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Controller regulating pv voltage

Master of none

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Mar 4, 2023
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New Zealand
4210an epever 40a controller with the following two panels connected.

2X A GRADE MONOCRYSTAL PERC 11BB 280W Panels

Maximum Power:280W (Pmax)
Maximum Power Voltage: 20.85V (Vm)
Maximum Power Current: 13.42A (Im)
Open Circuit Voltage: 24.18V (Voc)
Short Circuit Current: 15.13A (Isc)
Power Tolerance 3%

The tab two panels set up in series with 46v tested at the mc4 panel output and 46v at the controller terminals.

3210an epever 30a controller with the following single panel connected.

1X A GRADE MONOCRYSTAL 310W Panel

Maximum Power:310W (Pmax)
Maximum Power Voltage: 32.99V (Vm)
Maximum Power Current: 9.40A (Im)
Open Circuit Voltage: 40.44V (Voc)
Short Circuit Current: 9.85A (Isc)
Power Tolerance 3%

Single panelset with 37v tested at the mc4 panel output and 37v at the controller terminals.

Battery bank: Narada 6REXC-300

4 X 6V VRLA AGM sealed Lead Carbon 300ah batteries in 12v configuration. 600ah total.

Running mt-50s on both solar controllers configured with the following battery charge settings.

User
12v
600ah

Over Voltage Disconnect 14.7 V
Charging Limit Voltage 14.6 V
Over Voltage Reconnect 14.6 V
Equalize Charging Voltage shut off or 14.4 V
Boost Charging Voltage 13.8 V
Float Charging Voltage 13.5 V
Boost Reconnect 13.3 V
Low Voltage Reconnect 10
Under Voltage Warning Reconnect Voltage 11.5
Under Voltage Warning 11.5
Low Voltage Disconnect 11.0
Discharging Limit Voltage 10.5
Equalize Duration 0
Boost Duration 120 minutes

Troubleshooting:

All connections are tight and no issues with the mc4 connectors. 8.00mm² (8 B&S) from the batteries to each controller and 4.00mm² (4 B&S) from the panels to the controllers.

the 30a controller runs the 37v through the mppt charging program fine. If I connect either of the single 280W panels to this controller, it reads 23v and also charges fine.

If I connect the two panels in series to the 40a controller, without the battery connected, pv shows 46v.

With the single 310W panel connected to the 40a controller without the battery connected it shows pv of 37v.

If I have the batteries connected to this controller, the pv for the two panels in series reads pv of 14.7v not 46v and doesn't show as charging the battery bank. Note that the 3210an controller with the single panel connected holds the 37v and is charging the battery bank while this happens so can't be a battery issue.

If I connect the battery with the single 310W Panel to the 40a controller, the pv drops to 12v not 37v and doesn't charge the battery bank.

Do I have a broken controller? This was just purchased and added to the system along with the two new panels and two additional batteries to provide more overall capacity.
 
The controller may have a fault, applying solar Input without a battery connected could have confused or damaged the controller. Try battery first connection then solar.
Additional comment, the charge voltage, boost, voltage setting of 13.8 volts seems low for AGM batteries.
 
Hey I tried both connecting the battery first then solar. And without battery to see if the controller would read the pv correctly. Only without the battery would it pick up the correct voltage.

Battery settings are per the battery specs.
 
Without battery connected there is no large current flow as there would be going to an accepting battery bank. A lack of current going somewhere impacts the measured voltage drop through any existing resistance between the panels and the controller. I would verify all the connections between the panels and controller are secured and not fouled in some manner, and that the wire gauge is correct for the current traveling to the controller. Without current flow, resistance has no impact on voltage drop and you're measuring a static voltage from the panels at the controller. Also refer to your controller manuals fine print, most do not respond well to having panels connected with a battery connected first, many learn the hard way and burn up the controller.
 
Hey thanks for your reply. To be clear, the batteries were connected first and the problem existed then.

Disconnecting the batteries to see if the pv still showed the stunted voltage was just part of my troubleshooting process.
 
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