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Post by tonyqj on Nov 16, 2016 20:04:37 GMT
But they don't use 2kW and they'll be changing it for a 1500W one. Yes, 70 would be good but 50 should be fine (and cheaper). But they could do, and they will only change to 1500 when the other one dies which could be years. All very true - I was just trying to save them a couple of bob is all.
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Post by Ditchcrawler on Nov 16, 2016 20:13:30 GMT
But they don't use 2kW and they'll be changing it for a 1500W one. Yes, 70 would be good but 50 should be fine (and cheaper). But they could do, and they will only change to 1500 when the other one dies which could be years. Which was the reason given a couple of posts later as to why boat builders use small cables when they fit boat.
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Post by Deleted on Nov 16, 2016 20:20:38 GMT
But they could do, and they will only change to 1500 when the other one dies which could be years. All very true - I was just trying to save them a couple of bob is all. The solution to that is derate the 2000w inverter by using a 250a fuse when rewired with 50mm cable, remember, you protect the cable not the equipment.
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Post by Telemachus on Nov 16, 2016 21:22:25 GMT
Well personally I'd go for 70mm just because it's not significantly more expensive, but 50 would do.
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Post by tonyqj on Nov 16, 2016 21:39:10 GMT
All very true - I was just trying to save them a couple of bob is all. The solution to that is derate the 2000w inverter by using a 250a fuse when rewired with 50mm cable, remember, you protect the cable not the equipment. Did you mean 150A fuse perchcance?
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Post by Deleted on Nov 16, 2016 22:41:20 GMT
The solution to that is derate the 2000w inverter by using a 250a fuse when rewired with 50mm cable, remember, you protect the cable not the equipment. Did you mean 150A fuse perchcance? Yes, fat fingers on the keypad! For those that don't know why Tony pulled me up on it. 1500w/10v (fiddle factor for inverter loses) = 150a. I've got an appointment at tesco opticians next week....
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Post by smileypete on Nov 17, 2016 12:06:55 GMT
Just been thinking about this while i had my tea. The boat is as it was on construction from reading the folder which came with the boat so it met with the safety requirements i presume. The only thing added is 1 extra leisure battery. Seems crazy on a professionally fitted out boat that they would fit cable half the size that is needed. Is it just performance that is affected by this under sizing? They probably saved what? 50 or 60 quid in materials on a £60k approx boat when it was built. Barmy! Yeah but usually the buyers of new boats, who aren't the best informed, want maximum 'toys' for the minimum £££. Maybe they should offer an 'extra' pack which covers all these things. Or maybe said buyers should pay for an independent build surveyor.
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Post by bodger on Nov 17, 2016 16:22:02 GMT
if I buy a 15,000w inverter off that nice bloke in East Grinstead (assuming he's got time to send it in between changing the clothes on his rubber dolls) what size cable and fuse will I need. :-)
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Post by Deleted on Nov 17, 2016 16:25:14 GMT
As its a 48v unit then running the math 15,000w peak would be 312.5 amps.
There will be online calculators for cable size. I expect it would be quite big.
I hate electrical discussions !!
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Post by bodger on Nov 17, 2016 16:50:42 GMT
you'd need strong brackets to restrain the cables against twisting forces at those currents.
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Post by Deleted on Nov 17, 2016 16:59:47 GMT
you'd need strong brackets to restrain the cables against twisting forces at those currents. Would it be a case of solid copper bars connecting battery bank to inverter ?
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Post by JohnV on Nov 17, 2016 17:02:12 GMT
300 odd amps isn't that bad and 120sqmm needs quite a bit of force to twist
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Post by Deleted on Nov 17, 2016 17:04:17 GMT
Sorry to disappoint but if you are intending to get into a technical discussion about big inverters, batteries and associated connections I should mention that I am highly competent at knowing fuck all about it !
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Post by bodger on Nov 17, 2016 17:35:31 GMT
I had the misfortune to work on a project in Abu Dhabi where we had to provide, among other things, a sub-station incorporating a standby 120v battery bank capable of running the oil products export pumping station for 24 hours.
someone had mis-read the spec, which actually required power to be able to close all the main valves once, during a power outage of 24 hours; as a result the battery capacity was about 100 times larger than it needed to be and the batteries alone cost more than $1million.
the DC cables from the battery room were fixed to a steel frame made of 150mm x 150mm steel H-section to withstand twisting forces (motor effect).
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