Inverter question

[john hd]

gary

i would be interested to see what it would do on the hot box.

no doubt they are a quality unit, otherwise they would not be such big sellers.

john

[flitzwhopper]

Originally Posted by thecatsandi

Xantrex Technology Inc. - Recreational Vehicles - Prosine 1000 and 1800 - 120 VAC/60 Hz - Specifications
They are showing up to 90% efficiency.
I know for a fact the outback units for home use are around 90% as well.

obviously i was in err.... the ones you refer to are much more technologically advanced than the ones I had in mind. My experience is with the radioshack units such as
RadioShack.com - Power & Batteries: Car power: Power inverters: Whistler PI-3000W 3000W Power Inverter

many apologies

[rp709]

I am having trouble using a modified sine wave inverter to run the laptop. I plug it in (I have two different units that behave the same way) to the Airstream 12v socket and the inverters squeal a low votage warning, even if the coach batteries are full. If I plug the same inverter into the truck power socket they work fine. Any ideas?

[2airishuman]

Originally Posted by rp709

Any ideas?

hi rp'...

the 12 v outlet in question might REALLY have low voltage....

-have u measured the outlet voltage with a multimeter gizmo?

-do all of the 12v outlets inside the stream get this result?

-have u tried the 12v outlets while plugged into shore power?

-have u tried CLEANING the 12v outlets?

-pulled the outlet and check the wiring/connections?

a little corrosion can cause issues...

cheers
2air'

[lewster]

Originally Posted by rp709

I am having trouble using a modified sine wave inverter to run the laptop. I plug it in (I have two different units that behave the same way) to the Airstream 12v socket and the inverters squeal a low votage warning, even if the coach batteries are full. If I plug the same inverter into the truck power socket they work fine. Any ideas?

rp,

Check the voltage of your coach batteries independently with a quality VOM and see what the reading is. They might be showing low voltage under load, which means that they could be bad.

You could also charge them completely with a separate battery charger (with the negative terminal disconnected) and then load test them to see how they perform. This will tell you what their true condition is. I just don't trust battery level indicators.

[RoadKingMoe]

First, check the amperage or wattage requirement of the laptop power adapter. For example, if it is rated for 1.2A@120VAC, it can draw as much as 1.2 x 12 = 14 amps from your trailer batteries. If it is rated at 120W@120VAC, it can draw as much as 120/10 = 12 amps from your batteries. This multiplier and divisor in the previous formulas are what they are because the power adapter isn't 100% efficient.

Note that in both examples above, the amp draw from the batteries exceeds the 8 amp maximum of the cigarette lighter outlet on the Winegard anteanna plate and may cause it to melt and/or burn.

That amount of current will also cause a voltage drop, both in the wire supplied with the inverter, and in the wire running from the outlet to the trailer batteries. Although Airstream typically uses 12 AWG wire, this voltage drop can cause you to get a low-voltage warning on the inverter if the wire run from batteries to outlet is very long. It is generally best to wire an inverter to the downstream side of the big fuse coming from one of the batteries with as absolutely short, and as heavy as necessary, wire, fusing that wire adequately.

A voltage drop will not occur when you're using a meter to measure the voltage in the outlet without the inverter plugged into it. What you may see there is a voltage drop caused by other lights or appliances on the same circuit as the outlet.

Hope this helps,