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Old 08-24-2019, 10:18 AM   #1
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inverter woes...

So I went the cheap route. :/

The first one was an amazon wzrelb 2500W pure sine inverter for $200 on some sort of sale. It worked great until it went on fire after about a month under very low load.

So I sent that back and found a new one from the same brand, claiming to be more reliable! 18 month warranty, in fact. $400, 3500W, pure sine.

The problem with this one was that it pulsed... the light in my fridge looks like its pulsing, almost blinking, and its so bad it causes a pulse in my DC LED lights. I can't imagine that's good for the fridge or anything else. So I sent it back. Got another of the same model, figuring it was a fluke, and it was a lot better, but it has started acting similar to the first one, even making the DC lights pulse again after about two weeks.

I've tried it wired directly to the fridge with nothing else attached to the AC side and it still happens. The DC side has two charge controllers from the solar hooked up, plus 3 215AH 12V batteries. Cable sizes are currently not great, only #2, but I have it wired through a 15A breaker and the only load is the fridge that runs at about 60W and my PC at times (200W peak) so I think that should be okay for the moment, although 4/0 wires are coming soon.

The only thing that I have done that I know is wrong is that I did not ground the inverter to the chassis of the bus. I feel like that's a big risk to the electronics for the engine, especially knowing how shitty these inverters are so I was hoping to avoid that if I can, at least for the short term. I may run a ground into a stake in the earth to see if it helps...

Also, everything works fine on an ungrounded generator at the moment, no pulsing or weirdness.

Any thoughts? I'm likely going to just send this thing back to amazon and try a different inverter but I can't afford a $1200 unit at the moment and would prefer pure sine, but is anyone else using anything that they love?

Thanks for the help!

Rob

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Old 08-24-2019, 10:30 AM   #2
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I don't know what your expected loads are, but are you sure you need a 3500W inverter? We've got a 2000W Aims pure sine inverter/charger. It set us back about $700. I think even 2000w might be overkill for us. I've since learned that 2000w is pushing the limits of what a 12v FLA battery system should handle.
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Old 08-24-2019, 11:03 AM   #3
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Yeah, I think it's too much load for extended use but based on what I have seen in video reviews of these cheap inverters 3500W isn't what you think it is anyway. I figure it's good to have one with a high rating for surge capacity and if I ever do want to run the AC off of it for a short time, or the miter saw more likely, but I agree that it would murder the batteries for any extended use.

I plan on having 1800W of solar on the roof, so in peak sun the AC may be passable for an hour or two to cool the bus off when we return from someplace and I would like that to be an option without turning the generator on. In practicality I have HEARD of that working but I recognize it also may not.

AIMS has been good though? I saw a bad review of one taken apart and I have avoided them for that reason, but I may give them a shot considering where I am now.
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Old 08-24-2019, 11:06 AM   #4
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Maybe you can post the specific brand and model. I have a reliable inverters and they work well. We cook on induction and had no problems.

I blew one 2500 up because the fan got stuck and it overheated while we ran a 2600 watt shower water heating head for 20 minutes.

They are straight forward and pretty easy to fix.
If the led DC lights are blinking then I think it is more your charge controllers coming on and off.
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Old 08-24-2019, 11:12 AM   #5
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This is the unit:

WZRELB Full Power Endurable 3500W 12VDC to 120VAC 60HZ US DUAL OUTLETS LED DISPLAY PURE SINE WAVE INVERTER Power Converter, (RBP350012B1)

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I never had problems with the charge controllers before this inverter, and if I turn the inverter off the blinking on the DC side stops too. I am pretty sure the varying load from the inverter is causing the DC blinking, but I'll pull the charge controllers for a moment to see if that helps, it's something I have not done before and it's definitely worth a shot.
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Old 08-24-2019, 11:22 AM   #6
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Quote:
Originally Posted by rffffffff View Post
AIMS has been good though? I saw a bad review of one taken apart and I have avoided them for that reason, but I may give them a shot considering where I am now.
AIMS has been good so far. It's only been about 18 months though. I've also seen bad reviews. If it craps out for some reason, I'll likely go with a Magnum or Morningstar or something more name brand.
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Old 08-24-2019, 11:41 AM   #7
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Old 08-24-2019, 11:42 AM   #8
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That is the same unit I have now after I blew the 2500 version up. I am on 24 volt. These inverters first convert from 12/24 volt DC to 170/200 vdc and then convert that into 120vac. They have high frequency transformer and do not use a heavy 60 hz transformer. It is possible that the DC to DC conversion turns on off at most likely 60 or 30 hz.
If that makes it thru to your battery voltage fluctuating with that frequency then the battery / wiring impedance is pretty high.
Are the batteries old? Poor wiring.?
The other thing can be the led lights. If you use 12 vdc led lights then they come in two flavors. One use a resistor to limit the current... The other uses a constant current driver.. In the last version the light output is independent from the voltage. In the resistor regulated led the light output varies a lot with the voltage.

Good luck.j
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Old 08-24-2019, 11:43 AM   #9
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No change with the charge controllers disconnected.

12v side seems stable as the moment, it wasn’t last night, but the ac side is still pulsing.

