Boat electrics question
So i have a deep cycle battery powering my house electrics and a cranking battery to start the motor. I can charge either depending on the setting of the colhersy switch.
Both batterys are house in the rear storage area at the back of the cockpit.
All the house electrics, excluding the pumps, are located on or near the dash. They include nav lights, three radios (am/fm, 27mg, vhf), 12v accessory plug and sounder / plotter combo.
I think i need a heavier cable running from my house battery forward to the buzz boards under the dash. I have the voltage displayed on the sounder plotter and it drops quite drasticly when i transmit on vhf if i am not running the charge from the motor through the house batteey at the time.
Will heavier cables between the battery and the dash reduce the voltage drop? The distance is about 3.5 m i suppose.
Fish! HARD!
SpotHound
Posts: 439
Date Joined: 06/02/14
Yes
Yes, there are tables for this kind of thing on the net.
Faulkner Family
Posts: 18062
Date Joined: 11/03/08
a heavier cable in my
a heavier cable in my experience should do the job. when i rewired my boat i had the same issue until i put the heavier wire in
RUSS and SANDY. A family that fishes together stays together
Rob H
Posts: 5807
Date Joined: 18/01/12
Yes heavier cable will
Yes heavier cable will "probably" fix the problem.
But remember it is like a chain, only as strong as the weakest link.
Check for loose or corroded connections, damaged cable insulation, dodgy crimps etc first
VHF on 25W does draw a fair bit of power but what do you call "drastically"?
If that is the only noticeable problem then it may be manageable without replacing the cable, just check the stuff above.
If the plotter isnt dropping out, its probably not the end of the world.
Also, with your VHF best practice would be to use the lowest power setting and only use Hi (25W) if noone responds.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
ranmar850
Posts: 2702
Date Joined: 12/08/12
yes to the heavier wire
And, as others have said, if you are re-using any part of the original house supply, make sure everything is clean, tight and dry. And don't assume any existing cables are Ok internally, even if they look thick enough--if salt water works its way in, you get the "green death", and resistance to current flow goes up dramatically , causing voltage drop. Usually a 6mm2 House supply is enough for smaller boats, you won't get voltage drop over that length at the normal sort of loads you are likely to put on it. You may also consider fitting a VSR across that battery switch--if you connect it straight across the terminals that join the two batteries when you go Both, you will be charging that house battery the whole time your motor is running, but Your House load won't draw from your Start battery when the motor is shut down.
sea-kem
Posts: 15028
Date Joined: 30/11/09
Thanks for that info Ranmar,
Thanks for that info Ranmar, I'm getting close to refitting the project boat I'm doing and the main cabling size to the bus board was on my mind.
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ranmar850
Posts: 2702
Date Joined: 12/08/12
I'd call 6mm2 a minimum
Fine for boats that are just running a 7' combo and a VHF--I had to run a new feed (6mm2) for the Dommie when I got it, had an Elite-7HDI, plus another standalone GPS, 27mhz and VHF, plus large manually switched Rule bilge pump, and never had any issues.
For the new rig, I chose 6 B&S, which is 13.2mm2--that should be enough for all the fruit. Electric capstans and anchor winches have their own separate supplies, of course.
sea-kem
Posts: 15028
Date Joined: 30/11/09
yeah only running the
yeah only running the standard stuff, sounder combo, bilge pump, stereo, 27meg ,VHF and running lights when needed. I'll have a dual battery system which I reckon should be standard on all new boats.
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Rob H
Posts: 5807
Date Joined: 18/01/12
6B&S is what I ran as well,
6B&S is what I ran as well, sourced from BCF if I remember correct, tinned wire.
I run stereo, VHF, big light bar, Furuno, Lowrance and power outlets thru it with no problems.
The fridge runs direct off the stb battery with its own supply not thru the main supply.
I dont run a house battery as such, instead using one of the 2 outboard batteries.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
sea-kem
Posts: 15028
Date Joined: 30/11/09
Cheers Rob, I reckon I'll be
Cheers Rob, I reckon I'll be well within then. I've just oredered 10m 6mm dual core marine grade tinned wire off Ebay for $40.
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Rob H
Posts: 5807
Date Joined: 18/01/12
6 B&S and 6mm not the same!
6 B&S (AWG) and 6mm not the same!
6 B&S is 13mm2
Need to be a bit careful as sellers are a bit tricky.
