Exide / GNB Marathons are AGM batteries. What size interconnects

I have sourced some of these GNB Marathon M12V100FT 13.5 volt-13.8volt 110 amp hour batteries for a friend , 16 in total to configure for a 48volt system 4 strings giving a 400 ah 48v bank. They have come without interconnects so I will have to manufacture them . My question are

1.What guage wire would you reccomend for the series interconnects.
2.What guage wire for the parrallel connectors combining the 4 stings to a VFX3048E inverter. 230 volts export model 50 hz
3.Reccomended size DC breaker between batteries and inverter . Re this question I have in stock a 250 amp breaker and a 100 amp breaker I suspect the 250amp way too big, will the 100 amp be enough.

Thanks for all your help Nigel,learning every day !

Comments

  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Nigel,

    (1 and 2) The US National Electrical Code (NEC) Article 690.74 requires that 2/0 AWG wire or larger be used for battery connections and interconnects, subject, of course, to insulation specs and conditions of use. I believe the standard metric equivalent is 70 mm^2. The next commonly available size up here in the US is 4/0, and the metric equivalent is 120 mm^2

    (3) Check out this discussion re DC breaker for the VFX3048E: http://www.outbackpower.com/forum/viewtopic.php?t=2486&highlight=3048e

    HTH,
    Jim / crewzer
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    minimumly it should not be smaller than the biggest wire in the entire system. usually this would be wire going to an inverter, but is not limited to such. if such a system exists that need not have large wires it is still good to go as large as you can to keep interbattery connections low on resistance that increases imbalances and thus the need for eq charging more often. you want the battery bank to look as much like 1 battery rather than a group of interconnected batteries as is possible. though the wire resistances are small you must remember that the internal resistances of batteries are also small and the wire resistance can be large in comparison to the internal battery resistance. this could bring down the effective ah capacity of a battery bank as well.
    i would say that there isn't any hard and fast rule to it at this point because of the many differing circumstances that may arrise, but a good guess might be to double the size of the wire over the largest being used as it has to handle currents going into as well as going out of the battery bank. if that turns out to be a small wire because the the currents into and out of the battery bank are small then go larger anyway. it is also common for copper buss bars to be used instead of or in conjunction with large copper wire.
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Jim/Niel Thankyou for your replies.

    JimI had read this article recently and have re read again a minute ago. If we take it you size the breaker to protect the cabling. Taking that I suspect my friend will never buzz passed the standard 3 kw rating and definately not the rated 30 minutes 3300 w. If I sized a 100 amp breaker and used 50mm2 wire I dont think he will suffer many if any nusiance trips. The series terminals are very close to gether and I would find it difficult not impossible to wire neatly in70mm2. If you have any pictures of same or similar batteries series up and paralled that would be great.

    I know Im going toget shot down in flames here but if we have 4 parallel strings and the inverter pulls a 100 amps from the battery bank, I can see the paralleled conductors having to supply safely 100amps but wouldnt the interconnects on the series side only have to safely supply 25 amps each !

    Im not obliged by NEC but would follow if safety rather than code for code sakes apply:confused:
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    A little bit of self help ....helps searching for images on these batteries I found a PDF data sheet which shows very neat bussbars 2 inch x 0.5 inch strips (Cudos Neil) next hard part is finding a suppllier of such in my country of choice for copper bussbar. with little language knowledge Easy enough to fabricate.

    Still like comments on my series versus parralell current draw ? :confused:

    PS at a push since this buss barr is only 2inches long or less and 1/2 inch wide would I lose much using milds steel as a interconntect .in stead of copper! Is there an electrolisis issue with mild steel ? I need 12 series interconnects

    Doing the math 20 mm bar x 4 mm thick would give a 80mm2 conductor with only two inches long for each series interconnect ? dont suspect Id loose much steel over copper.I can source mild steel easily.

    Comments please
  • Solar GuppySolar Guppy Solar Expert Posts: 1,987 ✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Here is what I did ...

    I beleive its 1AWG and a pair of Cu lugs, all from Home Depot, I also used NoOx on the copper.

    I have 3 strings ( 8 205aH agms ), 2 strings for the XW-6048 and one for the GTFX3048.

    On the XW, runs the home AC no problem, a load of about 5kw
  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    straight, hard bolted connects make me nervous. I wonder what the summer/winter heat cold charging cycles do. Will the plastic cases flex and leak ?
    What about an upside down U shape, maybe made from 1/4" or 3/8" copper tubeing,
    with S.G.'s terminals soldered on ? The curve in the metal will take up any mech stress, you have lots of copper to carry the current, and you can always slip some heat shrink sleeve over it, after 1 trerminal is on, the heat from soldering the 2nd terminal will shrink the sleeve.

