Inverter problem I think? Xantrex SW3000

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Inverter problem I think? Xantrex SW3000

October 09, 2019, 05:24:01 pm

Original purchase in Jan 2019 and coach had a long period of sitting. Before purchase owner put in 3 8D flooded coach batteries and 3 chassi batteries all new. I'm sure in conversation with them that they let the batteries go dead several times and when I went to look at coach batteries were also dead.

I kept having problem with coach batteries and on a trip noticed that if I wasn't plugged in or if I didn't have the engine or generator running that I could not run the microwave for any longer than 10 seconds before the Low battery warning would come on and voltage would drop to 12.2 or lower. The low voltage light would be on in morning if I left the inverter on over the course of the night, if I wasn't plugged in. Thinking the batteries were the problem, I replaced them with 3 AGM Oreilly with 250amp hours each for a total of 750 amp hours. I also installed 200W solar on storage unit and keep unit plugged into that so wasn't seeing any problems recently. Noticed on the next trip when using the microwave with only inverter on, the same thing happened. Voltage would drop and Low voltage warning would sound from the inverter.

Spoke with a highly thought of vendor recommended by several on the forum and they said they quit selling the Xantrex equipment and they were sure that was where my problem was.

Xantrex has me chasing down voltage and troubleshooting. Found out from them that the inverter is a minimum of 10 years old since they quit producing them in 2010.
There steps were as follows
1 Check voltage at the battery 12.8
2 check voltage at the inverter 12.8
3 start Microwave and check voltage at the inverter dropped to 11.5 then 11.4 then 11.3

Called Xantrex back and they suggested the following
1 check all connections and make sure they are not loose for both + & -
2 check voltage at battery, inverter, and both sides of the fuse to see if there is a location where the voltage drops while the micro wave is running.

I will do that tomorrow and report back.

Any other forum suggestions would be appreciated

Thanks for your help.

Re: Inverter problem I think? Xantrex SW3000

Reply #1 – October 09, 2019, 05:41:51 pm

Buy a IR temp gun and shoot all cables and connections. Loose or bad connections will produce heat and you will able to see the higher temps.
Milwaukee Laser Temperature Gun Infrared 10:1 Thermometer-2267-20 - The Home...

Re: Inverter problem I think? Xantrex SW3000

Reply #2 – October 09, 2019, 05:55:56 pm

Sounds like a bad charger and now the batteries are toast. Or maybe they just let them go. But...
If so, replace with a Victron multiplus inverter charger and new batteries.
I'm sure many will give you advice on the battery side. If you can afford it, go lithium. If not or just want to stay with agm, there are lots of ideas here on the forums.
Once they get that low, lead acid batteries are toast.

Re: Inverter problem I think? Xantrex SW3000

Reply #3 – October 09, 2019, 06:31:50 pm

Quote from: Bob and Julie – October 09, 2019, 05:55:56 pm

Sounds like a bad charger and now the batteries are toast. Or maybe they just let them go. But...
If so, replace with a Victron multiplus inverter charger and new batteries.
I'm sure many will give you advice on the battery side. If you can afford it, go lithium. If not or just want to stay with agm, there are lots of ideas here on the forums.
Once they get that low, lead acid batteries are toast.

After using the microwave what does the voltage rise to? There may be nothing wrong other than setting the time and voltage drop allowed before shutting off on the inverter. I have the SW3012 which is just a later model of yours. If I have 12.3 in the morning and use the microwave it drops to the low 11's but bounces back up to 12.3 after the microwave shuts off. You are not going to draw 150 amps and hold the voltage even with brand new fully charged batteries.

Re: Inverter problem I think? Xantrex SW3000

Reply #4 – October 09, 2019, 06:44:38 pm

Correct. Battery voltage is/should be measured with BATTERIES AT REST.

If measured under a load, posted minimum voltage readings are MISLEADING.

Re: Inverter problem I think? Xantrex SW3000

Reply #5 – October 09, 2019, 06:57:08 pm

Will try again tomorrow and post readings at rest as well. Hope they are not toast! Ordered the IR gun.

