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  1. #1
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    Default battery distance to inverter issue

    hi I got new Deye inverter and have a bunch off good deepcycles (16)
    Quick question I removing my generator and have place in geni room for all batteries and have space for easy maintenance. issue is its about 15m from inviter one way.
    Is it an issue running so far due to losses? or is it not serious losses?
    If not what size cabling is recommended 35mm2 of 50mm2?
    Last edited by 519franco; 2021/06/21 at 10:06 AM.

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    Default Re: battery distance to inverter issue

    I fear you'll have double up, at least.
    70mm˛.
    The amps will be quite high, batteries to inverter.
    The reason why ideal install is the inverter is closest to the batteries as possible.

    Have a look here.
    https://www.punchlistzero.com/eu-and...ng-calculator/
    Last edited by swakop_toe; 2021/06/26 at 11:56 AM.
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  3. #3
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    Default Re: battery distance to inverter issue

    For Lithium batteries you can put them right next to the inverter.
    With lead acid, please keep them far away.
    I used to have mine close and after 2 years my inverter was rusting to pieces.

    Lets take 5kw at max load.
    So at 48V that should be 105 Amps.

    A 25mm2 single core cable is rated for 110 Amps.
    So, even 2 x 16mm2 or 2 x 25mm2 in parallel should be more than enough to cover the amps and volt drop.
    A 35mm2 cable is rated 130 Amps. Two of them might be overkill.

    Volt drop on 25m of 25mm2 single core cable, 48V and at 100Amps will be 0.2V!!!


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    Default Re: battery distance to inverter issue

    Quote Originally Posted by Wetkit View Post



    Volt drop on 25m of 25mm2 single core cable, 48V and at 100Amps will be 0.2V!!!
    I take it the 25m implies a distance of 12.5m between inverter and batteries. Revisit the volt drop calculation as I belief it is 2.06V

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    Default Re: battery distance to inverter issue

    Either way a 35mm sq cable will be just fine. Don't forget the volt drop, unless extreme is of little to no consequence in a situation like this.
    Cheers

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    Default Re: battery distance to inverter issue

    ok so if I get you guys.. 35mm cable is ok and distance to battery not a major issue?

  8. #7
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    Default Re: battery distance to inverter issue

    Quote Originally Posted by 519franco View Post
    ok so if I get you guys.. 35mm cable is ok and distance to battery not a major issue?
    It's a combination of distance and current. If the distance is doubled so does the volt drop. If your distance apart is 6.25m(run length 12.5m) with 25 sq mm the drop will be about 1.03V. Volt drop is normally a bigger problem than current carrying value. The guide line is to keep the battery cable as short as possible. Making sure that inverter and battery are not in the same enclosure.

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    Default Re: battery distance to inverter issue

    Quote Originally Posted by ekkekan View Post
    It's a combination of distance and current. If the distance is doubled so does the volt drop. If your distance apart is 6.25m(run length 12.5m) with 25 sq mm the drop will be about 1.03V. Volt drop is normally a bigger problem than current carrying value. The guide line is to keep the battery cable as short as possible. Making sure that inverter and battery are not in the same enclosure.
    the distance is 12.5m . 25m there and back.
    can build new enclosure about 3m away (6m there and back) price will be a little bit more if I build enclosure. but will be an eyesore hence moving batteries to geni room.
    But if 25m there and back is major issue will settle building an enclosure.
    have to make sure before doing on or the other..
    moving batteries to geni room is quicker and easier.

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    Default Re: battery distance to inverter issue

    Quote Originally Posted by 519franco View Post
    the distance is 12.5m . 25m there and back.
    can build new enclosure about 3m away (6m there and back) price will be a little bit more if I build enclosure. but will be an eyesore hence moving batteries to geni room.
    But if 25m there and back is major issue will settle building an enclosure.
    have to make sure before doing on or the other..
    moving batteries to geni room is quicker and easier.
    Volt drop still seems a bit high. You might have to compensate by setting the inverter to cut the battery out at a lower voltage.
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    Last edited by ekkekan; 2021/06/21 at 01:43 PM.

