictly apply."

https://www.samlexamerica.com/support/faqs/faq16.aspx

Try the cheater plug just to check if you have a neutral/ground bonding issue.

[Dave_in_Central]

I've tried it with all the breakers in the off position inside the RV, and still no luck with the 2,000W inverter. So there are no loads I don't know about.

12.2V to 13.1V at the inverter input connections.

I can run AC loads plugging directly into the inverter, like the lamp, an air compressor, and any number of power tools.

road-runner wrote:
Does the inverter shut down if you plug the 4.5 watt bulb directly into it, instead of through the shore power cord? You might have a load in the RV you don't realize. Water heater was mentioned. Other easily overlooked loads are the fridge and power converter. A basic and necessary troubleshooting step is to measure the DC voltage at the inverter input connections.

[Tom_M1]

From the Samlex website FAQ page:

"In some inverters designed for portable use, the two current carrying conductors connected to the "Line/Live/Hot" slot and the "Neutral / Return / Cold" slot of the receptacle ( for example, 15 A NEMA5-15R) are isolated from the metal chassis of the inverter. In these inverters, none of the two poles can be called Neutral as both these poles are isolated from the chassis of the inverter. Both the Line and Neutral slots of the receptacle will be at an elevated voltage with respect to the chassis - normally around 60 VAC (Half of the voltage between the two current carrying conductors). Hence, do not touch the neutral slot of the receptacle!

These types of inverters are designed to be connected directly to the AC loads. These are not designed to be permanently installed into household or recreational vehicle AC distribution wiring. As this type of connection / installation can not be classified as a permanent installation, the NEC requirement of grounded distribution system doesn't strictly apply."

https://www.samlexamerica.com/support/faqs/faq16.aspx

Try the cheater plug just to check if you have a neutral/ground bonding issue.

[road-runner]

Does the inverter shut down if you plug the 4.5 watt bulb directly into it, instead of through the shore power cord? You might have a load in the RV you don't realize. Water heater was mentioned. Other easily overlooked loads are the fridge and power converter. A basic and necessary troubleshooting step is to measure the DC voltage at the inverter input connections.

[BFL13]

So it is not a low voltage alarm, but one of the other "protections" shutting it down. Might be in the manual what protection it is that makes the inverter do all that as its signal.

It is annoying when the inverter does not have a display that shows a code for which fault it is not liking. Leaves you with trial and error for trouble shooting.

[Dave_in_Central]

I'm using the same load to test both inverters: one 4.5 watt LED light bulb that I can see from the truck.

I get alarm and shut off with the 2000W, and the 800W turns on the light.

BFL13 wrote:
Want does "works" mean? You are getting low voltage alarm and shut down with the 2000w but not with the 800w.

Are you trying the 2000w with a big load like the water heater on electric, but not when using the 800w? Does the 2000w "work" with the same load as the 800w?

If all it is that makes the 2000w not "work" is a big load, you can reduce the voltage drop so it stays above 11v under load, by using fatter wire between inverter and battery bank, balancing the bank better with no "downstream batteries", and making sure the batteries are well charged up (needs an hydrometer for that to be sure)

BTW that red plug above is not supposed to be used in the Code ISTR.

[BFL13]

Want does "works" mean? You are getting low voltage alarm and shut down with the 2000w but not with the 800w.

Are you trying the 2000w with a big load like the water heater on electric, but not when using the 800w? Does the 2000w "work" with the same load as the 800w?

If all it is that makes the 2000w not "work" is a big load, you can reduce the voltage drop so it stays above 11v under load, by using fatter wire between inverter and battery bank, balancing the bank better with no "downstream batteries", and making sure the batteries are well charged up (needs an hydrometer for that to be sure)

BTW that red plug above is not supposed to be used in the Code ISTR.

[Tom_M1]

Some inverters do weird things with the neutral and ground. Try a two prong adapter like the one below:

[Dave_in_Central]

Answering valhalla360's questions.

But before I do, this update.

The inverter I'm asking about is a Whistler Pro-2000, it outputs 115 volts (modified sine wave). When I connect the shore power cable to it, the RV gets power for a second, then the inverter goes into alarm mode (audible alarm, light blinking red-green-red-green, and power from inverter cuts off).

Last night, I was asked whether my inverter outputs 120 volts. I looked and the labeling on the inverter clearly states it outputs 115V (the Whistler Pro-2000). I also have an 800W inverter in the house that outputs 120V. When I tried using this inverter for shore power, I was successful in using truck's battery bank to provide power to the RV.

On to valhalla360's questions...

Question 1: Are they really deep cycle...or are they the combo batteries (which are really just starting batteries with a different label). 12v deep cycle batteries are hard to find and expensive. Most people parallel 6v golf cart batteries which are legitimate deep cycle batteries.

Answer 1: Batteries are combo batteries.


Question 2: What size cables and how long are they connecting the batteries to the inverter? 2000w is about 170amps, that takes a pretty thick battery cable and will kill a moderate battery bank pretty quick.

Answer 2: The cables that connect the inverter to the batteries are 2AWG and about 30 inches long.


Question 3: How are you replacing the power draw? The standard truck alternator will only put out the rated output for a short time and then it drops back significantly.

Answer 4:
I use a Schumacher battery charger to recharge the batteries. The battery bank is not tied into the truck's alternator. House current --> battery charger -->batteries.


Question 5: Does the inverter have a fuse/breaker? That would be a simple answer.

Answer 5: Inverter has an internal fuse, no breaker.

[Dave_in_Central]

I have a Whistler Pro-2000W inverter that produces a modified sine wave.

Here's verbiage about this from the WhistlerPro200 owner's manual:

Whistler inverters work in two stages. During the first stage,
the DC to DC converter increases the DC input voltage from
the power source (e.g. a 12 volt battery) to 145 volts DC. In
the second stage, the high voltage DC is converted to 110
volts (60 Hz AC) using advanced power MOSFET transistors
in a full bridge configuration. The result is excellent overload
capability and the capacity to operate difficult reactive loads.
The output waveform resulting from these conversions is a
"quasi-sine wave" or a "modified sine wave" as shown on
below. This stepped waveform is similar to the power generated by
utilities and has a broad range of applications.
The modified sine wave produced by the Inverter
The modified sine wave produced by your Whistler inverter
has a root mean square (RMS) voltage of 110 volts. The majority
of AC voltmeters measure RMS voltage and assume that the
measured waveform will be a pure sine wave.
Consequently, these meters will not read the RMS modified
sine wave voltage correctly and, when measuring your Whistler
inverter output, the meters will read about 20 to 30 volts too
low. To accurately measure the output voltage of your inverter,
use a true RMS reading voltmeter such as a Fluke 87, Fluke
8060A, Beckman 4410, Triplett 4200 or any multimeter identified
as "True RMS."

[wa8yxm]

Is the inverter a PSW or MSW
DO you have any kind of "Surge Guard" or Progressive Industries EMS? or competitor's product.

Some of those look at the wave form and will not pass MSW inverters.