Any other way to troubleshoot an inverter?

Re: Inverter problem I think? Xantrex SW3000

Reply #6 – October 09, 2019, 07:10:51 pm

I would check your re settable settings. You can download a manual from the Xantrex site or use the link I've attached. I would set the low battery dc cutoff to 10 to 10.5 volts should you find it higher. I believe this might eliminate your problem. If not I would do as Xantrex and others advised, checking voltage and connections.

The default is 10 amps, I have mine set to 10.5 amps. See page 39 in the manual, you can download from the link below.

As far as the quality of your unit it is excellent. I would not believe hearsay. You own a beast of a sine wave 3000 watt inverter/charger with an excellent and adjustable 150 watt battery charger. I've owned many Xantrex units because of their quality, and yes a replacement might be a Victron because of their bluetooth interface. Retailers love to knock product they do not sell and manufacturers love to recommend their newest product.

http://www.xantrex.com/power-products/inverter-chargers/freedom-sw-3000.aspx

Re: Inverter problem I think? Xantrex SW3000

Reply #7 – October 09, 2019, 08:21:33 pm

Wondering if you have a bad isolator- sounds like it could be bleeding amps through a bad diode when you are not plugged in or running engine or generator. This could take down both sets of batteries as they are connected and not separated ( isolated) as they should be at night. Just a thought.........hope you get it figured out and solved.

Re: Inverter problem I think? Xantrex SW3000

Reply #8 – October 10, 2019, 01:07:52 pm

I don't think the batteries were fully charged its been overcast for several days now, with the 200w solar plugged in, the charge at the solar controller was reading 13.1. Did not unplug solar and ran microwave for 2m. Realizing what I had done I then unplugged solar and let it rest, started with the inside panel at 12.8v

Jack,
Changed the low battery DC alarm as you suggested. Mine was set at 11.4. That cured the low battery alarm alert.

Brett and Craneman: measured voltage as follows

No Load
inside panel 12.8
Battery 12.8
Fuse both sides 12.75
inverter 12.75

With microwave on heated water for 2m
inside panel 12.1
Battery 12.0
Fuse both sides 11.4
inverter 11.3
Why would voltage drop so much at the inverter and both sides of the fuse when it is under load?

After resting with no load for 45m
inside panel 12.7
Battery 12.6
Fuse both sides 12.6
inverter 12.6

Does this seem like the inverter is working properly?

Will test again tomorrow.

Re: Inverter problem I think? Xantrex SW3000

Reply #9 – October 10, 2019, 01:22:09 pm

THIS is a problem:

With microwave on heated water for 2m
inside panel 12.1
Battery 12.0
Fuse both sides 11.4
inverter 11.3
Why would voltage drop so much at the inverter and both sides of the fuse when it is under load?

You need to trace down where you are loosing from 12.0 at the batteries to 11.4 at the battery side of the fuse.

Poor connection (positive or ground) at the battery is where I would start. Check the battery end of the cables to make sure you have clean "copper-colored copper", not green copper oxide which is a very poor conductor.

Re: Inverter problem I think? Xantrex SW3000

Reply #10 – October 10, 2019, 01:33:41 pm

Quote from: wolfe10 – October 10, 2019, 01:22:09 pm

THIS is a problem:

With microwave on heated water for 2m
inside panel 12.1
Battery 12.0
Fuse both sides 11.4
inverter 11.3
Why would voltage drop so much at the inverter and both sides of the fuse when it is under load?

You need to trace down where you are loosing from 12.0 at the batteries to 11.4 at the battery side of the fuse.

Poor connection (positive or ground) at the battery is where I would start. Check the battery end of the cables to make sure you have clean "copper-colored copper", not green copper oxide which is a very poor conductor.

Could the distance of the cables from the battery to the fuse and inverter cause the voltage loss?

Re: Inverter problem I think? Xantrex SW3000

Reply #11 – October 10, 2019, 01:51:21 pm

Tommy, I am glad you found out you had the incorrect low dc battery setting. This is a common mistake people make when they change their inverter/charger settings.

