is there anyone who can help me with my batteries

felix
felix Registered Users Posts: 12 ✭✭
in Off Grid Solar & Battery Systems #1
is there anyone who can help me with my batteries

setup for the kid 6 pcs. 24 v
absord V
float V
with more

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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    So you will have 3 strings of 2 batteries.

    Since you have a 24 volt system, you can double the charging voltage they give you (of 14.4 - 14.7 volts) to 28.8 - 29.4 volts and float (of 13.6 - 13.8 volts) to 27.2 - 28.6.

    With a single kid you don't need to worry about the max input amperage of 25 amps, since you have 3 strings and could take as much as 75 amps.

    I hope you purchased these as a back up or UPS, as they appear to be designed for float use rather than daily cycling, though I may be reading that incorrectly since they take such a high charge rate. My old and feeble mind...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • felix
    felix Registered Users Posts: 12 ✭✭
    edited July 2016 #3
    if I buy two batteries more , what is the best way to connect them
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Don't do it.  You already have three strings.  Four strings is too many (actually, three strings is too many IMO).  --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    While I agree with vtMaps that is a lot of batteries in parallel--Assuming you have to do this, then here is a description of how to parallel batteries:

    http://smartgauge.co.uk/batt_con.html

    What is not talked about in that link is, depending on the size of battery and diameter of the copper wire, you should probably have a fuse/breaker per parallel string of batteries (4 parallel strings, 4 breakers or fuses). It is possible for a shorted string to be fed power by the other 3 strings and overheat the batteries/wiring.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • felix
    felix Registered Users Posts: 12 ✭✭
    #6
    why is that too many
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2016 #7
    > What is not talked about in that link ...

    Also not talked about is the fact that batteries vary in internal resistance.  So their claims of "perfect balancing" are bogus (although with measurements and uneven cable lengths, one could get closer).  Method 3 is draw incorrectly in terms of cable lengths.  Drawings of 4 in parallel and reference to 8 is misleading.

    Common battery to battery variations can be the equivalent of 6+ feet of cable length.  Someone should create a reference page done right.

    I am available for custom hardware/firmware development

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  • felix
    felix Registered Users Posts: 12 ✭✭
    edited July 2016 #8
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #9
    If you put some load on your bank and use an ammeter to test each red link, what values do you get?

    I am available for custom hardware/firmware development

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  • felix
    felix Registered Users Posts: 12 ✭✭
    #10
    I'll try tomorrow is not home
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