iota charger on mod sine wave inverter?
Brock Solar Expert Posts: 639 ✭✭✭✭
For the past 4 years I have been using an iota DLS 54-13 as a backup to charge by battery bank from a xantrex 1750 inverter from an idling vehicle (with 120 amp alternator). This had worked for two years then suddenly stopped working. I sent it in and iota fixed it and sent it back no charge, I just figured it was a fluke it stopped working. Now the second unit, after about two years has done the same thing. I am wondering if the mod sine wave inverter is the problem? At one point I asked iota and they said anything between like 80 and 140 v was fine and I had heard it could even work with with DC on the input side? So I am wondering if I shouldn't look at a similar sized sine wave inverter or some other power source to charge in a pinch. Maybe a Honda 2000i or ???
3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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I would be suspicious.
Guessing, the Iota probably has the typical diode/capacitor front end that can be overheated by the square wave crest ("unlimited" current through diode as voltage rises from zero to ~150 volts or so, causing I2R heating of diode, wiring, input capacitor).
You could try a couple things--Use a IR thermometer to measure the input stage temperature (look for much hotter components/heatsinks on MSW power).
And, see what a Kill-a-Watt shows for Amps or VA (or better yet, if you have an RMS reading current meter, see what it reads). If it reads 20% or more current, then that would be a significant difference:
The Kill-a-Watt probably does not accurately represent the RMS current--But may still show a peak value that is higher than sine wave nominal.
It's in getting fixed right now. Good thought on the heat build up. It does have a thermostatically controlled fan which comes on, it doesn't seem to get much warmer than when on sine wave, but I have never measured it. So once I get it back your suggesting checking the amps in on the input of the unit itself? I do have a fluke RMS meter.
The odd part both times it worked fine for a charging session, I turned it off and the next time I went to use it, it was dead. So I am thinking maybe it is the hit on the start and somehow thats worse with the mod sine wave? I guess either way a sine wave inverter feeding it would be better.
If they tell you what failed--you may have a better idea.
There is the possibility that the diode is not heat sinked (or not very much of a heat sink)--So the overall power supply increase in temperature is not representive of one component (input diode or capacitor would be my guess) getting hot by itself.
There is an internal capacitor in the front end of the unit which is charged through a rectifier bridge circuit. If that capacitor is at zero volts (has bled down since the last time the unit was powered on) then the surge into the capacitor caused by the sudden inrush of current when the leading edge of the MSW square wave hits will produce more input current than at any point during operation. Once the capacitor is charged, the surge at the leading edge of the square wave will only have to make up the smaller amount of charge which was removed from the capacitor during the previous half cycle.
This can be a problem with normal switching mode power supplies even when operated from sine wave input because the power switch may be closed while the sine wave is at its peak.
But that surge current would last only a fraction of a cycle and the next cycle would be gradual. With MSW input, the surge would go in 1/4 cycle intervals at peak current until the input capacitor is charged.
One solution would be to add a series thermistor or other automatic "soft-start" circuit to the input of the Iota. Another would be to use a manual momentary switch to "pre-charge" the input through a series resistance before turning on the main AC feed. Knowing this possible cause of the problem, the Iota technicians might be able to use a higher current rated input diode.
PSW is the clean solution, although it seems to be a waste just to operate a battery charger!
Bill I hope I can find out what did fail. For all I know it could just be a normal failure, but twice makes me wonder.
I thought about plugging the iota in to a variable transformer and then dialing it up from 0, but leaving it in line would add more waste.
By charging the caps is that on the output side? It is normally left connected to the bank, so they are charged. I did think about disconnecting the charger from the bank, turning it on, then connecting it to the bank or wouldn't that serve any purpose?
Also about 3 out of 4 times when I turn it on it trips the inverter in overload and it’s not the input voltage side of the inverter. I am guessing it’s that big inrush current draw. Again once it gets going I have never had an issue.
As far as the inverter goes, I do use that same inverter when we go camping and having a PSW would be nice, so while this may be the driving factor, the PSW inverter would be an advantage for other things as well.
All of the off-line switcher front-ends that I've seen have an NTC Thermistor to do this very thing, as standard equipment. It really is required in any application, else switches fry, and fuses blow etc, respectfully, Vic
Oh the iota's pop like crazy when you plug them in, sine wave or not. It has always seemed a bit odd to me they didn't somehow address this maybe the thermistor thing should be in them all? I just figured they all do it, it must be normal?
I rest my case. :-)
Another incident of a device meant to be plugged into the 'unlimited power potential' of the grid. Also, strangely, meant to be left plugged in (for the most part).
In-line resister with a by-pass switch perhaps?
What size resistor and in between what two things?
The ntc resistors will only work on first plug in... It takes a free seconds for the ntc to cool down for them to be effective again.
I shouldn't think that would be a problem since you usually use a battery charger for a couple of hours before unplugging it.
Not knowing the internal circuitry of the Iota, I would not hazard a guess as to an appropriate size resistance.
Well, OK, but then this just one more reason that I'll not ever be using or recommending IOTA chargers. The thermistor is a $.20 part, pluis $.05 to stuff it.
