Advice Plz! Cable Size for 400ah battery string??? with room to grow?

[SunEagle]

so are you running a 12v battery bank? if so, do you prefer to run 12v for specific reasons?

I guess my reason is because the system is easily portable and was designed to also charge my RV coach battery system (which is 12volt) if the need should arise. I also built my 2 small systems about 4 years ago before I knew any better.

If I decide to enlarge the system and keep it fixed in my work shed I will more than likely go to 24volt

[texman38]

.I had a 2500w 12v unit

so are you running a 12v battery bank? if so, do you prefer to run 12v for specific reasons?

[SunEagle]

Thanks sun eagle, being that I want more than what my puny 1000wat inverter will pull even with surge, my question is will 2/0 battery interconnectors (not talking about wiring to the inverter, just between batteries) be sufficient? and if the inverter is within 4ft lets say of the batteries, what size inverter could i basically run b4 2/0 battery interconnectors would be insufficient? 2000w, 3000w, 4000w or more? in other words i doubt seriously that id ever be running anything over 2000 watt inverter (and i understand my system is not big enough at this point to run an inverter more than 1000w, but my point is to factor future growth so i'm not buy all this crap again down the line.... so 2/0 battery interconnectors seems way way overkill to be connecting 4 x 6v 200ah batteries.... but later as i decide to grow, again i just want something sufficient, and obviously having bigger connectors between batteries will be more efficient in terms of charging and discharging. Now here is the question in my mind that makes me say "what the heck" so if 2/0 cabling between batteries is standard practice (again ????) then haveing such large cables running through dinky ring lug type terminals with a 5/16 or 3/8 hole drilled so you can screw them on to you battery seems ridiculous to me (giant wire, dinky connector) seems like this is the weakest link in the system, is this just widely accepted or is there a better way of interconnecting batteries. anyway, again thanks a bunch i've come a long way in a short time thanks to you and mike...

You are correct that the battery connection point can be your weak link if you draw more amps than what they were designed for. That information should be available from the battery manufacture.

But I doubt that you need something that can handle more than 200 amps for a 24v 200Ah system so a #1/0 awg in air would be over kill and a #2/0 a waste of your money.

Something also to think about is that some inverters are very inefficient and will consume a % of their watt rating. The bigger the inverter the more watts it wastes just being turned on.

I have 3 different inverters (250w, 400w & 600w) and use the size I need for the application. I had a 2500w 12v unit but since it could draw over 200amps I felt it was a little dangerous so I got rid of it.

[texman38]

Wire size is determine by the amount of amps that can go through it as well as the distance that can affect the voltage to drop.

For a quick calculation to determine the amount of amps the wires will see between your battery and your inverter would be to divide the highest wattage rating of the inverter by the battery voltage. ie. 1500w / 24volt = 62.5amps.

Now be aware that most inverters have 2 ratings. The second is higher than the first and is usually based on the amount of watts that the inverter will see during a "surge". It may be only for a short time but your wires can get real hot very quickly if they are not sized for that surge amp.

While it might help shorten your time for me to give you a specific wire size and type I also do not want to provide you bad information based on not knowing how long the wires are and how they are being connected to your equipment. I would suggest you look at the calculations that Mike90250 has given you so that you can come up with the wire size first.

Thanks sun eagle, being that I want more than what my puny 1000wat inverter will pull even with surge, my question is will 2/0 battery interconnectors (not talking about wiring to the inverter, just between batteries) be sufficient? and if the inverter is within 4ft lets say of the batteries, what size inverter could i basically run b4 2/0 battery interconnectors would be insufficient? 2000w, 3000w, 4000w or more? in other words i doubt seriously that id ever be running anything over 2000 watt inverter (and i understand my system is not big enough at this point to run an inverter more than 1000w, but my point is to factor future growth so i'm not buy all this crap again down the line.... so 2/0 battery interconnectors seems way way overkill to be connecting 4 x 6v 200ah batteries.... but later as i decide to grow, again i just want something sufficient, and obviously having bigger connectors between batteries will be more efficient in terms of charging and discharging. Now here is the question in my mind that makes me say "what the heck" so if 2/0 cabling between batteries is standard practice (again ????) then haveing such large cables running through dinky ring lug type terminals with a 5/16 or 3/8 hole drilled so you can screw them on to you battery seems ridiculous to me (giant wire, dinky connector) seems like this is the weakest link in the system, is this just widely accepted or is there a better way of interconnecting batteries. anyway, again thanks a bunch i've come a long way in a short time thanks to you and mike...

