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Home Forums General Discussion Nickel Iron vs. Lead Acid — Off-Grid Battery Showdown

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  • #66442
    elnav
    Member

    The subject of battery technology will be an ongoing debate for some time.

    In the past five years lithium Ion has grown in prominence in automotive and marine applications in the sizes needed for an off-grid house.

    Yesterday a friend posted a lenghty technical post on another forum where he illustrated the cost effectiveness of this new techology.

    HOWEVER there is a fly in the ointment. This kind of battery requires special chargers and you cannot use regular 12V or 24V chargers suited to conventional lead acid.

    This also means solar power systems must use special chargers and at this time not too many vendors provide this.

    For this reason I would prefer NiFe technology because the cells can tolerate deep discharge and rapid recharge compared to conventional lead acid. Someone mentioned using only shallow discharge to about 30% in order to get long life. NiFe can tolerate far more so you do not need as large a battery bank for the same amount of daily energy consumption. The conventional thinking was you should size a bank to 3X as large to cover a multi day period of cloudy weather when solar panels or a wind turbine does not produce enough.

    I would counter this by saying a gasoline generator of very modest size cost far less and uses far less in fuel than the additional cost on battery capacity. Locally we pay $5.00 per gallon and one local food vendor runs a snack wagon he powers for about $1.50 per day to run his freezers and electric grill plus lights. He uses a 3kW generator running all day long.

    #66450
    Dustoffer
    Participant

    The old conventional thinking has been superceded. Instead of max 50% discharge and 3 days for no sun, lead acid system—it should be max 25% discharge and 4 days without sun. I found out the hard way that my insulated shed heated through uninsulated stud space on its attachment wall, would only last 2 days in sub zero weather. The inverters auto shut offed at 50% at 5 AM. I had stored the generator in an uninsulated matching attached shed–it wouldn’t start when it was that cold. So now I charge more often with it and store it in the garage which is semi-heated.

    Now, it is the NiFe that are the best to design a system with, or to convert to, if you have the room. Certainly less maintenance and much longer life. I’m not sure of their cold weather performance, but it couldn’t be worse than lead acid.

    I also would have insulated the entire inside of the inverter area with thick aluminum foil, that was never mentioned before. The RF/EMI will buzz phones and slow computers within 10 feet or so. Even the pure sine wave ones let it off and buzz some guitar amplifiers. I have had to aluminum foil all my inverter areas and put lock on filters on cords leading from them. It even escapes through cracks and holes.

    People talk of tiny houses, but a good solar electric system needs a tiny house itself!!

    #66451
    elnav
    Member

    why only 25% DoD. Acccording to the datasheet from the battery manufacturer NiFe can tolerate deeper discharge than lead acid and deliver the same number of cycles.

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