I believe you are correct, your batteries are not fully charged. Your water heater and microwave will put a 20 amp draw on your batteries and then it is common for rv batteries to drop into the 11 volt range when reading.

My solar controller bulk charges at 14.4, when batteries are full batteries float at 13.4. What solor controller do you have? You may need to run your gen for a few hours to top off your batteries. I use to have 150 watt solar (now I have 1187), with 150 amp solar, with your same Xantrex SW3000 150 amp charger, and 3 Lifeline 8D batteries. When dry camping I sometimes had to run gen for 2 hrs every 2 to 3 days depending on how much sun we had and how much power we used. You have a great inverter/charger, study the manual to make sure other settings are correct.

The following will spell out the 20 amp draw you did in your test, for you.

"Crank up your Onan or engine generator, or plug into shore power, and your voltage goes up to 14.0 – 14.5 volts, even when your battery is seriously depleted. Turn on a big load like the microwave (if you have a big inverter that will power it), and voltage dives down into the 11.5-11.8 volt range, even on fully charged batteries. Again in general, the bigger the charging current or load, the further above or below your resting voltage your system will be. So looking at the voltage doesn't give you an accurate reading on how charged your battery is – you have to adjust for loads and charging sources."

Understanding RV Battery Voltage and State of Charge | RV Lifestyle

Re: Inverter problem I think? Xantrex SW3000

Reply #12 – October 10, 2019, 01:55:46 pm

Quote from: craneman – October 10, 2019, 01:33:41 pm

Could the distance of the cables from the battery to the fuse and inverter cause the voltage loss?

Don't think its the distance, as the cable to fuse is 3' tops. Its on the next compartment over on the common wall between battery and fuse. Then another 3' to the inverter. Looks like 4/0 cable.

Re: Inverter problem I think? Xantrex SW3000

Reply #13 – October 10, 2019, 01:57:50 pm

Brett, I will check the connections and report back.

Re: Inverter problem I think? Xantrex SW3000

Reply #14 – October 10, 2019, 02:07:50 pm

Thanks Jack, good article.

Re: Inverter problem I think? Xantrex SW3000

Reply #15 – October 10, 2019, 02:17:38 pm

Quote from: craneman – October 10, 2019, 01:33:41 pm

Could the distance of the cables from the battery to the fuse and inverter cause the voltage loss?

Not if properly sized wire. What is length of wire run and what gauge? What wattage was the load?

Re: Inverter problem I think? Xantrex SW3000

Reply #16 – October 10, 2019, 02:38:39 pm

Quote from: wolfe10 – October 10, 2019, 02:17:38 pm

Not if properly sized wire. What is length of wire run and what gauge? What wattage was the load?

3' to fuse, 3' to inverter. 4/0 guage looks like. Microwave 850W

Re: Inverter problem I think? Xantrex SW3000

Reply #17 – October 10, 2019, 03:11:04 pm

Tommy, Since now we know you do not have an inverter problem (such good news), if you do not already have, I recommend to you to help moniter your batteries, an easy install, is to purchase a battery moniter, the Victron BMV 712 Smart that has a bluetooth app to show your readings..

I tested my readings this morning as follows on the Victron 712, by just looking at my phone Victron app. Batteries are three 8D AGMs, 90 days old, at 92% charge, voltage 12.5 with inverter and charger off.

With dc 150 amp draw (approx 20 amps AC from the pole) from batteries by turning on inverter and boiling water in microwave, batteries went to 11.8 volts, just as the above articleI posted, spelled out.

Most often we can only improve what we measure.

Battery Monitors and Monitoring Solutions - Victron Energy | Victron Energy

Re: Inverter problem I think? Xantrex SW3000

Reply #18 – October 10, 2019, 05:18:02 pm

Thanks Jack, I will look into the battery monitor.

Re did voltage to see if I did something wrong

No Load
inside panel 13.0
Battery 13.01
Fuse both sides 12.98
inverter 12.98

With microwave on heated water for 2m
inside panel 11.7
Battery 12.13
Fuse both sides 11.61/11.58
inverter 11.46

After resting with no load for 5m
inside panel 12.8
Battery 12.73
Fuse both sides 12.73
inverter 12.73

Checked and found I definitely had one loose cable connection (I could take it off without unscrewing the bolt). Tightened the connection and will have to redo voltage test tomorrow. None of the cables looked corroded, do have a rusty bolt on that loose connection, should I replace it?

