Problem with using CSW1012 inverter

[Kobus]

2019 Minnie Winnie 31K. Dual Coach batteries are 1 year old. CSW1012 inverter, rated 1000W continuous output, 2000W peak output.

Inverter power up normally when Inverter power switch is pressed but beeps and may even turn off when load is applied to output. Error codes happens immediately when load is applied.

Error codes are 101 and 105. Input voltage on inverter display fluctuates between 11.4V and 12V with the higher reading the moment a load is applied. Battery voltage at battery poles measures 12.38V after 2 days on shore power. Motor home engine is running when doing tests, but disconnected from shore power. Attempting to put a 200W load on inverter output.

Battery cables are clean and battery connections are tight.

Any ideas on why it cannot take a load of 1/5th of rated capacity?

[Ray,IN]

Have your batteries load-tested, I think you'll find at least one of them is faulty if they are the OEM batteries.
Another aspect;

Do you have a setting in your inverter for a low battery alarm? If this is set above 11V, then while the battery bank is being drawn-on the alarm will usually sound. While the inverter is drawing on the batteries they are depleting @ 10X the AC amperes being produced.
So if your appliance is drawing 10A AC, the batteries are losing 100A DC per hour.
You might find this interesting reading: The 12volt Side of Life (Part 1)

[Kobus]

Thanks. I've removed the batteries are are now slow-charging them. One was 12.42V (less than 75% charge) and the other at 12.80V (100% charge).

I'll charge both of them fully and then take them in for a load-test at O'Reilly. The batteries are only 1 year old, but I guess it's not impossible for it to be bad.

[creativepart]

Also, your inverter has a LVCO value set. That's the voltage at which your inverter will cut off to keep from draining your batteries.

Even with charged batteries in good condition attempting to run a very large electrical load on inverter can easily cause your battery voltage to sag to a level low enough that your LVCO cuts off the inverter, throws an error and beeps.

What are you trying to run with the inverter?

Also, one weak battery will pull down the other good battery to it's level. So, if one battery is at 12.8v and the other at 12.2v then both batteries will respond as if both are 12.2v.

[Kobus]

I'm trying to use a slow-cooker. The cooker is rated at 100W, so about 1/10 of the inverter rating.
I did notice that with a single 60W bulb, the input voltage displayed on the inverter screen dropped from 12V to 11.3V in less than 10 minutes.
Also the inverter screen never displayed more than 12V input, even though the lowest battery charge was 12.4V. The batteries are 2 Interstate HD24MDC-1 batteries, MCA 690, RC 140. Maybe there is a connection problem in the supply from the batteries? The battery connections was clean but the terminal nuts were tightened to just slightly more than finger tight. I should probably also check the cable connections on the inverter - the manual recommend to retorque the nuts every year. But it will be a real pain in the butt to access the nuts.

I'm busy charging the batteries on a battery tender and will then take them to be load tested. If they check out fine, I'll start on the cables.

[Kobus]

Problem resolved. Batteries tested good. As stated in previous post, the cable nuts on the batteries were not very tight. I tightened them properly and inverter can now supply full load.
As an added benefit, the interior lights does not flicker any more when starting the generator and the generator seems to start easier.