Maximum charge rate question

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yiannis5
yiannis5 Registered Users Posts: 14 ✭✭
in Off Grid Solar & Battery Systems #1
Hello guys,

Just a quick question which I am sure you will find silly.

My battery bank consists of 8 T105RE Trojan batteries configured for 24v.

I am aware that Trojan recommends a 10% charging rate based on the C20 rate of the battery.

In my case is it 10% of 225 which is the rate of one battery or is it 10% of 450 which is the amps of the battery bank die to the configuration for 24v?

Thanks!




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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited February 2017 #2
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    Theoretically the current in a parallel battery bank is equal for both strings, so you would use 10% of 450. In a simple restive circuit they would be equal, however as there are variations in batteries, the current may be slightly different, but should be close, in a healthy bank. If you have a DC clamp on ammeter you can verify this, if you don't, I would highly recommend getting one as it is an important tool to have at your disposal for maintaining your batteries.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • yiannis5
    yiannis5 Registered Users Posts: 14 ✭✭
    #3
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    Thanks for the reply. The reason I am asking is because I would like to know ideally how many amps my generator should produce in order to charge my battery bank correctly. I currently own a Honda EU26i (230v) which produces around 10amps which I think is low and not sufficient?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #4
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    Generator output 10A at 230V, with a 24V nominal chager you could easily charge your batteries, current is inversely proportional to voltage so 10A at 230V is approximately 900A at 24V, reduced as you will be at a higher voltage, say around 29V, but that far exceeds your requirements, so your generator is up to the task. 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
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    Just to clarify- if you are using a separate 24vdc/230vAC charger on the 230vAV output of the generator you're fine.

    If you're talking about the dc output of the generator, I believe that is 10A at 12vdc. You shouldn't try to use the dc output of the generator for battery charging.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • yiannis5
    yiannis5 Registered Users Posts: 14 ✭✭
    #6
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    Thanks for the answers - yes I am using a separate 24vdc charger.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #7
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    With generators and chargers, you HAVE to pay attention to the Power Factor of the charger, and the continuous rating of the Generator.
    If you have a   XYZ-2400 genset, most often the 2400 is a surge rating, with 1900w max 15min rating and 1700w continuous .

    And the battery charger, outputs 28V @ 35A is 980 Watts.   But with a PF of .5, you are asking the generator to supply 1470wats

    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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