Aux Input Suggestion...

[WizBandit]

What I would like to see, if an INPUT to the Classic is made available, is BTV input. (Battery Terminal Voltage) that the Classic can read as the voltage of the battery bank right at the terminals. A very accurate way for the classic to adjust charging. Just a suggestion.

[Vic]

Hi WizB ..

Well,  in looking at all of the  Aux 2 inputs,  seems to me that all of the Analog settings (like voltages)  are based on things that are not connected directly to the Aux 2 input.   This makes me believe that the Aux 2 as an input is a binary -- digital -- input.  High or low,  and nothing in between,  and all of the analog values are those that are measured elsewhere (like batt voltage etc).

It would be very nice if Aux 2  was an Analog input,  I have a favorite wish for the Classic if that were the case.    Am doing my customary guessing,    which is often wrong.

I had wondered if there could be a calibration value that would allow the CC Battery Output lead resistance to be entered,  or  inferred from a certain voltage drop at a specific current.   But this might just be too much to dream about.   There are limits ...      Guessing done for now,  Vic

[boB]

Actually Aux 2 is either an analog or digital input.

The software hasn't been made to really do anything with it yet, though.

Yes, it could read the batter voltage terminals but you would still have
the common negative line and if any significant voltage was across
that, it may not be very accurate.

We don't pay a lot of attention to the need for reading battery voltage directly because
that doesn't matter so much when in Absorb because the voltage drop is usually
fairly low then, unless you have big DC loads, which of course does happen.

When in MPPT mode, the voltage is below the set point and doesn't matter much
at all at that time.

Another way around this is to simply be able to calculate the voltage drop due
to output current from the Classic and take that into account, as long as the
Classic battery terminal voltage reading is correct.  Less wires.  Just enter the
battery wire gauge and wire length.

boB

[Vic]

Hi boB,

Thanks for the good news on Aux2 being Analog.

Had just found Register 4226: VauxA2D input (or similar),  so that did have me wondering about it being Analog.

This may not be the correct  place to note my secret desire,   but,   ...

Had wondered about using an Op Amp to scale the voltage from a shunt thai is in the negative lead of the battery bank.  Then having a menu that would allow one to set an EA value of actual charge current into battery.

Have noticed previously,  that there is a command via Modbus (or whatever you folks call it)  that does Force Float.   And a  number of refs to Bat Monitor  etc. Know that a Bat Mon is on the list of products from MN ...    But,  this is A/C season.  A/C loads are quite variable,  which makes a timed Absorption stage difficult to manage,  as the "ideal" time can change each day.   And so on.

I am really DAZZLED by all of the functionality and capability built into the Classic.  Simply amazin'!!
Thank You!
73  Thanks,  Vic

[boB]

Hi boB,

Thanks for the good news on Aux2 being Analog.

Had just found Register 4226: VauxA2D input (or similar),  so that did have me wondering about it being Analog.

This may not be the correct  place to note my secret desire,   but,   ...

Had wondered about using an Op Amp to scale the voltage from a shunt thai is in the negative lead of the battery bank.  Then having a menu that would allow one to set an EA value of actual charge current into battery.

Have noticed previously,  that there is a command via Modbus (or whatever you folks call it)  that does Force Float.   And a  number of refs to Bat Monitor  etc. Know that a Bat Mon is on the list of products from MN ...    But,  this is A/C season.  A/C loads are quite variable,  which makes a timed Absorption stage difficult to manage,  as the "ideal" time can change each day.   And so on.

I am really DAZZLED by all of the functionality and capability built into the Classic.  Simply amazin'!!
Thank You!
73  Thanks,  Vic

We actually talked quite a bit about using the Aux 2 input for an Ending Amps battery shunt input.
I think that the battery monitor is going to come faster than we thought now.  Shouldn't take
a rocket scientist to do that, but it will have a few other features while we're there I think.

As for Absorb being hard to manage, we heard you guys and the next version of software release
actually keeps the absorb timer from counting UP.  There will still be a way for it to count up
to maximum and hopefully that new method (called VariMax) will be implemented sometime
in the near future.  It will allow up-counting to maximum absorb time depending on
certain voltage and current parameters being met.  This would still allow a minimum absorb
time to be adhered to when the battery is already full and Classic has just been started up,
without having to have the battery monitor connected.  I know that you, Vic, will have
the BM but not everybody will.

For now, we will just stop the counter from counting down when voltage goes too far below
the set point.   This should be easier on your batteries.

boB

[Vic]

Hi boB,

Thanks for the info.  I'd get the MN BM if that was a good way to have battery charge current setpoint end Absorb.   But,  for me,  with FLA batteries,  measuring SGs is SSOOOOooo  easy,  that believe that I'd continue doing that to determine actual SOC.