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    Default Re: battery distance to inverter issue

    Yes, looks like I made a mistake on the volt drop calculation.
    Problem is, each cable ratings is different.

    For copper, the cable resistance looks to be around 0.78 Ohms/km.
    For 25mm2 the volt drop looks to be around the 2mV/A/m.

    In general running 2 smaller diameter cables is better than running a single thicker one.


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    Default Re: battery distance to inverter issue

    Quote Originally Posted by Wetkit View Post
    Yes, looks like I made a mistake on the volt drop calculation.
    Problem is, each cable ratings is different.

    For copper, the cable resistance looks to be around 0.78 Ohms/km.
    For 25mm2 the volt drop looks to be around the 2mV/A/m.

    In general running 2 smaller diameter cables is better than running a single thicker one.
    Using the 2mV per amp would give 0.2V for 1m at 100A.
    Different tables might give different values but I have it that 1x50 would be close to 2x25.
    Last edited by ekkekan; 2021/06/21 at 03:29 PM.

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    Default Re: battery distance to inverter issue

    if i was going to run 5m there (10m there and back) what thickness should I run?\

    and what thickness cable to run between batteries when i series 4 togeather?

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    Default Re: battery distance to inverter issue

    Quote Originally Posted by ekkekan View Post
    Volt drop still seems a bit high. You might have to compensate by setting the inverter to cut the battery out at a lower voltage.
    mmmm I get. Your calculation is using 50m of cable as far as I can see.

    35mm sq = 0.4886mOhm = 0.0004886 ohms (1 meter length) = R
    Length of 25 meters (12.5 go and 12.5 return) = R x 25 = 0.0122 ohms
    Volt drop = 122 ( current) x 0.0122 ( resistance of 25 m ) = 1.49 Volts total.

    That is absolutely nothing as far as the Inverter is concerned while driving the load.

    It is even less of a concern while charging.

    And probably neither here nor there even for low voltage cutout, which is in any event a seriously inaccurate arbitrary voltage.

    I am, as always, open to correction.
    Last edited by Fluffy; 2021/06/21 at 04:23 PM.
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  17. #14
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    Default Re: battery distance to inverter issue

    Quote Originally Posted by Fluffy View Post
    mmmm I get. Your calculation is using 50m of cable as far as I can see.

    35mm sq = 0.4886mOhm = 0.0004886 ohms (1 meter length) = R
    Length of 25 meters (12.5 go and 12.5 return) = R x 25 = 0.0122 ohms
    Volt drop = 122 ( current) x 0.0122 ( resistance of 25 m ) = 1.49 Volts total.

    That is absolutely nothing as far as the Inverter is concerned while driving the load.

    It is even less of a concern while charging.

    And probably neither here nor there even for low voltage cutout, which is in any event a seriously inaccurate arbitrary voltage.

    I am, as always, open to correction.
    Thanks for your valid inputs Fluffy. Yes my calc takes run length as the distance between the 2 points and thus conductor length is 50m.

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    Default Re: battery distance to inverter issue

    Hi if you want I have brand new 35mm sq. Permoweld cable I'm selling at R20/ metre. I have bought 16mm sq. Cable fir daul battery install and cost almost double this. Anybody for it is welcome. PM me for further details.

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    Default Re: battery distance to inverter issue

    Quote Originally Posted by 519franco View Post
    if i was going to run 5m there (10m there and back) what thickness should I run?\

    and what thickness cable to run between batteries when i series 4 togeather?
    100A is the max for 25 sq mm cable. I would guess not many people would run this kind of load for long.
    100A also happens to be a common max continuous load for 100Ah lithiums.
    I would use 25 sq mm for the 5m distance between and also between the 4 batteries.
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    Last edited by ekkekan; 2021/06/21 at 06:09 PM.

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    Default Re: battery distance to inverter issue

    I am now totally confused...lots of suggestions and no proper info.

    OP said he has a Deye Inverter...but no mention of size. Is it 3kW,3kVA or 5kW/5kVA. Or is it 24V /48V system?

    Post #3 Wetkit says let's take 5kW.

