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Thread: Amps Draw

  1. #1
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    Amps Draw

    I should know the formulae, but how many amps can a 3Kw Inverter draw from a 12V system?
    Somehow, I doubt a 50A Anderson plug connection would be adequate
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    SADLY SOLD MY04 D2a TD5 auto Classic and MY10 D4 2.7 both with lots of goodies.

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    JDNSW's Avatar
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    Quote Originally Posted by gavinwibrow View Post
    I should know the formulae, but how many amps can a 3Kw Inverter draw from a 12V system?
    Somehow, I doubt a 50A Anderson plug connection would be adequate
    So do I! Simply divide the 3kW expressed as watts, i.e. 3000w, by 12v, gives 250A, ignoring losses. Actually, seeing that at that load the battery will be lucky to produce more than 10v, make that 300A, if the inverter efficiency is 95% at full load (being generous), around 315A.

    I would be worrying about your battery rather than the Anderson plug!
    John

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    Quote Originally Posted by JDNSW View Post
    So do I! Simply divide the 3kW expressed as watts, i.e. 3000w, by 12v, gives 250A, ignoring losses. Actually, seeing that at that load the battery will be lucky to produce more than 10v, make that 300A, if the inverter efficiency is 95% at full load (being generous), around 315A.

    I would be worrying about your battery rather than the Anderson plug!
    Thanks John - it was a theoretical question, and you confirmed my thought that if it were even possible, it would have sucked the battery dry in a very short time.

    The 3000W version was a thought for the van, but the van doesn't have enough battery power to be viable.

    I also have a HD 600W inverter ex ambulance, and the 50A Anderson will just "qualify".
    MY16 D4 TDV6 - unmolested for towing "The Brick".
    MY95 RRC LSE Vogue Softdash "Bessie" from Aug 13 - with MY99 TD5 and 4HP24 transplants. Back home Aug 20 after being off road for periods totalling 3.5 years.
    SADLY SOLD MY04 D2a TD5 auto Classic and MY10 D4 2.7 both with lots of goodies.

  4. #4
    trout1105 is offline AULRO Holiday Reward Points Winner!
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    Quote Originally Posted by gavinwibrow View Post
    I should know the formulae, but how many amps can a 3Kw Inverter draw from a 12V system?
    Somehow, I doubt a 50A Anderson plug connection would be adequate
    You need to hook up the inverter directly to the battery/batteries with big arse cables even wired like this 3kva will suck them dry pretty fast

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    Quote Originally Posted by trout1105 View Post
    You need to hook up the inverter directly to the battery/batteries with big arse cables even wired like this 3kva will suck them dry pretty fast
    And you need to use decent copper cables, not the copper coated rubbish they usually supply.
    ​JayTee

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    Hi Gavin and just curious as to what you are planning to use that size inverter for?

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    How many amps…..pretty much what John said

    I would hard wire and as close as possible to the battery.

    I do read a lot of people buying 3000w inverters and wonder what they are connecting to them….

    we have a 2000w which is match to the max. Current draw from our lithium battery….I’d suggest matching your inverter to you appliances you are planning to use. .

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    Quote Originally Posted by drivesafe View Post
    Hi Gavin and just curious as to what you are planning to use that size inverter for?

    Hi Tim.
    Originally bought thinking to put in the caravan for SWAMBOS coffee machine which drew 2000w.

    She then bought a 12V version and the inverter has never been used and sat in the storage unit for the next 5 years.

    Now cleaning out the seacontainer and the original question was semi rhetorical.



    PS has my AGB-25 turned up yet?
    MY16 D4 TDV6 - unmolested for towing "The Brick".
    MY95 RRC LSE Vogue Softdash "Bessie" from Aug 13 - with MY99 TD5 and 4HP24 transplants. Back home Aug 20 after being off road for periods totalling 3.5 years.
    SADLY SOLD MY04 D2a TD5 auto Classic and MY10 D4 2.7 both with lots of goodies.

  9. #9
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    Quote Originally Posted by gavinwibrow View Post
    PS has my AGB-25 turned up yet?
    Yep and will be bock to you this coming week.

    Just a suggestion, unless you do actually intend to use the inverter, put it up on fleebay.

    In a caravan situation where you have a few batteries, OK, but too much work in anything else.

  10. #10
    Homestar's Avatar
    Homestar is offline Super Moderator & CA manager Gold Subscriber
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    I’ll be shopping for at least a 2000 watt inverter next year, probably slightly larger but want a decent one not a cheap one. Will be running the coffee machine from 200Ah of lithium so that sides not an issue - just can’t find a unit anywhere near as good as my old 600 watt Selectronic unit I’ve got currently.


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