6mm can be 6mm2 or 6mm dia but 6B&S (same as AWG) is completely different but confusing
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
scottnofish
Posts: 1621
Date Joined: 28/08/07
I run 16 mm2 on mine
Never had my sounder or gps shutdown .my mate has same boat only running 6mm2 and sounder shutsdown when starting engines.always go bigger than you think you need .6mm is good for about 30 amps but by the time you add up sounder gps,stereo,deckwash , vhf ,lights and what ever else you have running it soon adds up.if anyone is after cheap battery cable just let me know i can get any size cheap
sea-kem
Posts: 15028
Date Joined: 30/11/09
Probably everyone except me
Probably everyone except me eh? :P
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randall df223
Posts: 6454
Date Joined: 08/08/11
Is 16mm2 the cross section
Is 16mm2 the cross section area of the tinned cable? And how does this equate / compare to something that is marketed as 6mm (eg by whitworths) ??
Should i be sourcing it from somewhere else?
Fish! HARD!
sea-kem
Posts: 15028
Date Joined: 30/11/09
Mind blown Rob, you have me
Mind blown Rob, you have me there lol.
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Starbug
Posts: 563
Date Joined: 27/08/09
Just beware of the amp
Just beware of the amp ratings. the 50A stated is its maximum current draw it can handle without melting the insulation.
A 4m run of 4.58mm2 at 50A will see a 1.544V volt drop. Around 13%.
I generaly aim to keep volt drop to within 4%
When calculating your volt drop in tthe circuit keep in mind the return circuit. A 4m run is actully a 8m of cable.
Rob H
Posts: 5807
Date Joined: 18/01/12
as youve said
I have never quite got how they can quote an amp rating for a cable.
The amp load/volt drop is a factor of the length of the cable run so 50 amps down a given cable size at 1 meter will be totally different to a 10 meter run.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
Starbug
Posts: 563
Date Joined: 27/08/09
Yes. 50A is the maximum
Yes. 50A is the maximum current before the cable insulation is overheated. Its big, impressive, and makes people buy it! Its not wrong, just misleading!
sea-kem
Posts: 15028
Date Joined: 30/11/09
Foer what I'm running I
Foer what I'm running I think it will be fine.
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Dale
Posts: 7930
Date Joined: 13/09/05
Go 6mm as a minimum, that should sort any voltage drops.
"Just because you are a Character, Doesn't mean you have Character."
Mr Wolf
Deleted
Posts: 6265
Date Joined: 26/04/14
if its never done this
if its never done this before i would be looking for the green death
sea-kem
Posts: 15028
Date Joined: 30/11/09
Yeah it was all through my
Yeah it was all through my batt cables when I gave the boat a birthday before Xmas.
Love the West!
ranmar850
Posts: 2702
Date Joined: 12/08/12
Tinned cable will certainly slow it
But you can never escape it completely. Tinned cable, and make sure the end of the sheathing where it has been cut is completely sealed will give the best life. Were you getting bad starting issues with the stuff through the cables?
sea-kem
Posts: 15028
Date Joined: 30/11/09
Yeah I checked the main
Yeah I checked the main battery earth cable and that was rotten. The main battery cables still fine all sealed an uncompromised. I changed out bilge and running lights cables.
Love the West!
randall df223
Posts: 6454
Date Joined: 08/08/11
No it has always been an
No it has always been an issue. When i re-wired the front of the boat i used tinned marine cabling rather than the auto and heat shrinked all the connections. But i havent replaced the cable from battery to buzz board and i think that a) isnt 6mm, and b) isnt tinned.
I do want to go for the vsr eventually. For now though i start on the motor on "1" and let it charge for a bit before switching over to "2". I never run on "both".
The voltage alarm has been set to 10 or 11 volts (cant remember which) and regularly goes off when i use the radio if the charge is going into the cranking battery.
Will replace the cable with 6mm tinned and see what difference it makes.
Cheers for the responses.
Fish! HARD!
Dale
Posts: 7930
Date Joined: 13/09/05
https://www.redarc.com.au/images/uploads/files/wire_gauge_worksheet.pdf
"Just because you are a Character, Doesn't mean you have Character."
Mr Wolf