Hi community
is it safe that my 24 volt battery output 28.8 volt ? The batteries are charged by Bluesolar MPPT 100/50
asked
is it safe that my 24 volt battery output 28.8 volt ?
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.
@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-jFsd
looking 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 ) 
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!
@Stefanie Thank you very much for your clarification
My batterie are 12 volt 230 Ah (C100 rating)
