Peukerts law

mountainman
mountainman Registered Users Posts: 439 ✭✭
edited February 2019 in In the Weeds--Member's Choice #1
I'm been trying to understand Peukerts law. Doing some experimenting on different loads on my 208 a/hr 20hr rate @12 volt bank 10.4 amps at 20 hours battery would be empty. My daily usage of 1000 w/hrs comes to 41.66 watts per hr or 3.472 amp/ hrs  or c60 discharge rate. Question is since I'm discharging roughly  3 times slower than c/20 what would my new capacity equal to. Also if I double my battery bank to 416 amp hrs 1000 daily w/hrs at roughly c120 wouldn't my true capacity be even higher than with  the smaller bank? Just trying to make sense of it all. Does anyone have any knowledge of Peukerts they wish to share. Thanks in advance.
2kw array 6 345 q cells  make sky blue 60 cc
 6 230ah GC @36 volts 
18 amp accusense charger. 3650 champion 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    The Smart Gauge Website has way too much on Peukerts Law:

    http://smartgauge.co.uk/technical1.html
    http://smartgauge.co.uk/technical2.html

    There is not a lot of information from battery mfg. about their Peukerts Factor, but here are a few:

    https://www.solar-electric.com/deep-cycle-battery-faq.html

    Trojan T-105 = 1.25; Optima 750S = 1.109; US Battery 2200 = 1.20

    And some more information from Wiki:

    https://en.wikipedia.org/wiki/Peukert's_law

    In the above links, are some formulas that can be used to calculate the P.F. from a chart of C8 and C20 or C100, etc. battery AH capacities.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mountainman
    mountainman Registered Users Posts: 439 ✭✭
    #3
    Thanks @Bill just what Im looking for
    2kw array 6 345 q cells  make sky blue 60 cc
     6 230ah GC @36 volts 
    18 amp accusense charger. 3650 champion 
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    You are very welcome MountainMan.

    Take care,
    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Just remember, gaining capacity via underrated bank size, will leave you short when the batteries start to degrade in a couple years. 
    your 100ah bank, that you cleverly calculated to be 150ah, will decrease proportionately when you bank is at 80ah capacity 

    Size your recharging capacity to the normal 20h rate, so a 100ah bank wants 10-15a charge source, you wont need a 15-20a charger.
    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 ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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