There is no question the you MN guys  do a great job designing,   implementing and improving your porducts.  So,  am certain that for many of us  your BM will be very whiz-bang,  and a must-have for all of us with Classics.

Thanks again for being so responsive.   No other company even comes close to Midnite's connection with their customers.  Thank you very much,   Vic

[Kent0]

I'll add my voice in favor of battery voltage sense terminals. A couple years ago I installed a system at a remote cellular site and was required to put the charge controllers, four in all, in a separate building that was 100 feet away. Fortunately the Morningstar charge controllers have remote voltage sense, that feature made the remote location workable.

[boB]

I'll add my voice in favor of battery voltage sense terminals. A couple years ago I installed a system at a remote cellular site and was required to put the charge controllers, four in all, in a separate building that was 100 feet away. Fortunately the Morningstar charge controllers have remote voltage sense, that feature made the remote location workable.

100 foot battery lines from the CC    I would not advocate doing that and if the inverter and/or equipment that was drawing
off that same battery bank and sharing the same battery cables would be asking for disaster, normally.

We are going to be writing/drawing up a "best practices" paper on this very thing soon.

So, that being said, if it was just the charge controllers 100 feet away or they were on their own battery lines, the
voltage drop calculation inside the CC should take care of having to run extra wires.  Does that sound
viable in a case like this, Kent ??

boB

[Kent0]

I agree that long cables between the batteries and charge controllers should normally be avoided. I've put PWM charge controllers in telco offices before and didn't have interference issues or problems with the telco. For this cell site and company the concern about possible interference was overwhelming and they weren't going to allow a PWM charge controller in the same room as the cell phone transmitter, so, it ended up 100 feet away in another building. The 1/0 charge controller output cables ran directly to a large bus where the batteries were connected in parallel. The #14 AWG voltage sense wires went to the same bus. I think it was four sets of batteries and each set was connected to the bus with reasonably short runs of 400 kcm locomotive cable. The voltage drop in the charge controller's 1/0 output wires was about 2.5% or 1.4 volts. If that much voltage drop isn't accounted for, it will put the charge controller in absorption mode prematurely.

Firmware to correct for line losses in the output wiring is a good idea, in this case, it would have worked as well as the extra #14 AWG sense wires. Obviously, if the output wire and load wire is shared, like the 2/0 or 4/0 wiring often is shared in power systems, it would be difficult to accomplish with firmware, but the remote sense wire still would work.

Here's another idea: a networked voltmeter that senses the battery voltage directly and shares it with all of the charge controllers and inverter/chargers. That way every device in the system has the same info about the battery. No more discrepancies between devices.

[Vic]

Since I am notoriously BAD at guessing, ...   but,  ... I had wondered if any MN Bat Mon might just have such a Networked Bat V sense function.  It mught be a bit slow,  but would prob not be required to do any real-time sensing,  as much as perhaps a compensation value that had been previously measured,  and  applied to the value measured at the CC output Battery terminals.

Seems that this case you cite is (hopefully) at the extreme of any that might be encountered.
'Tis a good thing that I am not designing these things!
Vic

[boB]

Firmware to correct for line losses in the output wiring is a good idea, in this case, it would have worked as well as the extra #14 AWG sense wires. Obviously, if the output wire and load wire is shared, like the 2/0 or 4/0 wiring often is shared in power systems, it would be difficult to accomplish with firmware, but the remote sense wire still would work.

Sharing the charging and load wires for a long run to the batteries can be very bad because any large
transient loads (like the input capacitors of an inverter) will draw current directly from the CC.
We can now account for that though in our 250 CCs and coming up on all the 150s and 200s.
It's not as big of a problem on the lower voltage CCs.  But 100 feet is a LOT !!!

Just the input ripple of an inverter could cause problems...  But, this, being a cell phone
site  may not have that problem, unless it is running inverters for air conditioners which
it may be doing here.

Here's another idea: a networked voltmeter that senses the battery voltage directly and shares it with all of the charge controllers and inverter/chargers. That way every device in the system has the same info about the battery. No more discrepancies between devices.

We are working on a nice solution to this that will take care of knowing battery current as well as telling the Classic(s) what
the battery voltage is.

boB

[boB]

Since I am notoriously BAD at guessing, ...   but,  ... I had wondered if any MN Bat Mon might just have such a Networked Bat V sense function.  It mught be a bit slow,  but would prob not be required to do any real-time sensing,  as much as perhaps a compensation value that had been previously measured,  and  applied to the value measured at the CC output Battery terminals.

Seems that this case you cite is (hopefully) at the extreme of any that might be encountered.
'Tis a good thing that I am not designing these things!
Vic

Yep !  Voltage too !

boB