need help determining breaker or fuse size

notsobrightnotsobright Solar Expert Posts: 247 ✭✭
I just bought a Duracell 1500w inverter and I am trying to figure out what type of fuse to use on the main positive line from the battery.

http://www.duracellpower.com/power-inverters/recreation-inverters/inverter-1500.aspx

from the manual:

To select the correct fuse type and size. if you are using one battery to power your inverter and its short-circuit current rating is 500 A, the total short-circuit current rating is 500 A

once you have determined the total short-circuit current rating of your battery, pick the fuse/circuit breaker's interupt capacity based on the short-circuit current calculated.


well my batteries specs dont show a "short-circuit current rating"

its a Lifeline GPL-4DA heres the specs I have:http://www.lifelinebatteries.com/rvflyer.php?id=5


can anyone help me determin how many amps of fuse I need and also is there anything available that can bolt directly to the batteries terminal and have the cable bolt to it so I dont have to re do the cables?


thanks

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: need help determining breaker or fuse size

    This is how the American Yachting Society recommends maximum interrupt current...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,359 ✭✭✭✭✭
    Re: need help determining breaker or fuse size

    I think duracell is going to have problems with the manual, as their gear burns up.

    The way I would chose (and I'm not claiming this is 100% correct) is to look at the surge rating of the inverter (and since their manual is not readable by my PDF viewer, I'll wing it) and guess at 2,000W surge. So the minimum fuse looks to be about 166A. My Gut says that's outrageous. If I scale back, to the 1,500W cont. rating, the fuse is 125A.
    To safely handle 125A, All your wires ( + & - ) would need to be #0 gauge ( 0.3249")
    http://www.powerstream.com/Wire_Size.htm

    I don't think battery size really has any bearing as to the fuse, the fuse is generally used to protect the wire from a short, and the wire causing a fire. The fuse needs to be large enough for the product to run at full power (1500W, 125 A) and the wire needs to be large enough, that that amperage does not make it hot and ignite the insulation.

    The battery needs to be large enough to supply this amount of power, otherwise, it's voltage will sag, and the inverter will shutdown due to under-voltage.

    The general rule of thumb is 1000W for 12V. 1001-2000W for 24V, 2001-4000W for 48V, otherwise, the amps required, exceeds the battery and wire capacity.
    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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  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: need help determining breaker or fuse size

    Actually NSB is asking about the current "interrupt" requirement for the fuse is the maximum current from the battery the fuse can "interrupt" without failing.

    If you have too large of battery bank (and too heavy of wire), the maximum current for a dead short will be in the many 1,000's of amps. So your 200 amp fuse will open if the Inverter fails--but instead of the current flow stopping--a too small of interrupt current fuse (or breaker) will just vaporize the metal in the area and have nice hot plasma arc instead (and plasma arcs are very low resistance).

    One battery spec. I saw for a the Optima type was something like 3,000-4,000 amp range for maximum current dumped into a dead short.

    In practice, not only the battery current capability, but the resistance of the distribution wiring (which limits maximum short circuit current by adding addition resistance) helps limit the maximum current too. [fixed: too not "tool"]

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • john pjohn p Solar Expert Posts: 814 ✭✭✭
    Re: need help determining breaker or fuse size

    does anyone have an english translation for this??To select the correct fuse type and size. if you are using one battery to power your inverter and its short-circuit current rating is 500 A, the total short-circuit current rating is 500 A
    And what if you using 4 batteries in parallel??
    I believe using a fuse to fully cover the surge rating of an inverter is not good.
    lets take example of 15000w anverter on 12 v(not a good idea anyway should be using 24v)125a now surge 3000w will be 250a,, and you now have a problem of cable thickness
    In most cases a 1500w inverter is never going to be used close to its limit.it is usually used because some appliance connected to it has a high start up current demand but that be for mabe 2 seconds.A 100 amp fuse can withstand that for that time period.
    I would be suggesting a fuse about 150a absolute max.
    But as I said for 1500w you should be using 24v its just way too hard to handle cables #00 and maintaining the connectors to be perfectly clean as losses very easy to get in the connectors at these currents
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: need help determining breaker or fuse size
    BB. wrote: »
    This is how the American Yachting Society recommends maximum interrupt current...

