Dangerous Ecoflow kit?

[Nedge68]

if you check using the link to the calculator I posted previously it says 16mm is OK for 2m at 60A, amazing difference an extra 4m makes…

 

[Hoovie]

I was commenting on GJ installation where he has a 6m length this is very important factor, and there are many others that can cause you to de-rate the cable. The IEE on-site guide is lacking when it comes to DC installs.

I fully agree that the cable supplied with Johns install was inadequate. But then saying it should have been 50mm2 is something I don't agree with. if you do think that, that is fine. I don't. simple as that.

 

[Hoovie]

if you check using the link to the calculator I posted previously it says 16mm is OK for 2m at 60A, amazing difference an extra 4m makes…

And I will tell you that I think THAT is wrong. Why so I say that? As I have around 2M of 16mm2 cable on my 60A B2B and I will be replacing it with 25mm2 (or even 35mm2 just as it is easy to do) when I get round to it. as I feel there is a bit too much heat generated. it is not dangerously so by any means but as I said earlier ... heat = waste.

But people are entitled to think what they want. and there are plenty of other calculators which will give different answers - some higher, some lower.

 

[funflair]

No, but I have never seen a commercially produced motorhome with a 60A B2B, ours is 20A, but it also only has a lead acid leisure batter. lf you upgrade to Lithium and your B2B to 60A you need to rate the cables to suit, How would You calculate the size then? As Lenny says the sizes keep volt drop to 3% which is the normal acceptable limit.

Ours is 90A B2B factory installed and the manufacturers recommendation is 25-35mm depending on cable run being less than 6m or less than 9m, for a 60A they go from 16mm to 35mm again depending on cable run less than 6m to 12m.

 

[Lenny HB]

Slightly different with a B2B as it will compensate for the volt drop on the input side.

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[Nedge68]

so using that calculator would actually UNDERSIZE cables for some uses. use a 4mm for a Compressor Fridge on a 6M run and you will get an high voltage drop on the compressor surge and unless the battery is maybe 80% SOC, you will have a battery that is fine but a fridge that reports low voltage.

Next, for the typical B2B installation, most installers (including Professional installers) use the chassis as a common ground. Using your online calculator again, check the cable needed for a 60A B2B with a chassis return instead.
Also, you will probably have put the voltage as "12V"? You won't be driving the B2B at 12V from the alternator, but between something like 13.8 - 14.5V. That makes a fair old difference as well.

When using a tool to work out sizes, it is important to enter ALL the factors in.

I was using Gadget John’s Ecoflow system, the only data I had was 60A 6m and it was a return system, i.e. 2 cables (Not using chassis ground). I did use 12V but as you will see if you use 14.5v you get the same answer of 50mm. They should not have supplied such a small gauge cable and absolutely not one with an horrendous “join“ in it.

 

[autorouter]

I don't agree, his cable sizes are correct if you want to keep losses to under 3%.

Most B2B installations have much shorter cable runs than 6m, most under 2m so you could use 16 mm2.

Agreed. If you use a different cable size calculator you get much the same results. These also agree with my own spreadsheet calculations starting from scratch, but I don't expect that will cut much ice. These apparently OTT cable sizes for a 6m 2-way cable run are a very good reason why 12V electrics are a bad solution for high power electrics. Also why it's advised to keep the high amps cable runs as short as possible.

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[Nedge68]

And I will tell you that I think THAT is wrong. Why so I say that? As I have around 2M of 16mm2 cable on my 60A B2B and I will be replacing it with 25mm2 (or even 35mm2 just as it is easy to do) when I get round to it. as I feel there is a bit too much heat generated. it is not dangerously so by any means but as I said earlier ... heat = waste.

But people are entitled to think what they want. and there are plenty of other calculators which will give different answers - some higher, some lower.

Yes 50mm does seem over the top, and most probably won’t fit the terminals!!! The better manufacturers actually give tell you the maximum cable size, and recommended sizes per length eg Victron 12/12/30A terminal max 16mm2
and minimum sizes on length 5m -16mm.

