Inverter cable size

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Twin

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Planning to install 1500W inverter (12V) with peak load (1 min.) < 1730 W / (1 sec.) < 2650 W. Manufacturer recommends min DC cable size of 50 mm2 or 1/0 AWG. According to spec 50 mm2 nominal current rating is 345A, thus 4140W.

Isn't 50 mm2 an overkill? Initially was looking at 35 mm2 240A or max 40 mm2 300A cable.
 
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If the inverter is near the battery then why scrimp on copper?
If the inverter isnt near the battery then you must consider volt drop and not just cable capacity.
See http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.5127&voltage=12&phase=dc&noofconductor=1&distance=1&distanceunit=meters&amperes=200&x=74&y=15 for a volt drop calculator.
An example for 33mm^2 (AWG 2) at 200A gives 0.21 volts drop per metre run (not there and back)
At 3m you loose 5% in the cable meaning the inverter needs to draw 5% more current... 210A
 
Why wouldn't you follow the manufacturer's instructions? Do it properly the first time, then you won't have to do it again later when you find problems.
 
It's little to do with current carrying capacity and all to do with voltage drops. The thicker the cable the better.
 
Where did you find 345 amps for 50mm2 ?

The industrial table I use shows Tri rated heavy duty cable 50mm2 is rated at 204 amps with no de-rating factors applied. At this current draw the cable would be getting towards 85oC assuming an ambient of 45oC. On an average UK day of say 15oC then expect the cable to be reaching 55oC.

Can't see your cable carrying 345 amps unless it is glowing red hot !
 
Twin said:
Here https://www.12voltplanet.co.uk/CABSCBATXFLX50PNT.html
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I'll stick with my table thanks. I don't get much popularity nor repeat business if I start setting large air conditioning chillers on fire. The table does not differentiate between AC and DC - current is current.

https://www.dropbox.com/s/iglvw4j7s21i56j/Cable ratings.pdf?dl=0

I would hazard a guess that the rating you are looking at is assuming use of the cable for starter motors, where it is only on for a few seconds. Your inverter could be on for prolonged periods.

I just noticed the price - try your local City Electrical Factors - we buy 50 or 100m at a time, for which we pay ~ £3.50 / m exc vat. They will sell shorter lengths too.
 
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Twin said:
Planning to install 1500W inverter (12V) with peak load (1 min.) < 1730 W / (1 sec.) < 2650 W. Manufacturer recommends min DC cable size of 50 mm2 or 1/0 AWG. According to spec 50 mm2 nominal current rating is 345A, thus 4140W.

Isn't 50 mm2 an overkill? Initially was looking at 35 mm2 240A or max 40 mm2 300A cable.
Click to expand...

Make and model of inverter please ?
 
PaulRainbow said:
50 mm2 would be appropriate, but only if you keep the cable run short, i wouldn't go above about 1.5m if possible. If you do go longer, you will need to increase the cable size. Be sure to fuse the inverter cable close to the battery.
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Thanks. It will be about 1m of 50 mm2 cable from battery to Mastervolt Mastershunt (with main 500A T-fuse) >DC Distribution#1 >DC Distribution#2. Inverter then will be connected to DC Distribution with 300A ANL fuse, cable about 1m, but definitely not longer than 1.5m.

I was wondering would it be fine to connect Blue Sea ML-Remote Battery Switch (Latching Relay) just before Mastershunt? Ideally it should be Mastershunt >Latching Relay >DC Distribution, but I want to connect Mastershunt and DC Distribution directly like this https://images.mastervolt.nl/files/MasterShuntdistrifront.jpg
 
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As a matter of interest, although not necessarily relevant, I have a 2500W inverter charger with 4m return trip of cabke to the battery bank and back. I can't recall the the detail but I ended up with 95mm2 cable, which has an outside diameter of about 23mm including the casing.

I must have concluded that 70mm2 was too thin, as 95mm2 was quite difficult to source.
 
Richard10002 said:
As a matter of interest, although not necessarily relevant, I have a 2500W inverter charger with 4m return trip of cabke to the battery bank and back. I can't recall the the detail but I ended up with 95mm2 cable, which has an outside diameter of about 23mm including the casing.

I must have concluded that 70mm2 was too thin, as 95mm2 was quite difficult to source.
Click to expand...

