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Charge Controller Question
(06-19-2020, 06:58 PM)Wolf Wrote:
(06-19-2020, 06:32 PM)OffGridInTheCity Wrote: Controllers - I have 3 x Midnite Classic 150s, the oldest is 2 yrs..........................................
Yea I  have looked at them and they do look nice. Would you get 2 for my small system? I don't mind spending money but ~1400 for 2 with only 3000W of panel. Or get 1 and keep the MSB as backup. LOL
Also if I do use only 1 how do you think it will work with my panels easterly and westerly orientation? 

On another note today the MSBs worked just fine. Shrugg


I would start with one.  The Classics handle a 4000w range -   Assuming your arrays (East and West) are similar panels/wired for a similar voltage, then I don't see why one wouldn't work.  My panels wired in 3s.   Each Midnite does a 3s5p set of panels.  Some of the 3s(s) are shaded in first 1/2 of the day but the voltage is fine and parallels in with the other (unshaded) 3s(s) and things seems to work very efficiently - e.g. a common voltage (+/- 10%) but differing amps is the best design for the controller's MPPT.    

The Classics have more than one MPPT tracking algorithm with 'custom adjustments' to fool with if you're so inclined.   I use "Legacy P&O".

This is the default mode for PV systems and has a very fast sweep (typically1/2 second or less) that will re sweep at user adjustable sweep intervals, unless the Classic finds that it needs to do a sweep on its own because of changing conditions. The timed sweep interval is user adjustable and is in units of minutes. SOLAR mode is typically best for PV systems, especially if there is partial shading at times during the day. SOLAR mode is best suited for shaded or un shaded PV arrays that are at least one nominal voltage above the battery voltage. For severe partial shading or PV arrays with nominal voltage equal to battery voltage, you may also want to try Legacy P&O (Perturb and Observe) MPPT mode.

Legacy P&O
Legacy P&O (Perturb and Observe) mode is a slow tracking mode similar to the Micro Hydro mode but with the difference that it is slightly faster and will shut off if the power source goes off.
It has two settings that are user adjustable. Sweep Interval is the time between mini sweeps, in minutes, and sweeps around the present (i.e. the last found) MPP Voltage. The range of this sweep is determined by the Sweep Depth user adjustment and is expressed as a percentage of Watts that the sweep started from. For example, if in Legacy P&O mode, the Classic was outputting 500 Watts and the Sweep Depth percentage was set for 10% (50 Watts), the sweep will bring the input voltage DOWN until the output power drops down to 450 Watts, then will sweep UP in voltage until the power drops again down to 450 Watts and then go back to the newly found MPP Voltage, waiting for the next sweep.

This is typically used for PV (solar) input sources and tries to follow, on a slow dynamic basis, the changing conditions of the input source. This mode has one user adjustment which is a forced sweep perturb trigger interval for times when the input condition changes do not trigger a dynamic sweep. The interval is in units of minutes

U Set VOC%
This is a fully manual mode based on a percentage of VOC. The Classic will sweep based on the user set time in minutes and then park at a user set percentage of the VOC the Classic found on that sweep. This mode is useful for testing or constant voltage sources.

(06-19-2020, 07:03 PM)completelycharged Wrote:
(06-19-2020, 06:32 PM)OffGridInTheCity Wrote: becasue my 80a circuit breakers tripped (and 4awg wire won't handle it)

4AWG is rated for 130A and I have installed km of it for house incomming mains (100A fused)

My solar is fed off two 8AWG and gets upto about 55A on each cable, granted it gets warm... not hot. and at the limit as to what I find comfortable to use it with. 8AWG is rated for over 70A but that's hot to the touch and would cause thermal expansion/contraction issues if cycled daily.

If your breakers are tripping due to heat at 80A then your terminations may be the issue because 4AWG cable will transfer qute a bit of heat away from the breaker.
I have 3 x Midnites - each has a +/-  4AWG that's 15ft from the controller to control box bus.   4 of the wires share a 1" flexible conduit (the other 2 have their own 3/4 EMT).   The 4 wires coming out of the 1" flexible conduit peak around 70-80a / 55C  (130F) inside the control box at mid-day.    Here's a pic showing the wires coming into the control box and the temperature probe showing 55C temps....     

I'm going with <60C is 'OK' in my mind.  After all, wire is rated for this and the Midnites run 55C PCB and FET temps each summer day and the 4 AWG wire connects into the PCB at the Midnite itself.  
Its amazing how much the wire length affects things - e.g.  1 inch vs 1 foot vs 15 feet can really make a difference.   In the control box above I had a 1 inch 4 AWG segment (for a short while) connecting the bus to the shunt - and it handled 200a OK.  Didn't even get warm!   But I couldn't take it so I replaced it with a 2/0 segment Smile

Messages In This Thread
Charge Controller Question - by Wolf - 06-19-2020, 04:36 PM
RE: Charge Controller Question - by Wolf - 06-19-2020, 05:18 PM
RE: Charge Controller Question - by Wolf - 06-19-2020, 06:58 PM
RE: Charge Controller Question - by OffGridInTheCity - 06-19-2020, 09:07 PM
RE: Charge Controller Question - by Wolf - 06-19-2020, 10:49 PM
RE: Charge Controller Question - by Wolf - 06-20-2020, 10:36 AM
RE: Charge Controller Question - by Wolf - 06-24-2020, 02:46 PM

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