Power inverters

[Chicken lights]

Sounds odd to connect to two batteries unless they are in parallel. Most inverters are 12V not 24V. Not sure what you have there.

The cable size called for is bigger than you are using, but either way, a 2 or 4 cable suggests 12V not 24. Typically lower voltages require bigger cable. I know that isn't intuitive. Just trust me on that one.

What does it call for and what are you feeding it?

Regardless, back to the cable for a second. Big cables need GREAT connections. A poor or small connection will cut the cables capacity out from under it. Cable Clamps don't generally cut it. Needs to be a regular battery clamp bolted onto the battery terminal. Not always easy to do for secondary loads. But you can get battery clamps that will connect two high current loads at once. That's probably what you need here.

The draw too high suggests a short circuit or a load not designed for an inverter - eg a 120V device on a 240v circuit.

Also possible the load doesn't like a square wave power source or something like that.

Do you have a decent multimeter? If you have a good one, you can measure the voltage drop across one of the cables to calculate actual input and output current and voltage. Don't try to use the meter in current mode unless you have a current loop for it - you will fry it.

At any rate, my very first check after looking at wires and connections would be to do voltage and current checks on everything.

It’s a 12v system

The theory on hooking to two different batteries is that you aren’t “pulling” through one battery. The way it was explained to me was, if you have (more so starting the motor) both positive and negative on the same battery, that one battery does more of the “work”, and over time it will be weaker than the rest.

These are a 3/8” NC post style battery, generally the cable ends are soldered or crimped on the cable, then a 3/8” nut secures it to the battery post

 

[Susquatch]

It’s a 12v system

The theory on hooking to two different batteries is that you aren’t “pulling” through one battery. The way it was explained to me was, if you have (more so starting the motor) both positive and negative on the same battery, that one battery does more of the “work”, and over time it will be weaker than the rest.

These are a 3/8” NC post style battery, generally the cable ends are soldered or crimped on the cable, then a 3/8” nut secures it to the battery post

OK, I understand what you have now. My diesel pickup truck is wired the same way.

Wiring has resistance. The bigger the wire, the less the resistance. The resistance in the wiring biases the load to the battery with the shortest wiring. Wiring them like you have effectively puts the same length of wire on both batteries. It isn't the whole story though because batteries also have internal resistance which can also imbalance the loads if they are different - and they usually are!

Next step is to measure loads and have a look at the waveform of your inverter output.

 

[Susquatch]

Just for reference when all you have is a voltmeter without extremely high amperage capability. (Most common meters are limited to 10 amps.)

You can measure high currents without a high current multimeter or a current loop or a calibrated shunt.

I = V/R

R =0.253 ohms per thousand feet for #4 cable & 0.160 for #2. That's 0.000253 ohms per foot for #4 and 0.000160 for #2

Let's say for the heck of it that your #4 cable is 10ft long. Measuring the voltage (using a mV scale on your meter) across that 10 ft should give you

25 mV for 10 amps
50 mV for 20 amps
100mV for 40 amps

Etc.

This example also demonstrates why balanced lead length is important. 400 cold cranking amps would result in one whole Volt loss across a 10 ft #4 cable!

It's also why long extension cords should be 12 gauge instead of 14 16 or 18.

 

[Darren]

In the automotive world its not uncommon to see a 1-2v drop accross 6ft of wiring between a starter motor and battery during cold cranking.

 

[jcdammeyer]

View attachment 27490Still no bueno. I’m not understanding this

Sept- Truck running, high idle, wouldn’t run the microwave

Sept- Truck running, low idle, printer plugged in (not printing), laptop wouldn’t power up

Oct 4- First phone call to tech support, 45 minutes on hold, got cut short because I had a meeting, their initial thought was the printer was a power hog (?)

Oct 28- 4 new batteries, alternator was new around May 2022, found 3 bad battery cables, fixed 2, had to leave the 3rd

Still will not run the microwave. Says it’s 1100 watt input, 700 watt output (truck running)

Owners manual says I should be running 2 gauge wire, I have 4 gauge, it’s approximately 6 feet from the batteries to the inverter

Positive for the inverter is on one battery, ground is on an opposite battery

Within 10 seconds of running the microwave, the voltmeter on the dash drops dramatically (truck running), and the error message E06 flashes, connected load is too high

Other than another call to tech support, which I’ll do next week, I’m stumped

I have a couple of questions.
1. Those appear to be vehicle flooded lead acid starting batteries rather than AGM sealed batteries. Is that correct?
2. Have you installed a BMS of some sort to track battery status?
Something like this:

https://www.amazon.ca/Battery-Capacity-Percentage-6x3-3x1-4cm-2-4x1-3x0-6inch/dp/B08JZ9RFR5/ref=sr_1_16

or something like this:

Wanderer 10A PWM Charge Controller 12V/24V With Bluetooth Module

Renogy Wanderer 10A PWM Charge Controller with Smart 4 Stage PWM charging, integrated 5V 2A USB ports. AGM, Gel, Flooded, and Lithium battery option ready, with RS232 port.

ca.renogy.com

The problem with lead acid batteries is if they are taken down below 50% State of Charge (SOC) their life is almost cut in half.
Lead acid batteries also require Bulk, Absorption and Float charge states. The Absorption can take hours before 100% SOC is reached. And when a Lead Acid battery doesn't reach 100% the next time that 100% value is a bit lower resulting in a battery that can never reach it's fully charged state.

Battery Charging Tutorial | ChargingChargers.com

Battery charging tutorial

www.chargingchargers.com

 

[Chicken lights]

After an hour with tech support, the consensus is a short in the inverter. They’ll send me a replacement and I’ll send them mine back. Had a local shop look at it once I made it home, they couldn’t find anything wrong with my install. That was part of my argument with Magnum, was two other inverters ran on this setup fine, why is your inverter balking at remotely working.

I had no issues with Napa replacing the first Samlex under warranty, but it IS nice dealing with companies that stand behind their products.

The saga drags on