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Thread: Cold Cranking Amps vs Amp Hour

  1. #1
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    Default Cold Cranking Amps vs Amp Hour

    How do you compare deep cycle batteries when some are sold in Cold Cranking Amps and other are sold in Amp hours?

    My two older 120 watt panels, laying just flat on the ground for at least half an hour, in August, and about 11:00 in the morning, tested out at 103 watts each.

    What type of battery would you use and how many would these panels fully charge? Is there a good place outside Texas where shipping is free?

    "Tight Wad Bill"

  2. #2
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    Cold cranking amps is a measure for SLI batteries (starter, lights, ignition) for cars. They do not handle deep cycles very well, lots of thin plates for quick amps. Take them down to 40% of capacity (60% discharged) and they will die within a dozen cycles. 4 year life

    Deep cycle batteries
    Thick heavy plates, to release amps over a 20 hour discharge period. Likely could not support enough current for starting a car. 7-10 year life

    Marine Deep Cycle batteries. An in-between hybrid. Ok for solar if you only need one or 2, and don't mind them lasting 2-3years

    For your 120W panels, a single 100AH battery for each panel is a good start. Too large of battery, you cannot recharge in 1 day, too small will not last you all night.

    Batteries are so heavy, they never ship free.
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:
    http://www.solar-guppy.com/download/...calculator.zip
    http://www.solarpaneltalk.com/showth...oss-calculator

    http://www.mike-burgess.org/PVinfo_2.html

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

  3. #3
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    Default

    Thank you for your help and insight. An extension to the battery question:

    When getting an inverter, say 2,500/5000 watt size, should there be a super large fuse/breaker between the battery connection and the inverter?

  4. #4
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    Yes, the inverter manual should state what size to use. A 2,000 watt inverter, at 120V supplies 16.6A at the AC outlet.

    The feed from the battery bank @ 12V will be 191 amps, if the inverter is 85% efficient. The general rule of thumb, is 12V in series, for every 1,000W of AC load.
    1,000 W 12V (96)
    2,000 W 24V (96A)
    4,000 W 48V (96A)

    Trying to manage 100Amps at DC voltages, is tough, cables heat up, connections heat and melt terminals. So you use higher voltage battery banks.
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:
    http://www.solar-guppy.com/download/...calculator.zip
    http://www.solarpaneltalk.com/showth...oss-calculator

    http://www.mike-burgess.org/PVinfo_2.html

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

  5. #5
    Solar Fanatic
    Join Date
    Aug 2009
    Posts
    118

    Default

    Believe it or not, I can remember a farm pickup with a 6v, black tar topped battery. When the 12v car came to be, I was amazed how much smaller the battery cables were!!

    So, I can understand about a higher battery bank voltage for a higher input voltage inverter would make those battery cables tend to be much cooler and smaller. And now I realize why sizing the battery bank to what the panels can recharge during a day or three, as well as to the amount of power needed to live in the house.

    Keeping efficiency up and both equipment and material costs down is still the perimeter for living within a home comfort level. You've be a lot of help, thank you!

    Bill

  6. #6
    Moderator
    Join Date
    May 2009
    Location
    off grid retirement in Northern Calif
    Posts
    7,422

    Default

    You are most welcome.
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:
    http://www.solar-guppy.com/download/...calculator.zip
    http://www.solarpaneltalk.com/showth...oss-calculator

    http://www.mike-burgess.org/PVinfo_2.html

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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