help from Victron users or specialists needed

[pelissima]

I use a Victron Phoenix 12V 30A to keep 3x100 batteries in parallel happy. Worked well for 7 years.
Batteries are now 2 years old and tested yesterday by big resistance to be in good order.
The symptom that puzzles me is this. It now goes through stage 1 (bulk, stopping at 14.4V) and stage 2(absorption) it proceeds to stage 3(float) but at 15.5V although the stored value is 13.3 so I turn it off.
I would like to leave it on for an hour or so to see what happens but I hang back.
Do you have any ideas?
A similar mail to Victron support produced no reply yet.

 

[David2452]

Provided they are vented, flooded lead acid batteries and in a well vented place I see no harm if closely monitored as your 15.5v is around that used to desulpate on some charger settings.

 

[Plevier]

By big resistance I guess you mean a high rate discharge test? If so that tells you very little about the usable capacity of house batteries. It only checks high rate performance. It doesn't really carry over as the limiting factors are different.
Even if your batteries are AGM an hour or so at 15.5V is not going to hurt (but don't do it every week!)
Can you monitor the charging current?

 

[Plevier]

Looking at p4 of the manual, it has an equalisation mode 1V higher than normal which is what you are getting.
It is activated by switching off and on again within 2 seconds.
Might you have had a brief power interruption that has triggered it?

 

[pelissima]

By big resistance I guess you mean a high rate discharge test? If so that tells you very little about the usable capacity of house batteries. It only checks high rate performance. It doesn't really carry over as the limiting factors are different.
Even if your batteries are AGM an hour or so at 15.5V is not going to hurt (but don't do it every week!)
Can you monitor the charging current?

You are correct. It was only a high discharge test.By the way, how do you measure the usable capacity ?
Monitoring the situation, what does the charging current tells us -in stage 3 or equalisation mode??

 

[Plevier]

You are correct. It was only a high discharge test.By the way, how do you measure the usable capacity ?

### With a capacity test with a realistic load over a realistic time period. there is no other way. (Open cct voltage or specific gravity will give you a good indication of state of charge if you already know the battery is healthy, but it will not tell you if an unknown battery is healthy or whether its capacity is good.)

Monitoring the situation, what does the charging current tells us -in stage 3 or equalisation mode??
### A single measurement tells you little. Trend can be helpful, and if it increases much when the extra volt goes on.

.

 

[pelissima]

Thank you,

I will go that way