My install and review of the AIMS Prius 2kW Pure Sine Wave Inverter for Backup Power Generator

Midnight Solar makes excellent

that will accept up to 250V (solar) input to the HV battery pack, but i wonder how sharing that connection might effect the car's ability to compensate.

The scenerio I see, is that the Prius is only going to cycle to get 2 Bar in the HV pack before it cuts-off. Meanwhile, the HV pack is trying to support a 5-stage mppt cycle to fill the house bank. It seems you could get into a point of diminishing returns that the ICE would be running almost constantly WHEN the Midnight Solar is pushing max amperage to get the 48V House bank to 80% before switching to the next charging stage where it begins to taper down.

Look at the similarity:
Prius delivers high current to 80% State of Charge, and backs off.
Solar charge controller charges high current to 80% before tapering off, but is still charging (in stages) to full capacity.

You have a charging system feeding a charging system. Is this sustainable?

Look at this way. You are trying to push the power of a 90 pound HV pack into a storage bank of Eight 6V RE batteries that probably weigh 62 lbs each, or almost 500 pounds of house battery.

90 lbs to feed 500 lbs.

Your ICE is pushing that. Bad idea?

 

Nooooo, it was a joke...

 

Nah. It won't push any harder than it's designed to, and it'll just hum along for as long as it takes, then end up stopping for a while. Could be easier on it (and disturb you less) than the more-frequent cycling using just the 90 lbs directly.

 

The potential for a problem exists if the end-user is drawing a lot of power off the 48V Bank. The Midnite solar charger is going to draw what it needs to try to maintain the 48V, it might end up having to do a force charge on the Prius to put the HV battery pack at full bars, so that Midnite solar can draw it down to top off the house Bank.

 

You've got a good point there but my house would have to be consuming more power than my inverter is even capable of. In other words that won't be a problem. It's a 5000 watt inverter with a 10000 watt surge. The Prius battery is certainly capable of delivering 10000w with no problem and 5000 Watts continuously. Sure the Prius probably can't maintain 10000 Watts for very long but neither can the inverter. The Internal combustion engine will start and ketchup no problem. I will not have to manually go out to force the high-voltage battery to full bars before I turn on something large.

 

I'm not charging one battery off the other. I'll set the output of the midnight classic to the same voltage as the house battery bank. I'll disable all the stages and turn it into a constant voltage power Supply. That way it's not trying to charge the house battery. However when I turn on a load that load will try and bring the house battery voltage down. The midnight won't let that happen. At least it will try it's hardest to maintain that voltage. And if it gets maxed out it will not be damaged because they're designed to hold at their Max output without self-destructing.

 

@Travis Sanders Okay, I see where you're headed. I still think it could work, but I'd still be concerned about the Prius & midnight working too hard to bring up that house battery. I don't know how bad yours is- I've seen some very bad ones and I may be inferring something worse than your reality.

Anyway I'm just concerned that you might reveal that the Honda genny has actually been limiting your overnight fuel burn, and the Prius + midnight may have the ability to try too hard and wind up burning even more fuel. If the Midnight lets you adjust and program well enough, you might not have a problem at all.

I wouldn't be too worried about the admittedly odd draw pattern of the MPPT vs. the Prius HV battery.

 

somebody asked why not power the house directly off the high-voltage battery? Well that's because I don't have an inverter capable of 250 volt input.
And I don't want one because my solar system produces 5000w & the highest V my charge controller can go is around 60 volts output. So I cannot charge the Prius battery from the solar panels. Nor do I want to get a high voltage inverter because then I would have to switch from my regular inverter to the Prius inverter at sunset and any time you do a switch the lights blink clocks get reset the Xbox shuts off the Wi-Fi turns off and then all hell breaks loose. the DC to DC step-down in the Midnite is very efficient and its output will be going directly to the inverter only when a load demands it.

