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Open Roads Forum  >  Tech Issues

 > Question: Truck Battery Bank for Shore Power

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Dave in Central NC

Broadway, NC

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Posted: 06/30/20 09:40am Link  |  Quote  |  Print  |  Notify Moderator

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

Victoria, BC

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Posted: 06/30/20 09:49am Link  |  Quote  |  Print  |  Notify Moderator

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.


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road-runner

Oregon

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Posted: 06/30/20 10:17am Link  |  Quote  |  Print  |  Notify Moderator

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.


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Tom_M

New Hope, MN

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Posted: 06/30/20 10:46am Link  |  Quote  |  Print  |  Notify Moderator

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.


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Dave in Central NC

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Posted: 06/30/20 10:47am Link  |  Quote  |  Print  |  Notify Moderator

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.


* This post was edited 06/30/20 11:08am by Dave in Central NC *

Dave in Central NC

Broadway, NC

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Posted: 06/30/20 11:04am Link  |  Quote  |  Print  |  Notify Moderator

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.


road-runner

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Posted: 07/01/20 10:56am Link  |  Quote  |  Print  |  Notify Moderator

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.

BFL13

Victoria, BC

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Posted: 07/01/20 11:18am Link  |  Quote  |  Print  |  Notify Moderator

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.

pauldub

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Posted: 07/01/20 11:58am Link  |  Quote  |  Print  |  Notify Moderator

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.

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