Re doing the Battery Box

audredgeraudredger Solar Expert Posts: 272 ✭✭
B.B. asked "(you have fuses/breakers at the end of each series string of your bank--or is everything just tied together with heavy cable?).":confused:

Well, I once thought that the 250 amp breaker at the end of the string was "good enough":blush: I now know it isn't!:cry:

To refresh: I have 24 L16H's; 6 banks of 4. 2/0 interconnects within a bank & 4/0 bank to bank.

The plan is to fuse each bank:;) Saw these on another thread http://www.blueheronmarine.com/Blue-Sea-5191-Terminal-Fuse-Block-5551 thought they were just the ticket but, now question whether they might spark inside the battery box?

Planning to use 100 amp fuses then, run 6 equal length (10')#2 cables to a bus bar. 4/0 cable from bus bar to 250 amp inverter fuse. Bus bar to be located outside of battery box.

4/0 Negative cable to remain unequal length and all tied together.

Question 1): If all the positive cables are the same length & size and, the negative cable is oversize, should that not balance the banks?

Question 2): am I better off (safer) to use 6 http://store.solar-electric.com/fb-110t.html of these outside of the battery box and build a bus bar to tie them together? This would leave the 10' of #2 cable "unprotected".

BTW: as per the blue sea calculator our host has provided http://beta.circuitwizard.bluesea.com/ #2 should carry 100 amps @ 24 volts forever.

Be patient, I'm not stupid just ignorant (uneducated):p
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Comments

  • icarusicarus Solar Expert Posts: 5,306 ✭✭✭✭
    Re: Re doing the Battery Box

    The Bluesea fuses are ignition protected according to the specs. Since they are designed to be installed in boats explosion hazards are significant.

    http://www.blueheronmarine.com/Detail.bok?no=5552

    Tony
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    The reassurance helps... just feels iffy... Battery box is vented but a 47 cu/ft box can hold a lot of hydrogen!
  • PhotowhitPhotowhit Solar Expert Posts: 5,010 ✭✭✭✭
    Re: Re doing the Battery Box

    I'm sure you can find a busbar, but I would use a power distribution block, they also make fused distribution block for auto use that I sometime recomend for people doing off grid installs instead of a combiner box, but better(?) than in line fusing.

    NAWS sells some here;

    http://store.solar-electric.com/16220-2.html
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    Was thinking more like http://www.blueheronmarine.com/Blue-Sea-2107-Powerbar-5117 six legs in, one out.
  • icarusicarus Solar Expert Posts: 5,306 ✭✭✭✭
    Re: Re doing the Battery Box

    Think about a voltage controlled (battery gassing voltage) Zepher fan. Set to turn on when batteries gas, off when the voltage drops, draws ~5 watts.

    Tony
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    Got one. Just don't trust it to totaly evacuate all the gases
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    Regarding over sized negative cables... It is the total resistance of the string (positive+negative+connections) that should be equal between all the strings.

    If all strings have the same sized negative cables (awg and length), then it will not hurt the balance. If on string has short/heavy cable and the other are long/light cables--then the strings will not be in balance.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    Thank You Bill, Was hoping that by "restricting" one side it might balance. learn Learn LEARN
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    Well, it is true that adding resistance does make the balance better... As long as the wire is still the correct gauge for the application.

    You are correct that "over sized" wire can make the issue of balancing heavy currents in a bank worse... Because the resistance of the wire "drops out" of the equation and the resistance of the battery and the electrical connections (and fuses/breakers) becomes the major elements in the resistance.

    A 3' length of wire is a pretty fixed resistance. Your connections and battery internal resistance may be more variable...

    To see what kind of resistances we are looking at--Take a look at a typical Optima Lead Acid Battery spec... The internal resistance for a 50-60 AH battery may be 0.0025 to 0.003 Ohms.

    Using this typical copper wire resistance chart--we see that large diameter wire has very low resistance per foot too:
    0 awg = 0.0983 ohms per 1,000 ft
    2 awg = 0.1563
    4 awg = 0.2485
    6 awg = 0.3951
    8 awg = 0.6282
    10 awg = 0.9989

    If we assume a 60 AH battery is around 0.003 ohms, then a 600 AH battery/bank could be around 0.0003 ohms...

    Or, about the same resistance as 1 foot of 4 awg wire...

    So--it kind of gives you an idea of the values you are looking at here... And how the wiring (and electrical connections, over current protection devices) for a large bank actually set the current balance more than the internal resistance of the battery itself...