 

Let's say for some reason I get home from work after sundown and the house battery is dead. Then I hook up the Prius to the house battery. I now have the choice to change the output voltage of the midnight to match the dead battery therefore the only time the Prius will deliver power is when a load tries to bring the voltage down even further. I also have the choice to raise the voltage and try and charge the house battery. And do be aware that the midnight knows the difference between amperage going to the house battery versus amperage going to the houses inverter. I also have the ability to program the midnight not just by the voltage set point but the actual wattage going into the house battery. So I could in fact program the midnight to allow only 100 watts into the house battery if I wanted to.
the midnight classic charge controller is the most programmable and customizable charge controller on the market. I've messed with them alot I understand them quite well within the Applications I've used them. But I've never tried this yet so I'll be learning some new things.

 

If you think you can program it to replace usage losses without overtly charging the house battery then I think you'll be set.

Sounds like I should read up on the Midnight... I've been using a decidedly non-programmable Morningstar with our offgrid setup for about 10 years. It's been good but very occasionally the charge voltage exceeds the inverter's hi volt cutoff by a measly .2V or so. *argh*

 

I contacted midnite classic tech support. He said it would likely pop the fets and they could fix it for around $150. He said the setting to try would be the setting where I choose the percentage of voltage open circuit to utilize. so the midnight checks for the open circuit voltage and then tries to drag the voltage down to the percentage that I specified. It still does some kind of an mppt sweep that will interfere with the Prius when its internal combustion engine is trying to charge its high voltage battery.
It sounds to me like the charge controller does a bunch of fancy things in the background in order to accomplish its sweep. If it's not expecting a high wattage forced increase in voltage it may smoke.
On the other hand he said connecting too many solar panels to the charge controller is not a problem. Like there could be enough solar panels to replicate the Priuses maximum abilities and a cloud passing by changing the voltage will not be a problem so I'm not sure how these two situations differ and think it's worth a try.

 

Did you actually tell Midnite Tech support that you were feeding a Prius (instead of solar) to their charge controller?

 

To me, MorningStar is like the middle product catagory. Budget is Meanwell, middle is MorningStar, top is Midnite solar. I've never used solar completely off-grid, only for convenience power to outbuildings.

 

Yes & he said that would void the warranty but the midnight that's only $300 on eBay has no warranty anyway.

 

I read an interesting old thread here where a guy used a rectified AC output from a small generator to feed into a midnight classic using the hydro setting with good success. This is very promising.

Experimental 48VDC Generator

 

I feel like I need to start my own thread and point people to it from here and stop hijacking this one. This thread is similar but it's not quite the same thing.

 

I live in WI. You could find someone near you to do it for you. An independent shop?

 

Okay I did start my own thread and I've had a semi success at using the midnite classic 250cp as a DC converter tethered to the Prius high voltage battery.


Prius as backup generator with midnight classic as voltage converter possible? -

Solar Panels - Solar Panels Forum

 

I finally got around to trying harder, and the problem wasn't even that hard to find. There was a terrible solder joint at the neutral output wire from the circuit board. If I remember from looking at it when I first tested the thing, it looked attached, but the other day when I decided to poke at it some more, that wire finally pulled right away from the board (taking a little of the board's copper with it). I thought "gee, could that have been the only problem all along?" and poked a meter probe at the land on the board where the wire (should have been) attached and saw a lovely 119 volt sine wave, so I went ahead and made a better connection there, and I think it's fixed.

It would have been a simple fix except the access isn't great. There is a great big heatsink attached to the board, cooling the heaviest-duty semiconductors, but there are also several semiconductors mounted to the underside of the board and heatsinked directly to the bottom of the aluminum case. I was glad I noticed that before I did anything rash like loosening the board mounting for better access, because that would probably have set me up for lots of fun with heatsink compound getting it all assembled again. So I decided to just work from the top of the board and with what little access I had to the bottom—luckily, that neutral connection is right at the most accessible edge of the board.

It's a high-current connection with copper on both sides of the board, and to make up for the bit of copper that came away from the board with the old wire, I bent some 12 AWG solid copper into an L shape, put it through the hole, and lifted it while heating until the bottom of the L worked itself into the fairly generous solder blob existing on the bottom of the board. Then I wedged it in place with a silicone kitchen spatula from the bottom and added more solder from the top. I don't think it's going to go anywhere. One of those repairs that takes a couple days' off-and-on headscratching to plan, and then only maybe 20 minutes to execute.

