Inverter low voltage shutdown issue

[thumper-tx]

My trailer is a 2016, 21, old body style.

When I try to run the microwave off of the inverter it shuts down after about 15 seconds and gives a low input voltage error code. Is there anything other than bad batteries that would cause? The batteries that came with the trailer died after about 6 months and Interstate replaced them under warranty with new ones. That makes these batteries about 14 months old.

When the microwave comes, the battery voltages starts dropping quickly and hits about 10.5 in 10-15 seconds, tripping the inverter off.

So, do I have more bad batteries or are there other things I should check.

Thanks in advance for any help on this.

[Brian B-P]

How well charged are the batteries before trying the inverter?

If the batteries are well-charged before using the inverter, and the high current demand of the inverter (while running the microwave) drops the voltage severely, there is too much resistance somewhere. Internal resistance in the battery would be a battery condition problem, but there could also be a bad connection somewhere in the wiring between the battery and inverter, due to corrosion or a loosened nut or bolt.

[sclifrickson]

What are your charging setup and regimen?

[BN49]

You might check the 2 15 amp breakers in the sub panel under the dinette seat which are the breakers for the 120V outlets. When I was having electrical problems I found a loose wire at one of the breaker connections that appeared to have been arcing. After tightening the connection the electrical problems went away.

[Bill and Earline]

I had this same symptom that was corrected by working on the crimp connector of the heavy wire at the battery. On mine, the crimp connector needed to be crushed tighter so that it was no longer loose.

There's probably a better way to make sure this connection is secure and is sending full electricity through that wire, but for now it's ok, and I bring a large vice grip. I may include a big C-clamp to really put some pressure on that connector, when we start the season next month. Thanks for reminding me.

[thumper-tx]

Originally Posted by sclifrickson

What are your charging setup and regimen?

Before fall storage I charge fully and they flip the battery cutoff switch. During the winter I plug into shore power about every 6 weeks for a half day and top off the charge. The first time the error started was during a stop at the beginning of a 8 day trip. I tried it again after returning [and the trailed had been plugged in and charging] for 8 nights.

[thumper-tx]

Originally Posted by BN49

You might check the 2 15 amp breakers in the sub panel under the dinette seat which are the breakers for the 120V outlets. When I was having electrical problems I found a loose wire at one of the breaker connections that appeared to have been arcing. After tightening the connection the electrical problems went away.

Thanks for pointing this out! This is not where I would have initially looked and will check it out today.

[AllanEdie]

Originally Posted by thumper-tx

My trailer is a 2016, 21, old body style.

When I try to run the microwave off of the inverter it shuts down after about 15 seconds and gives a low input voltage error code. Is there anything other than bad batteries that would cause? The batteries that came with the trailer died after about 6 months and Interstate replaced them under warranty with new ones. That makes these batteries about 14 months old.

When the microwave comes, the battery voltages starts dropping quickly and hits about 10.5 in 10-15 seconds, tripping the inverter off.

So, do I have more bad batteries or are there other things I should check.

Thanks in advance for any help on this.

If that voltage decline is at the battery posts, and accurate, then your problem is batteries. Poor connections between the batteries and the inverter will not cause the voltage failure that you describe if the measurement is accurate at the battery terminals.

If the voltage that you describe is at the inverter, then you could have the connection issues others describe, or a wire size issue between the inverter and the battery. Did the inverter ever work the microwave properly when the batteries were new? Wire size is often an issue with large loads like that, but it does not affect voltage at the battery, only at the inverter under load.

If you can let us know exactly how and where the voltage decline you describe is measured, I may be able to advise further.

If it turns out that the batteries are the problem, the cause would be either defective batteries again, or that they were discharged too deeply during use in the previous season. Taking them below 12volts repeatedly will kill them in fairly short order.

[Ron in BC]

Originally Posted by Bill and Earline

I had this same symptom that was corrected by working on the crimp connector of the heavy wire at the battery. On mine, the crimp connector needed to be crushed tighter so that it was no longer loose.

There's probably a better way to make sure this connection is secure and is sending full electricity through that wire, but for now it's ok, and I bring a large vice grip. I may include a big C-clamp to really put some pressure on that connector, when we start the season next month. Thanks for reminding me.

I solder that type of connection.

Ron

[Brian B-P]

Originally Posted by BN49

You might check the 2 15 amp breakers in the sub panel under the dinette seat which are the breakers for the 120V outlets.

Originally Posted by thumper-tx

This is not where I would have initially looked and will check it out today.

Checking these connections is prudent, but a bad connection in an AC component won't cause the DC voltage drop that is causing the inverter to complain.

