Hi, how do you go about selecting the correct battery fuse size?

1 X Inverter: Luxpower SNA5000

1 X Battery: Greenrich 1,5C rated

Battery cable: 35mm2

Battery fuse standard sizes: 125A, 160A

I'm not sure how much current the inverter is capable of drawing. The battery can easily deliver 150A based on the 1,5C rating. I've tried looking up the cable size current carrying capacity but there is too much variability in the info I'm finding so I'm not sure what to make of it.

38 minutes ago, Munzee said:

Hi, how do you go about selecting the correct battery fuse size?

1 X Inverter: Luxpower SNA5000

1 X Battery: Greenrich 1,5C rated

Battery cable: 35mm2

Battery fuse standard sizes: 125A, 160A

I'm not sure how much current the inverter is capable of drawing. The battery can easily deliver 150A based on the 1,5C rating. I've tried looking up the cable size current carrying capacity but there is too much variability in the info I'm finding so I'm not sure what to make of it.

My standard welding cable rating for 100% duty cycle cable shows 220A. If you have 1x1.5C battery you can use the 160A or the next size higher. Not sure what the next standard size fuse is. 

I doubt you will be using the inverter at 100% load as it will give you less than 1 hour at full load during LS. 

49 minutes ago, Munzee said:

Hi, how do you go about selecting the correct battery fuse size?

1 X Inverter: Luxpower SNA5000

1 X Battery: Greenrich 1,5C rated

Battery cable: 35mm2

Battery fuse standard sizes: 125A, 160A

I'm not sure how much current the inverter is capable of drawing. The battery can easily deliver 150A based on the 1,5C rating. I've tried looking up the cable size current carrying capacity but there is too much variability in the info I'm finding so I'm not sure what to make of it.

Keto battery disconect with 2x 200 amp fuses for pos and neg.

https://www.sustainable.co.za/products/keto-battery-disconnector-with-200a-fuses?variant=40898808512705&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjw756lBhDMARIsAEI0AgkZpGbKSYtkiXHI9NNKJ93SZxi0AXHEdhRykSlYk7mnuTYKA2HJQewaAqG3EALw_wcB

10 minutes ago, TaliaB said:

Keto battery disconect with 2x 200 amp fuses for pos and neg.

No need to buy such an expensive one. This one with 2 x 200A fuses with do the job:

https://www.liteglo.co.za/shop/onesto-fsd1-250-2-2-pole-250amp-fuse-switch-disconnector/

 

Edited July 7, 20232 yr by PowerUser

7 minutes ago, PowerUser said:

No need to buy such an expensive one. This one with 2 x 200A fuses with do the job:

https://www.liteglo.co.za/shop/onesto-fsd2-400-2-2-pole-400amp-fuse-switch-disconnector/

 

Keto for 160A happens to be the same price as this link around the R1200 level. 

5 minutes ago, Scorp007 said:

Keto for 160A happens to be the same price as this link around the R1200 level. 

The OP needs one for 200A fuses. It’s over R2700 from @TaliaB link

 

The one I posted is about R800. 

Edited July 7, 20232 yr by PowerUser

The legal requirement for the fuse is determined entirely by the wire. For standard 35mm² PVC wire, the fuse may not be bigger than 125A (which is anyway more than what the inverter will draw at full power).

If it is high voltage/non-standard wire, then it may be legal to use a larger fuse - refer to the wire manufacturer for details (but no idea why you would want to?).

Also, you can not use the welding rating.  '100% duty cycle' in terms of welding means 5 minutes continuous and then a chance to cool.  The rating of the same wire when used as GP cabling will usually be substantially lower.

There are 2 types of cables that can be used with high current dc applications fine strand and ultra fine strand the more flexible the cable the higher the strand count. Attached Afrox welding cable rating but true what @JustinSchoemansaid you need to check manufacturer rating chart 

http://www.afrox-welding.co.za/en/products_services/arc_accessories/welding_cable/weld_cable/index.html

Here is an extract from one manufacturer's datasheet for one type of cable:

Note how exactly the same 35mm² cable is rated at 252A for welding, but only 160A for wiring.

You can not take the welding rating and use it for wiring.  If the manufacturer does not specify a wiring rating, then use the SANS rating for the cable size and insulation type.

I already have the battery disconnect fuse holder. Just trying to decide on which fuse to get. 

 

Interesting information there @JustinSchoeman. 

 

I'm not able to find the actual manufacturer datasheet. What is printed on the side of the cable reads: Yulan car cable 1x35 300/500V

 

The supplier I bought the battery disconnect from mentioned that most people just buy the 160Amp fuse. But it doesn't make sense to me. 

