Thoughts on Midnite Classic 250

I have always regarded Midnite as Tier-1, and they have a good reputation. I now have concerns.

I have encountered an outfit that purchased 8X DC-Solar trailers, and I am helping them figure stuff out - what works, what they need, etc. On at least 2 of them, the Classic 250s have failed. One turns on, boots up, shows the display, but it shorts the PV circuit. The other simply makes a buzzing sound with nothing on the display when battery power is applied. I have confirmed with Midnite Support that these are failure conditions.

MNPV6 boxes are used to provide both the PV and battery breakers.

Of the inverters I have looked at on these trailers, the longest on-time unit is about 20,000 hour. This is the equivalent of 2.5 years of continuous use. I think it's reasonable to assume the MPPT operated for the same period of time.

This is a 25% failure rate in 2.5 years of operation on units that are likely about 8 years old. That's not encouraging.

This user has also been in contact with another user that has several trailers. According to them, they had to replace three failed units (not sure of the percentage).

I am concerned that the Classic 250 is not as reliable as one would infer from their reputation.

Considerations:

1. These installations are pretty brutal, i.e., metal boxes that live outside with questionable ventilation next to two big SMA 6kW inverters.
2. They are actively cooled with fans. If the fans fail, I suspect the units would eventually fail. Not necessarily a quality issue, but a potential vulnerability.

Midnite indicated a $200-275 typical repair cost (can be much lower and much higher) with a 6 month warranty on repairs. Unfortunately, the 250 is limited to 55A output on a 48V system, which puts even the repair cost at a premium. I am much more inclined to install a Victron 250/100 MPPT for $625 or so rather than pay the typical repair cost.

$625 for 100A MPPT with a 5 year warranty and passive cooling.
$475 for 110A MPPT with a 6 month warrant and active cooling.

I'm sure there are a lot of people out there who can say "I've had mine for 15 years, and it works great." I'm just wondering if these aren't the best choice for this installation type.

Thoughts?

Interesting. In have a Midnite Classic 150 in service for ~4 years now and it has been perfect. No issues, does what it is supposed to do. As you said, you're expecting some posts like this in reply. But I am surprised that if there were several 250's failing in a short time, Midnite wasn't more interested in looking into it.

I babysit a neighbor's property with a midnite 150. The cooling fan makes horrendous noise and is likely to fail soon. Not sure of the age but 6-8 yo. Curious if there are fan issues with your units.

sunshine_eggo said:

These installations are pretty brutal, i.e., metal boxes that live outside

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It's this imo. They're stationary equipment, not suitable for the way it was treated on DC trailers. Hopefully they got 8x Kubotas at least.

Victron is probably the right choice if it's taken as a given that they're going to invest in revitalizing these trailers. But my question would be why.

Of course it’s impossible to say what the Victron failure rate would be in the same brutal environment with their passive cooling.

And obviously you’re aware this is a small sample size but it doesn’t hurt to solicit opinions.

This is the typical state of a Midnite from the best condition DC solar trailers I've seen, with the other half of them being a lot worse than this.

Imo whatever weathering condition causes that kind of dust pattern implies a real bad condition for any stationary purpose hardware. That's infiltrative dust and moisture. Not to mention the actual running conditions. Probably 140+ in that box in the sun, easily.

HighDesertOffgrid said:

I babysit a neighbor's property with a midnite 150. The cooling fan makes horrendous noise and is likely to fail soon. Not sure of the age but 6-8 yo. Curious if there are fan issues with your units.

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They do make replacement fan kits:


MidNite Solar MNCLASSIC FAN KIT Replacement Cooling Fan, Qty. 1

"This kit contains two cooling fans and one turbo fan used in all MidNite Classic model controllers. These are replacement fans for use in the repair of the classic with a damaged or worn out fan. Older Classic models will require removal of the FET bar to install the cooling fans. The replacement Sil Pad is included for use on these older models. On newer models the cooling fans should be replaced through the port on the rear of the Classic."

hwy17 said:

This is the typical state of a Midnite from the best condition DC solar trailers I've seen, with the other half of them being a lot worse than this.

Imo whatever weathering condition causes that kind of dust pattern implies a real bad condition for any stationary purpose hardware. That's infiltrative dust and moisture. Not to mention the actual running conditions. Probably 140+ in that box in the sun, easily.
View attachment 202340

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Can only imagine how caked with dust it is internally.

JoeHam said:

Of course it’s impossible to say what the Victron failure rate would be in the same brutal environment with their passive cooling.

And obviously you’re aware this is a small sample size but it doesn’t hurt to solicit opinions.

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So the Victrons are rated for full output at 40C, and max temp of 60C.

Here's a guy that tested his 250/100 at really high ambient temps.