[SunEagle]

I think Mike convinced me to buy them... And yes, i saw the 16 ton hydrolic crimpers on ebay for like $35, i think i read the 70mm die would do 2/0, but, I really dont care to make all of them either (time is money) so would you mind giving me a breakdown of the cables and lengths and gauges needed for my 4 x 6v battery bank? and where to get some UL stamped lugs/wires at an affordable price (i was headed down the path of 2/0 wires, is that too big? not big enough, or just about right? thanks Sun Eagle... getting closer... additionally what size wire would i run from my battery bank (4 x 6v in series = 24v) to the power inverter if it were 1000w or 1200w or even 1500w and last if you were to recommend any particular brand or size power inverter? Thanks Sun Eagle!!!

Wire size is determine by the amount of amps that can go through it as well as the distance that can affect the voltage to drop.

For a quick calculation to determine the amount of amps the wires will see between your battery and your inverter would be to divide the highest wattage rating of the inverter by the battery voltage. ie. 1500w / 24volt = 62.5amps.

Now be aware that most inverters have 2 ratings. The second is higher than the first and is usually based on the amount of watts that the inverter will see during a "surge". It may be only for a short time but your wires can get real hot very quickly if they are not sized for that surge amp.

While it might help shorten your time for me to give you a specific wire size and type I also do not want to provide you bad information based on not knowing how long the wires are and how they are being connected to your equipment. I would suggest you look at the calculations that Mike90250 has given you so that you can come up with the wire size first.

[texman38]

Again, from post #4, 4ga is OK, 2ga is a bit better and 1/O overkill. 2/O is going to be real clumsy to handle. I don't know the overall lengths, things could be long enough that 2/O is not large enough, you are the man on the spot, figure the lengths and put that into the calculator, is it less than 3% loss ?

Thanks Mike, OK, what I was saying was I plan to use 2awg for the CC (you suggested 4awg) My CC will be near the battery bank so no need for a calculator, I was just up-sizing the cable from what you suggested for efficiency and possible future upgrade. The 2/0 cabling I was wanting to use on the battery interconnects, my question again is this, is 2/0 cabling "good enough" for now and for future builds??? 2/0 is huge, only 1 size bigger from what I've seen, but what puzzles me is the crappy 5/16 ring terminal that connects it to the battery??? is there not a better way of interconnecting batteries, just seems ridiculous, giant cable, funneled into dinky ring terminal. I'm use to dealing with the A/C side, 2/0 cable would be under a huge lug on a bus bar... something is missing in the D/C world, or I'm just not getting it. Thanks Again Mike!!!

[Mike90250]

Again, from post #4, 4ga is OK, 2ga is a bit better and 1/O overkill. 2/O is going to be real clumsy to handle. I don't know the overall lengths, things could be long enough that 2/O is not large enough, you are the man on the spot, figure the lengths and put that into the calculator, is it less than 3% loss ?

[texman38]

I have no idea of the layout of your bank, and what the interconnects are going to be. Map it out, the inverter cables are the ones that end up being critical, because they are usually longer.
Use the caculators I listed in post #4 of this thread, and you can figure it out yourself and run it past us for a sanity check.

mike i found these on ebay that look good with ul stamp? AWG #2/0 Black Battery Interconnect Cable 12" with 3/8" Lugs ASSEMBLED IN USA

[texman38]

I have no idea of the layout of your bank, and what the interconnects are going to be. Map it out, the inverter cables are the ones that end up being critical, because they are usually longer.
Use the caculators I listed in post #4 of this thread, and you can figure it out yourself and run it past us for a sanity check.

Thanks Mike... i will you use probably 2awg for the inverter (as long as it fits... but again the size of the battery cables is still something i need advice on??? 2/0 sound about right? and where do I get reasonably priced UL stamped battery cables? so size and where to buy is what I need advice on? I can figure out the lengths myself, but if they are lined up like in my golf cart there is a very short cable hooking pos to neg, not sure how that would work with 2/0 cabling.... so if you have any suggestions on how to arrange a 4 battery bank so that cabling makes more sense, especially with such thick wires, plz plz plz let me know... Thanks!!!

