question

maloya avatar image
maloya asked

Switching from 12V MPPT to 48V MPPT

"We have a sailing boat with two battery banks: a 12V house bank (600A) and a 48V electric motor bank (600A). Our solar panels are connected to a 12V MPPT charge controller. We would like to automate the process so that when the 12V battery bank reaches 100% charge or 14V, the solar panel power switches to the 48V MPPT charge controller to begin charging the 48V battery bank. Essentially, we want the system to switch from the 12V MPPT to the 48V MPPT automatically. While we could use a manual switch, an automatic solution would be preferable. Any suggestions? Thank you in advance.

Gustavo"

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.

2 Answers
delf67 avatar image
delf67 answered ·

If you have some sort of intelligent control on the 12V system (Cerbo GX for example), it should be fairly straightforward to automate a suitable DPDT relay on the solar panel input to the MPPTs. A bit more info on what kit you have installed would be helpful.

5 comments
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.

kevgermany avatar image kevgermany ♦♦ commented ·
Might not work well. There's no guarantee the MPPT will recognise the switch in battery voltage.
0 Likes 0 ·
delf67 avatar image delf67 kevgermany ♦♦ commented ·
The way I read the question there are 2 MPPTs, one on the 12V and one on The 48V. So it's switching the panels between MPPTs, not switching a single MPPT between different voltage batteries.
-1 Like -1 ·
kevgermany avatar image kevgermany ♦♦ delf67 commented ·
I missed that, sorry.
0 Likes 0 ·
maloya avatar image maloya commented ·

Thank you for the answer, I have on the 12V system a servo GX that is right

0 Likes 0 ·
maloya avatar image maloya commented ·
I have to find out a bit more about the DPDT relay and what type I should use, and how to connect, and configure to the Servo GX
0 Likes 0 ·
delf67 avatar image
delf67 answered ·

You will need a DPDT relay with a 12V coil that is rated to switch the maximum voltage and current your panels will supply. The panels will feed into the COM (common) contacts, the 12V MPPT will be on the NC (normally closed) contacts and the 48V on the NO (normally open) contacts.

The coil needs to be fed from a 12V source through relay 1 on your Cerbo.

In terms of configuration, I would propose you set the relay up for generator start/stop based on SOC.

You will have to "reverse" the switching of the relay because the function is designed to close the relay on a low SOC and open the relay on a higher (100%) SOC, whereas you want it to do the opposite.

Everything needs to be fused as appropriate.

Does that make sense?

DPDT_wiring.jpg


dpdt-wiring.jpg (133.1 KiB)
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.

maloya avatar image maloya commented ·

Thank you very much. I will start looking for the correct relay as you recommend.

Regards

0 Likes 0 ·