Parallel MPPTs showing different yields

Question

question

mstr-cmdr asked Jan 28, '19

Parallel MPPTs showing different yields

I have just installed another MPPT charger in parallel - one 100/50 and one 100/30. The 100/50 PV input is from 2x 300w (12vdc) panels. The 100/30 PV input is from 2x 130w 12vdc panels).

Both MPPT BAT +ve outputs are paralleled to a 65A CB and thence to a battery bus (+ve); the BAT -ve outputs are paralleled to the -ve battery bus. Both PV array inputs are connected to its respective MPPT via a 2P1T isolator switch in-line for each separate array.

Today I checked the outputs of both MPPTs via bluetooth - the 100/50 yielded 780w; the 100/30 yielded 170w.

Both arrays are within 1m of each other and are oriented the same; both are free from any shadowing. Both MPPTs are configured identically.

Why is there the difference in yield between the two MPPTs? What can I do to have both feeding a similar wattage?

battery charging

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Modifications Space

Node Red Space

Answer 1 · 2019-01-28T10:42:08Z

Guy Stewart (Victron Community Manager) answered · Jan 28, 2019 at 10:42 AM

There is only a problem if the batteries aren’t getting full.

Did the batteries reach float?

3

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

mstr-cmdr commented · Jan 28, 2019 at 08:53 PM

Yes. 28JAN: 100/30 was in "float" for 515 min (VBmax 14.28), and the 100/50 for 368 min (VBmax 14.32).

PVmax for each respectively: 20.99v and 21.08v.

0 ·

Guy Stewart (Victron Community Manager) ♦♦ mstr-cmdr commented · Jan 28, 2019 at 09:33 PM

If the batteries are in float, then PV power is constrained to prevent over charging.

It sounds like your system is working as intended.

0 ·

teds mstr-cmdr commented · Jan 29, 2019 at 09:10 PM

I have a system like yours in that I have a 100 watt panel connected to a 75/15 and a 140 connected to a 75/15. Then they are both connected to the battery. What I find is the 140 watt panel starts charging much sooner in the day which keeps the 100 watt panel from starting to charge until it gets above the charge the 140 is putting out into the battery. So like you at the end of the day the 140 has put out a lot more than the 100. I think I would like a way to hold back the 140 till the 100 is putting out enough to start charging and then let the 140 also charge. Hope that makes sense.

0 ·

question