Some calculators:bus bar R & wire table

sunbunny
sunbunny Solar Expert Posts: 59 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
Refound a DC bus bar Resistance calculator:
http://www.bdbatteries.com/buss-bars.php

And a wire gauge sizing table:
http://www.powerstream.com/Wire_Size.htm

And a charging voltage versus battery temperature table for the truly obsessed :D
http://www.powerstream.com/SLA.htm
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Some calculators:bus bar R & wire table

    thanks for the one with the bus bar resistance calculator as that does make it easy to find a bar's compatibility with the desired wire size used. when using bus bars as parallel battery tie points i always advocated going at least 2x the size needed to reduce the resistance at least by 2. this is important when drilling into solid bus bars for taps or connection points and even more so if 4 or more taps/connections are made.
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #3
    Re: Some calculators:bus bar R & wire table

    I have read several of these threads about bus bars, but is there really a benefit of using a long bus bar for the parallel connections of a bank (connected at the battery posts) vs just using a large gauge wire; all being the same exact length?
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Some calculators:bus bar R & wire table
    jcheil wrote: »
    I have read several of these threads about bus bars, but is there really a benefit of using a long bus bar for the parallel connections of a bank (connected at the battery posts) vs just using a large gauge wire; all being the same exact length?

    Bus bar is a common connection point for mounting multiple large gauge wires of all equal length from multiple battery strings. You can't really duplicate that function with a big piece of wire, can you?
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #5
    Re: Some calculators:bus bar R & wire table
    Cariboocoot wrote: »
    Bus bar is a common connection point for mounting multiple large gauge wires of all equal length from multiple battery strings. You can't really duplicate that function with a big piece of wire, can you?

    Yes I understand that possible usage of it. However I was asking about it in a different sense but I guess I didn't explain it well enough.
    I have seen an installation where in a 12v bank consisting of 12 6v batteries, 2 in series, 6 in parallel, instead of wires connecting all of the (+) an (-) together [on the parallel connections only, the series connections used wires] they used a large bus bar with 90-degree angle brackets connected to the battery posts and connected to the bar. So essentially, it looks like a huge handle to pick up 6 batteries.

    I was wondering if it is worth the expense of the bar setup instead of using the properly sized wires, all the same exact length.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #6
    Re: Some calculators:bus bar R & wire table

    You can always use insulated posts, just a single bolt and nut with all your crimped lugs stacked up.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Some calculators:bus bar R & wire table
    jcheil wrote: »
    Yes I understand that possible usage of it. However I was asking about it in a different sense but I guess I didn't explain it well enough.
    I have seen an installation where in a 12v bank consisting of 12 6v batteries, 2 in series, 6 in parallel, instead of wires connecting all of the (+) an (-) together [on the parallel connections only, the series connections used wires] they used a large bus bar with 90-degree angle brackets connected to the battery posts and connected to the bar. So essentially, it looks like a huge handle to pick up 6 batteries.

    I was wondering if it is worth the expense of the bar setup instead of using the properly sized wires, all the same exact length.

    There are other schemes which utilize rigid metal bars to connect batteries, both for parallel and serial connections. There are advantages and disadvantages. The main advantages being consistent and high current capacity with no 'weak spots' such as crimped lugs. The main disadvantages being the lack of flexibility requiring precise positioning and a lot of exposed conductive surface that needs avoidance/protection.

    For most people the wires to a given common point are much easier to cope with. zoneblue is talking about the "poor man's bus bar"; stacking the lugs up on a single bolt and making sure it is insulated from contact with other conductors (such as bolting through wooden mount).

    There's always more than one way to do something. Figuring out which is best for you is usually the tricky part.
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