Voltage drop to 1200 watt inverter

[Williebago]

Getting used to a 2019 new RV with residential refrigerator which is on a Xantrex Freedom X 1200W inverter with auto transfer feature and remote monitor. Bedroom and entertainment receptacles on a separate identical 1200W inverter. There is a Digi Level monitor panel which shows house and battery voltages and I had two 170W Zamp solar panels and Zamp 30 Amp charge controller mounted beside these other three monitor panels.

When parked and no generator, shore power, or load on either inverter the four panels all agree on the voltage of the batteries which are 4 Interstate Deep Cycle RV/Marine 12V Group SRM 24.
When the refrigerator is running (not start up load) the inverter voltage indicates a voltage that is 0.3V below the other three monitor panels showing the battery bank voltage. Inverter shows an output load of 85 to 95W. I do not know the wire size or exact length (yet) but the length is probably 8 to 10 feet.

So my question - Is the inverter input voltage reading accurate enough to believe the 0.3V voltage drop on the 12V input side and is that a reasonable number or should it be a 0.1V loss?

[wolfe10]

NicodemusY wrote:
Actually maybe it is possible I misread the meter and it draws 0.4 Amp. It's only a few years old. So, 240 x 0.4 would come out to 96 watts? That will make it more likely to start but not very well I guess.
The 12.6 volts was the reading before the subsequent attempt just prior to the inverter failing. I did though use a fully charged jump starting battery (12v 19 amp/h) just for proof of concept, so no, it was not hooked up to any panels.

240 VAC????

How about 120 VAC, or please tell us what inverter you have. Yes, 240 VAC inverters are made, but very rare in an RV.

[NicodemusY]

Actually maybe it is possible I misread the meter and it draws 0.4 Amp. It's only a few years old. So, 240 x 0.4 would come out to 96 watts? That will make it more likely to start but not very well I guess.
The 12.6 volts was the reading before the subsequent attempt just prior to the inverter failing. I did though use a fully charged jump starting battery (12v 19 amp/h) just for proof of concept, so no, it was not hooked up to any panels.

[Veebyes]

2 group 24 batteries. I would not chuck simply for the sake of chucking them but do you have space for a pair of group 27, a pair of group 31s, a 4D, even an 8D?

Use the 24s on another vehicle or as a power source with an inverter for emergency power at home to charge phones, maybe run a TV or two when the weather takes out home power.

[RJsfishin]

quote:
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Even with a full load on the inverter, I would want the voltage drop on each leg to be LESS THAN 0.1V !
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What a ridiculous statement ! You live in a dream world !!

[theoldwizard1]

Williebago wrote:
So my question - Is the inverter input voltage reading accurate enough to believe the 0.3V voltage drop on the 12V input side and is that a reasonable number or should it be a 0.1V loss?

Part of the difference is due to calibration error, or lack there of. The only way to know for sure, is use a separate meter with long enough leads to measure directly form the positive terminal on the battery to the positive terminal on the inverter. The do the same for the negative connections.

Even with a full load on the inverter, I would want the voltage drop on each leg to be LESS THAN 0.1V !

[theoldwizard1]

CA Traveler wrote:
Let's be clear: Marine batteries are NOT deep cycle batteries other than the label. A little better than starting batteries but much less than say 6V GCs.

PNW_Steve wrote:
Truth on the batteries.

The misrepresentation of those "RV/Marine" batteries by the big box stores pisses me off! WAY to many people waste their money thinking that they got a great price on deep cycle batteries.

Preaching to the choirs guys !

Four 6V golf cart batteries would have about 450 Ah of capacity. Four group 24 batteries about 320 Ah of capacity. The golf cart batteries probably would cost less.

[Shadow_Catcher]

I have been using Amsoil for decades and just carry a couple of extra quarts. My last Subaru had about 300,000 on it.

[PNW_Steve]

CA Traveler wrote:
To answer your question: Yes, No, Maybe.

Buy a reasonable digital voltmeter for $10 and measure the battery voltage and inverter DC input voltage at the inverter DC input terminals. 0.3V drop is certainly possible given whatever wiring you have.

Let's be clear: Marine batteries are NOT deep cycle batteries other than the label. A little better than starting batteries but much less than say 6V GCs.

Truth on the batteries.

The misrepresentation of those "RV/Marine" batteries by the big box stores pisses me off! WAY to many people waste their money thinking that they got a great price on deep cycle batteries.

The inverters battery voltage is read at the inverter side of the battery/inverter DC connection. If you have a measurable voltage drop on the DC connection that will show up on the DC voltage display.

If the battery measures 13.8v AT THE BATTERY and you have a significant load on one inverter, that inverter will display battery voltage minus voltage drop. The inverter with no load will experience an insignificant voltage drop on the DC connection. That too will manifest in the inverter DC voltage display.

This could present as one inverter (no load) displaying the same voltage as your battery monitor and the second inverter(running a load) showing a lower voltage.

I apologize for the disjointed reply. I find myself having a challenge communicating coherently when typing with one finger on a touch screen. I sound much smarter when I have my laptop. 🙂 🙂

[time2roll]

Yes put your voltmeter right on the battery terminals, then the inverter input terminals, then back on the battery. Compare and post the results.

[CA_Traveler]

To answer your question: Yes, No, Maybe.

Buy a reasonable digital voltmeter for $10 and measure the battery voltage and inverter DC input voltage at the inverter DC input terminals. 0.3V drop is certainly possible given whatever wiring you have.

Let's be clear: Marine batteries are NOT deep cycle batteries other than the label. A little better than starting batteries but much less than say 6V GCs.

[pianotuna]

No meaningful answer can be made without knowing the wire size and length of run.

It would be good to know what the wattage is for the fridge. A Kill-a-Watt meter would be a good addition. Measure on shore power, and measure on inverter power.

[Lwiddis]

Solar panels don’t agree...or comment...on batteries or their voltage. They solely offer electricity to the batteries through the controller.

[BFL13]

Doesn't make sense as such. Are both inverters on the same battery bank or is the bank split so half is to each inverter?

What do you mean by "house and battery voltages"? There are house battery and engine battery.