Because the bottom of that L now comes a bit close to the case, I coated a square of thin plastic with some Plasti-Dip and stuck that on the case just below it. AIMS used a similar technique themselves in between a few items they did not want to meet.

I'm not a big fan of the AIMS practice of directly soldering heavy-gauge wires to circuit boards. It takes a lot of heat to do right (because the heavy wire is such a good heat sink), and as in the case of this neutral connection, sometimes it doesn't turn out well. Meanwhile the heavy wire also gets quite stiff and can put a lot of stress on the board. And it complicates disassembly—it's possible that the failure of this neutral connection could have been caused by somebody trying to move the back panel for access, as that's where the wire directly went, short and stiff. (It had definitely been opened up when I received it, even though the seller listed it as "Brand new, in box." Some of the cover screws had been replaced by non-metric #4 size, cutting new threads in the aluminum so the old metric screws wouldn't hold any more. I bought more of the #4 screws so at least they all match now).

I ended up tapping a new hole in the case to add a little three-position Euro terminal block and terminate the neutral, ground, and line connections from the board there, so there is an easy place to make back panel connections and those wires will not be moving or putting any new stress on the board. Between the board and the Euro block, the new piece of solid wire makes a bit of an arch, so it has some give when it thermally expands.



While I was in there, a few other things seemed worth addressing.

This unit was apparently a limited run that had been ordered by Jack Chen to sell on eBay. AIMS doesn't seem to have kept any record of how they built it. The smarts board has a number ZXB-KZ11-02 silk-screened on it, and the grunt board has FYQ-2F0002F. Maybe AIMS does have some information about those particular boards.

The smarts board just mounts on top of the grunt board, mating by a couple of dual-row headers, and held down by one M3 screw into a standoff. But the standoff was too short for the height between the two boards, so they had used an extra-long screw and just tightened it partway until the smarts board was kind of bowed in the middle, and called it a day. I extended the standoff by an extra 5mm and some change (a few washers between the standoffs) so the board can be securely mounted and not flexed in the middle.

The boards need 24 VDC for their logic to operate, generated from the 200ish VDC input. Taking the idea of modular design to the extreme, this inverter gets that by having an entire Mean Well NES-50-24 power supply mounted intact in the back corner. It sits close enough to the main board that AIMS slipped a couple more plastic-separators-coated-in-glop between its metal case and two inductors on the main board, and even slightly bashed one corner of the Mean Well case to make more room:



The Mean Well, at least, has a nice terminal strip for its connections to the rest of the unit, a nice change from the everything-soldered-to-everything of the rest of the unit. But I wish they had used more wire colors. In particular, the same color red is used for the 200ish VDC brought to the Mean Well's input and for the 24 VDC from its output, and both wires run clear to the front of the inverter and run under the smarts board, so it's quite hard to see which is which. So I blobbed those wires here and there with some blue and white Plasti-Dip (respectively) and put corresponding blobs on the terminal strip to keep them straight.

There is a power switch on the back panel, but it's just a low-voltage switch connected to the FYQ board, telling the inverter whether to operate. The input from the battery is directly tapped off to the Mean Well, which is powered and producing 24 VDC inside the inverter whenever there's power coming in. When installed in a Prius, that will be whenever the car is in READY. So the little green LED on the Mean Well (which is just visible through the air holes in the back panel) can be used as an indication that power's coming in. (The green LED on the back panel only lights when the inverter's switch is on.)

The back panel looked like this (photo from page 9 of this write-up by somebody else):



Four NEMA 5-15R receptacles and a terminal strip, and a separate grounding stud (internally connected to the G on the terminal strip and grounds of the NEMA 5s). You can see the on-off switch above the receptacles, and to the left a blanked-off rectangular opening. I would bet that was some 7-segment voltage/power display in some other AIMS standard model that this was modified from. The tiny green LED above it is the only outward indicator on this model. (Inside, there are six small LEDs on the smarts board, labeled HL1 to HL6, and I don't know what they are supposed to mean, but HL1, HL4, HL3, and HL5 all seem to be on when it's operating normally.)

