Glitches and Problems with Midnite Solar Classic 150

[Mike90250]

Generally, Bulk and Absorb voltage is about the same, when the voltage rises to that setting, the Absorb cycle starts.
Absorb starts a timer or watches an amp meter, to decide when to terminate, assuming you have set it right for your batteries.

When Absorb completes, the controller falls back to Float voltage.

The Classic graphic panel is very busy, I like using their Local App (via my wi-fi link) to monitor things.

Midnight Solar forum http://midniteforum.com/index.php
Midnight downloads http://www.midnitesolar.com/firmware...reProduct_ID=2

Glad that you don't have 70V at the 48V battery!

[dharry]

Sorry Mike, my bad. I realized that wasn't battery voltage, it was panel voltage, another in my many learning experiences on this oroject!

And, looking at the wiring diagram I do see now that the output from the controller can go straight to the inverter so 70v would definitley be too high for the inverter input.


My bulk stage tops out at 59.5v nominally and more like 60-60.5 with the Temp compensation now in winter. Does that mean that the controller is holding the input voltage at the topend of Bulk (~60v) during bulking? I was watching the power and current during charging today and it did seem to work out to about that for the battery input voltage.

[Mike90250]

Actually my system has been running fine lately, thank you.

Please provide a link to a tech article that says 70v in is not normal during bulking, that is the first time I have heard that opinion......

ya know, knock yourself out. 70V applied to a 48V bank, is going to end badly for the batteries. I said so.
Normal EQ voltage for generic flooded batteries are about 15.5V for a 12V battery, which goes to 62 v for a 48V bank. EQ cycles are pretty hard on batteries, so they are only suggested to be done when specific gravity readings diverge or no more than once a month.

I would direct you to read the datasheets for your batteries to see what voltage you should be charging at.

Here is the master link to the bible on batteries -http://jgdarden.com/batteryfaq/carfaq.htm
charging regimes here: http://jgdarden.com/batteryfaq/carfaq9.htm#stages

Now if you are seeing 70V at the input of the charge controller, that is a very different thing, and likely it's just fine. You can measure your batteries directly with a portable VOLT meter set to the proper range setting.

This was a pre-wired power center and the wires that run from controller to power center appear to be 4 ga, but I cannot be sure, I am sure, however, that they are plenty big with solid connections. I can't see how any of this would hurt an inverter - this is the voltage going into the batteries, not into the inverter.

Pre-wire just means that the factory can screw it up!
My inverter will fault at 69V and go into alarm and dies at about 71V. The XW6048 is one of the largest inverters around, and is really robust, but 70V will give it a headache !

What model is your charge controller and inverter, that may help us help you better.

[dharry]

MIKE - you got me thinking that the "Vin" showing on the controller display, which I thought was the voltage into the batteries, is really just the voltage coming in from the panels. If that's so, is there any way to tell what voltage is being put into the batteries at any given time?

[dharry]

re the comment I put in BOLD. You have a PROBLEM . Look for a loose wire connection between the charge controller and the batteries - or the wire is too small, is heating , and has high resistance. 70V in bulk is NOT normal. It will eventually fry your inverter or start a fire.

Actually my system has been running fine lately, thank you.

Please provide a link to a tech article that says 70v in is not normal during bulking, that is the first time I have heard that opinion.

All wires connections are solid and all gauges are significantly oversize and the runs are very short (8 ga 2' tray wire from combiner to power panel, 4/0 ga 4' wires between battery bank and inverter). This was a pre-wired power center and the wires that run from controller to power center appear to be 4 ga, but I cannot be sure, I am sure, however, that they are plenty big with solid connections. I can't see how any of this would hurt an inverter - this is the voltage going into the batteries, not into the inverter.

[Mike90250]

Hmmmm, i'm no EE so maybe one of the experts will chime in. My system came pre-wired so i haven't though much about other ways to do it. In terms of PV versus battery voltage, it seems like the PV should always be close to 50% higher than the batteries to allow for sub-max panel power and have enough extra to equalize,,etc. in my system, natteries are nominally 48 v but the panel VoC pushes or even exceeds 90v pretty regularly and the Battery In voltage is typically mid to upper 70s during Bulking. I'll have to think about how that voltage difference is affecting the common PV-battery ties at the + and - buses. Not sure.

re the comment I put in BOLD. You have a PROBLEM . Look for a loose wire connection between the charge controller and the batteries - or the wire is too small, is heating , and has high resistance. 70V in bulk is NOT normal. It will eventually fry your inverter or start a fire.

[dharry]

Sort of. I have 2 negative (DC and PV) 2 positive (DC and PV) and one ground leaving my classic. The PV negative comes directly from the combiner box into the classic ( no common battery bus bar in between). In my configuration my PV array voltage (~110v) does not match my battery bank voltage 48v so a common DC negative would be incorrect (to my way of thinking anyhow).