"- 70C ambient surrounding victron (2in above Victron)

- 80C case temp (middle top surface of Victron)

- 90C terminal temp (thermocouple touching the "battery -" phillips screw during 100A output)

The 90A current limit seems to allow this setup to run indefinitely whereas 100A output only lasted about 1 hour before a terminal overheating error code appeared (occurs at 90-91C terminal temp)"





Basically he ran at 90% output indefinitely at 70C, and finally after an hour at 100% it finally error coded when the terminal temps exceeded 90C. It seems like a passive Victron SCC would have been a better choice for a fully enclosed cabinet like those solar trailers versus the fan cooled Midnites. Now before the recent price cut the 250/100 was closer to $1000 versus $650 now, so the Midnite classics were prob the cheaper choice.

The midnite 250 on the dc solar trailers aren’t the full feature versions either. They lack some internal functions. It would seem those variants (likely compounded by the elements) suffer errors compared to the rest

There are the "lite" versions available, but they have the LCD screen, maybe midnite made a special batch with display but no arc fault. As a portable light trailer they prob don't fall under NEC jurisdiction.


NOTE: The primary difference between the Classic and Classic Lite is the Classic Lite has NO LCD (Liquid-Crystal Display) and NO built in Arc-fault Protection. NEC (National Electric Code) 2011 requires an ARC FAULT detector on all charge controllers and inverters operating above 80VDC."

Steve777 said:

Interesting. In have a Midnite Classic 150 in service for ~4 years now and it has been perfect. No issues, does what it is supposed to do. As you said, you're expecting some posts like this in reply. But I am surprised that if there were several 250's failing in a short time, Midnite wasn't more interested in looking into it.

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They were very interested in having them sent in for repair at my expense.

I personally wouldn't expect them to be that interested. I think these trailers were a boon for them, and the way it has ended is likely advantageous to them from a reduced support expective. I do not blame them.

HighDesertOffgrid said:

I babysit a neighbor's property with a midnite 150. The cooling fan makes horrendous noise and is likely to fail soon. Not sure of the age but 6-8 yo. Curious if there are fan issues with your units.

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This is my suspicion as the primary issue exacerbated by the nature of the installation. My neighbor's FM80s are both fan cooled, and he makes sure to check that they're working during the hot months.

hwy17 said:

It's this imo. They're stationary equipment, not suitable for the way it was treated on DC trailers.

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Definitely a factor.

hwy17 said:

Hopefully they got 8x Kubotas at least.

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Sadly no. 7 are the basic panels+batteries and 1 has the kubota and lights package.

Many batteries were completely shot. The batteries for these things are ABSURD!!! $18K for 1080Ah FLA. $347/kWh.

The same outfit is charging them $1K to go through each battery, sort the cells and reassemble "good" batteries from the best cells. That's pretty economical at this point as they have a cell recovery rate of 75%.

They are open to Lithium or other FLA options. I was surprised to see that Rolls FLA is VERY competitive to these batteries. A nearly equivalent bank of Rolls 6V would be < $8K. I am hesitant to recommend lithium to them at this point as their understanding of all of this is very, very basic, and I'm trying to get them to be mostly self-sufficient.

hwy17 said:

Victron is probably the right choice if it's taken as a given that they're going to invest in revitalizing these trailers. But my question would be why.

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Sunk cost... and have you seen those luscious pairs of SMA beasts? I swear every time I open the doors, at least one of them looks at me seductively. Please don't tell Victron.

hwy17 said:

This is the typical state of a Midnite from the best condition DC solar trailers I've seen, with the other half of them being a lot worse than this.

Imo whatever weathering condition causes that kind of dust pattern implies a real bad condition for any stationary purpose hardware. That's infiltrative dust and moisture. Not to mention the actual running conditions. Probably 140+ in that box in the sun, easily.
View attachment 202340

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None are that bad, and they haven't cleaned them since taking ownership. The one I opened to troubleshoot the PV shorting was not significantly dirty, but we have discussed the best procedure for blowing out the equipment regularly. I'm guessing the doors have stayed closed most of their operational life... which might be part of the issue. I'm contemplating something like an HVAC intake register with a filter to allow a LOT more airflow.

JoeHam said:

Of course it’s impossible to say what the Victron failure rate would be in the same brutal environment with their passive cooling.

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Agreed. Mine has worked very well hitting 40°C battery temps inside a blue shipping container in 95°F+ ambient up North. Regardless, down here in the valley, more consideration needs to be given to cooling.

JoeHam said:

And obviously you’re aware this is a small sample size but it doesn’t hurt to solicit opinions.

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Regardless, a random sample of 8 with a failure rate of 25% is cause for concern. Some unknown upstream factor may have influenced it (hey let's send that shitty batch of trailers to that auction"), but it can't be dismissed. Considering these results in conjunction with the second user, it doesn't help.

