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emcee · 07-23-2020, 08:22 AM

The goal is to power the refrigerator from the inverter while on the road.

Here’s my setup: 800 watt pure sine wave inverter connected directly to batteries. Disconnected 120 volt circuit that powers refer from panel. Put plug on the end of the wire and plugged it into the inverter. Turn on refer (nothing else powered by the circuit). Inverter supplies 120 volts to refer but the inverter input voltage drops to 12.1 volts in a few minutes. Also the inverter fan runs about 1/2 the time. This is with the coach plugged into the house (30 amp).

The converter is an ELX-45.

The batteries are a brand new pair of 6 volt golf cart batteries.

The refrigerator (Norcold N821) should only draw about 350 watts max (3 amp fuse).

Is it the converter?

Danlb · 07-23-2020, 09:10 AM

While I am not an expert in this area, I understand that you need about 10 times the listed amps on a 120V appliance from your batteries to power the device thru your inverter. A 3 amp 120V rating will require about 30 amps at 12V from your batteries. When you put a load like that on your batteries voltage drops, so 12.1V is not unusual. Your converter is probably a 45 amp unit and is working to charge your batteries to replace that 30 amp draw. Your converter's purpose is to try to keep your batteries charged, not run the fridge.

paul65k · 07-23-2020, 09:12 AM

Few questions;

What is the brand of inverter?
What is the distance between inverter and batteries?
What gauge wire are you using between the battery and the inverter?

Answering these questions can help us better answer your question

Talloaks · 07-23-2020, 09:14 AM

If your 3 amp fuse is holding, then your issue is not on the load side of the inverter. At 800w continuous rating, even at 80% efficiency your inverter is not overloaded. Let's look at the supply side from your battery. A little more info would be helpful. When you read 12.1 vdc at the inverter, what do you read at the battery terminals? How long is the run, and what size is the wire, from the battery to the inverter? What brand and model of inverter? What type of connection did you use to connect "directly" to the battery?

And OBTW-- did you install a fuse between the battery and inverter?

Could be some clues in the answers to these questions.

emcee · 07-23-2020, 05:17 PM

This is the inverter: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It came with 2' long "battery" cables and they are just long enough to connect to the batteries.

There's no fuse in line with the battery connection.

The inverter has a digital display of source and output voltage. The source voltage was shown to be 11.9 volts (this is what initially got my attention) but I measured 12.1 - 12.2 volts (with the refrigerator connected ) at the batteries and right on the inverter terminals.

I originally had the inverter fed from the battery disconnect output (leftmost terminal shown in the attached photo) and this allowed me to disconnect the inverter completely when desired. This also puts a fuse inline with the battery. I may change the wiring back to this configuration as I didn't see any difference with the inverter connected directly to the batteries.

So I think DanL is right in that the converter can't keep up with the load. The voltage bottomed out at 12.1/12.2 and this was while the refrigerator was cooling starting from about 85 degrees. I also think that after the refrigerator is cool then the voltage will increase while the refrigerator is just maintaining the temperature setpoint. I couldn't prove this today as the refrigerator gave the the "no cooling" fault after about an hour. I'm hoping this was because the MH isn't level enough. I might level it (not easy since the seats are out) and try again tomorrow.

rbTN · 07-23-2020, 06:30 PM

certainly not an expert, but the inverter can only produce voltage based on what it has to work with so even if you have a 4k inverter, the batteries will only provide the 12.1v you are seeing so I think it is not an inverter problem but a supply problem. From what I read the inverter carried the load, but the supply voltage dropped which is not a result of the size of inverter

also when I apply a load to the batteries the voltage drops, but will show some recovery when the load is removed.

What did the batteries read after you turned of the fridge and inverter, and 30 mins later?

sibe · 07-23-2020, 07:00 PM

where to start..

1.. Are your Batteries at a full charge 12.5ish - 12.6 resting no charge input..

2.. your wiring is WAY undersized for use with an inverter,,
that aligator clamp on I hope is not part of inverter,,

a 800 watt in has a potential to surge 80 amps at 12vdc.. a 2 guage wire is min IMO.. you have 8 guage at best in picture that can take 40 amp on a perfect day... if run directly off battery posts,,

your 350 watts will pull 28-32 amps in 12 volts.. normally a pre cooled rv fridge with run cycle 40-60% of time in normal temps..

your battery load in perfect charge is 220 amp Hr,, lead acid will draw the first well so that is the first 2 hours expect voltage to be 12.1-12.2,, after 5--7 hours you maybe get to 11.8 as your load is toasted..

