It looks like the setup does not fully charge the battery (2x200Ah in parallel). Now after 3 discharge/charge sessions the voltage does not get higher yet as 26,8V. With these voltage the battery doesn’t get into the celbalancing mode. The config of the Phoenix and Small BMS is done as recommended for lithium.
Any advices or experiences?
Thank you, Martien
During absorption charge have you measured the voltage at the Phoenix terminals and the battery terminals to see if your problem is voltage drop.
Secondly, your batteries when delivered will be 45-50% full so they will have needed 8-9 hours charging from empty to get to full. Are the LEDs going from bulk to absorption to float. It may be that the charger has not got the batteries full yet.
I measured once last days during Bulk charge: at the Phoenix terminals 26,9V and at the battery terminals 26,7V. In between is a fuse, 1,5 meter 16mm2 cables and a Cyrix relais for overcharge protection.
I have seen only once during a charging session that the Phoenix went from bulk to absorption to float. Cell voltages were then about 3,34-3,35V. No Cell-balancing occurred yet (cell status detection starts at 27,6V according the manual), but as such are all 16 cells at same voltages. Until now i haven’t seen higher cell voltages.
Phoenix config is: 28,4V absorption, 2 hour absorption, 27V float.
Thanks again.
Voltage drop is not an issue. I do not know why it is not working as expected then. The manual does not list a maximum bulk time. I still think a 25A charger is small for 400Ah of lithium, it may have been OK for 400Ah of lead at a push but not lithium. Have you anything to check the 25A is being added to the battery or os the charger supporting other loads at the same time.
One thought, have you still got temperature compensation running as that can reduce voltage and you should not have that enabled for lithium.
Thanks again.
There are no other loads at the same time. According the BMS history 11kWh went out and 15kWh went into the battery up till now. A long charging duration is no issue from a user perspective (setup is used in a small pleasure craft). Indeed, one of the big questions is maybe if a bulk current of 25A is too low for 400Ah LFP?. In the manuals is as such no minimum bulk current requirement mentioned for LFP batteries. Also for example, the 15kW LFP battery in my plug-in car can also be charged with a 3,7kW home charger..
Due to space limitations I can’t install a much larger charger. I consider to replace the current Phoenix by a Victron Phoenix Smart IP43 24v/25A charger, for which i have heard that it works well with a 100Ah LFP NG battery setup. But I haven’t heard about experiences with a 400Ah setup, so the second big question would be if a IP43 25A charger for a 400Ah LFP battery would work better?
No temperature compensation is applied. Thanks
Your car example, 15kW charged by 3.7kW is a ratio of about 4. Your boat battery at 400Ah and 25V = 10kW but you are charging it at 25A at 25V = 0.6kWis a ratio of 16, so it is relatively much smaller and will take a considerable time to charge and you are taking out more than you are putting in. The manual says 400aH of lead acid as max capacity, lithium is roughly double the usable capacity so 200Ah. You just need to leave it longer on charge and if it is stopping part way through turn it off, disconnect it and restart, it may have some form of max timer not mentioned in the manual. The other thing is if it is getting hot it may reduce the charge current, do you have a way of knowing the actual charge current.
I can not think of anything else to say.
You are charging at 0.06C that equates to 14~16hour charge time depending on Soc, maybe you must consider Victron Skylla-i 24/80(1+1) then you will be charging at 0.2C or 4~5h charging time and you could also top up your starter battery at the same time.