My inverter/charger melted down.
I am wondering if I can put AC Mains through a varactor bringing it down to 90 volts or so run that through a full wave bridge rectifier and put that to the PV input.
I understand that AC Mains are considered "stiff" for mppt. Is it possible to turn the mppt off ect.
Quote from: 1brad on July 19, 2015, 11:25:29 PM
My inverter/charger melted down.
I am wondering if I can put AC Mains through a varactor bringing it down to 90 volts or so run that through a full wave bridge rectifier and put that to the PV input.
I understand that AC Mains are considered "stiff" for mppt. Is it possible to turn the mppt off ect.
Hi 1brad,
Welcome to the Forum.
This topic has come up a number of times, here.
First, a Varactor would probably not be the device that might want to use.
If this WAS a good idea, and it seems that it is NOT a good idea, you would probably want a step-down transformer, a fuse/circuit breaker, a Rectifier and Capacitor bank, a resistor to make the power source less stiff, an Ammeter on the output, and a circuit breaker on the output, etc.
This could work, if the resistor were just the correct size to do the job.
Then one would want to run Legacy P&O Mode. And, perhaps you could set the Voc %, etc.
BUT, this has been actively DISCOURAGED by MidNite Engineering/Tech Support as RISKY, and probably a Warranty Voiding approach.
In the interim, you might want to find a Variable Autotransformer (Variac(r)), a step-down transformer, ammeter, voltmeter (the Classic could monitor the battery V), circuit breakers, etc, and construct a DC charger for your batteries, where YOU or another humans could be the Charge Controller, using the Variac to control the charge current and voltage.
If your battery bank is 12 V, you could use a Automotive charger in the interim. Or, you could possibly divide your battery bank into segments of 12 V batteries, and charge them individually. Using auto chargers requires careful monitoring of the battery voltage, and battery temperatures, etc, while your Inverter/Charger is getting repaired or replaced.
Perhaps a neighbor has a spare inverter or charger that you could use, and so on.
FWIW, Opinions, Good Luck, Vic
Since it was a modified sine wave inverter I have decided to replace it. I have spent hours trying to figure out the best inverter.
Here are the three options I have come up with:
I would like to have some redundancy
1. 2 Exeltech XP 1100 watt with an Automotive Battery charger.
The problems here is that they can't be paralleled, I could split it at the breaker box however if one goes bad I have to rewire or use a set of transfer switches like blue sea. With this set up I could use it as a "power share" running the charger off a 15 amp circuit similar to the Xantrex set up. I like this however it would be better if I could parallel the inverters.
2. Outback these seem to be good however I can't afford to have 2 for redundancy and there is no "power share"
3. Xantrex SW3000. These seem to be nice however my experience with xantrex has not been good I have went through 3 in the past year. Parts are not available for them I have to send the whole unit in for repair. I can't afford 2.
I am kinda leaning toward a custom build with Exeltech and a battery charger. I dont know if the battery chargers are Power Factor corrected The Exeltech is easy to set up with the Midnight 150 to turn off and on so I can set it to heat my water and run the fridge without killing the battery. However without being able to parallel makes things difficult.
I live off grid in a motorhome and the Xantrex died in the hottest part of the summer.
Is Midnight planing to release an inverter anytime soon?
Hi 1brad,
Just a quick post ...
If you have been through three or four inverters in the past year, it is quite possible that there is something very wrong with some part of your system, or perhaps with the demands placed upon the inverters.
If you can buy a quality, name-brand inverter, you really should need little or NO redundancy.
When I mentioned perhaps using an Auto charger, previously, it was meant in the context of something that could kind of keep your batteries reasonably charged while your inverter was repaired or replaced. And perhaps, something that you might already have.
Automotive 12 V chargers usually do not do a very good job completely charging batteries, and they can fairly easily overcharge batteries. And, essentially, none of them have a Battery Temperature Sensor (BTS), which can be very important in RV applications.
There are other stand-alone battery chargers -- IOTA, Meanwell, etc that might do a better job, compared to an Auto type charger.
Perhaps you could tell us more about your system, loads on the system, and so on.
More later, Thanks, Vic
It is a simple system. It runs two heating elements sometimes a fan and sometimes an AC unit. The first xantrex blew as soon as I connected DC to it no load sitting on a bench. And the polarity was correct.
So I should just buy an Outback then? about 2000.00 for one.
I would like to get a Midnite inverter charger if they are going to make one.
Yes, inverters are indeed a class of product that you get exactly what you pay for. And they do cost a bit. Price of admision, but trying to shortcut that rarely leads to happiness.
OK 1brad, thanks for that bit of information.
As zoneblue mentioned, there is almost no way to build a power inverter/charger that is very much less expensive than those offered by those already on the market, unless important corners are cut. Such cutting cuts into reliability and capability. The inverters and inverter-chargers that seem cheap, really are cheap.
