General Gel Settings

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #32
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    Re: General Gel Settings
    Ohmslaw wrote: »
    I am sorry I was not clear. There will be three banks of 16 batteries each. A total of 2700 ah at 20hour . I will bring the three strings to the buss bars and then connect the buss to the 6 outback 3600 watt inverters. Fuse sizing recommendations? 2/0 battery interconnect and 2/0 to the buss? 4/0 to the inverters?
    negative on one end and positive from the other?

    Attachment not found.

    Ah, we may need a bit more clarification.
    Is this going to be three separate 900 Amp hour systems or is there going to be connections between them on the DC side? Because if there is you are looking at some massive current potentials here.

    If separate and there's two VFX3648 per bank you're looking at 150 Amps per set as nominal current. That is 0 AWG minimum. Wiring from batteries to bus bars has to be able to take the maximum current with minimal Voltage loss. Usually this is the inverter load (charging most often is much lower current) so 2/0 is not unreasonable for that. The same size would go from the bus bars to the inverter, except in this case where you have two in parallel: the battery to bus wire has to take the current of both inverters (150 Amps) but the bus to each inverter is 1/2 that (75 Amps) and therefor smaller wire can be used (1 AWG). Most of the time people will just go for the largest needed and use it in both locations: it won't hurt. Negative and positive will carry the same current per circuit and so have the same wire sizes.

    Outback, incidentally, has quite a lot of wiring diagrams for various configurations of their inverters. I mention this because it sounds like you could have a 7200 Watt 3-phase system design going, and that is tricky stuff to get right. For example if the AC output of the inverters is coupled the DC input must also be, hence the potential high current issues on the DC side.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #33
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    Re: General Gel Settings

    I am concerned about that charge rate because when I enlarge the pdf to 150% so I can see it they appear to give exactly the same rate for GEL, AGM, and FLA.

    That does not sound right to me at all.
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  • Ohmslaw
    Ohmslaw Registered Users Posts: 9 ✭
    #34
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    Re: General Gel Settings

    This is a single system with 6 inverters connected to the three banks of 900 ah. The system had 5000 ah of flooded cells removed. Single phase 240volts. The system worked for years this way until the batteries gave up. Customer wants maintenance free batteries.
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  • Ohmslaw
    Ohmslaw Registered Users Posts: 9 ✭
    #35
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    Re: General Gel Settings
    Cariboocoot wrote: »
    I am concerned about that charge rate because when I enlarge the pdf to 150% so I can see it they appear to give exactly the same rate for GEL, AGM, and FLA.

    That does not sound right to me at all.

    I do see that. I will call Deka in the AM to clarify.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #36
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    Re: General Gel Settings
    Ohmslaw wrote: »
    This is a single system with 6 inverters connected to the three banks of 900 ah. The system had 5000 ah of flooded cells removed. Single phase 240volts. The system worked for years this way until the batteries gave up. Customer wants maintenance free batteries.

    Just to be clear here: AC outputs of all six inverters coupled or not?

    Another thing: 2700 Amp hours isn't going to replace 5000 Amp hours. For the capacity involved most people would suggest forklift batteries, but they are flooded.

    Perhaps you should look at some AGM choices for this? Or maybe you already have. They are generally more suited to RE use. Concorde actually makes so very high capacity 2 Volt AGM's around 1000 Amp hours each.
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  • Ohmslaw
    Ohmslaw Registered Users Posts: 9 ✭
    #37
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    Re: General Gel Settings

    A/C output coupled. I agree with the flooded batteries. Customer refused. The agm batteries had a longer lead time. We are getting a 6000 ah bank in the future. This is temporary. I just need to protect the bank and not over charge it. The generator is on 24/7 right now. Rolls makes a great flooded battery but the customer went through ten years of maintenance and has had enough. Also the 5000ah was in five banks. I am limiting it to 3 for charge balance reasons. I think going over two is problem but I have to.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #38
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    Re: General Gel Settings
    Ohmslaw wrote: »
    A/C output coupled. I agree with the flooded batteries. Customer refused. The agm batteries had a longer lead time. We are getting a 6000 ah bank in the future. This is temporary. I just need to protect the bank and not over charge it. The generator is on 24/7 right now. Rolls makes a great flooded battery but the customer went through ten years of maintenance and has had enough. Also the 5000ah was in five banks. I am limiting it to 3 for charge balance reasons. I think going over two is problem but I have to.