The four NEMA 5 receptacles are all wired backwards with respect to the terminal strip: the wide (neutral) blades wired to L, the narrow (line) blades wired to N. Because the inverter itself doesn't bond either side to ground, you might never notice, or only if you were using the receptacles and the terminals at the same time. But if you added an N to G jumper on the terminal strip to make it a ground-referenced source, then any circuit tester would tell you the receptacles were backward. I wonder how that got through design review.

Like everything else, the connections to the receptacles were soldered. In fact, they're PC-mount receptacles all soldered to a PC board behind the back panel, with the big heavy L, N, and G wires soldered to (the wrong positions of) that. Like I said about heavy-wires-soldered-to-circuit-boards, the biggest soldering gun I own couldn't make enough heat to even start to soften any of those solder patches. So the whole group of receptacles and their PC board got disassembled with extreme prejudice, and I'll do something else. (Right now I'm just connecting to the little Euro-block I added inside.)

There is room to do some carving of the back panel and add a standard 20 amp GFCI there. I thought I might have to relocate the power switch over to the blanked-out "display" area, but it wouldn't even have to move; there's enough room for a GFCI below it. I'll probably do that eventually, and feed the external terminal strip from the GFCI output terminals.

That would make it no longer correct to bond the N and G external terminals, as doing that would defeat the GFCI. There's plenty of room inside to add a little four or five hole ground bus, allowing it to be configured properly upstream of the GFCI as bonded or not, as an application demands.

For testing, I was pleased that the unit will start up (and even run a 25 watt light bulb!) from a little benchtop supply I have that will make 240 VDC but only at a fifth of an amp. The supply goes into constant-current mode while the inverter's capacitors are charging, and again briefly after the power switch is turned on, but recovers and the inverter happily does its thing.



Looks pretty good, only some tiny beauty marks around the zero crossings. Of course this is at very light load. It will need to be wired to a much more powerful supply (like the car) to test with heavy loads.

For a way of making heavy wire connections to circuit boards that's nicer than just trying to solder them, you can look at hobbit's photos from one of the old ConVerdant 3kVA units (huge, heavy, built like tanks):



Each connection location gets a threaded metal standoff soldered at four points, and the wire is finished in a ring terminal and bolted down. Much nicer. (But those units sold for much more than the AIMS.)

Weirdly, hobbit found that that one also came with receptacles on the back that had line and neutral swapped, and he chopped them out and added a correctly-wired one of his own. There was more of an excuse in that case, because it came with some bizarre "universal" receptacle that's supposed to fit n different nationalities of plug.

 

Wow! @ChapmanF, great rebuild! I was the one who wrote the PDF for the installation guide. People with this unit should be aware that in the original configuration there was a DC negative to ground (chassis) short on the 240V input side that should be resolved by following the @AHetaFan procedure:

As described to me by Andrew from AIMS Tech support: The connection to ground was through the mounting screw with a metal flat washer next to the large heat sink on the DC input side. I removed all 4 screws for the DC end cap and the 2 top screws on the AC end cap. (The cover is now off and the DC end cap is tethered only by wires allowing access to the mounting screw) After removing the mounting screw I cut the ground trace on the PCB and also counter drilled it out. Reinstalled mounting screw and problem was fixed.

After removing the cover and DC end cap on my inverter, I noticed that a large capacitor made it difficult to access the nut on the top of the mounting screw and blocked vertical access to the mounting screw on the top side of the board (necessary to drill out the circuit path through the screw hole in the board). I had to carefully bend this capacitor to the rear to move it out of the way. For my fix, once I had the mounting screw removed I used an X-Acto knife to carefully slice the circuit trace around the screw hole off of the top of the board and a 11/64 drill bit to remove the circuit trace from inside the screw hole in the board. In an abundance of caution I slid a 1/4" long piece of 3/16 OD heat shrink tubing down through the screw hole to ensure the edge of the circuit trace on the underside of the board can not contact the screw. I reinstalled the mounting screw, washer and nut. I carefully bent the capacitor back into it's original position, attached the DC end cap and lid. I now measure over 30 Megohms the (limit of my meter) to ground for both DC - and DC +​

It is odd that AIMS doesn't have the schematics for the unit, maybe the "corporate knowledge" left the company or they are considered proprietary. My concern is that when/if mine fails, troubleshooting and repair may be a little difficult.