[thumper-tx]

Originally Posted by AllanEdie

If that voltage decline is at the battery posts, and accurate, then your problem is batteries. Poor connections between the batteries and the inverter will not cause the voltage failure that you describe if the measurement is accurate at the battery terminals.

If the voltage that you describe is at the inverter, then you could have the connection issues others describe, or a wire size issue between the inverter and the battery. Did the inverter ever work the microwave properly when the batteries were new? Wire size is often an issue with large loads like that, but it does not affect voltage at the battery, only at the inverter under load.

If you can let us know exactly how and where the voltage decline you describe is measured, I may be able to advise further.

If it turns out that the batteries are the problem, the cause would be either defective batteries again, or that they were discharged too deeply during use in the previous season. Taking them below 12volts repeatedly will kill them in fairly short order.

I measured voltage at the battery and at the 12v outlet in the trailer. Both locations showed rapid voltage drop that led to inverter shutdown within about15 seconds. I turned the inverter off and plugged an old style hand held spotlight into the 12v outlet and after about a minute the battery voltage had only dropped by .10 . I know this is a much lower load than the inverter / microwave but did not cause a big voltage drop.

Yes, the inverter ran the microwave without issue for the first 18 months.

Isn't it possible that the inverter could have internal issues that cause a higher than normal power draw. all connections at the battery and inverter are tight.

I didn't mention it in the initial post but the 200A fuse at the battery post had a tiny hairline crack like it was about to fail completely which I found by wiggling wires and seeing it arc. It has been replaced but no impact on the situation.

[thumper-tx]

The Samlex inverter manual troubleshooting guide also says that sulfation in the battery can cause current drop at the post during high capacity load. I don't have a way to check internal battery resistance so I will need to take it to a distributor to see if that has happened I guess.

[AllanEdie]

Given that you have confirmed the voltage decline at the battery, I am reasonably sure that your battery is the problem. If you have it load tested, you will get your answer. Its performance under small loads tells you very little or nothing about its real condition.

It is possible that the battery failed due to a flaw, but also because of repeated deep discharges. If you do not have a battery monitor, you might want to consider installing one, and monitoring it to determine whether you are keeping the batteries above 50% charge. The deeper you go beyond that, the earlier they die. If you take them all the way down, you will usually kill them in short order.

[citabria90]

Hmmm . . . interesting problem.
• try running another high-amperage appliance such as a corded hand vac or another microwave unit. If you still get the extreme voltage drop, this would rule out a malfunctioning microwave.
• borrow (or buy) another inverter and connect it. If you STILL get the voltage drop, then it's the battery or its connections. If you don't get the voltage drop, then you can assume a defective inverter.

Chuck

[citabria90]

Personally, I'd suspect the inverter . . .

[Vermilye]

As others have noted, where the voltage drop is taking place is something worth determining. With the inverter running at a heavy load, check the voltage at the battery terminals, and again at the inverter input terminals. The difference is the loss due to wiring.

If the batteries are pulled down as much as the inverter, the wiring is probably OK, and the batteries are suspect. If the batteries show a considerable higher voltage than the inverter input, look for undersized wire, or bad connections on the 12V wiring.

[citabria90]

One other point to aid in troubleshooting . . . when you get the low-battery error, disconnect the cables from the battery, and then measure the voltage at the battery terminals. If you measure the battery voltage while the battery is still connected to the inverter, you may get an erroneaus and misleading voltage.

Chuck

[Ron in BC]

Originally Posted by citabria90

One other point to aid in troubleshooting . . . when you get the low-battery error, disconnect the cables from the battery, and then measure the voltage at the battery terminals. If you measure the battery voltage while the battery is still connected to the inverter, you may get an erroneaus and misleading voltage.

Chuck

That wouldn't work for me. When the microwave is on my battery display drops down to just under 12 volts. As soon as the load is off they bounce right back up to where they were or .1 volt lower.

Ron

[Brian B-P]

Originally Posted by citabria90

If you measure the battery voltage while the battery is still connected to the inverter, you may get an erroneaus and misleading voltage.

The voltage at the battery terminals while the inverter is drawing current would be an erroneous and misleading indication of the state of battery charge; however, it is exactly the information needed about the voltage available to the inverter. If this voltage dips really low (and it does), then there is a battery problem. If the battery voltage recovers when the load is removed that means that the battery is charged, but not that the battery is good.

[citabria90]

Hmmm . . . I'm not sure.
Perhaps the OP should do a detailed investigation of his cabling setup (although I think he did originally state that all was working normally at the beginning). If that's the case, then something has changed (or failed).

I'm skeptical of the battery (BTW, one battery or two in series) failure, mostly because it seems to me to not be a common occurrence

OP – what is the ratine of your inverter, and what size cables do you have between the inverter and the battery?

So many variables.

Chuck