    On a 48 Volt system with bus bars four parallel strings should not be an issue. Provided it's all put together right and maintained. I don't know how he thinks he's going to avoid maintenance even with skipping out on checking cells (I'll bet they were a lot of small batteries together so - more cells and more problems).

    If the AC side is coupled the DC side should be too, which makes fusing the individual battery strings important. This could be one reason why he had battery problems (imbalance in draw between them due to slight resistance differences in the lines). How the gen is connected ... that can be another nightmare, especially if there are autotransformers involved.
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  • Ohmslaw
    Ohmslaw Registered Users Posts: 9 ✭
    #39
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    Re: General Gel Settings

    Ac coupled and dc coupled. I will run the three banks to a buss bar and then connect to the inverters with equal length 4/0 cables. How should I layout the batteries within the bank and what is the recommended fuse size for all connections. I will fuse the positive cable from the banks to the buss bar and the inverter cables at the buss which lead to 175 amp breakers at the inverters. I planned on hooking up the batteries 4 rows of four with the buss connected to the center row @ opposite ends. I am not sure if this is the best way.
    The site has two FM 80 charge controllers and one autotransformer . Outback says I need two more transformers. I will use a Pentametric to start the generator and monitor the charge discharge cycle. The generator is connected to the inverters to charge the batteries. I can limit the charge current via the mate 3. I also found another doc that shows 30% c20 charge rate.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #40
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    Re: General Gel Settings

    What you are really constructing here is one large battery bank which terminates at the bus bars. At 2700 Amp hours it has twelve parallel strings. I'll go ahead an say this is inadvisable even for a 48 Volt system.

    There are two schools of though about individual string fusing. One says each string should be fused to its portion of the whole (total expected maximum current / number of strings). The other says they should be fused for the total each, so that one may take over if the other fails. Note the context inferring only two strings in the latter.

    So with a total of six 3600 Watt inverters the maximum running current should be about 450 Amps. Divide by the 12 strings you get 37.5 Amps each. Follow the NEC derating rules for fuses and you're looking at one 60 Amp fuse per string. You could go as large as 100 Amps with suitable wire size. Do not use battery post terminal fuses (such as Blue Sea) here: they aren't suited to 48 Volt systems. You will need either T type fuses or for preference circuit breakers like this: http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/stfubr1/pamodccibr.html

    There is no way two FM80's will keep 2700 Amp hours charged. Maxed out they will provide a charge rate of about 6% and will need nearly 10kW of array to do so.

    I also do not see how all that current is going to be read by a Pentametric or any other battery monitor.

    If Outback says it needs two more autotransformers it probably does, although I hate to think what the AC configuration is.

    Right now I'm actually hoping I've misunderstood your specifications because this sounds like a nightmare of a system.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #41
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    Re: General Gel Settings

    P.S.: The MATE III is for programming the inverters, not limiting current from controllers (which can be done with the controllers. Obviously this system needs a MATE (not necessarily a III) and a HUB 10 to work right.
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  • ButchDeal
    ButchDeal Solar Expert Posts: 35 ✭
    #42
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    Re: General Gel Settings
    Cariboocoot wrote: »
    P.S.: The MATE III is for programming the inverters, not limiting current from controllers (which can be done with the controllers. Obviously this system needs a MATE (not necessarily a III) and a HUB 10 to work right.

    The Mate III will also program the OutBack controllers (FM80s)
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  • Ohmslaw
    Ohmslaw Registered Users Posts: 9 ✭
    #43
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    Re: General Gel Settings
    Cariboocoot wrote: »
    P.S.: The MATE III is for programming the inverters, not limiting current from controllers (which can be done with the controllers. Obviously this system needs a MATE (not necessarily a III) and a HUB 10 to work right.

    Thank you. I was referencing the programming with the mate3. The system already has one and we switch amperage settings depending on the generator that is being used.
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