 

[Hoovie]

Yes 50mm does seem over the top, and most probably won’t fit the terminals!!! The better manufacturers actually give tell you the maximum cable size, and recommended sizes per length eg Victron 12/12/30A terminal max 16mm2
and minimum sizes on length 5m -16mm.

Indeed so. You cannot fit a strand thicker than a standard 16mm2 cable into a 30A Orion-Tr cable. (I always use the Pin terminal connectors with the Victron Orion 30A as the bare cables are a real pain if you need to refit a cable in situ).

 

[Tombola]

I always use the Pin terminal connectors with the Victron Orion 30A as the bare cables are a real pain if you need to refit a cable in situ).

Good tip

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[Hoovie]

Good tip

For anyone looking for 16mm2 pin connectors, this is probably the best one from a reliable quality source - https://uk.rs-online.com/web/p/crimp-pin-connectors/8092366.
For anyone who likes to use bootlace ferrules, the connector is so tight for a 16mm2 cable the extra space a ferrule takes up stops it fitting! (I love Victron kit generally, but the connector size and style on some of their products can be very annoying - the same issue is true of the MPPTs - the 100/20 Controller won't take 6mm2 solar cable).

 

[Gromett]

it is important to enter ALL the factors in.

I did note that none of you mentioned that the rating is when the cable is in free air. If you put it in conduit/trunking or anything else that insulates it, it keeps in heat and you need to derate accordingly.
Also running multiple cables side by side, you also need to derate.

 

[Gromett]

Also, you will probably have put the voltage as "12V"? You won't be driving the B2B at 12V from the alternator, but between something like 13.8 - 14.5V. That makes a fair old difference as well.

Just noticed this. I think you will find it doesn't make any difference.
In this context the losses in the circuit in watts is dictated by the resistance of the cable and the current flowing in it. The formula is
W = I²R

No mention of voltage there.

 

[Hoovie]

Just noticed this. I think you will find it doesn't make any difference.
In this context the losses in the circuit in watts is dictated by the resistance of the cable and the current flowing in it. The formula is
W = I²R

No mention of voltage there.

There is on the calculator that is being linked. Check again.

 

[Hoovie]

I did note that none of you mentioned that the rating is when the cable is in free air. If you put it in conduit/trunking or anything else that insulates it, it keeps in heat and you need to derate accordingly.
Also running multiple cables side by side, you also need to derate.

Again, there is on the calculator being linked to. Rightly or wrongly, THAT calculator is the one that is under discussion to work out cable gauge? Check again.

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[autorouter]

Both of you are partly right. W = I²R is correct, the power wasted and the voltage drop do not depend on the battery voltage. It would be the same watts wasted and voltage drop if it was a 240V supply giving out 60A.

But the percentage loss would be different. A voltage drop that's 3% of 12V (ie 0.36V) would be 2.5% of 14.5V and 0.15% of 240V. It's the principal reason houses use 240V not 12V, so they can use less copper, even though 240V is dangerous.

 

[Gromett]

Both of you are partly right. W = I²R is correct, the power wasted and the voltage drop do not depend on the battery voltage. It would be the same watts wasted and voltage drop if it was a 240V supply giving out 60A.

But the percentage loss would be different. A voltage drop that's 3% of 12V (ie 0.36V) would be 2.5% of 14.5V and 0.15% of 240V. It's the principal reason houses use 240V not 12V, so they can use less copper, even though 240V is dangerous.

Correct. My point was that mentioning voltage is pointless as it plays no part in the calculations.

 

[Hoovie]

Correct. My point was that mentioning voltage is pointless as it plays no part in the calculations.

It plays a part in determining the cable thickness, which is the whole conversation.

 

[Gromett]

It plays a part in determining the cable thickness, which is the whole conversation.

It doesn't. I am sorry but my memory may be a bit fuzzy on this. We had to go back to first principles on this topic and calculated the required csa of a cable required given the materials resistivity and it's temperature coefficient.

At no point did we consider the voltage of the DC circuit. We considered the voltage drop but that was calculated using I x R.

