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BMS/Inverter cable gauge question.

Stepandwolf

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I saw a similar question asked but from another angle so I thought I would try and ask it from my perspective.

I am going to be buying the Victron Multiplus 3000VA inverter, and for now, it looks like I will be pairing it with a 250A Daly Smart BMS. The BMS will be connected to 8S Lishen 280A cells. Obviously, I want to insure the BMS cables can handle the full draw from the inverter.

The 250A model is rated for 250A continuous power. I just asked the rep what the battery lead cable sizes for it were, she said 2AWG. 2 gauge is rated for 181A on the charts I have seen. The cable charts show a single 1/0 or dual 2's. Since I am looking at "generic" cable specifications, maybe they don't apply to this situation.

The Daly rep indicated they tested the cabling, and I am sure they did, but could she be correct that 2 gauge is adequate, or even more than adequate?

I noticed the drawing for the BMS logic board has two connectors, so it could support dual wires, but it doesn't seem to be how they are wiring the 250A model for sale.

I bet someone else has had the same question and knows what to use. Thanks!
 
I am having the same dilemma. I'm seeing 2/0 for half a meter at 250 amps DC
 
The ampacity of the wirea also has to do with what kind of insulation material being used, if you use the slicone wire the ampacitity rating will be higher than the same wire gauge using lower temperature rating, that is why the expensive BMS uses silicone wire, at the same time you have to calaculate your system acceptable Voltage drops of the wire.

 
Perhaps I am doing it wrong, but I get 125 amps at full 3000 watts draw, add some fudge factor, and the 2 awg wire installed on the 250 amp Daly seems quite adequate for my purpose (running a 24v Multiplus 3000 watt inverter). Yes, I am going with 2 awg welding wire.

 
Do NOT forget that wire sizing for DC is also dependent upon the length of the wire run as well. The longer the run the bigger the wire to prevent voltage drop/loss.

ALSO A POINT TO NOTE.
Wire Gauges are being tossed around like Candy at Willy Wonka's. There is a HUGE difference between 2 gauge & 2/0 gauge. So do be careful and be certain you are looking at the RIGHT gauging for your application. There is also a significant difference between Fine Copper Wire stranded cable versus "coarse" (thicker) wire stranded cables.

I use 4/0 Premium Royal Excelene fine copper Welding Cable. 24V System can draw 250A and charge at 150A. I can tell you that even those get Warm when at high amps. My wire runs are 10' from Inverter to Battery Bus and 4' from battery Bus to Pack 3/8" Lugs.

Chart from SouthWire - Royal Excelene Welding Wire
Excelene-Wire-Info.JPG
 
Do NOT forget that wire sizing for DC is also dependent upon the length of the wire run as well. The longer the run the bigger the wire to prevent voltage drop/loss.

ALSO A POINT TO NOTE.
Wire Gauges are being tossed around like Candy at Willy Wonka's. There is a HUGE difference between 2 gauge & 2/0 gauge. So do be careful and be certain you are looking at the RIGHT gauging for your application. There is also a significant difference between Fine Copper Wire stranded cable versus "coarse" (thicker) wire stranded cables.

I use 4/0 Premium Royal Excelene fine copper Welding Cable. 24V System can draw 250A and charge at 150A. I can tell you that even those get Warm when at high amps. My wire runs are 10' from Inverter to Battery Bus and 4' from battery Bus to Pack 3/8" Lugs.

Chart from SouthWire - Royal Excelene Welding Wire
View attachment 41180

Yes, 2/0 (aka 00) is significantly different from 2 gauge. That's why I like the calculator from Blue Sea, not only are they reputable and know what they are doing, but it tells me that 4 gauge at 150 amps for 6 feet is good, so I went with 2 gauge. I went with TEMCo, simply because I don't trust Chinese cable manufacturers to not lie.


I have indeed heard good things about Royal Excelene, but I also have prior experience with TEMCo products and I know that you get what you pay for, and they stand behind their product. I've also heard great things about Royal Excelene.


They appear to have identical specs, but the Royal Excelene is cheaper (at least for 2 awg).