If there is no specific rating, then go with the SANS defaults, which would be 125A if the cables run in an enclosed conduit.

According to the attached image, what is QF?

They have QF3 In>140A

Max: 140A from the battery

And then recommended DC breaker 150A. Not sure what breaker is this refering to? 

3 minutes ago, JustinSchoeman said:

If there is no specific rating, then go with the SANS defaults, which would be 125A if the cables run in an enclosed conduit.

Battery is just beneath the inverter and wall mounted. Not planning on having the battery cables in trunking because it's a short distance. Not sure if this changes anything?

Well, then it is easy.  The manual says a circuit breaker of at least 140A, 150A recommended.

35mm² cable in free air is rated to 162A.

So use a 160A fuse.

Thanks @JustinSchoeman

18 hours ago, JustinSchoeman said:

 

Also, you can not use the welding rating.  '100% duty cycle' in terms of welding means 5 minutes continuous and then a chance to cool.  The rating of the same wire when used as GP cabling will usually be substantially lower.

What time frame would chance to cool be after the 5min continuous use? 

That Inverter will shut down if it reaches 100A and it's running purely on battery. It is also limited to 100A max charge current.

1 hour ago, zsde said:

That Inverter will shut down if it reaches 100A and it's running purely on battery. It is also limited to 100A max charge current.

This seems like a very valid response. Even if the battery can supply 1.5C=150A and the fuse switch 200A?

Eish i am back in Gauteng until end Aug to complete a project quoted on 3 months ago big project but i will post in showcase towards next week.

This morning i was asked by my brother in law to come and check an installation done at his friends house, the inverter system is working but a burning smell came from somwhere. I arrived and by face value could see it was not a neat install and they couldn't get hold of the installer. 3kw Fivestar inverter paired with 2.4kwh N- Energy 24v lfp battery. I switched the Eskom supplying to inverter off and checked the load was running at 1280 watts drawing around 52 to 55 amps from the battery. Left it to run for half an hour and went back to check if i could smell anything burning and yes not very distinctive but it was there. Placed my hand on the inverter casing but no heat on the outer cover. As i bent down to look at the battery my eye caught it, a distinctive yellow mark on the top pos battery connection on the battery fuse disconect. I thought loose connection checked but top and bottom was tightened down good. Put my hand on the side of the Fivestar discconect and it was hot realy hot. Switched inverter off open the battery disconnect check resistance of both fuses both good. Put fuses back disconnected inverter and battery and checked resistance with my MT 985 on milliΩ scale. Neg 122mΩ Pos 942mΩ and there it was 22.6 watts of wasted energy in form of heat. That is why for me i rather spent more money on a good quality battery disconnect i.e Jean Muller than these cheaper disconnect versions. Also found no earth/neutral bond on output of inverter no relay no permanent bond nada. Rectified that situation as well.

 

Good morning

We specified my fuses using this napkin math:

Max Inverter Spikey Load(8800W) / Lowest battery Voltage (48V) = 183.33 A 

Then for variance sake(temperature of fuses and tolerances considering temperature change) we add 25%.

183.33 x 1.25 = ~230A 

We have two 250A fuses on my battery array lines, the manual also asked for these

Please make sure cables match fuses ratings, eg. 160A =>35mm² and 250A => 50mm² etc...

Regards

Edited July 9, 20232 yr by ZS1SCI

18 hours ago, Scorp007 said:

What time frame would chance to cool be after the 5min continuous use? 

I really can't find that link again.  But the basics SANS requirements remain the same.  You either need to use the current carrying capacity tables in the SANS spec, or that provided by the manufacturer.  I sincerely doubt that that includes 'off label' manufacturer specifications (eg welding specifications).

2 hours ago, ZS1SCI said:

Please make sure cables match fuses ratings, eg. 160A =>35mm² and 250A => 50mm² etc...

How are the cables going to be mounted? What is their max conductor temperature (PVC/nitrile/etc)? How long are they?

Likely somewhere between 70mm² nitrile covered wire (short, in free air) and 120mm² PVC covered wire in a conduit.

Everying you need to calculate wire size and ampicity in this charts and tables according to Sans 10142-1 

2020-Charts _ Tables.pdf

3 hours ago, JustinSchoeman said:

I really can't find that link again.  But the basics SANS requirements remain the same.  You either need to use the current carrying capacity tables in the SANS spec, or that provided by the manufacturer.  I sincerely doubt that that includes 'off label' manufacturer specifications (eg welding specifications).

I would have thought that Aberdere that have been manufacturing cables for decades is a trustworthy source to use.