The only time the actual circuit voltage would be of interest is if you wanted to limit the voltage drop as a percentage of the source voltage.

I suspect we are starting to talk at crossed purposes here. So I will make this statement and leave it at this.

Using the nominal voltage (12v) or the measured voltage at rest (12.8v) or the charging voltage (14.5v) will have zero impact on the cable size selection in practical terms.
The only factors that will be decisive are the length, the current to be carried, if the cable is 2 way or 1 way and if it is enclosed or in free air.

 

[Lenny HB]

The only time the actual circuit voltage would be of interest is if you wanted to limit the voltage drop as a percentage of the source voltage.

But that is exactly what we want to do.

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[Gromett]

Also, you will probably have put the voltage as "12V"? You won't be driving the B2B at 12V from the alternator, but between something like 13.8 - 14.5V. That makes a fair old difference as well.

Just to be clear. This is the bit I was querying. 12v vs 14.5v will make no difference to the cable size calculations in our applications.

 

[Hoovie]

Just to be clear. This is the bit I was querying. 12v vs 14.5v will make no difference to the cable size calculations in our applications.

Wrong

 

[Fragle]

Interesting reply from Gadget John on instagram this morning

 

[Gromett]

Wrong

You insisted I look at your calculator... So here we go.

@60A 12v vs 15V

Or at lower current levels.
@20A 12v vs 15v

If I am wrong, I would hate to see what being right means?

Also, you will probably have put the voltage as "12V"? You won't be driving the B2B at 12V from the alternator, but between something like 13.8 - 14.5V. That makes a fair old difference as well.

Using 12v or 14.5v in these calculations makes absolutely no difference.

 

[Hoovie]

#1. It is not MY calculator
#2. It is rounding the cable sizes to available gauges. Try adapting the the length of the run for example and you will see how it varies.
I don't know why you are insisting on something you know (I hope!) is wrong. Saving face because you made a statement you feel you have to stick to it?
I really am not bothered. As I said earlier, different people have different options. I have already said that calculator (note ... THAT calculator, not MY calculator) is flawed as it also undersizes cable recommendations as well due to the lack of data inputs it allows

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[Hoovie]

You insisted I look at your calculator... So here we go.

@60A 12v vs 15V

View attachment 716797View attachment 716796


Or at lower current levels.
@20A 12v vs 15v

View attachment 716798View attachment 716799

If I am wrong, I would hate to see what being right means?



Using 12v or 14.5v in these calculations makes absolutely no difference.

Just to illustrate I will do the screenshots for you so you can see. As per my previous note, I am not that bothered, but as you feel the need to quote my posts, I feel the need to reply to correct you where you are wrong.
OK. Imagine you don't have a 6M run but just 4M (just as likely. actually more likely). What is the effect of the voltage on your 20A demand in terms of the cable THAT calculator recommends at the two different voltages you say has no bearing on the results?

Think that settles that "makes no difference" arguement?

 

[Hoovie]

Interesting reply from Gadget John on instagram this morningView attachment 716808

yup, that is a fair statement from him in quite a few ways, considering how the initial post here was worded.

 

[Gromett]

Just to illustrate I will do the screenshots for you so you can see. As per my previous note, I am not that bothered, but as you feel the need to quote my posts, I feel the need to reply to correct you where you are wrong.
OK. Imagine you don't have a 6M run but just 4M (just as likely. actually more likely). What is the effect of the voltage on your 20A demand in terms of the cable THAT calculator recommends at the two different voltages you say has no bearing on the results?
View attachment 716832View attachment 716833
Think that settles that "makes no difference" arguement?

I stand corrected. Not sure where I am going wrong here. Going to have to dig into my text books. I am absolutely certain from memory that we didn't use an input voltage in our calculations.

 

[Gromett]

I will add though that I would rather use the Nominal voltage (12v) and have a bigger cable, rather than the actual voltage (14.5V) which would result in a smaller cable.

 

[Gromett]

Interesting reply from Gadget John on instagram this morningView attachment 716808

Any link to it?

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