Dimensions (Quasi-Sine 2000W Inveter) Voltage Drop Problem & Shut Down

[imnprsd]

My 2004 Dimensions 2000W inverter (Model# 12X20B3R4T with 100A Charger) is drawing down my house batteries in 30 minutes or less; and when the voltage drops below ~11V it shuts down!

So I don't know if I have a bad inverter or a bad set of house batteries?

I think my 3 year old house batteries are good. They are 4-6V-GC2-Golf Cart type batteries, in series and parallel (12V system), and they are supposed to store 430AH.

I currently measure 12.4 volts on my house batteries using the shunted voltage meter in my RV power panel. And I measure 12.4 volts at the battery bank with the inverter switched off; and the inverter charger function set to 0 amps...

...Then I turn OFF my shore power, and turn ON my inverter to produce 120V power at 350watts inside my coach, and what I see is my house battery voltage dropping immediately down to 11.8V... .and every five minutes or so I lose another -0.1V.

So it does no take long for my inverter to suck the power out of my house battery bank and then my inverter shuts down.

==> So I go outside my camp spot and flip the shore power breakers (50A) ON and immediately my inverter charger starts pumping 14.6V into those DEPLETED house batteries at 70A... then the charged quickly drops to 40A in about 5 minutes; and then the charger remains in "Accept Mode" but the current drops to 10A in about 10 minutes. So the charger in the inverter is working. What I do not know if if my batteries are so sulfated that the battery bank will not accept more charge?

I double-checked my house battery voltage on each battery at 6.4V; and I checked each battery cell with a hydrometer; and every cell passes. I even took the batteries to First Interstate and each 6V battery PASSED on their load tester machine. (Albeit they only held the load on for 3 seconds so now that I think about it, maybe this is not the right way to conduct a 150A load-test?)

I also read that hydrometer readings do NOT verify your batteries ability to sore Coulombs of charge (AH). So how do you really know when or if your house batteries are "SULFATED" they will not accept a charge?

Can golf cart batteries pass the voltage and load test, but not be able to power an inverter for more than 15 minutes? ...Are these car battery testers accurate when used on golf cart batteries?

=== MORE DIAGNOSIS ===

I then unhooked my inverter, and battery disconnect cables, from the house battery bank; then I joined these cables together with a bolt; and then I used jumper cables to power my inverter using my 12V tow car battery. ...And again, the voltage dropped from 12.2 volts down to 11.8V immediately when on 120V inverter power.

Note: The inverter output is working fine and is stable; and it does not matter if I have 350A draw on the inverter or if I have no draw on the inverter... just turning "ON" the inverter to generate 120V causes the voltage at the house batteries to drop down to 11.8V and it keeps dropping fast!

So what more can I do to:

A) Verify my house batteries need replacing; or...

B) Verify my inverter needs replacing?

[imnprsd]

Supplemental Info:

I disconnected the inverter to battery temperature sensor and just left it open. This sensor has 2 wires that are supposed to be connected to the NEGATIVE battery post.

Immediately, the voltage drop was gone. I.e., the 12.4 on the house batteries (before turning on the inverter) remained at 12.4V after I turned on the inverter. ...So I went to the store and left a 50A fan while I was gone. ...But 1 hour later, when I got back, the inverter was off and the red inverter "off light" on the display panel was lit. ...And my house batteries indicated 12.4 volts. So now what to do?

==> I saw a YouTube video posted by PCS Electronics who said you cannot bench test this type of Dimensions Inverter without connecting the temperature circuit to a 22K ohm resistor that is supposed to simulate room temperature. So tomorrow I will get a 22K ohm resistor and hook it up to the 2 probe wires, and then I will run the inverter in 120V output mode to see what happens.

[imnprsd]

Turns out, 22K ohm resisters are only available on Amazon, but instead of going that route I called Sensata/Dimensions and they confirmed the inverter will not run without a Battery Temperature Sensor (BTS) connected.

The BTS is thermistor that senses temperature, and acts as a safety switch to shut the inverter off in the event your batteries overheat.

I found another video on inverter BTS sensors and they recommend you do not connect the BTS to the negative side of the battery as recommended. They said you would be better off to just zip-tie it in the battery compartment (to the side wall, and just lave the metal-eye unconnected, but not taped) making sure there is no chance the end of the BTS can touch a "+" terminal, because the slightest touch to positive, according to the video, will blow an IC in the inverter and render the whole inverter unusable for evermore!!!

So I ordered BTS Part# 611622-15 from Sensata/Dimensions by emailing their customer service. ...TAT is 5 business days and the cost is $39. Note: At some point Sensata will no longer have this part available and they do not recommend using a 22K ohm resistor that will disable the safety feature and purpose of having a BTS in the first place. So if you do use a 22K ohm resister you are doing so at your own risk.

[imnprsd]

What I learned is that badly sulfated batteries will test good on the voltmeter and even on the hydrometer, but will not handle any load above 350W for more than 15 minutes.

OTHER SIGNS YOU NEED NEW HOUSE BATTERIES

...Your voltage will drop right away when you switch the inverter on, because it draws current out of the house batteries to operate.

...Your voltage will drop rapidly under load; and when you turn off the inverter your voltage will immediately bounce back.

...Pulsing 4 deep cycle batteries is a waste of time! ...you might be able to bring back an engine-start battery to 50-70% SOC, but weak deep cycle house batteries are of no use to anyone; and pulsing them will just make things worse since you will be creating different cell voltages and internal resistance in a deep cycle battery.

...So to get the most battery life out of my NEW house batteries, I bought a Victron IP67-17A charger and I will use this as my main charger when I have shore power available. And when I need a fast charge I will turn on my Dimensions Charger.

...I also like the Victron Bluetooth App for monitoring and controlling the charger without a Remote Display Panel. Plus I think this Victron will do a better job charging my house batteries than the 2004 vintage (3-Stage) Dimensions Charger inside my Dimensions Inverter.