question

swiftrv avatar image
swiftrv asked

MPPT 75/15 adding extra Solar panel

Current Setup is as follows.

two 60 watt panels in parallel. So 12 volt system on a Swift Explorer caravan.

mppt 75/15 Two lithium 120 amp hour batteries in parallel

We find in winter the current system struggles to totally recharge our batteries. Outside of winter it is not an issue.

Question, can I add a 100 watt solar panel.

** please note that the existing two 60 watt panels are now 9 years old, so may not be performing to 100%.

van is kept in a shed when not in use. We rarely venture out in January/February.

MPPT Controllers
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

3 Answers
bathnm avatar image
bathnm answered ·

@SwiftRv You would have 220watts of solar. At 12v that would be 18A. That is greater than the 15A capability of the MPPT. You would be over panelled. However in winter that will not be an issue, in summer you will be pushing the MPPT to its limits. Adding a second MPPT for the extra panel is an option.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

Michelle Konzack avatar image
Michelle Konzack answered ·

How high is the V0 of the panels?

If it is under 75V the the option would be putting both panels in series wich is an advantage from Autum over Winter to Spring.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

swiftrv avatar image swiftrv commented ·
Unfortunately for the two 60 watt panels I don’t know.

what I may need to do is remove those panels and add two new 100 watt panels.

0 Likes 0 ·
jetlag avatar image
jetlag answered ·

According to the datasheet, the MPPT 75/15 can candle up to 220W for a 12V System. So no problem here, but the problem I see here is, that you should not connect PV Modules with different voltages together in parallel.

A possible solution could be, to disconnect the 2x60W panels, and connect a mobile additional e.g. 120W panel instead. This mobile panel could then be perfectly adjusted to the sun, so the outcome is much better anyway... (I guess the 2x60W panels are mounted on the roof?)

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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