2/0 inline fuse holder?

Chris Miller
Chris Miller Solar Expert Posts: 49 ✭
in Off Grid Solar & Battery Systems #1
Can anyone tell me where to get a fuse holder for my 2/0 battery cables? Right now I am running 1 string of batteries interconnected with 2/0 but connected to the inverter with #2 and it goes thru an 80 amp breaker. But I am adding two more strings and would like to fuse each string down at the battery and then go to the inverter with the 2/0 instead.

Any suggestions?
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: 2/0 inline fuse holder?

    Blue Sea post fuses perhaps? One per string.
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  • Chris Miller
    Chris Miller Solar Expert Posts: 49 ✭
    #3
    Re: 2/0 inline fuse holder?
    Cariboocoot wrote: »
    Blue Sea post fuses perhaps? One per string.

    Thanks, I bet those will work well!

    What's the rule of thumb for fusing these things? I'm already protecting the FM-80 with an 80 amp breaker up in my E-panel. Once I make it into 3 strands should I just divide the 80 amps by 3 and round up to the next size fuse for each?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: 2/0 inline fuse holder?

    These fuses will go between each battery string and the common connection/bus bar? In that case they have to be able to take the maximum current expected. Since you are using 2/0 wire that would be 200 Amps expected? Enough to power the inverter to full output anyway.

    In that case you can either put 200 Amp fuses on each string (remember; it's there for when something goes really wrong) or try to divide it up evenly and get 80 Amps per. If you use the lower Amp fuses and one gives out or the wiring is bad on one line you can have a cascade failure as the current load shifts to the remaining strings - and overloads them. Most of the time either one of these will work because you probably will not be operating near maximum capacity.

    Were it me, I'd pick full size fuse per string.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #5
    Re: 2/0 inline fuse holder?

    Would this breaker work ok?

    140 AMP 12V DC CIRCUIT BREAKER
    ps82-150amp%281%29.jpg
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: 2/0 inline fuse holder?

    "12 Volt" is a nominal rating. Does it have any specific rating?
    Looks like the kind used in certain automotive applications. Usually you can use auto stuff on 12 Volt RE applications provided it is of good quality. There's the catch. Some of us have seen some 'standard' 12 Volt blade fuse holders melt down when asked to carry their supposed continuous rating. I even have a "300 Amp" 12 Volt battery switch that couldn't actually manage 1/10th its rating.

    So how confident are you in the product?

    I bet some of the guys on here have had 1st hand experience with that unit or something very similar.
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #7
    Re: 2/0 inline fuse holder?
    KnowledgeSponge wrote: »
    Would this breaker work ok?

    140 AMP 12V DC CIRCUIT BREAKER
    ps82-150amp%281%29.jpg

    They are junk , I have a few , broke some just using, so the broken ones I tested till they melted..
    My testing is always stinky fun :-)

    Those are for the boom-box crowd

    VT
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  • Chris Miller
    Chris Miller Solar Expert Posts: 49 ✭
    #8
    Re: 2/0 inline fuse holder?
    Cariboocoot wrote: »
    These fuses will go between each battery string and the common connection/bus bar? In that case they have to be able to take the maximum current expected. Since you are using 2/0 wire that would be 200 Amps expected? Enough to power the inverter to full output anyway.

    I hadn't even considered a common bus bar? All I hear about online is keeping resistance down by limiting the number of things between the batteries and the charge controller. That along with achieving perfect load balance by using perfectly equal wire lengths, termination methods, etc.

    Then in other posts I pickup from people that it's a good idea to introduce fuse holders, bus bars, and cut off switches on each string of batteries.

    I'm probably just missing something. The fuses make perfect sense to me, the bus bar and switches i'm having a hard time wrapping my head around.

    Do you have an example of a wiring diagram for multiple strings that correctly utilizes a bus bar?

    I truly appreciate the help.... not trying to be difficult but so much of this is new to me and I just want to get it right.
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  • KnowledgeSponge
    KnowledgeSponge Solar Expert Posts: 173 ✭✭✭
    #9
    Re: 2/0 inline fuse holder?
    CDN_VT wrote: »
    They are junk , I have a few , broke some just using, so the broken ones I tested till they melted..
    My testing is always stinky fun :-)
    Those are for the boom-box crowd
    VT

    ok,
    What did you end up using?
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  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    #10
    Re: 2/0 inline fuse holder?

    Very similar to what Coot posted ,
    VT
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #11
    Re: 2/0 inline fuse holder?
    Chris Miller wrote: »
    I hadn't even considered a common bus bar? All I hear about online is keeping resistance down by limiting the number of things between the batteries and the charge controller. That along with achieving perfect load balance by using perfectly equal wire lengths, termination methods, etc.

    Then in other posts I pickup from people that it's a good idea to introduce fuse holders, bus bars, and cut off switches on each string of batteries.

    I'm probably just missing something. The fuses make perfect sense to me, the bus bar and switches i'm having a hard time wrapping my head around.

    I think the issue is that parallel battery banks are not an optimal solution. To minimize the problems with parallel banks it is very important to use low resistance connections so that each parallel string of batteries sees equal resistance.

    However, good wiring does not eliminate the problems with parallel banks. Therefore it may be wise to introduce fuses and switches as a safety measure and also to assist in isolating and testing individual strings.

    One of the problems with parallel batteries is that when one cell ages or fails, it may be difficult to notice until the whole bank fails. This is because when one cell in one parallel string fails, it is compensated by the other parallel strings. When you turn off your charger you may see one string discharging into another parallel string.

    Think of it like a single engine airplane... There is a certain probability that the engine will fail on the next flight. Now suppose you have a two-engine airplane with two of the same engines. The probability of one engine failing is now TWICE the probability of engine failure on the single engine plane.

    So it is with batteries... if you have three parallel strings you have three times the probability of a cell failing, and when one goes down they all go down. On average, parallel strings of batteries do not last as long as single strings.
    Chris Miller wrote: »
    I'm probably just missing something. The fuses make perfect sense to me, the bus bar and switches i'm having a hard time wrapping my head around.

    I too have trouble wrapping my head around bus bars, fuses and switches... but that is because I have a hard time wrapping my head around why anybody would have parallel battery strings.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #12
    Re: 2/0 inline fuse holder?

    .VTMAPS.I too have trouble wrapping my head around bus bars, fuses and switches... but that is because I have a hard time wrapping my head around why anybody would have parallel battery strings. Hard not to have series and parallel strings if you using Lithium Ion Phosphate batteries.They are far easier to manage if you use the 10ah ones rather than the 200h a ones and even if using the 200ah ones you need parallel and series if you doing even 48v system
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  • Chris Miller
    Chris Miller Solar Expert Posts: 49 ✭
    #13
    Re: 2/0 inline fuse holder?
    vtmaps wrote: »
    I too have trouble wrapping my head around bus bars, fuses and switches... but that is because I have a hard time wrapping my head around why anybody would have parallel battery strings.

    --vtMaps

    You must be a really rich man. $4,000 vs $15,000 is pretty easy for me to wrap my head around.
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