Hmmmm, i'm no EE so maybe one of the experts will chime in. My system came pre-wired so i haven't though much about other ways to do it. In terms of PV versus battery voltage, it seems like the PV should always be close to 50% higher than the batteries to allow for sub-max panel power and have enough extra to equalize,,etc. in my system, natteries are nominally 48 v but the panel VoC pushes or even exceeds 90v pretty regularly and the Battery In voltage is typically mid to upper 70s during Bulking. I'll have to think about how that voltage difference is affecting the common PV-battery ties at the + and - buses. Not sure.

[sunny79]

Hi Sunny, the Classic chasis is grounded directly (dedicated wire) to the ground bus bar in the power center. There is a separate dedicated line from the Classic to the DC negative in the power center, which is also where the negative PV connects in. This is what you were referring to, right?

Sort of. I have 2 negative (DC and PV) 2 positive (DC and PV) and one ground leaving my classic. The PV negative comes directly from the combiner box into the classic ( no common battery bus bar in between). In my configuration my PV array voltage (~110v) does not match my battery bank voltage 48v so a common DC negative would be incorrect (to my way of thinking anyhow).

[dharry]

Out of curiosity do you have negative PV landed to the classic? My owners manual said it was optional which seemed just wrong so I landed negative PV directly to the controller.

Hi Sunny, the Classic chasis is grounded directly (dedicated wire) to the ground bus bar in the power center. There is a separate dedicated line from the Classic to the DC negative in the power center, which is also where the negative PV connects in. This is what you were referring to, right?

[sunny79]

Out of curiosity do you have negative PV landed to the classic? My owners manual said it was optional which seemed just wrong so I landed negative PV directly to the controller.

[Sunking]

Sunking - Thanks for the reply. I'll buy that, but then what is a reasonable amount of voltage drop before the controller wakes up and accesses more power from the panels?

First requirement would be the controller would have to be in FLOAT MODE because in Bulk or Absorb the controller is already pumping as much as it can so any additional load would just draw the voltage down further. Then even in Float Mode if the load is demanding more than the panels can supply at that time your voltage is going to sag because the batteries have to make up the shortage.

Just a hunch here but I believe we already discovered your batteries are too small for the panel wattage you are running and I suspect you are putting too much load on them and they just cannot support the load demand and thus you see voltage sag. Try this after sunset. Turn everything off, measure the voltage on the battery term post or Open Circuit Voltage. Then hit them with a load by turning stuff on, then measure the battery voltage again and see what you get. If the voltage drops more than 2% (.24 volts for each 12 volts or 1 volt on a 48 volt system) would indicate too small of a battery or a battery on its way to being a Boat Anchor.

[dharry]

Sunking - Thanks for the reply. I'll buy that, but then what is a reasonable amount of voltage drop before the controller wakes up and accesses more power from the panels?

[Sunking]

It was a figure of speech in an example. 1 mv is not enough to really be measured when operating at double digits voltages. Not even a volt meter can pick that up as it would be outside the accuracy range of 1%. 1 mv to 10 volts = .01%.

[dharry]

Mike - That's extremely helpful. If the charge controller should cut in with a 1 mV change in the batteries, that explains why when my works, it is seamless/instantaneous. There is some glitch, either in the external wiring to the controller or within the controller itself (my vote) that does not see the V drop sometimes. As I said, my batteries are allowed to drop several volts with no action from the controller - and this is with no shortage of sunlight. I live in sunny new Mexico and when it's clear, as it has been, my 2400 W panels can turn out over 3K and yet the battery is discharging and the controller is using allowing only 3-600 watts in.

I bought this as a pre-wired power center from Northern Arizona. The power panel came assembled, from Midnite Solar I believe. All the major wiring looks great and I have checked tightness on everything. Flaky grounds can sometimes cause weird intermittent problems but they all seem fine. It's brand new, no rust.

The intermittent charge controller issue combined with the intermittent display problem makes me think it is internal to the controller. I sure wish I had a non-MidNiteSolar controller that I could hook up just to see how it worked.

Thanks for your help Mike. Is that 1 mV battery drop action level shown somewhere so that I can wage the battle with MidNite solar and maybe get some action on this? I don't see it in the spec sheets anywhere. Or is that just something you have gleaned over the years?

[Mike90250]

A charge controller is only interested in maintaining a preset voltage on the batteries. It can't tell if there is a load or not on the batteries, it should see the voltage drop 0.001 volt, and apply more power to keep it constant. If it runs out of sun, then the voltage sags. I've never seen the behavior you describe, with any controller I've worked with (trace, morningstar, classic). I'm thinking you may have a flaw in your wireing or connections, and the controller is not able to function properly.

And remember, even a tiny bit of haze can/will cut solar production drastically. Not just 10%, but more like 50%. When cloudy, I get less than 9% of PV nameplate power.