midnite classic creating 117V at pv input

[australsolarier]

snapshot when midnite classic was reversing

[zoneblue]

Well what can you say... the moral of this thread, and one i linked to for that matter, is that if you muck about with anything long enough youll discover new things. Most people actually connect their arrays, and thus never find such interesting and useful things.  Enjoy!

[Vic]

HELLO AGAIN   ...

i haven't actually checked the other midnite in 12 volt configuration if it is doing the same thing. as there is a converter connected to it, pulling down the battery voltage might trigger the midnite to come out of his "rebellious state"   ...   
greetings urs

Believe that the "converter"  that you mentioned,  that is connected to another "midnite",  is a battery charger,  connected to a MidNite Classic CC.

If this is true,  this is not a recommended practice,  in general.  Power supplies,  connected to the input of many/most MPPT CCs are often too "stiff" for these types of CCs to find Vmp,  when they Sweep.  This could damage the CC.

Also,  believe that one approach that CCs use for Thermal management,  is to move the Vin away from Vmp,  to limit current/power/heat.

Depending upon the nature of the external power source,  you may need to place a series resistor in the Vin lead to the CC,  to help protect the CC.   Believe,  that having a power source with an output voltage near that of the battery will help reduce the risk,  at least somewhat.

FWIW,   Vic

[australsolarier]

vic,
well, as a matter of course i presumed that everybody knows an inverter is connected to the battery and not the pv input.
what i was trying to say, when the midnite goes to float whilst a load is connected to the battery (the inverter  connected to that battery) that reversing might not occur. like i said i have not checked it yet.

MY INVERTER IS CONNECTED TO THE BATTERY NOT THE PV INPUT. and the solar panels are oriented towards the sun .......... if anybody doubts it, i can send pictures as evidence.

one interesting fact with the lifepo4 batteries is, when the charging falls from absorption to float, for about 30 seconds or there abouts, all the electricity for the inverter (hooked up to that battery) comes from the battery and non from the midnite classic. until the battery voltage drops near the  programmed float voltage.

as far as i am concerned i am pretty sure the midnite engineers and designers know about that reversing.

vic, i hope i cleared up  the problem thinking i hooked up an inverter to pv input and i sincerely hope i did not hook up the inverter to the pv input whilst thinking it is hooked to the battery. and i sincerely think you did not even in your wildest dreams  think of hooking up your inverter to the pv input.

as far as i am concerned this thread should be about the reversing of the midnite and not where people think i hooked up the inverter or if a breaker is broke. i can actually replicate it. and i can understand some people do not believe it. then again i do not believe the earth is flat also.

greetings from a somewhat frustrated urs

[Taos]

You don't have to shout ! More people might help you if you had a better attitude.there I said it for all the great members that give there time and info  for free! I will not respond to this thread so if you got something nasty to say inhale and suck it up.

[Vic]

HELLO AGAIN  <snip>  ...
   ...   i haven't actually checked the other midnite in 12 volt configuration if it is doing the same thing. as there is a converter connected to it, pulling down the battery voltage might trigger the midnite to come out of his "rebellious state".

interesting to say the least.
greetings urs

Hello again australsolarier,

Well,  the above is a "quote" that was edited to try to focus on just that one part.

This quote came from australsolarier,  regarding part of his/her system.   In NA,   converter commonly means a battery charging device used in our RVs (Caravans).

I did not mention an Inverter,  or where anyone's inverter happened to be connected,  or not connected.

The word "converter"  does NOT mean an Inverter to us,  here in this other country.  Perhaps it does have that interchangeable meaning,  there.

There is almost no one here,   that is doing anything other than trying to help others.   There will usually be a lack of information in posts from those asking for help,  and often,  there is some ambiguity in the way some "information" is written.   Believe australsolarier  made a statement about disconnecting the PVs from the "midnite" input ...   this implied to some of us,  that a wire had been disconnected,  rather than flipping the DC input breaker to Off.   This might lead some of us to believe that disconnecting a HOT DC cable could have caused some transient condition in the "midnite",   and so on.

Not all of us are perfect!   Imperfect Vic

[offgridQLD]

Well living with them every day and relying on them to keep the house running. I like to know all the quirks of the classics charge controllers.

I'm from Australia (QLD) I also run 400ah 48v (calb lifepo4 lithium batterys) . So perhaps I can try and replicate your finding. Perhaps the issue is stimulate by how stiff the voltage is on the lithium's when they have no load in float though I wouldn't think so.

As you mentioned I also notice that there is a period of time after the end of absorb befor the charge controllers need to do anything to maintain float V . Its nothing unexpected as the voltage is so stiff on the lithium's that even with a small base load it takes a surprising amount of time to bleed the surface charge off.  Lead acid plummets almost instantaneous as soon as you take the charge off.

