Battery charging

Plucka
Plucka Registered Users Posts: 130 ✭✭
in Solar Beginners Corner #1
I have a Pro Charging Dual Pro DC to DC 15 amp running off my alternator when I'm driving but I also have solar charging at the same time to my lithium batteries and when I'm parked I often run a generator to a 20 amp lithium battery charger. I feel my batteries aren't charging fast enough.With two charging units does one dominate the other and one not charge.It's winter here and my panels only put out 20 amps for 4 hours plus less other hours.I turn all power off including the inverter and I still can't fully charge my 360 amp/hr lithium batteries in a reasonable time  [ 2-3 hours ] After that time the best I get to is 13.6 volts.Is there a problem or don't I have enough amps charging? 
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #2
    If that 13.6 volt reading is while the battery is resting then it is between 90% and 100% SOC. Pretty much full. Float voltage is 13.35V for a 12 volt LFP bank. 

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #3
    How deeply discharged is the bank? If, at best, you can produce ~35a of charging, can you reasonably refill a 360 ah bank from the state discharged in the tme available?

    As to the question about two charging sources, it's possible one source will quit charging prematurely if they read different voltages, or are programmed differently.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Plucka
    Plucka Registered Users Posts: 130 ✭✭
    #4
    Thanks for your answers .In the summer the solar charge [37 amps ] went to 14.2 volts then stopped charging and dropped back to 13.8 volts at rest.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #5
    14.2 or 3.55V per cell is a good absorb setting if there is a balancing BMS. The 13.8 reading should continue to drop to 13.4 which is the resting voltage for a fully charged LFP bank. Sounds like your system is working very well.  
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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