Another vendor I can recommend is Powerwerx, they will custom build cables for you:

 
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TEMco, Southwire (who makes the Excelene) and a few others are very good quality proper cables. For such a key critical piece it's got to be right & it's got to be good, cheap wire can kill. I first built my system with a 3kw Inverter & 2/0 wire, when I upped to 4kw I had to up the wire to 4/0 which was a COSTLY LESSON because I had debated going 4/0 at the start but decided not to. I would never ever play the double wire game some do, lessons learned a LONG TIME AGO and never forgotten, I have scars that remind of that folly. Warn people to not do it and they do it anyways while dumping on the messenger... I gave up warning folks as it's pointless, 1 of 10 may listen.
 
Yes, 2/0 (aka 00) is significantly different from 2 gauge. That's why I like the calculator from Blue Sea, not only are they reputable and know what they are doing, but it tells me that 4 gauge at 150 amps for 6 feet is good, so I went with 2 gauge. I went with TEMCo, simply because I don't trust Chinese cable manufacturers to not lie.


I have indeed heard good things about Royal Excelene, but I also have prior experience with TEMCo products and I know that you get what you pay for, and they stand behind their product. I've also heard great things about Royal Excelene.


They appear to have identical specs, but the Royal Excelene is cheaper (at least for 2 awg).

Another vendor I can recommend is Powerwerx, they will custom build cables for you:

Hopefully you noticed that the length of wire is different between those two Amazon listings. That makes it so the Excelene is quite a bit more expensive for the same amount of wire. 25 ft of both red and black of TemCo is $90, while the same amount of Excelene is $122.
 
Hopefully you noticed that the length of wire is different between those two Amazon listings. That makes it so the Excelene is quite a bit more expensive for the same amount of wire. 25 ft of both red and black of TemCo is $90, while the same amount of Excelene is $122.
No, I hadn't noticed that. Both are high quality and you should shop around for the best price. I would not recommend buying any made in China. You want pure copper with as many small conductors as possible (that means a large cable made with many small strands). Do not use CCA (copper clad aluminum) which many vendors don't disclose.

Most people don't realize when sizing wire that the ampacity rating is for a 30 degrees Celsius rise in temperature of the wire. Always go at least one size larger. Also be aware, if you put it in conduit, the temperature rise of the cable goes up. Always upsize from any calculator (fuses on the line will also add quite a bit to the temperature rise).
 
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There is a YouTuber that recently had her panel wired by an electrician who charged $30 or $35. She brought him her panel that had the components mounted on it. He provided the proper cable, lugs, did the crimping and wired it up for her. Much cheaper than buying the parts and a crimper that will be used one time and tucked away. In that she is gorgeous, she might have gotten a hottie discount, but if you will never use the crimper again, it makes sense to hire someone if they are affordable as her electrician was.

I am still concerned that the Daly cables are below the rated requirements. Speaking of which, my Daly Elect. BMS showed up today, ahead of schedule. They put down 816 vs. 916 for my house number. The DHL driver mentioned his consternation locating my house.

Daly said the BMS would come with a "manual", but came with a wiring diagram. The wiring diagram is for a bank of 16550 cells, a totally different wiring configuration than an 8 cell system. It is not only not a manual, but is just a wiring diagram for a configuration very different than mine. That doesn't even delve into the instructions that aren't appropriate but are incomplete and written for a different configuration. I expect to have questions to assure myself I don't turn into toast :)
 
There is a YouTuber that recently had her panel wired by an electrician who charged $30 or $35. She brought him her panel that had the components mounted on it. He provided the proper cable, lugs, did the crimping and wired it up for her. Much cheaper than buying the parts and a crimper that will be used one time and tucked away. In that she is gorgeous, she might have gotten a hottie discount, but if you will never use the crimper again, it makes sense to hire someone if they are affordable as her electrician was.

I am still concerned that the Daly cables are below the rated requirements. Speaking of which, my Daly Elect. BMS showed up today, ahead of schedule. They put down 816 vs. 916 for my house number. The DHL driver mentioned his consternation locating my house.