Furneax Riddall or 12 Volt Planet !

The thin wall cable for 12 volt use is only 17.9 mm overall diameter
 
Twin said:
Thanks. It will be about 1m of 50 mm2 cable from battery to Mastervolt Mastershunt (with main 500A T-fuse) >DC Distribution#1 >DC Distribution#2. Inverter then will be connected to DC Distribution with 300A ANL fuse, cable about 1m, but definitely not longer than 1.5m.
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Keep the cables as short as you can. The 300a fuse is suitable for the inverter, bear in mind the 500a T fuse will be over rated for the 50mm cables. Also bear in mind that neither are protecting the 1m of cable from the battery to the Mastershunt. You may also want to fit lower rated fuses to the cabling that supply distribution/switch/fuse panels. You seem aware of such things.

I was wondering would it be fine to connect Blue Sea ML-Remote Battery Switch (Latching Relay) just before Mastershunt? Ideally it should be Mastershunt >Latching Relay >DC Distribution, but I want to connect Mastershunt and DC Distribution directly like this https://images.mastervolt.nl/files/MasterShuntdistrifront.jpg
Click to expand...

I don't think either will cause the boat to burst into flames, but connecting how you describe would mean that when you leave the boat the battery monitoring is disabled.

Mastershunt >Latching Relay >DC Distribution should mean that battery monitoring still takes place when the DC distribution is isolated.

I'd run this by Mastervolt for a definitive answer.
 
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PaulRainbow said:
I don't think either will cause the boat to burst into flames, but connecting how you describe would mean that when you leave the boat the battery monitoring is disabled.
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Indeed if Mastershunt is used as a main monitoring device, but e.g. in this case http://www.powerproducts-mobile.com/files/img/systems/schemas/ST_DRAINVEHICLE_1177x847px.png MLI battery has internal, more accurate shunt and latching relay controls are directly connected to BMS, so it can cut off all loads.
 
PaulRainbow said:
If you are not using the Mastershunt for battery monitoring, why are you fitting it?
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Basically Mastershunt would hold T-class fuse and act as a back up monitoring device. Battery BMS would supply voltage to Alpha Pro charge regulator, alternatively this could be done by Mastershunt. If BMS fails (if this happened once, it could happen twice, believe me) it would be possible completely disconnect BMS and still have prolonged engine use with proper 3-step battery charging (one click to change shunt device in Alpha Pro configuration). No doubt it could be possible to measure voltage manually and cut off alternator at e.g. 14.25V, but such alternative does not look very appealing while at sea. Considering T-fuse holder price, additional 150 euro is a small price to pay.
 
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Twin said:
Basically Mastershunt would hold T-class fuse and act as a back up monitoring device. Battery BMS would supply voltage to Alpha Pro charge regulator, alternatively this could be done by Mastershunt. If BMS fails (if this happened once, it could happen twice, believe me) it would be possible completely disconnect BMS and still have prolonged engine use with proper 3-step battery charging (one click to change shunt device in Alpha Pro configuration). No doubt it could be possible to measure voltage manually and cut off alternator at e.g. 14.25V, but such alternative does not look very appealing while at sea. Considering T-fuse holder price, additional 150 euro is a small price to pay.
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The T class fuse, at 500a, is very over rated for 50mm cable. Another point about fitting the remote battery switch prior to the Mastershunt is that the switch will not have any protection. I think you need to rethink your cable sizes and fuse ratings.
 
PaulRainbow said:
The T class fuse, at 500a, is very over rated for 50mm cable. Another point about fitting the remote battery switch prior to the Mastershunt is that the switch will not have any protection. I think you need to rethink your cable sizes and fuse ratings.
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Thanks. How about 400A T-class fuse then? Or even lower? Or it would be better to increase battery> latching relay >Mastershunt cable to e.g. 70 mm2? I'm aware latching relay would would be exposed, but it has 500A Continuous Rating and 700A (5 min) Intermittent Rating https://www.bluesea.com/products/77...Switch_with_Manual_Control_Auto-Release_-_12V

Also wondering about quality of cables. Is it safe to buy e.g. from here https://www.ebay.co.uk/itm/Flexible...m=201701872149&_trksid=p2047675.c100009.m1982
 
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