Glitches and Problems with Midnite Solar Classic 150

[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]

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.

[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]

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.

[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?

[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]

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]

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!