Victron smart 12.8v smart lithium battery

YerfYerf Registered Users Posts: 39 ✭✭
Hi

Can someone please explain how discharge and charge currents work for these batteries.

It says in the data sheet that the 100 A 12.8v lithium battery has a recommended charge current of below 50A and a recommended discharge current below 100A.

If I had a bank of 4x4 100 A batteries (4 in series 4 in parallel) so a 51.2 v 400 Ah battery bank what would my ideal charge and discharge current be?

Comments

  • BB.BB. Super Moderators Posts: 26,837 admin
    Yerf, feel free to post a link to the battery pack.

    50 amps per string, 4x parallel strings * 50 amps per string = 200 amps maximum rate of charge for proposed battery bank.

    I do not know of any minimum charge rate (although, some rechargable battery chemistries have "odd behavior" when they are full--A slight drop in charging current, or even batteries get cold near full charge, etc.). In those cases, sometimes a minimum rate of charge is recommended so that those small changes, such as small voltage drop when full, are not missed. Many lithium batteries do not like to be over charged/trickle charged as this can dramatically shorten their life. Aiming for ~20-90% state of charge/cycling is common practice for many battery chemistries.

    You need to know exactly what chemistry (Lithium) you will be working with... The operating voltage range needs to be programmed correctly to limit the chance of damage (or worse) to your battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • YerfYerf Registered Users Posts: 39 ✭✭
    Hi

    These are the batteries in question https://www.victronenergy.com/batteries/lithium-battery-12-8v

    I've attached a datasheet.

    Can you also advise me on the size of the fuse for a battery bank consisting of 16 x 100Ah batteries in 4 strings
  • BB.BB. Super Moderators Posts: 26,837 admin
    Regarding fusing, what peak charging/loads do you want to support.

    In general, off grid systems discharge at c/8 to c/20 (long term average discharge rate) and charge at c/20 (5%) to c/8 (13%) to c/5 (20% genset) rate of charge.

    Li Ion batteries usually support much higher charge/discharge rates than we need.

    If you have different needs (power tools, etc.), then things would be different.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • YerfYerf Registered Users Posts: 39 ✭✭
    Hi

    Charging at around 10 kw and load at around 15 kw
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    FWIW - I think you need a total of 5 fuses/breakers. One would protect the inverter/charger and positive wire from there to where the parallel battery connections are made. The wire and breaker sizes should be spec'd by the inverter manufacturer.

    The other 4 protect each connection from the 4 series string to the parallel connection so you don't get 3 strings feeding current into a short fault in any 1 string. With max recommended charge rate of 50a, a 63adc breaker seems reasonable to me. If polarized, I think (counterintuitively to me) the + breaker post would point away from the battery and to the parallel point, as that would be the source of current in a fault.

    My thoughts only.
    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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