    -Bill

    wow, unless Im misunderstanding it, according to that I need a 5000 amp circuit breaker. is this correct?
    mike90045 wrote: »
    I think duracell is going to have problems with the manual, as their gear burns up.

    what do you mean? its actually manufactured by Xantex and badged/sold by Duracell. but the manual must have been translated and retranslated.
    mike90045 wrote: »
    The way I would chose (and I'm not claiming this is 100% correct) is to look at the surge rating of the inverter (and since their manual is not readable by my PDF viewer, I'll wing it) and guess at 2,000W surge. So the minimum fuse looks to be about 166A. My Gut says that's outrageous. If I scale back, to the 1,500W cont. rating, the fuse is 125A.
    To safely handle 125A, All your wires ( + & - ) would need to be #0 gauge ( 0.3249")
    http://www.powerstream.com/Wire_Size.htm

    claims to be capable of handling 3000w surge. I am using some pretty hefty battery cables salvaged from old Fiats, much larger than average cars since they had the battery mounted at the other end of the car from the engine but I dont know what guage. it appears to be at least .3333" (1/3") though.


    mike90045 wrote: »
    The battery needs to be large enough to supply this amount of power, otherwise, it's voltage will sag, and the inverter will shutdown due to under-voltage.

    The general rule of thumb is 1000W for 12V. 1001-2000W for 24V, 2001-4000W for 48V, otherwise, the amps required, exceeds the battery and wire capacity.

    ahh.. well, the situation is this is for my Van/RV. I allready have a SureSine 300w for normal use and this Duracell is really only for a rare occasion when the SS300 isnt enough. like if I want to run a tablesaw or something and mabey a small air conditioner (mabey)

    BB. wrote: »
    Actually NSB is asking about the current "interrupt" requirement for the fuse is the maximum current from the battery the fuse can "interrupt" without failing.

    yeah, I think. I just want something in line to sever the connection should things go bad so I wont have FIRE.

    BB. wrote: »
    If you have too large of battery bank (and too heavy of wire), the maximum current for a dead short will be in the many 1,000's of amps. So your 200 amp fuse will open if the Inverter fails--but instead of the current flow stopping--a too small of interrupt current fuse (or breaker) will just vaporize the metal in the area and have nice hot plasma arc instead (and plasma arcs are very low resistance).

    hmmm... mabey this wasnt such a good idea..
    BB. wrote: »
    One battery spec. I saw for a the Optima type was something like 3,000-4,000 amp range for maximum current dumped into a dead short.

    speaking of Optima batteries. I purchased their "starting" battery (red top) a few months ago. only for the engine but I have the SunSaver Duo set up to use 10% available solar to keep it topped off. since I have the remote meter and can keep an eye on it I noticed it allways goes down to 12.6v overnight. I though mabey I had something draining it so I removed it for a few days and tested it and still down to 12.6v.

    so I took it back and asked them If I could replace it and they said OK then I asked if I could check voltage on the ones they had in stock and all those were sitting at 12.5v so I decided to keep the one I have.

    kinda disapointed in it because of that but its nothing really. its just that all my other starting batteries rest at 12.7 or higher and they are half the price of the optima but they dont have the 5year warranty and also not AGMs. oh well, just thought I would mention it.

    BB. wrote: »
    In practice, not only the battery current capability, but the resistance of the distribution wiring (which limits maximum short circuit current by adding addition resistance) helps limit the maximum current tool.


    tool? I assume a typo for "pool"?

    probably no way to calculate that additional resistance, no?


    thanks for all the input again guys. Im learning alot of valuable stuff here and thats the main reason Ive become a regular NAWS customer.

    I wish that Kill-a-watt wasnt on backorder, Im anxious to find out what different stuff draws arround the house.

    got that KC130 and 40 in and the 130 is allready mounted with its twin and the 40 goes on the cargo trailer next. manily for the onboard alarm system.. weve had a rash of trailor thefts arround here recently. Im finding out just how trick the latest auto alarm systems are too. I could easily booby trap the trailer with deadly force if needed but the pager works upto 1 mile so no need for booby traps.

    I like the extra remote switching capabilities so much Im upgrading the vans alarm too now just so I can turn on/off stuff with the remote! another feature is being able to control upto 4 cars with a single remote. in my case the van and the cargo trailor.
    john p wrote: »
    I would be suggesting a fuse about 150a absolute max.

    dont you mean "absolute minimum"? didnt see a 150a but going by your suggestion I found a 175amp flat fuse that goes inline so I put it between the inverter and the battery cable. better than nothing but would this be enough to eliminate any possibilities of fire due to an inverter malfunction? I just want to be certain I am not gonna burn down my vacation home! Ive spent alot of time/money in this rig.

    thanks again Guys!
  • GroserGroser Registered Users Posts: 10
    Re: need help determining breaker or fuse size

    I have a xantrex prosine 1800. surge is 2900. I have a LittleFuse MEGA 175 amp
    inline fuse between the inverter and bats. I have nearly maxed out the inverter
    with a microwave and the fuse held. hope this helps.
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: need help determining breaker or fuse size
    tool? I assume a typo for "pool"?
    Sorry--that was "too" as in also...
    probably no way to calculate that additional resistance, no?
    Actually, it is not too difficult... Using:

    V=I*R; I=V/R=V/(R1+R2+R3+...)