Video of the fridge: https://youtu.be/BIdqFe3bDBc
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Old 08-24-2019, 11:49 AM   #10
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I made the mistake of not grounding the inverter, I was sweaty and working in the bus and bumped the ungrounded inverter and it shocked the crap out of me. I grounded it to a chair rail. Shouldn't effect any of the electrics of the bus.
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Old 08-24-2019, 11:58 AM   #11
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I just wired the leds strings to the 12v directly, no controller at all. Perhaps that’s a problem? They work just fine almost all of the time, just blink when the inverter issue is at its worst. I haven’t checked the current draw but they don’t do anything to the batteries in terms of discharge and the wires are tiny so I never worried about it.

The 12v pulsing happened all of the time with the second inverter but only once with this one, and I can’t duplicate it. Right now it’s only the 120v side that pulses. The computer runs fine, but that blinking fridge light is driving me crazy. I wish i still had an oscilloscope, but I feel like I’m gonna burn through fridge compressors if it stays like that. The blink continues with the compressor off too, btw, so I think it’s not really load related, unless perhaps the 3500w version doesn’t handle the small load that well?

Batteries are brand new and I have 3 wired in parallel (crown cr-215, 12v 215ah), albeit with 2awg wire but it should be fine for this kinda load until the 4/0 arrives. I’m
Pretty experienced with wiring and electronics, I used to service MRI and CT scanners, and I’m confident that I have good connections and solid enough wire for the load that I have at the moment.

I’m wondering about noise and grounding more than anything else if it’s not just a bad inverter... maybe I’ll try to ground it all to earth temporarily and see if it helps.

I hate that these things have 60v on the hot and 60v on the neutral... makes me not want to ground it to the chassis at all even though I know I’m supposed to.

Am I crazy to consider running the ac ground to the 12v negative terminal?
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Old 08-24-2019, 12:10 PM   #12
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ok, I watched your vid..so i misunderstood, I thought your 12 volt Dc led were pulsing. Is this an LED light inside the fridge or a normal bulb?


Does the frequency of the pulsing change when you add another load?
i will try it with my inverter and see if is the same. My fridge runs of 24 volt and we use the inverter only for induction stove and tools.



Later J
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Old 08-24-2019, 12:13 PM   #13
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Soooo maybe I figured it out with all of your help.

I noticed the blink got faster when the fridge compressor came on.

I turned the toaster oven on for a second and the blink immediately stopped. I didn’t want to run that thing at however many amps it was drawing on the 12v side for long on the 2awg wires, but I think I’m running into an issue with too small of a load for the size of the inverter. Give it some real load and it seems just fine, but even the fridge plus the PC and monitor isn’t enough to quell the pulses.

I guess I have to decide if I want to keep this thing, go down to a smaller unit, or try another inverter from a different manufacturer that may be more stable at low draw.

Not sure what to do but at least I have some insight into what’s going on. Perhaps grounding will help clean it up at low power, I’ll try that too before I decide what’s next.

Keep chiming in if you have inverter recommendations, seems like aims may be worth a shot if I switch this out.
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Old 08-24-2019, 12:18 PM   #14
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The 12vdc was pulsing too with the second inverter and for a moment with this one but I can’t reproduce that at the moment.

I just posted again re:loads. It’s incandescent bulb in the fridge, just a little 10w thing I think.

I would love to know if your inverter pulses an incandescent bulb if nothing else was on it, but I don’t know how hard those are to find these days!
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Old 08-24-2019, 12:23 PM   #15
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Great, the 3500 is made pretty nice on the inside. All there inverters are modular. I have a 500 watt, 2500 and 3500.. all 24 volts.
The 2500 is maxed out on the components. the 3500 has an easy job. The 3500 is a module that can go up to 4000 watt. I will post a picture of the guts.
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Old 08-24-2019, 01:02 PM   #16
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Would this happen with a modified wave inverter?
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Old 08-24-2019, 01:17 PM   #17
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Pics of the reliable inverters inside. 500 watt and 3500 watt. The controller boards are the small standing PCB. Same in both units. Price new on fleabay about $6. The MOSFETs and igbt are $20 for 10 pieces

The pure sine wave part is taken care of an asic processor designed for this purpose... EG8010.

The DC conversion part is done with a ka7500c.

I like the layout because it is easy to repair in this throw away society and the parts are cheap.

Later johan
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Old 08-24-2019, 01:24 PM   #18
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Marc. The modified wave inverters generally use a large heavy transformer. A complete different design.
Probably not.
The op' s inverter like mine has a design issue that it is actually two inverters in one. A DC to DC conversion and then a DC to Ac conversion. The two modules are working together to get the highest efficiency and best wave form. I guess in this case it is not very good in working together at very low power levels. Just like an engine is shaking more at idle.

Later j
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Old 08-24-2019, 03:33 PM   #19
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So I tried mine with a 60 watt lightbulb and no flickering whatsoever.
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Old 08-24-2019, 04:14 PM   #20
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I've been running this pretty regularly for a year with no issues. No heat, no noise, no fluctuations in output, and they're dirt cheap and work on extended voltage range which is good with lithium and other non lead acid batteries too.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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