    Steel gets rust and corrosion easily, and with the humidity from the batteries and acid, it may not last long. Also, at high currents, you will see loss, you are not looking at 2", but 12 of them, and now you have 24" of the steel conductor.
    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 ,

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    steel may or may not be a problem for bussbars. it does have more resistance than copper and could cause galvanic reactions at the connection points. stainless can avoid some of the galvanic reactions, but it still has higher resistance than copper. just because it is in a bar doesn't mean it may be low resistance as it will have to figured for its equivalency to the wire and as in what resistance will it yield. this will be in ohms and will have to specify for what length it applies. it is common to see it in ohms per 1000ft here in the states.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    I've had good luck with Thomas & Betts / Blackburn type "BTC" connectors from Home Depot.

    See: http://www-public.tnb.com/util/docs/CG_MC_Full.pdf (page 66).

    HTH,
    Jim / crewzer
  • nigtomdawnigtomdaw Solar Expert Posts: 705 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Thxs points noted though the solid buss bar I made reference to (although probably copper/tin coated was from the manufacturers PDF spec sheet.

    The batteries are not the same as SG.s they are side contacts

    http://www.tpscrail.com/products/gnb/PDF/Racks/Marathon_sprinter_relayrack.pdf

    see page 14
    These batteries are from memory 14 inches long 10 inches high and 4 inches wide the terminals are on the front top 4 inch wide bit
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    interesting arrangement and maybe if you have bolts of the right size you could double up on the bussbars too. no matter what you go with some reaction may occur on the metal so maybe some way of coating the bars to protect them could be in order just like that done on battery posts.
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Do not solder your cables... If there is a short, the solder can easily melt and cause the ends to fail.

    A couple of other problems, if you don't use the right flux (rosin core)--you can get corrosive flux in the wire braid which is impossible to clean out. Also, when you solder stranded cable, where the solder "stops" becomes a pivot point for any flexing--causing early failure in your cable connections (why crimp type connectors are used just about everywhere for reliable cable connections).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    those are some good points bill.
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects
    BB. wrote: »
    Do not solder your cables... If there is a short, the solder can easily melt and cause the ends to fail.

    A couple of other problems, if you don't use the right flux (rosin core)--you can get corrosive flux in the wire braid which is impossible to clean out. Also, when you solder stranded cable, where the solder "stops" becomes a pivot point for any flexing--causing early failure in your cable connections (why crimp type connectors are used just about everywhere for reliable cable connections).

    -Bill

    I used your almost exact quote for our new "tip of the week" header on our website, you are famous now. ;)
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects

    Wow! 15 minutes of fame on the Internet. :blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects
    BB. wrote: »
    Do not solder your cables... If there is a short, the solder can easily melt and cause the ends to fail.

    A couple of other problems, if you don't use the right flux (rosin core)--you can get corrosive flux in the wire braid which is impossible to clean out. Also, when you solder stranded cable, where the solder "stops" becomes a pivot point for any flexing--causing early failure in your cable connections (why crimp type connectors are used just about everywhere for reliable cable connections).

    -Bill

    My friend had troubles, melting the terminals off his batteries, on his EV. He'd have to wire around the bad battery, and the battery shop would cast a new terminal onto the stub. He'd draw over 400A going up a hill.
    I hadn't thought of the system drawing so much, it could melt the solder joints, even in a failure mode.

    The crimps you speak of, are not hand crimps, they are machine made crimps, as you can't get the required pressure by hand. (pardon me sir, if you can crimp them by hand!)
    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 ,

  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects
    mike90045 wrote: »
    The crimps you speak of, are not hand crimps, they are machine made crimps, as you can't get the required pressure by hand. (pardon me sir, if you can crimp them by hand!)

    There are hand crimpers for almost any size lug. Some are hydraulic, some are long handled (up to 4 feet) leveraged. They are not cheap though, costing up to $500 or more for the larger sizes.
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects
    BB. wrote: »
    Wow! 15 minutes of fame on the Internet. :blush:

    -Bill

    That is incorrect, Internet fame is gauge by hits per day.:p
  • GreenerPowerGreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: Exide / GNB Marathons are AGM batteries. What size interconnects
    nigtomdaw wrote: »
    ...I can see the paralleled conductors having to supply safely 100amps but wouldnt the interconnects on the series side only have to safely supply 25 amps each !
    ...Still like comments on my series versus parralell current draw ? :confused:
    A battery string with the least internal resistance would supply more current in a parallel configuration. So, the current is not always devided equally among the strings. I would suggest to put a fuse in each string. This is to protect the wire and a string that goes bad. If one string has a short cell for example, the remain strings would try to "charge" this string and there is nothing to limit the current.
    GP
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