    Or:

    Ishortcircuit=V/R=12 volts of the battery / (Rbatt+Rwire1+Rwire2+Rwire3+etc.)

    Where Rbatt was equal to 0.0030 Ohm of the battery, and RwireX is the resistance of each length of wire (look up in a table of copper wire and resistance per unit length).

    Here is one such wire resistance table by gauge (not vouching for accuracy) that gives Ohms per 1,000 ft (divide by 1,000 for Ohms per ft)...

    You can see that a smaller gauge and/or longer length wire is somewhat your friend when limiting maximum current.

    But, yea--you are looking at a 159-200 amp fuse rated to interrupt a 5,000 amp current source.

    Windsun/NAWS will have to tell you what the ratings are of the fuses they carry are (I could not identify them)... I am sure if you email or call them directly (contact information) they can give you the answers. Windsun may or may not see the questions on the forum as they do not monitor here for business related questions.

    For example, this Bussman Telecom products catalog (PDF Download Here) has fuses with IR=100,000 (I think this is "inrush current").
    dont you mean "absolute minimum"? didnt see a 150a but going by your suggestion I found a 175amp flat fuse that goes inline so I put it between the inverter and the battery cable. better than nothing but would this be enough to eliminate any possibilities of fire due to an inverter malfunction? I just want to be certain I am not gonna burn down my vacation home! Ive spent alot of time/money in this rig.
    That is why you need to look at the "whole system"... The correctly rated fuses/breakers and the appropriate wring/connectors can go a long way to helping to prevent those fires.

    And it was these secondary issues (finding a fuse/breaker with a high enough IR rating that would fit in the equipment I designed) that was sometimes very difficult to do. But, it was required for safety.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notsobrightnotsobright Solar Expert Posts: 247 ✭✭
    Re: need help determining breaker or fuse size

    great info. now Im almost certain the 175amp fuse I purchased is not designed to "interupt" 5000amp since it was a replacement part to go on OEM autombile starting batteries. (and it looks rather thin compared to the ones on the NAWS page in your link)

    Interupt Rating is a new one for me. Im still a little confused though because I dont understand "the maximum current from the battery the fuse can "interrupt" without failing."

    I thought that when the fuse interupts the current is when it fails or blows but your saying a fuse can interupt current without blowing? whats happening when a fuse is "interupting" if its not "blowing"?

    thanks
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Re: need help determining breaker or fuse size

    I am guessing--but if you have very high currents--instead of the fuse "opening" on failure--the fuse starts to arc across the two poles like an arc welder (or--in theory, the fuse could self destruct and send flames and shrapnel around too/instead).

    DC Current, interestingly, actually sustains arcs better than AC current. AC circuit breakers/switches/etc. have higher voltage and interrupt ratings than their DC specs. (for switches that have both AC and DC ratings).

    I have heard that companies where they test fuses/breakers and other very large equipment for over current/voltage testing can get very interesting.

    Bussman has the capabilities of testing:
    Testing Services

    Compliance Evaluations for Components and Assemblies
    Performance Testing

    Cooper Bussmann, the leader in circuit protection technology, provides the electrical industry the Gubany Center, the most comprehensive facility for testing electrical devices over the widest range of volt, amp and frequency combinations possible:
    • Up to 300kA at 750Vac, three-phase
    • Up to 100kA at 1000Vdc
    • Alternating current frequencies from 50Hz to 60Hz
    The Gubany Center is certified to perform UL witnessed testing; we can even provide a UL field engineer to witness and certify your test results. The Center is also accredited by ASTA and CSA and is an ANCE Designated test facility. We follow procedures established under ISO 9001.
    100,000 amps * 1,000 volts = 100,000,000 watts

    Stand back! :D

    -Bill

    PS: San Onofre Nuclear Generating Station generates ~2,200,000,000 watts -- that one test would be ~5% of the output of a nuclear power station. :D

    PPS: Added missing link to table of wire size vs resistance to my previous post.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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