They should be happy to repair them forever FOC. Opinions, Vic
Not that I want to get a different charger, but what other options are there for 54v 10 to 15 amp chargers? Honestly I thought about getting 4 less expensive 12v chargers and putting them on the bank, but likely 4 of an OK charger would cost more than 1 good charger anyway. Although I could easily flip them on one at a time, eliminating that surge
I see the point of the the sharp edges of a MSW source charging the input capacitor quickly but what happens when you plug it into a sinewave
and the AC input happens to be at one of the peaks of the sinewave when plugged in ? Very similar to a square wave don't you think ??
Except that a "typical" power supply will have a some sort of input current limit (usually an NTC resistor--high resistance when cold, low resistance when hot).
This works pretty well when plugging in a supply to AC Power and will limit the inrush current for the first few cycles/seconds.
Once the PTC is hot--It does not do well in protecting against line hits (of short duration) or from the MSW near vertical wave front.
Usually, PFC (power factor corrected) power supplies will not have a problem with either (initial surge or MSW wave forms)--They are designed to emulate the I=V/R of a resistor (R is variable depending on the power draw of the power supply when operating loads).
It is possible that they may put an inductor in series to limit maximum current--But other than specialized supplies (i.e., cheap units for fixed power applications), I have not heard of it being done for generic power supplies (not that I have a lot of experience in the field).
It certainly is. Hence the Iota making a big bang when you plug it in even with PSW or POCO. But maybe not as big.
With a sine wave, if you switch the AC on at the voltage peak, the surge will be large, but it will not last more than the time it takes to get down the slope of the sine wave closer to zero. Then the next half cycle will start fairly smoothly, rise to a peak and then taper off again. If the input capacitor is not fully charged in the first two half cycles, the effect of the PSW and the MSW will probably be fairly comparable. But the odds of hitting the peak of the voltage waveform with PSW will be relatively small, while the chances of hitting the peak voltage of MSW will be .5 and you know that the voltage will likely remain high for an average of 1/8 cycle and 1/4 cycle in the worst case.
I think that over many starts the odds of an MSW inverter eventually trashing the input diodes or blowing a fuse are higher than for a PSW inverter.
Have not done all the math, just going on a fairly well tuned intuition.
Face it, IOTA is a Cheap Power Converter made to be plugged into a RV to give you DC output, that has had a battery algorithm added to it. For the money they do a pretty good job. As the RV market dried up, they have pushed it more as a Battery Charger than Power Converter. There are alternatives at 3 times the price. If you think they are crappy, try a Power Max and some of the other ones out there.
It's about time someone made a proper battery charger for deep cycle batteries. Something like ... oh ... a MidNite Classic but with an AC input.
You'd get no argument here. I just bought a Magnum MM-1512 and remote thinking I'd have a 70 amp charger I could control the output on. The problem is when the charger in gauges no matter what you set the output to it goes to wide open and then will settle back to the percentage of output you have set. The problem with that on a Honda EU 2000 it kicks out a fault and you have to shut the generator down and try again. How can a 70 amp charger go up to a momentary 143 amp output, when you have it set to 20 % output ?? ( that is what the remote shows ). With the ECO off it will start, but still does the same thing.( goes to wide open output ) All this weirdness just makes it pretty much useless.
Outback's built-in chargers have their quirks, but they don't do that!
I'm not familiar with the Magnum programming, but there ought to be an input limit setting on it to prevent overloading the gen. A percent of the charger's maximum is only half the equation; what about the loads that are passed through? Is there no setting for maximum AC input current? There should be.
In this case I don't even have a output of the inverter hooked up and it's shut off on the remote. You can set the power share to 5 amps or 60 amps, it doesn't seem to matter, when the charger ramps up goes to wide open then settles back to the percent setting you have programmed for the charger.
I bought it thinking, how nice it would be to have a variable output charger to compliment a Honda's EU 2000's output so you could run variable loads.
Sounds like it is time to call the factory for tech support--That does not sound right (and I have not heard that complaint before).
Do you have the output of the charger directly connected to the batteries? I could understand this behavior if there is a diode between the charger and the batteries so that its electronics are not getting any power until you turn the AC on. Most CCs specify that they need to be connected to the batteries first before the input (AC or DC) is energized.
It's hard wired to battery bank with #2 cables. I am going to try one more thing and put a load in the inverter output and see if that makes any difference in the charger. You can see the inverter pick up the AC input and the charger shows 0 amps. The display will show 4 amps as the charger kicks in and then it will just go wild. Like I said I have seen 143 amps showing on the display before it kicks out.
A comment on your use of your truck as the end-game power supply. That's fine for the occasional camping trip for an hour charge every other day in camp to get from 50% to 80% (which you would probably do faster just using jumper cables), if you don't have a genset. But to do this often I would take your own suggestion to get a Honda inverter-genset. You'll get much better fuel economy per watt that way.
Very strange indeed. Looking at the 1512 on the interweb, it seems to be an inverter/charger. The "then it just goes wild" sounds a bit like the Magnum trying to invert and charge at the same time and chasing its own tail.