Given what we know of your needs for the system, have little to offer. But going through three or four inverters in a year may not have been inexpensive for you.
Many inverter-chargers will run 24/7 for a decade or two, if properly installed, and not traumatized by untoward incidents, etc. But few of them will have been made by the corner-cutter companies, far offshore (IMO).
Some say that if one watches an Auction site for some time, one might be able to find a deal on a good inverter, like an Outback, or other quality one, but there is always some risk.
Sorry have not been more helpful. Good Luck! Vic
I never tried to "cut corners" I have 4 SW315 Solar World Panels a set of Trojans Midnite 150 and I soldered all the wiring ect.
I bought a Xantrex Freedom 458 because I am new to this and thought it would be good. Looking at Inverters dont seem to be anything that is made to flexible. Xantrex is made in china now as are Outback stuff. Exeltech is made in TX and they make stuff for the military. However their units cant be paralleled except for their MX series that are twice expensive as an Outback.
If they could be paralleled I could run 4 600 watt inverters and not worry about one going bad. That seems Ideal to me. And cost could be spread out.
Quote from: 1brad on July 23, 2015, 06:16:59 PM
I never tried to "cut corners" I have 4 SW315 Solar World Panels a set of Trojans ...
... If they [inverters] could be paralleled I could run 4 600 watt inverters and not worry about one going bad. That seems Ideal to me. And cost could be spread out.
Hey 1brad, I did was NOT saying (or even thinking) that YOU had cut corners.
Was trying to refer to inexpensive inverters being inexpensive and cheap, as the usual way to make inexpensive, things that really need to be expensive, was for some manufacturers to CUT important corners, in order to offer an inexpensive (and at the same time CHEAP) inverter or inverter-charger.
If you buy a GOOD QUALITY inverter, and pay a reasonable price for it, and it is not abused, it will almost always run for 10 years, or often, many more years than that.
I should not say this, as it is tempting fate, BUT, no inverter in use here has never ever had a hiccup. No smoke, buzz, flame, Zzzzzzzzzzzztttttttttttt, or anything similar. Four of them in two separate systems have just over ten years of 100% continuous operation on them.
Buy quality, of appropriate specifications for what you need it to do, and you should only have to buy it once, generally. Sometimes an event, lightning, or something, and a good inverter can become toast. Grid-connected inverters live a difficult life, but for off-grid use life is easier on them.
Many Schneider Electric's electronic items ARE made in China (too bad, IMO). Believe that some/many/most (?) OB products are made in India.
If I needed to buy an inverter-charger tomorrow, it would probably have to be Schneider XW+es. Would avoid the Schneider Conext SW, as they have had some reliability issues, at least in recent past. OB should be fine.
Not to be too preachy, But, really, you should not need much redundancy in inverters if they are well made, and not overstressed or traumatized, IMO. FWIW, Good Luck! Your friend, Vic
Looking around I see that folks are using these 12 volt grid tie inverters to go to 12 volt battery bank and supply 120 volt. Has anyone done this?
I could put a signal generator on the line
For what its worth, I did at one point put a rectifier on my generators AC output and then ran the DC output straight into a classic 150. I used the hydro mode and set a Power point.
This worked and charged the batteries for a number of days (which was all required to get my hydro back up).
The classic survived fine (and is still in use!) the generator ( A home depot cheapo) has since had an electrical failure and been replaced. I suspect I stressed something in that unit via this approach.
I'm sure adding cap's etc would help smooth everything out.
So in short, this sorta works for an emergency, but something is prob. going to break.
E
Hi eben..,
It is not really a question of weather or not this approach will work SOMETIMES, but, IMO, weather the designers of the Classic CC think that it is a generally good thing to do, and what might be the risks.
Here is one Thread where this is touched on:
http://midnitesolar.com/Forum/index.php?topic=1380.0
There, boB stated,
"We don't really advocate using rectified power lines going into the Classic. Yes, it can be done
but it may result in operation that could void the warranty in some cases.
The series power resistor is also a good idea to give some Voc to MPP V cushioning
and DC input voltage distance. If that idea is foreign, you should probably use your
inverter/charger to charge the batteries during times of bad weather.
A lot of people want to rectify the line for some reason but they usually also have
an inverter with charger built in. These inverter/chargers are made to charge batteries
from AC. I highly suggest using that charger with the grid or generator.
You can also buy a 12V battery charger that operates from AC. Harbor Freight had some of these
for around $30 each recently. If 24V bank, use 2 12V chargers. If 48V battery, use 4 12V chargers.
boB"
There are other similar threads. At least one Classic user completely TOASTED a Classic with his/her setup, and seemed to be looking for vindication.
My read from the Engineering personnel at MidNite, is that it is NOT generally a good idea to use a Line-Operated supply connected to a Classic. And probably a bit risky to do so with any MPPT CC, without specific direction to the contrary from the manufacturer of the CC in question ...
FWIW. Vic