Sizing a 24V Deep-cycle Battery System for a specific application

ynanperilloynanperillo Registered Users Posts: 2
Hi Everyone,

I have some devices that I need to connect to an OFF-GRID Power Source consisting of a;
(1) unit 500w Solar Panel
(1) unit 500w Wind Turbine
(1) unit hybrid charge controller
(1) unit pure sine wave inverter

All the devices must connect to a power strip that is connected to the inverter output.

Here are the Devices that I am going to use along with their DC-rating
*antenna - 8.5W max consumption, power supply is 24V 0.5A PoE adapter
*camera1 - 10W, 5V 2 A adapter
*sensor1 - 216mW, 12V 1A adapter
*sensor2 - 180mW, 12V 1A adapter
*RTU1 - 6W, 12V 2A Adapter
*RTU2- 4W, 12V 2A Adapter
*IP Phone - 12W. 12V 2A Adapter
*Amplifier - 200W, connected directly to 220v output of the inverter

BUT I do not know how can I determine the following;
1. Ampere-Hour size of the (24v) deep-cycle battery to be used
2. how many deep cycle batteries I need to use to provide at least 72-hours of operation for my devices

I do not know how can I compute for these things given that;
*I only have the DC ratings of my devices, I do not know how long can a FULL-CHARGED (24V) Deep-cycle battery system provide for the Inverter to produce 220V for 72-Hours.


Thank you...

Comments

  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    I do not know how long can a FULL-CHARGED (24V) Deep-cycle battery system provide for the Inverter to produce 220V for 72-Hours.
    Welcome to the forum,

    The only way to answer the question is know your load... how much DC current does the inverter draw while operating your AC loads. 

    It is not hard to measure the AC load of your devices... watthour meters are cheap.  So measure the AC load of your devices, and tell us the model of your inverter.  The inverter will use a certain minimum amount of power and have a certain conversion efficiency.  If we know the AC output of the inverter, we can calculate its DC power input and that will be the critical number we need to answer your question.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 29,509 admin
    I guess you are in the Philippines?

    For solar power systems, as vtMaps says--It starts with knowing your loads... Not only Watts or Amps (@ xx Volts), it is how many hours per day you want to run them...
    • 10 Watts * 1 hour per day = 10 Watt*Hours per day
    • 10 Watts * 24 hours per day = 240 Watt*Hours per day
    • 1 amp (at 12 volts) * 8 hours per day = 8 AH per day
    • 8 AH per day * 12 volts = 96 WH per day
    Do you have a specific Inverter/Hybrid Charge controller you are thinking of using (Links)?

    In general, you will need to design your loads to conserve as much energy as possible. For example, you have some 12 volt loads--If they can run from a 12 volt battery (~10.5 to 15.5 VDC). Sometimes, it is better to just put in an AC inverter (stable AC voltage) and isolate the DC loads from the very wide voltage range of a typical DC Solar Battery Bank.

    For an AC inverter--If you stay with a 12 VDC battery bank, this MorningStar 300 Watt unit is pretty nice (120 VAC US, 230 VAC for other regions):

    http://www.morningstarcorp.com/products/suresine/

    That inverter takes ~6 Watts just being "turned on without any AC load"--If you have small devices that take a few Watts (or less) loads--Perhaps direct 12 volt connection to battery or smaller 12 volt to 12 volt buck/boost DC converters would be better for those loads and only run the inverter when needed (the Morningstar is nice, has both remote on/off input, and low power "search mode" which may help conserve power). If you have to send energy longer distances, 230 VAC may be a better choice (sending lots of 12 volt current over longer distances can be a huge problem because of voltage drop)..

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ynanperilloynanperillo Registered Users Posts: 2
    vtmaps said:
    I do not know how long can a FULL-CHARGED (24V) Deep-cycle battery system provide for the Inverter to produce 220V for 72-Hours.
    Welcome to the forum,

    The only way to answer the question is know your load... how much DC current does the inverter draw while operating your AC loads. 

    It is not hard to measure the AC load of your devices... watthour meters are cheap.  So measure the AC load of your devices, and tell us the model of your inverter.  The inverter will use a certain minimum amount of power and have a certain conversion efficiency.  If we know the AC output of the inverter, we can calculate its DC power input and that will be the critical number we need to answer your question.

    --vtMaps

    Hello,
    Thanks for the answer! :)
    I attached here the datasheet of the Inverter and charge controller that I will going to use.


    Inverter

    Charge Controller

  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Hello,
    Thanks for the answer! :)
    I attached here the datasheet of the Inverter and charge controller that I will going to use.
    I didn't answer your question... other than to say that you need to measure your load before the question can be answered.

    The inverter appears to draw 0.7 amps X 24 volts = 16.8 watts.  If you turned on the inverter without a load, it would consume 16.8 watts X 24 hours = 0.403 kilowatthours per day.  (By the way, my ultra-efficient refrigerator draws that much every day).

    The inverter has a maximum efficiency of 90%, so if you are drawing 200 AC watts, you are drawing at least 222 watts from the battery.   These inverter losses must be added to your load (still to be determined) before you can calculate the size battery you need.

    The 'under voltage shutoff' of the inverter is 21.6 volts.  That is too low to protect the battery... that shutoff voltage is to protect the inverter, not the battery. 

    The controller has optional temperature compensation... do you have a remote battery temperature sensor for the controller?  Also, the controller is a PWM type...  whether it is suitable to your application depends upon the specs of your solar panel (which you have not mentioned).  I can't tell from the spec sheet whether the controller has adjustable charging parameters.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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