question

slim-hammami avatar image
slim-hammami asked

is it safe that my 24 volt battery output 28.8 volt ?

Hi community

is it safe that my 24 volt battery output 28.8 volt ? The batteries are charged by Bluesolar MPPT 100/50

MPPT Controllers
screen-shot-2020-05-07-at-74117-pm.png (155.7 KiB)
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
Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @Slim Hammami,


yes. Nothing to worry about. Your MPPT charger is doing exactly what it should.
24V is the nominal voltage, which is not the same as the charging voltage. In your case 28.8V (14.4V for a 12V battery) is the Absorption voltage. Depending on your battery type and brand this could be different. So check the data sheet for your battery or tell us the type of your battery and we can help you further, if needed.

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.

slim-hammami avatar image
slim-hammami answered ·

@Stefanie Thank you for your reply

I am using acid lead battery type. 8 batteries , 12 volt @230hA each set in parralel and serial to deliver 24 volt @ 960 hA. Here is the link to the batteries specs https://drive.google.com/open?id=1aSWjSxLH9bHfJoNYXUzX8Kkz7MM-jFsdlooking at the DC voltage arriving the phoenix inverter , I understand your comment about the MPPT normal behaviour. Between sunrise and sunset the inverter is getting energy directly from the solar panel not the battery. I have attached my graph , but any explanation to the quick drop in the graph ( in the red circle )


screen-shot-2020-05-07-at-100159-pm.png (47.0 KiB)
screen-shot-2020-05-07-at-101115-pm.png (186.3 KiB)
2 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.

Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ commented ·

The voltage drop is also normal. There MPPT has 3 stages, Bulk (delivers as much current as possible while voltage is rising up to 28.8V), Absorption (keeps voltage at 28.8V while charge current decreases until the battery is fully charged) and Float (battery is fully charged, only a very small current is flowing, no need to keep the voltage any longer at 28.8V, so it drops down to float voltage of like 27.6V). So the voltage drop in the red circle is stage 3, when the charger has finished absorption phase and is going to float phase.

There is no info in your document about charge parameters for your batteries. I'm not a fluent french speaker, but it looks like they are ordinary 12V / 200Ah (C20 rating) wet lead acid batteries. Without knowing the exact charging parameters in your MPPT, I would say they look good for this kind of batteries. Nothing to worry about.

Make sure your loads can handle 28.8V!

0 Likes 0 ·
slim-hammami avatar image slim-hammami Stefanie (Victron Energy Staff) ♦♦ commented ·

@Stefanie Thank you very much for your clarification

My batterie are 12 volt 230 Ah (C100 rating)

0 Likes 0 ·