12vdc inverter and 48vdc inverter hook up

blangsonblangson Registered Users Posts: 2
I am currently operating a 12vdc input inverter which produces 110vac power using 4 - 12vdc batteries.  I  have a new requirement of  220vac power and have a 48vdc input power inverter which can supply the proper voltage and current for this new requirement.  Is it possible to hook up the two inverters to the same battery bank (one inverter hooked up in series and one inverter hooked up in parallel at the same time)?

Comments

  • EstragonEstragon Registered Users Posts: 1,543 ✭✭✭✭
    The short answer is yes, you could reconfigure the batteries in a series string for 48v, and take 12v off part of the string.

    This is a bad idea though for a number of reasons, and assuming your 220vac load is a large load it wouldn't run long (or maybe not at all). You are almost certainly better off getting a properly sized 48v bank for your new load.
    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
  • BB.BB. Super Moderators Posts: 26,837 admin
    If you put your 4 batteries in series--You can get 12 volts across each battery and 48 volts across all batteries.

    The difficulty is that when you have a "matched" string of batteries and draw current from one 12 volt battery and 48 volts from all 4--You end up with an "unbalanced" discharge. Now--You have problems charging the battery string.

    If you have a 48 volt charger, then 3 of the batteries will be charged while the 4th is not. Then you have to either "over charge" the 3 batteries to "leak current" to charge the 4th, or you have to have a second charger on just the 4th battery (can work--But really not recommended).

    But there is no way you can wire the 4 batteries to give you full current on 4 batteries in parallel (12 volts) and 4 batteries in series for 48 volts at the same time.

    I highly suggest that a system should be designed to support your loads. The loads drive the sizing of the battery bank. The both the size of the battery bank and your loads (and amount of sun) drive the solar array/backup genset design.

    And a warning--In general, 48 vdc input inverters are fairly large--And most 12 volt batteries are fairly low AH ratings... For example, a typical 12 volt storage battery is around ~100 AH. 4x of these batteries would (reliably) supply about 1,000 Watt maximum AC inverter.

    And another issue with higher input voltage/higher wattage inverters is that they have higher "tare losses"--Basically, the power needed just to turn on. A small 300 watt 12 vdc inverter may take 6 watts. A typical 48 vdc inverter may take 10-20+ watts--More losses. More battery storage. More solar array to keep batteries happy.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • blangsonblangson Registered Users Posts: 2
    Thank you for clearing this up for me.

  • MenaMena Registered Users Posts: 4
    I haven't do things like you but I have a similar connection problem. I'm now traveling in USA and have car cigarette lighter with 2 sockets and 2 USB ports. I just bought a coffee maker and a 300W power inverter that has only two AC outlets. But it is not enough for me to charge my other electronic devices like cameras. So, is it safe to plug the 300w power inverter into the 2-socket cigarette lighter? so that I can the cigarette lighter USB ports and power inverter AC outlets. Anyone know how to deal with this problem?
  • Raj174Raj174 Solar Expert Posts: 461 ✭✭✭✭
    Hi Mena,
    The 12 volt outlet in your car has a fuse. The amount of watts it will supply will depend on the fuse rating. For example, my car has a 15 amp fuse for the 12 volt outlet. That's 180 watts. Find out what the fuse rating is for your car and multiply it by 12 for the maximum amount of watts available from the outlet.
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 195AH HI Power LiFePO4 no BMS, 4000W gen.
  • EstragonEstragon Registered Users Posts: 1,543 ✭✭✭✭
    Also check the amp rating on the socket device itself. It may be fine for charging small stuff, but a coffee maker might be too much.
    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
  • BB.BB. Super Moderators Posts: 26,837 admin
    Reliably, you can pull 10 amps for a few minutes (10 amps * 12 volts = 120 watts). Any more than that--Highly suggest that you properly attach a heavier harness (plus fuse or circuit breaker) directly to your battery/battery bank. Any decent sized AC inverter--pretty much requires a bolt up cable connection between the battery bank and inverter DC input. Jumper Cables (with alligator clips) will generally not work either.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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