Current system is made up of:
- 12 x 2V 960AH FLA batteries
- 3 x 350W panels connected to a Xantrex 150V/60A charge controller
- 3 x 350W panels connected to a Victron 150V/60A charge controller
- Trace SW4024 24V inverter
I have plans to be out of the country for 6 months but am concerned about leaving the battery bank unattended.
I am planning on turning off the Xantrex charge controller and only using the Victron being fed by 3 x 350W panels.
My thought is to set the Victron charger to 27.2 volts across all charging parameters (bulk, absorption, & float). Would this be enough to prevent unnecessary gassing of the batteries? Should I use an even lower voltage and go further and limit the charger output to say something around 10A?
There will be zero loads and the Trace SW4024 inverter will be turned off while I'm away. I will also put a full charge into the batteries (via generator) just before I leave.
Thoughts?
Info on my battery bank (from manufacturer):
Table 1: Recommended Voltage and Current settings for recharging Davidson Batteries
Specific Gravity
The specific gravity of your Davidson battery is somewhat different from other brands of battery. They are actually fully charged at a lower specific gravity than most batteries and as a result they will actually be charged before most hydrometers will indicate full charge. The most accurate way to use a hydrometer to measure state of charge is to take note of when the specific gravity stops rising. Take readings every 1/2 hour during the last part of Absorption Stage, when the hydrometer does not rise from your last reading the batteries are fully charged.
The correct fully charged specific gravity of your Davidson battery is:
1.265 - 1.275 ( this will vary dependent on battery age, condition and ambient temperature)
Safe Operating Voltage
Another result of the special formulation and design of these long lasting deep cycle batteries is that they tend to operate at lower voltages than most higher specific gravity batteries, thus the safe operating voltage range of Davidson batteries is lower than most other batteries.
It is quite normal and safe to operate your batteries as low as 2 Vdc per cell5. They should always be recharged when they reach a standing voltage of less than 1.975 per cell6. Table 2 shows the conversion of Volts per cell settings to 12, 24 and 48 Vdc values.
Table 2: Converting Volts per cell to battery bank voltage.