Re: Inverter problem I think? Xantrex SW3000

Reply #19 – October 10, 2019, 05:25:14 pm

No, as long as you can tighten it up, rust on the bolt is not a problem.

Could you replace it-- sure. But, it is not causing a voltage drop if it is tight.

Re: Inverter problem I think? Xantrex SW3000

Reply #20 – October 13, 2019, 08:41:41 pm

Jcus, Jim c. (Sorry I had cranemans name here before by mistake)
How much difference in temperature will there be with a loose or bad connection on a battery terminal. Does 1 degree, 2 or is it more like 10 degrees difference in temperature that indicates a bad connection? Got the IR gun and will try it out tomorrow. Just curious on how to interpret if the temps are different. Will a terminal with the battery temp sensor hooked to it read different than a terminal with nothing else connected to it?

Re: Inverter problem I think? Xantrex SW3000

Reply #21 – October 13, 2019, 08:45:07 pm

Voltage is a better gauge of bad connection. Voltage on one side of a connection should be the same as the other. I never used a IR temp. for connection problems use them for wheel, tire and bearing temps.

Re: Inverter problem I think? Xantrex SW3000

Reply #22 – October 13, 2019, 09:40:24 pm

Quote from: Tommy D – October 13, 2019, 08:41:41 pm

Jcus, Jim c. (Sorry I had cranemans name here before by mistake)
How much difference in temperature will there be with a loose or bad connection on a battery terminal. Does 1 degree, 2 or is it more like 10 degrees difference in temperature that indicates a bad connection? Got the IR gun and will try it out tomorrow. Just curious on how to interpret if the temps are different. Will a terminal with the battery temp sensor hooked to it read different than a terminal with nothing else connected to it?

If most of your connections are, say 80 f. and you find one at 85 f, would make sure that one was clean and tight. A good connection will be about ambient temp. Temp sensor will not affect terminal temp if it is a good connection. Check wire temps too, found I had one that was hot inside a crimped connection.
Best done after, or during a heavy load. Any bad connection will cause resistance, which causes heat, thus he higher temps.
https://dam-assets.fluke.com/s3fs-public/2562804_6250_eng_a_w.pdf

Re: Inverter problem I think? Xantrex SW3000

Reply #23 – October 13, 2019, 10:32:02 pm

Quote from: jcus – October 13, 2019, 09:40:24 pm

Best done after, or during a heavy load. Any bad connection will cause resistance, which causes heat, thus he higher temps.
https://dam-assets.fluke.com/s3fs-public/2562804_6250_eng_a_w.pdf

Actually ONLY done under high load. At low load, even a bad connection is usually able to pass a few amps. Think of a bad connection as a 10 gauge wire. vs 4/0 cable. Small loads, no problem. Large loads-- it suddenly becomes a large RESISTANCE.

Re: Inverter problem I think? Xantrex SW3000

Reply #24 – October 13, 2019, 11:04:10 pm

Quote from: wolfe10 – October 13, 2019, 10:32:02 pm

Actually ONLY done under high load. At low load, even a bad connection is usually able to pass a few amps. Think of a bad connection as a 10 gauge wire. vs 4/0 cable. Small loads, no problem. Large loads-- it suddenly becomes a large RESISTANCE.

Actually Wolfe, ran my ac off inverter for an hour, shut down, and 20 min later checked temps, they were still high on the bad connections, could take a while for the heat to build up, and a while, to dissipate. On ships with switchboards where checking voltages would be dangerous, switchboard rear panels are removed and a thermal imaging camera, [more expensive version of an ir gun] is used to check for any hot spots, indicating a less than optimum connection. Standard PM on most ships. If a hot spot is detected, power to switchboard is secured and connection repaired.
FLIR TG275 Thermal Camera for Automotive Diagnostics | FLIR Systems

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