    Normally I would run a fuse double the size of the inverter. 3kW @ 48V would require a 125A fuse. 5kW @ 48V would require at least a 200A fuse.

    Thus cabling should match these values, or do I have it wrong?

    I would run 35mm sq as a minimum on 3kW system and 50mm sq on 5kW system.
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  21. #18
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    Default Re: battery distance to inverter issue

    Move the inverter to the battery room?
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  22. #19
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    Default Re: battery distance to inverter issue

    Quote Originally Posted by Prof View Post
    I am now totally confused...lots of suggestions and no proper info.

    OP said he has a Deye Inverter...but no mention of size. Is it 3kW,3kVA or 5kW/5kVA. Or is it 24V /48V system?

    Post #3 Wetkit says let's take 5kW.

    Normally I would run a fuse double the size of the inverter. 3kW @ 48V would require a 125A fuse. 5kW @ 48V would require at least a 200A fuse.

    Thus cabling should match these values, or do I have it wrong?

    I would run 35mm sq as a minimum on 3kW system and 50mm sq on 5kW system.

    What distance - 20km ??

    Complete overkill.

    ----------------------

    Also remember you want the fuse to blow way before the cable melts. The reason the fuse is there is to protect the cable.

    ---------------------

    Once upon a time people ran mains cabling for batteries, then somebody said "no, are you mad", "the thicker the better" And then everybody went gaga and made the Zambians rich.

    ---------------------

    My rule of thumb - 5kW system 48V - 25mm sq up to about 5m away. 125A fuse. Run the system at an average continuous load of about max 4kW for load shed type periods. 100% duty cycle load, I wouldn't like to cruise at much more than 3kW average. Cables and fuse will handle startup peaks of way more than 5kW.
    Cheers

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  23. #20
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    Default Re: battery distance to inverter issue

    Dye = Ohm = Sunsync Inverters

    Manual :
    https://investsolar.co.za/wp-content...IH-5T48-SS.pdf

    Battery input voltage = assume = 48 V
    5 kW Charging and discharge current = 120 A (max)
    8 kW Charing and discharge current = 190 A (max)


    Length of cable = 15 m

    Assuming you will use welding cable : https://www.aberdare.co.za/product-c...general-wires/

    No temperature, sunlight or grouping deratings applied (best case scenario considered)

    Cable size = Max Current , Voltdrop in millivolts per Amp per Meter
    16 mm2 = 131 A , 1.6 mV/A/m
    25 mm2 = 177 A , 1 mV/A/m
    35 mm2 = 220 A , 0.8 mV/A/m
    50 mm2 = 280 A , 0.6 mV/A/m



    5 kW inverter volt drop @120 A
    16 mm2 = 0.0016 V x 120 A x 15 m (x2) = 5.76 V
    25 mm2 = 0.001 V x 120 A x 15 m (x2) = 3.6 V
    35 mm2 = 0.0008 V x 120 A x 15 m (x2) = 2.88 V

    8 kW inverter volt drop @190 A
    25 mm2 = 0.001 V x 190 A x 15 m (x2) = 5.7 V
    35 mm2 = 0.0008 V x 190 A x 15 m (x2) = 4.56 V
    50 mm2 = 0.0006 V x 190 A x 15 m (x2) = 3.42 V

    For PowerFlex cable single core:
    https://www.voltex.co.za/wp-content/...-and-Wires.pdf

    Cable size = Max Current , Voltdrop in millivolts per Amp per Meter
    16 mm2 = 76 A , 2.8 mV/A/m
    25 mm2 = 104 A , 1.7 mV/A/m
    35 mm2 = 125 A , 1.3 mV/A/m
    50 mm2 = 148 A , 0.9 mV/A/m
    70 mm2 = 187 A , 0.7 mV/A/m
    95 mm2 = 232 A , 0.5 mV/A/m

    So we need to know which cable you care going to use before we can tell you the correct size as there is a massive difference in the ratings even between the same size copper cables.....
    Last edited by Tiaan Pot; 2021/06/21 at 08:00 PM.

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