    So, insuring that the electrical connections around the battery banks is very important to the ability of the batteries to properly share current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    Got it. Speaking of wire/cable resistance; most of us use welding cable for our battery connections, in a DC system is there any difference in resistance between welding cable, multi strand USE and single conductor? Assuming same gage & material.

    Was told once upon a time; DC flowed on the surface of the wire and AC flowed in the core? Sounded like B.S. to me; electrons are electrons wether they flow in a loop or just bounce back and forth????
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    There is a difference between AC and DC current flow in a wire... DC flows through the entire cross section. AC flows in the "skin" of the wire...

    Skin Effect:
    Skin effect is the tendency of an alternating electric current (AC) to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core. That is, the electric current tends to flow at the "skin" of the conductor, at an average depth called the skin depth. The skin effect causes the effective resistance of the conductor to increase with the frequency of the current because much of the conductor does little. Skin effect is due to eddy currents set up by the AC current. At 60 Hz in copper, skin depth is about 8.5 mm. At high frequencies skin depth is much smaller.
    Methods to minimise skin effect include using specially woven wire and using hollow pipe-shaped conductors.

    This chart includes the skin depth frequency for various wire sizes for solid conductors.

    If you were to look at the huge AC "bus bars" in a power substation--they are actually hollow.

    For welding, very fine wire allows for a more flexible cable and reduces work hardening of the copper wire.

    If you start to add high frequency to welding--then you probably have skin depth issues in the design of the power system.

    Then there is PWM mode in solar charge controllers---They probably cycle around 10-20 kHz (guessing)--so you can have skin effects in your solar array/battery cabling too... However, with PWM, they only go into less than 100% on when reducing current/power flow because the battery is nearing full charge--so I would not be concerned design a "normal" system (other than Radio Frequency Interference--which is real and can be a real pain because of PWM/MPPT controllers--a few mfg. do offer FCC class B on their equipment--which I think, should be required for all equipment).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,420 ✭✭✭✭✭
    Re: Re doing the Battery Box
    audredger wrote: »
    Was told once upon a time; DC flowed on the surface of the wire and AC flowed in the core? Sounded like B.S. to me; electrons are electrons wether they flow in a loop or just bounce back and forth????

    That's called "Skin Effect" and does not happen at 60 hz. You have to go to several KHz to start to measure it.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    Re: Re doing the Battery Box

    AND, the higher the frequency the thinner the depth of the skin. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    Actually, the skin effect is 8.5 mm or 0.33 inches for 60 Hz... For higher currents.

    For a 4/0 cable, the transistion frequency is only 125 Hz... From the chart, it looks like 60Hz currents over ~600 amps--it starts to be a real issue that needs to be addressed...

    Obviously, much more than "we" deal with here...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    :confused: Now I'm in a real quandary; do I use litz wire to reduce the skin effect, copper tubing to increase the surface area or, copper rebar to increase the cross section?:confused: LOL

    Think I'll just use welding wire! Already have it laying around....
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    And; there is the issue that single phase inverters have a 120 Hz ripple imposed on the DC current (300 amps is possible in DC inverter input)...

    For DC bank wiring... I would avoid welding cable (difficult to find crimp fittings that fit--welding cable has more "air space" and does not fit standard crimp connectors). And look for cable that is appropriate for the environment (acid resistant). Also very fine cables are difficult to use screw type clamps to make good connections,\

    Using copper plumbing--may have too much other alloying elements to have the resistance of "pure copper wire"...

    Standard stranded cable is fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    The fittings are available locally at the "Battery Store"; crimp & then solder.
    Cable has UL label and is represented to be "acid proof"

    With all do respect and No disrespect intended, on this one, I disagree.
  • mike95490mike95490 Solar Expert Posts: 8,420 ✭✭✭✭✭
    Re: Re doing the Battery Box
    audredger wrote: »
    The fittings are available locally at the "Battery Store"; crimp & then solder.
    Cable has UL label and is represented to be "acid proof"

    With all do respect and No disrespect intended, on this one, I disagree.