Though that's not the issue.  This (self consumption) state you have triggered looks like it's something to avoid. Not a common situation to be in but still it's a situation you found your system in and the results are worth mentioning. Thanks for sharing.

I will let the battery hit float and then switch the breakers off  for the PV input and see what happens. I guess you will want no DC loads on the battery other than the classic So I will switch the inverter off to then.

Will report back over the weekend. Though I am using 1849 firmware.

Kurt.

[australsolarier]

hi kurt,

i know you well from the australian energy matter forum. naturally i was following your threads with your system and programmed it to similar voltages, absorb 56, float 53.6v. i will take the opportunity here to express for all your and gordon's pioneering work. sincere thanks!!!!

as i mentioned several times before, there is nothing hooked up to the battery, yet, except of course the midnite and the blue ev power bcu pack, which draws maybe 40mAs.

however it was mentioned before on this thread that the latest firmware limits that reversing state to 90 seconds. i can defenitively replicate it, but i totally agree with you, it is not good to let the midnite classic run in that state.
the 400ah/48v lifepo4 (i got the green coloured cbs )battery is brand new, the inverter not here yet. so i hooked it temporarily up on three panels leaning on the wall. after float, the battery being fully charged and the system working, i turned of the breaker, dismantled the temporary wiring, and carried the 3 panels away onto the floor of the veranda.
however i then noticed that intermediate state between float and resting. and that lasted several hours. turning the midnite of and on it then went to resting mode.

at the moment i am grid connected. when the 60cents feed tarif is cancelled end of next year, i then will fully use the new system. i am a bit ahead timewise with the purchases and installation, as the ossi dollars seems to be on a downhill course.
thanks for your support kurt

greeting from nsw
urs

[australsolarier]

vic,

i am sorry if i confused you with the word converter. i did mean inverter

all the best
urs

[mike90045]

I think I head about an old version of firmware, that under certain conditions, could allow some sort of backfeed as you described.

Normally, battery voltage, or something lower is present at the solar terminals after dark..

[Resthome]

Just for the record, I believe Halfcrazy (Ryan) answered the OP's  question a few posts back. While I haven't seen a post from boB you can take Ryan's word for it that this situation you have created apparently has been corrected in later firmware. He works for MidNite and was previously the Tech Support Manager.

And yes I can confirm Win10 did not work for firmware updates for me and we are waiting for Ryan to let us know when a new and simpler firmware update method is available.

[dgd]

Australsolarier,

Next time you see this 'reverse' would it be possible for you to use a mutimeter and see if the voltage is 117v at the Classic PV terminals when the PVs are disconnected?
And perhaps again after 30 minutes or so.
This would ensure there is a maintained voltage present and the reading you see is just not a meter reading not being cleared by the Classic's cpu.

A further test would be to place a small load over the PV input terminals in the Classic, something that just draws a few watts and again see if the multimeter shows the 117 volts is being maintained.
A GU10 230v 20 watt halogen light should be ok as it will draw about 5 watts at 117v, it may even glow dimly

dgd

[ClassicCrazy]

Before the Classic came onto the market , one of the things being mentioned was that it would have  a snow melting mode where the Classic could reverse some power back into the panels to heat them up a bit. This feature never came into being . But I just remembered this and perhaps the reverse power being seen is some part of the hidden features Ryan mentioned , maybe some part of the code for that activates under the conditions Astralsolarier creates ?

snow melt thread
http://kb1uas.com/mnsforum/index.php?topic=660.0

Larry

[CDN-VT]

Before the Classic came onto the market , one of the things being mentioned was that it would have  a snow melting mode where the Classic could reverse some power back into the panels to heat them up a bit.
Larry

So how would that work with panel having blocking diodes installed in them ?
I have seen one 300W Canada Solar that was damage on shipping (fork from lift truck pierced it) And on disposing of it , I noticed black diodes in the wire combiner box.

Other was a few small Asian no brand that also had diodes .


VT

[australsolarier]

dgd,

i did measure it with the fluke voltmeter. just to give you an idea, when i first discovered this reversing, it lasted from from 10.58 to 16.48 hours. then i disconnected and reconnected the battery. it then fell into resting mode and 39.odd volts (as recorded on the mymidnite website).

and yes i was tempted to see how much power i could draw. however, i am not in the situation of ryan serial blowing up of midnite classics. i have to pay for them. this one set me back 1350AUS$ with the whizzbang jr. it gets quite warm doing it.

i was watching the 12v system (also has lifepo4 battery, 12v/300ah) today falling into float mode. it did it rapidly, no intermediary reversing state. the inverter was  drawing 750 watts though.
turning off the breakers on the 48v system during bulk, it goes into that intermediary state for about 30 seconds before hitting resting mode.
both midnite classics have the same software, 1923 loaded.

greetings urs