My little piece of peace

[masalai]

I am told electricity runs on the surface and there are 2 surfaces in a tube(for almost 8cm skin section), weight is about the same as tinned fine wires bought cable used to deliver for 2 x 10 Kw 48VDC motors on another boat, and we figured, slightly better skin section... I need a specialist low volt sparkie to verify the numbers 48 VDC nominal, how many amps? then what would be the equivalent in fine wired tinned bought cable...

[masalai]

Originally Posted by masalai

Torqeedo (2 year replacement guarantee) electric drives (I call them "outboards") that require 48VDC and can use 4400watts for a short time and cruise easy at 500 to 2500watts... should give me up to about 6 knots in "no wind calm seas" - for more data I will have to wait 'till it is launched... Solar panels (2000watts and have room for a discrete 3000watt installation), 21hp kubota DC charger and batteries with appropriate inverters will power the domestic stuff, generator to catch up if the batteries lag a little and whilst "motor-sailing" on a cloudy day.

I need the 48v for the above, 2 x torqeedo 4.0R which actually peak out at 4400watts 48VDC each

[Landlubber]

Mas,

Solid wire is not allowed on boats, both by regulation and common sence.
Fulti strand wire absorbs harmonic shocks and tends to not break under repeated vibrational forces.

Sectional area is the area of wire we use mate, measured now in MM 2.

4400W / 48 V = 92 amps, say 100.

Using battery cable (tinned to help prevent capilliary salt water damage), is still going to be the best deal, as long as the cables are not too long (keep the batteries near the motors), you do not need any thicker than 25mm2.
25mm2 is good for 3M distance, 35mm2 for 6M distance and 50mm2 for 10M distance. The best of thgese would be the 50mm2 because it allows nearly double the ampacity required (less resistance) and it is still physically light and very flexible.
Remember when sizing wiring that the run length is actually twice the measured length (the power comes from the battery and back to the battery to complete the circuit).

[Boston]

Most of my domestic stuff is standard domestic, and these Hi-Tech batteries with a 10yr guarantee at more than 3 times the price of a standard car one with a 3 yr guarantee??? - Had a good brain fart the other day, half inch copper waterpipe with thick insulation makes an excellent conductor for the 48v cable at less resistance and greater surface section to carry more amps or same amps at less $$$... flatten the ends and copper connect to busbar for distribution & fuses at either end and after busbar... Is that good or have I miscalculated somewhere?

wont work mate
the juice will ground out to the water in the pipes
at best it will cause electrolytic destruction
at worst when the girl flips on the bidet for the first time she is in for a surprise

not sure about boat electrical
its been a while
but when I built my horse camper trailer code dictated sso wire for both ac and dc applications with crimp connectors

[masalai]

But, but, but it is a bus-bar for the 48V from generator (forward of the mast), batteries (just aft of centreboard), & electric motors (just aft of the aft berths) - no water through, just as a bus-bar... So if that is not recommended/advised then back to 600 strand tinned copper cable.... 240V AC stuff must have a separate earth (copper or other earthing plate below the waterline) and that earthleakage trip fuse thingy.. - - and ac will be isolated from DC stuff)...

[Frosty]

He did not say he would have water IN the water pipes!! Just use the surface area to carry the load.

I can understand you Mas.

However the cat that I look after has been sold,- I might have mentioned it but is was put up for sale about 10 minutes after sea trials with Vetus electric motors,-- a disaster to say the least.

The calcululations as to how much power they used was way out.

He needed a 100amp batt charger to keep them running and his 240AC gen was'nt big enough to run that.

Maybe Mass is a bit cleverer than my mate was. I hope so.

[Frosty]

Phew nearly posted on top of you there mas.

Regarding earth of AC. You might want to think about how many appliances you buy these days needing earth. Almost everything I buy is 2 pin except the microwave.

In a marina you are putting yourself up as the ground system if thiers fails, like what happened here and my missus screemed "sinking" one night and saved the guys boat 60 ft steel that had no bottom in it.

I have but 2 wires on my AC --in and out. I always wire like that. I don't have any trouble because I don't have anything to have trouble with.

The kettle is plastic , all my power tools are plastic along with the blender , rice cooker, and fridges and the washing machine.

Those few that dont,-- have plastic handles anyway, and if its shorting to earth it probably wont work in which case it is replaced. But none of this has happened.

Now!!! what is the earth for?

[Landlubber]

The only way to be sure of AC being isolated from the shore power system is to use an isolation transformer on the boat as close to the shore power inlet as is possible, that way there is NO contactable direct return to earth in case of power failures.

[masalai]

Landie thanks for the post, but to clarify - NO shore power, just inverters for "domestic stuff" (ro watermaker @AU$4k, 'fridge option, freezer option - may stick with 24vDC boxes - washing machine, microwave, vacuum cleaner and electric cooktop...) The 2 electric drives are 48v DC max draw is 4400W each but cruise expected to be less than 2000 watts each. The rest - marine stuff - will be 12 or 24VDC. My electrical energy will be 48VDC solar PV panels and/or 48VDC genset using Delco alternators rectified to meet charging requirements of the "house bank" batteries.

[Landlubber]

Mas, seriously do you expect that 2.6hp is enough to make your boat"cruise"....2000W / 750 is the approx hp. It will make the boat move in calm water for sure, but any more than 10 knots of wind and you will need a lot more hp to drive all that windage.

[masalai]

If you are referring to the Torqeedo, YES - a single one is pushing a 45 ft? tri at 6knots (calm seas/no wind) with estimated weight of 3.5 tonnes plus... The genset will make 6000watts...

[masalai]

Here is the panel for the "chain-plate" built in and preparation for the doorways - standard strengthening and sealing of the balsa...

[Fanie]

Nice going Mas.

[masalai]

From the trip up to the Sunshine Coast, on another 44C build, a davit and mounting system to be fitted soon... slight over-engineering, with a capacity of about 500kg each...

[Frosty]

500kg??? each???

Mas, mas, mas, I don't think so.