    I think the terminals need to be UL cert for the wire too. And don't bother with solder, as it can wick into the strands and make a stiff spot where it will crack.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    The stiff spot can be a problem... try to have enough slack so I don't bend at the lug.... Have had some factory lugs pull off....trying to have a better electrical connection...... yes, rosin core solder Mike
  • solarvicsolarvic Solar Expert Posts: 1,053 ✭✭✭✭
    Re: Re doing the Battery Box

    There was a magazine article a few years back in Home Power magazine about making homebrew battery cables. You clean off enough insulation and flaten in a vise. Fill it with solder and drill a hole for the battery bolt. I was thinking of trying that for battery cables. S:Dlarvic
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    That would do in a pinch.... I would rather give our host $0.70 an end and, buy the crimper @ $26. I have over $34,000 invested in this system, getting cheap at this point doenen't make cents. Knowing that you've tried to everything right? Pricless.
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Re: Re doing the Battery Box

    My two cents--good crimp and avoid the solder for reasons above...

    A good crimp and you should not get any solder down into the hermetically crimped joint. A bad crimp and solder can get in--then revisit the crimp ends and crimp tooling--solder should not be able to flow into the joint.

    But--yes, I have soldered heavy lugs on cables too... :blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    The crimper I have leaves much to be desired..... may need to invest some $ with our host. Would like to see a crimper like a Kearney Swager. I used them when I was an aircraft mechanic.
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Re doing the Battery Box

    For DIY people, like myself, crimping may be the weakest skill link. I bought and used the hammer crimper sold at NAWS to make all my 4# & 8# connections. The tool is manufactured by Noco. Their site advertises "crimps wires with a swing of a hammer." Call that 3 swings of the hammer.

    I used a short handled 2lb hammer. As each lug was seated (hammered) the only test I could perform was... could I pull the wire out of the lug! Sometimes, I could. So I discarded the lug, reformed the strands of the cable, and WHACKED a new lug on with a few more swings of the hammer.

    Tall Girl of this forum once said she would not trust any crimp other than a proper one, i.e., one made by a proper (read hydraulic/expensive) crimping tool. I now see her point. OTOH, I have had no problems, but I may be on borrowed time.

    I think the principle of no solder on hi amp lugs is a good one.

    I will be redressing my lugs this spring with more WHACKS, tape and heat shrink and then torque the bolts.

  • icarusicarus Solar Expert Posts: 5,306 ✭✭✭✭
    Re: Re doing the Battery Box

    The trick with the hammer crimper is to put it on a hard (massive) surface, anvil is nice, and hit it HARD with a heavy hammer. I use a ~3# hand sledge and it works great!

    Harbor Freight or Northern sells a pretty inexpensive hydraulic crimper, but I suspect the quality is not real good.

    Tony
  • mike95490mike95490 Solar Expert Posts: 8,420 ✭✭✭✭✭
    Re: Re doing the Battery Box

    Attached, pic of CRIMPED, overheated cables.

    Now imagine, if you had a soldered connection, the solder melting, and dripping on the battery case. I'm a convert to hydraulic crimp connections.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Re doing the Battery Box

    Yikes, that is scarry. Now i will argue, properly sized wire and a tight connection "should' not get that hot.
    your point is taken.
  • bobdogbobdog Solar Expert Posts: 191 ✭✭
    Re: Re doing the Battery Box
    mike90045 wrote: »
    Attached, pic of CRIMPED, overheated cables.

    Now imagine, if you had a soldered connection, the solder melting, and dripping on the battery case. I'm a convert to hydraulic crimp connections.


    What were those wires going to anyway?
  • mike95490mike95490 Solar Expert Posts: 8,420 ✭✭✭✭✭
    Re: Re doing the Battery Box
    mike90045 wrote: »
    Attached, pic of CRIMPED, overheated cables.
    bobdog wrote: »
    What were those wires going to anyway?



    Don't know - not my setup, but a good example of the crimp holding on, keeping the redhot wires attached, and not falling off.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • PhotowhitPhotowhit Solar Expert Posts: 5,010 ✭✭✭✭
    Re: Re doing the Battery Box

    Here's a photo of the actual battery box and electrical cabinet.I'll add the former drawing for discriptive use;
    bb.jpg?t=1267052370
    Battery-box.gif?t=1267052606
    FWIW - I couldn't remember my user name for my web site, so I got a Photobucket account, Today my junk mail went from 3-4 to 14!

    Sorry for the poor photo quality, it's a section of a photo I took to show the tool box/work table I built, that you can just see the 'roof' of at the bottom. Some day I'll get some real photos up, likely the day after I hook up the extra combiner box in the photo, which will be the day after I mount the Rogue charge controler in the electrical cabinet, the day after I mount my 30 year old panels on the 3rd frame on the left of the 2 shown, etc, etc,...

    Sorry wrong thread, I'll leave it here as well hope thats 'kewl'
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
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