MPPT PV Watts not closely matching Open Voltage

pablo · 09-21-17, 09:51 AM

Hi,

I am very new to solar and I'm seeing something on my MPPT's monitoring display which I am not quite understanding.

When I conduct an Open Voltage test of my panels near the MPPT, I see under so-so sun, 32+ VDC/ 6.8 amps Let's say roughly 217.6 watts.

When I immediately connect the PV to the MPPT and I create a draw of more than 62 watts, I'll start to draw from the battery.

I would have thought that I would be able to draw 200+ watts from the PV's before tapping into the batteries.

As a newbie, do I have a fundamental misunderstanding?

Details

Two Costco Golf Cart batteries connected in series for 12V/220 AH
100' of 12g stranded cable between the PV's and the MPPT - more on this shortly.
A 40 amp controller[1]
Two 280 watt solar panels[2]. Due to minimal sun, they're in parallel.

100' run

This location is our cabin. We only use it during the summer time. It points north and is shrouded by trees. Perfect for summer and horrible for solar!

I have measured the DC loss and it is not significant.

References

Controller - EPSolar Tracer 4215BN MPPT Charge Controller - EP Solar - Brands | HES PV
Canadian Solar panels - CS6K-M

ps: as I am new to the forums I am not allowed to use URL links in my posts yet.

09-21-17, 09:51 AM	#1
pablo Lurking Renovator Join Date: Sep 2017 Location: Canada Posts: 3 Thanks: 2 Thanked 0 Times in 0 Posts	MPPT PV Watts not closely matching Open Voltage Hi, I am very new to solar and I'm seeing something on my MPPT's monitoring display which I am not quite understanding. When I conduct an Open Voltage test of my panels near the MPPT, I see under so-so sun, 32+ VDC/ 6.8 amps Let's say roughly 217.6 watts. When I immediately connect the PV to the MPPT and I create a draw of more than 62 watts, I'll start to draw from the battery. I would have thought that I would be able to draw 200+ watts from the PV's before tapping into the batteries. As a newbie, do I have a fundamental misunderstanding? Details Two Costco Golf Cart batteries connected in series for 12V/220 AH 100' of 12g stranded cable between the PV's and the MPPT - more on this shortly. A 40 amp controller[1] Two 280 watt solar panels[2]. Due to minimal sun, they're in parallel. 100' run This location is our cabin. We only use it during the summer time. It points north and is shrouded by trees. Perfect for summer and horrible for solar! I have measured the DC loss and it is not significant. References Controller - EPSolar Tracer 4215BN MPPT Charge Controller - EP Solar - Brands \| HES PV Canadian Solar panels - CS6K-M ps: as I am new to the forums I am not allowed to use URL links in my posts yet.