Hi.
Years ago, bought a new inverter; 12V to 120VAC/60Hz. Did not work unless the battery was being charged (over 13V) - Returned to vendor.
I used instead, a UPS inverter hooking an external car battery. Same story. Engine had to be running for the inverter to work.
Yesterday got a 400W 12V to 120VAC inverter. Same crap. Red light indicating lack of input. They NEVER work at 12V input. They want over 13V under load.

Any magic to modify them to run from 12V down to 10V input ? Of course no chinese schematics available.

 

Hi.
Years ago, bought a new inverter; 12V to 120VAC/60Hz. Did not work unless the battery was being charged (over 13V) - Returned to vendor.
I used instead, a UPS inverter hooking an external car battery. Same story. Engine had to be running for the inverter to work.
Yesterday got a 400W 12V to 120VAC inverter. Same crap. Red light indicating lack of input. They NEVER work at 12V input. They want over 13V under load.

Any magic to modify them to run from 12V down to 10V input ? Of course no chinese schematics available.

No magic, just physics. Power in must be greater than power out. Sometimes it must be much greater. When the input voltage drops the demand for current increases. Sometimes that demand for increased current cannot be satisfied. This surprises you why exactly?

 

Perhaps your 12V wiring is not heavy enough? 400W is going to draw over 40Amps. Inverters need to have as short as possible LV leads. Personaly have never had any trouble with 12V to AC inverters & ive had 150W & 600W & 1000W. The 1000W one did require some seriously heavy cable.

 

You don't get what you don't pay for with cheap Chinese electronics.

I've had this inverter since I started my 12vdc solar project. It's still running after years of 7/24 service.
https://forum.allaboutcircuits.com/...ic-controlled-battery-array.32879/post-218885

https://www.amazon.com/Xantrex-PROW...rowatt+sw+2000+inverter&qid=1602291978&sr=8-1

• Built-in digital display for DC volts and output power
• Built-in USB port. Meets stringent UL458 regulatory standard. Low voltage shutdown (10.5 Vdc). Low voltage alarm (11.0 Vdc). Over voltage protection (15.5 Vdc)
• Dual gfci AC receptacles for safe Operation
• Heavy duty terminals for trouble-free Battery connection

I run 0000 gauge wire for the battery connections to reduce low-voltage cutouts at high power.

 

When the inverter was running under load, did you measure the DC voltage at the battery terminals and then at the inverter’s input terminals?

I worked at a place which we manufactured DC/AC inverters, and DC voltage loss due to any number of reasons, was the main service issue.