Daly said the BMS would come with a "manual", but came with a wiring diagram. The wiring diagram is for a bank of 16550 cells, a totally different wiring configuration than an 8 cell system. It is not only not a manual, but is just a wiring diagram for a configuration very different than mine. That doesn't even delve into the instructions that aren't appropriate but are incomplete and written for a different configuration. I expect to have questions to assure myself I don't turn into toast :)
For that price, sounds like he just charged her for parts, definitely a hottie discount.

You are now introduced to the Daly we all know and love, the "we gave you a manual, it must be your fault it died". The BMS works well actually, but there is a reason I bought a 250 amp BMS for a 125 amp load. I also made sure it was the version without a fan, since in my experience a cheap Chinese fan will last about a year. Make sure to plug in the balance/sense leads last, since that seems a common way to kill them. When you get it hooked up, likely you will need to activate it as well.
 
There is a YouTuber that recently had her panel wired by an electrician who charged $30 or $35. She brought him her panel that had the components mounted on it.
Please link to the channel.
That is a very clever idea.
I wonder how many electricians have crimpers for compression lugs?
I thought they used mechanical lugs.
 
Please link to the channel.
That is a very clever idea.
I wonder how many electricians have crimpers for compression lugs?
I thought they used mechanical lugs.

Yes, except my wife is over 55 so probably doesn't qualify for the hottie discount! ;)

But, I will add that if you are in the Phoenix area and wish to drive to Mesa (60 and 202 area) that I probably have any crimp tool you might need.

Probably won't do many people any good, but I'm offering.
 
Please link to the channel.
That is a very clever idea.
I wonder how many electricians have crimpers for compression lugs?
I thought they used mechanical lugs.
I don't know if there is where she mentions the electrican, but she does show the board with the mounted components:

Lex and Riot

BTW, she is hot enough in this video but less hotness than her other videos.
 
I have to chime in here: Welding cable is better in every way:

The insulation is rated to a higher voltage and it's considerably tougher, there is slightly more copper in the same outer diameter so ampacity is higher (tightly packed fine strands vs looser packed thicker strands) and not least of which it's a hundred times easier to bend a tight radius than normal battery cable. I think it might be cheaper too.
 
I have to chime in here: Welding cable is better in every way:

The insulation is rated to a higher voltage and it's considerably tougher, there is slightly more copper in the same outer diameter so ampacity is higher (tightly packed fine strands vs looser packed thicker strands) and not least of which it's a hundred times easier to bend a tight radius than normal battery cable. I think it might be cheaper too.
Better than what, exactly?
 
If you're talking about automotive battery cable, then yes. Marine battery cable, as in Ancor 105°C engine room rated cable, then no.

The primary advantage I can see from the Ancor cable is tinned strands.

Comparing different brands at 2 gauge I see:

Ancor = 665 strands of 30 gauge tinned
Temco = 624 strands of 30 gauge untinned
Royal Excelene = 651 strands of 30 gauge untinned
Super Royal Excelene = 1651 strands of 34 gauge untinned (only rated to 90 degrees Celsius for insulation)

Certainly using tinned strands is superior in a high corrosion environment, but I'm sure that you also pay for it. Realistically, try to avoid puncturing the insulation and use heat shrink to avoid most corrosion problems.
Apparently the "Super Royal Excelene" is only available in orange. I hadn't known about it until I started looking up specs, it seems a really good choice (I live in the desert, not on a boat). If you are counting on the insulation to withstand temperatures above boiling water, you've probably sized it wrong.
 
I also noted the limited choice of colors on the Super Royal Excelene, and was disappointed. I can see where the environment in the desert could easily approach egg-frying surface temperatures. Perhaps 105° C is not enough.

Cost comparison (could not find a cost for Super Royal Excelene):

Temco 2 AWGamazon.comRed/Black combo89.95501.80
Ancor 2 AWGfisheriessupply.comRed, Yellow, Black94.69501.89
Royal ExceleneWireandSupply.comRed, Black92.50501.85

I'd add that the extra few pennies for tinned cable would be well worth it.
 
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