G00SE said:

The midnite 250 on the dc solar trailers aren’t the full feature versions either. They lack some internal functions. It would seem those variants (likely compounded by the elements) suffer errors compared to the rest

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This wasn't mentioned by Midnite Support, and it would be good to confirm. Outwardly, they looks exactly like the standard Classic. Do you have any documentation to that effect?

The type of failure you mentioned with pv being shorted together is consistent with putting power on the pv side without a battery connection. I have seen this with IN and OUT breakers, people turning on breakers out of sequence.
Its very important that the cc senses battery voltage first.

sunshine_eggo said:

$625 for 100A MPPT with a 5 year warranty and passive cooling.
$475 for 110A MPPT with a 6 month warrant and active cooling.

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One thing you may want to consider if it's going to be in basically a sealed box is downsizing to the 250/85. Shares the same frame as the 100 so should have more heatsink per W of output. Save a little and run it at 85A, versus paying for a 100 and derating it to 90A for example. I have two 150/35s, same size as the 150/45s so gives me a little comfort.

sunshine_eggo said:

Sunk cost...

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I fear that for all the money lost on DC Solar the first time around, the trailers are out there doing it all over again and worse.

But that's solar equipment for ya. It flickers between gold and scrap depending on whether it's beneficially operating or not.

My Classic 250 failed a few years ago as well and had trouble getting support then for whatever reason. That's why I switched to Victron and have 4 separate Victron charge controllers now that haven't had any issues.

Knowing what sort of “company” DC Solar was, I’m surprised there’s even ones that still work, not due to Midnite.

Such a shame quality hardware was gobbled up and trashed.

seneysolar said:

The type of failure you mentioned with pv being shorted together is consistent with putting power on the pv side without a battery connection. I have seen this with IN and OUT breakers, people turning on breakers out of sequence.
Its very important that the cc senses battery voltage first.

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Disagree.

This is not supposed to be an issue with the Classics, and it's not a thing on most modern MPPT. Victrons boast about not needing to even be connected to a battery and can be powered purely by PV.

from page 6:

For routine, user-approved maintenance:
• Turn off all circuit breakers, including those to the solar modules, batteries and related electrical connections before performing any maintenance.

No order specified.

and

DC and Battery-Related Installation Requirements:
Shut off all DC breakers before connecting any wiring

No order specified.

The only time order is specified is when resetting an arc fault.

No warning associated with damage that may occur with improper connection order.

Brucey said:

One thing you may want to consider if it's going to be in basically a sealed box is downsizing to the 250/85. Shares the same frame as the 100 so should have more heatsink per W of output. Save a little and run it at 85A, versus paying for a 100 and derating it to 90A for example. I have two 150/35s, same size as the 150/45s so gives me a little comfort.

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Good idea, but I don't plan to leave them as sealed boxes. The 100 will be to manage TWO trailers replacing two 55A C250 in a 4S5P configuration. For proper charge current, each trailer battery needs 2 trailers worth of panels.

hwy17 said:

I fear that for all the money lost on DC Solar the first time around, the trailers are out there doing it all over again and worse.

But that's solar equipment for ya. It flickers between gold and scrap depending on whether it's beneficially operating or not.

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The alternative is to start over with a lot of work and a lot of cost. They need power in 4 locations (deep well pump moving 1200 gal/day, RV, casita, shop), so the trailers made a lot of sense to them.

They're sitting at about $60K total cost (21kW PV, 96kW inverter, about 200kWh of total battery capacity) vs. $200K to get grid power, so the short path is to figure out how to optimally use what's on hand.

As with all these projects, getting CONSUMPTION data is the real challenge, and I can't tell you how many times my answers to their, "do you think this will work?" is "we can't know without knowing your consumption."

rhino said:

My Classic 250 failed a few years ago as well and had trouble getting support then for whatever reason. That's why I switched to Victron and have 4 separate Victron charge controllers now that haven't had any issues.

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Pandemic related?

740GLE said:

Knowing what sort of “company” DC Solar was, I’m surprised there’s even ones that still work, not due to Midnite.

Such a shame quality hardware was gobbled up and trashed.

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LOL... What's really shocking is that they used such premium hardware. The trailers are high quality too. It's like they found the perfect answer to the question, "How do we take a bunch of really good shit and arrange/package it in a way that maximizes suck?"

They were being billed out at $150K each... WTF???!!!

sunshine_eggo said:

They need power in 4 locations (deep well pump moving 1200 gal/day, RV, casita, shop), so the trailers made a lot of sense to them.

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I don't underestimate the cost of building ground mounts anymore, after I did mine. So I do see a decent value in the mounting aspect of the trailer alone... if it gets to the beneficial operation state.

sunshine_eggo said:

They were being billed out at $150K each... WTF???!!!

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Basically what the electric buses are these days, gov spending billions of tax dollars on junk