[Mike90250]

I have no idea of the layout of your bank, and what the interconnects are going to be. Map it out, the inverter cables are the ones that end up being critical, because they are usually longer.
Use the caculators I listed in post #4 of this thread, and you can figure it out yourself and run it past us for a sanity check.

[texman38]

Neither that hammer crimper in your other post or this crimper will get you a proper termination for your wires. You need a hydraulic type crimper similar to the one in Richiep's post but even that one (which I own) will not do the best job on some wires.

If you plan on trying to save money making your own cable then at least look into purchase quality (and expensive) tools.

I think Mike convinced me to buy them... And yes, i saw the 16 ton hydrolic crimpers on ebay for like $35, i think i read the 70mm die would do 2/0, but, I really dont care to make all of them either (time is money) so would you mind giving me a breakdown of the cables and lengths and gauges needed for my 4 x 6v battery bank? and where to get some UL stamped lugs/wires at an affordable price (i was headed down the path of 2/0 wires, is that too big? not big enough, or just about right? thanks Sun Eagle... getting closer... additionally what size wire would i run from my battery bank (4 x 6v in series = 24v) to the power inverter if it were 1000w or 1200w or even 1500w and last if you were to recommend any particular brand or size power inverter? Thanks Sun Eagle!!!

[texman38]

If you insist on making this a DIY, then you must realize you are not going to be making good, reliable connections with the parts & tools you have selected.
Cable is cable.
Lugs are supposed to be tin plated, so the copper does not oxidize and cause high resistance connections
Crimps really need to be done with hydraulic crimper. Look for the 16 ton hydraulic crimper (flea bay) and make sure it has dies for your lugs and cable.
Make sure your die/lug/cable all work together, sacrifice a crimp. Cut it off the cable, clamp the flat part of the lug in a vice, and with a fine blade hacksaw, cut through the middle of the crimp, slowly, gently and carefully. You want to look at the strands inside the crimp. and see if the are fused together and to the shell of the lug. If loose strands fall out, you have a wrong size somewhere.
Ideally, you use certified dies, that imprint their UL code into the lug.
CrimpLugDeformed.jpg

Ok Mike, you are right, and I really dont care to make all of them either (time is money) so would you mind giving me a breakdown of the cables and lengths and gauges needed for my 4 x 6v battery bank? and where to get some UL stamped lugs/wires at an affordable price (i was headed down the path of 2/0 wires, is that too big? not big enough, or just about right? thanks mike, sorry to keep hitting you up for info, you seem like a great guy so thanks

[Mike90250]

If you insist on making this a DIY, then you must realize you are not going to be making good, reliable connections with the parts & tools you have selected.
Cable is cable.
Lugs are supposed to be tin plated, so the copper does not oxidize and cause high resistance connections
Crimps really need to be done with hydraulic crimper. Look for the 16 ton hydraulic crimper (flea bay) and make sure it has dies for your lugs and cable.
Make sure your die/lug/cable all work together, sacrifice a crimp. Cut it off the cable, clamp the flat part of the lug in a vice, and with a fine blade hacksaw, cut through the middle of the crimp, slowly, gently and carefully. You want to look at the strands inside the crimp. and see if the are fused together and to the shell of the lug. If loose strands fall out, you have a wrong size somewhere.
Ideally, you use certified dies, that imprint their UL code into the lug.
CrimpLugDeformed.jpg

[SunEagle]

or do i need these crimpers?

Neither that hammer crimper in your other post or this crimper will get you a proper termination for your wires. You need a hydraulic type crimper similar to the one in Richiep's post but even that one (which I own) will not do the best job on some wires.

If you plan on trying to save money making your own cable then at least look into purchase quality (and expensive) tools.

[Richiep]

Hey Texman,
I'm wrestling some of the same questions and also shopping for wire and crimping tools.

The largest wires I'll be using right now is 2AWG so I'm looking at this crimper

https://www.amazon.com/gp/product/B0114QC3OY/ref=crt_ewc_title_huc_3?ie=UTF8&psc=1&smid=A3O4LZF7PHWTGN

And this cutter

https://www.amazon.com/gp/product/B0002YUR70/ref=crt_ewc_title_dp_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Here's a thread I started somewhat related to this subject. It evolved into the importance of good cripms

https://www.solarpaneltalk.com/forum/solar-panels-for-home/solar-panels-for-homes-with-solar-batteries/362647-found-some-4awg-in-my-vehicle-use-it-for-my-control-board

Good Luck!
Rich