Placing a fuse on every solar battery?

softdown
softdown Solar Expert Posts: 3,937 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
I’ve seen this recommended a few times. Anybody doing it?
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
· Share on Twitter

Comments

  • SumPower
    SumPower Registered Users Posts: 85 ✭✭
    edited March 5 #2
    Every source of power needs an Over Current Protective Device installed to protect the conductors from geting to hot to cause a fire. And to protect people from getting injured or shocked.

    Every battery string I have has a breaker.
    · Share on Twitter
  • softdown
    softdown Solar Expert Posts: 3,937 ✭✭✭✭
    #3
    Don’t recall seeing systems with a fuse on each battery
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,664 admin
    #4
    At the very least, the usual requirement is one Over Current Protective Device per "string" of batteries.

    If you have one series string, 1 fuse.

    If you have two series strings, 2 fuses.

    etc.

    Actual practice can have two fuses per "floating" (no ground bonding)string, one at + output, and a second on the - output. This is done to provide more robust fault coverage (I.e, a multiple shorts in a "floating" power system).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • softdown
    softdown Solar Expert Posts: 3,937 ✭✭✭✭
    #5
    Yes, having a fuse on every string is accepted practice. 

    Since lithium fires are toxic it seems like more fuses on lithium batteries is prudent. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,664 admin
    edited March 6 #6
    If your battery bank is (for example) negative grounded (frame, house green wire/ground rod/etc.), one fuse per series battery + bus connection is sufficient.
    If you have multiple 3.7 volt cells in parallel, then the set connected in series for 12/24/48 VDC etc., should each cell have its own fuse... One could argue that, but I have never seen that done (lots more fuses). That would help protect against a single cell going shorted...
    But again, I have not seen that done, and I would suggest that the expense, complexity of extra wiring, etc. would make small AH Cell Lithium batteries an unsupportable configuration.
    If you are concerned about fire and byproducts (a real concern)--Install in separate shed/root cellar/or similar. Not a bad idea anyway (Battery "shed" separate from home/critical buildings).
    Also, in reality, fuses/breakers are to protect your wiring from starting a fire, not to protect attached "devices".
    Installing (or purchasing batteries with BMS) a battery management system for your Lithium bank is probably the best solution.
    Lots of protection, over/under voltage cells, over current charging/discharging current, much more precise and accurate over current protection vs fuses/breakers, over/under temperature of cells, shutdown of bank if any parameters are exceeded, etc.
    Bill "not a battery system engineer" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter

Categories