I have run 2 full on tests with 300AH after an equlize charge, one on room temp fridge strt up and one test with a pre cooled fridge run prior..

best I got was 10 hrs till I hit 11.9 volts... I have 2/0 cables lacing batteries to inveter,,

twinboat · 07-23-2020, 07:23 PM

I agree Exactly with what sibe said.

Upgrade the wiring and be sure to upgrade the jumper between the 2 6volt batteries.

Why are you running a gas/electric fridge on inverter power ? Its the most economical way to do it.

Run it on gas or buy a resedental fridge. That will draw 1/3rd the power of a absorbsion fridge.

theoldwizard · 07-23-2020, 07:30 PM

Quote:

Originally Posted by emcee

The goal is to power the refrigerator from the inverter while on the road.

You need a DC-DC battery charger. Several different brands available, Redarc, Renogy, CTEK.

Pappion · 07-23-2020, 07:32 PM

Checked the specs on similar ELX converters (did not find elx45). The voltage regulation is poor. 13.5v nominal, dropping to 13.1v fully loaded. Then dropping off the cliff with more load.

At 12v the frig inverter is a 30 amp load. You may have other 12v loads.
I doubt the wire gauge from converter to inverter or battery is heavy enough.

IMDiesel · 07-23-2020, 07:47 PM

emcee,

Here is a direct quote from the amazon link you provided.

"If you want to power up a refrigerator, we suggest you use 10 times higher power inverter."

and therefore it seems you are not within specifications.

I see their are larger ones available.

Good Luck !

theoldwizard · 07-24-2020, 03:36 AM

Quote:

Originally Posted by emcee

The goal is to power the refrigerator from the inverter while on the road.

Here’s my setup: 800 watt pure sine wave inverter connected directly to batteries. Disconnected 120 volt circuit that powers refer from panel. Put plug on the end of the wire and plugged it into the inverter. Turn on refer (nothing else powered by the circuit). Inverter supplies 120 volts to refer but the inverter input voltage drops to 12.1 volts in a few minutes. Also the inverter fan runs about 1/2 the time. This is with the coach plugged into the house (30 amp).

The converter is an ELX-45.

The batteries are a brand new pair of 6 volt golf cart batteries.

The refrigerator (Norcold N821) should only draw about 350 watts max (3 amp fuse).

Is it the converter?

I just re-read the initial post. This is kind of a weird setup with the refrigerator running 100% of the time on the inverter !

For the test the OP is doing, I would blame the converter. It should not let the voltage drop that low. I would get a Progressive Dynamics 60 (or higher) converter. A properly sized converter should be able to keep the voltage above 13 volts all of the time.

For "on the road" you absolutely need a properly sized DC-DC battery charger ! Only a DC-DC battery charger will guarantee that you are above 13 volts all of the time.

Not surprised that the fan runs >50% of the time. I would have bought the the 1500W inverter.

sibe · 07-24-2020, 10:45 AM

I understand the Dc to DC from rig altenator... I am not sure how my old RV chgs battery while I drive but it does.. I have not load tested altenator with inverter loaded and driving.. I had in my old rig as it had a 230 amp Alt.. my newer rig is 130 so I would be a tad carefull

I run propane on fridge when i can..

When on Inverter you should not be using the converter/chg and battery if hooked to shore... that defeats or comprimises.. kind of running a loop that uses more power,,

My system ( I added on a transfer and intverter....) when I fire inverter, transfer switch does total power to inverter and DROPPS power off the Converter/CHGR which is a PD 60amp with smart circuit..

IMO you still need to wire up and check your charge rate/full

RVingNow · 07-24-2020, 11:28 AM

Quote:

Originally Posted by emcee

The goal is to power the refrigerator from the inverter while on the road.

If that's the case then this is not really a battery issue. It's not hard to get the 35amps needed to run the reefer from the alternator. (How big is your alternator?) Make sure your wiring is sized sufficiently, 8ga or larger for longer runs.

Regarding the 12.1v measurement. Seems reasonable given the small bank size and heavy draw. (Look at the C5 rating for a GC battery.) However, I don't understand why it's 12.1 if the converter is on. If off, ok. If on, it's not charging the batteries for some reason. You should get 35amps from the converter without any problem. (It's rated at 45.)

BTW what's that clamp on the far right circuit breaker in the picture?