Author Topic: Battery cable size  (Read 385 times)

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Offline Neal

Battery cable size
« on: August 18, 2017, 08:24:24 PM »
Process of buying cables for battery move to cuddy.  I need 20 feet to and from. So 40 feet total length.  I have a Honda 135 with a 51 amp alternator.  So I went to blue sea chart and it says #2 wire.  Did I calculate right?  What size cable did most of use for battery Change to cuddy?   Thanks


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Offline Neal

Re: Battery cable size
« Reply #1 on: August 18, 2017, 08:34:18 PM »
One more question.  Since I am planning on putting a post where batteries were located in stern to hook up all wires and running cables from post to cuddy. The bilge wire will not be hooked up to battery and will only come on with battery switch on. I never plan to leave in slip.  So I guess ok if automatic bilge only comes on with battery switch on.  Thx


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Offline milos dad

Re: Battery cable size
« Reply #2 on: August 19, 2017, 09:19:21 AM »
One more question.  Since I am planning on putting a post where batteries were located in stern to hook up all wires and running cables from post to cuddy. The bilge wire will not be hooked up to battery and will only come on with battery switch on. I never plan to leave in slip.  So I guess ok if automatic bilge only comes on with battery switch on.  Thx


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I bought a new Rule 500 auto bilge pump to replace the functioning original pump.  The new pump comes on frequently to check for water.  I doubt that the amp draw is much, however, as my boat is mostly on the trailer, I installed a three way switch (momentary on, off, and on).  While on the trailer, I leave the switch off.  If at a slip, I would leave it on, and if draining the water when under power, momentary on.  I still like to be connected to a battery for the auto function, although rarely used.  I don't get rainwater in the boat with the trailering cover installed.
Rick
87 Sea Hunter with 94 Honda 45
2009 6 hp Merc kicker

Offline StreamFixer

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Re: Battery cable size
« Reply #3 on: August 20, 2017, 09:26:33 AM »
Look at the price difference between #2 and 1/0, then go with marine 1/0 and be done with it...  #2 might do, but 1/0 does it for sure and the cost is a one time thing.  I went with #4 and then had to purchase 1/0  Electrical system, especially main line to and from the battery, is not the place to save $$$ when working on our boats.

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline Neal

Re: Battery cable size
« Reply #4 on: August 20, 2017, 12:45:02 PM »
Thanks steamfixer.  I went to seawave systems and they say I need a 3/0 with 135 amp. 40 feet and 3% drop.  I choose 135 amp for hp of motor/ Honda 135.  Which some said to calculate amps.  This is a very confusing topic.  Go to four websites and get four different answers. 


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Offline StreamFixer

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Re: Battery cable size
« Reply #5 on: August 20, 2017, 02:32:38 PM »
You should be able to find starting amperage draw for the motor in the manual or call a dealer/installer.  add 20% and you should be safe.  The starter amps are only required for a minute or so until the motor catches then demand will go down to just a few amps to run the whole system.  That may help you to understand the difference between a starter battery and marine battery needs.  One is built to deliver a hell of a lot of amps for a short duration, the other, fewer amps but for a much longer period.

You are designing (building) a system to handle starting starting...  The rest will take care of itself.

StreamFixer
'97 19SC w/ Salt Boss Top
'03 Yamaha 115 EFI
'05 Yamaha T8 Solas 4 blade prop

"By the grace of God we travel upon the rivers and sea..
They, like He, are mightier than me."  Mike Jesperson aka 'Nalu'

Offline DevMah

Re: Battery cable size
« Reply #6 on: August 20, 2017, 07:26:06 PM »
Thanks steamfixer.  I went to seawave systems and they say I need a 3/0 with 135 amp. 40 feet and 3% drop.  I choose 135 amp for hp of motor/ Honda 135.  Which some said to calculate amps.  This is a very confusing topic.  Go to four websites and get four different answers. 


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Neal may I ask where you got the 135Amps from...I hope you are not confusing 135hp with 135A.

FYI
My Yammy 150 draws between 100 and 125A temperature dependant.

The calculation done for 135A @ 40' is correct.

http://circuitwizard.bluesea.com/


Dev.


2015 21' Sea Ranger
2015 Yamaha F150
2013 Mercury 9.9 Bigfoot 4 blade
2012 Lund 1650SS  w 2012 60HP Mercury-Sold

Offline Neal

Re: Battery cable size
« Reply #7 on: August 20, 2017, 07:38:21 PM »
I saw a post that said rule of thumb is engine hp is amps.  I cannot find anywhere amp draw for Honda 135.  I think I will get 1/0 like stremfixer said. 


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Offline DevMah

Re: Battery cable size
« Reply #8 on: August 20, 2017, 08:04:33 PM »
I saw a post that said rule of thumb is engine hp is amps.  I cannot find anywhere amp draw for Honda 135.  I think I will get 1/0 like stremfixer said. 


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You are confusing working hp.... 746 watts equals 1hp.

The starter draw for your engine is the required current to make your starter turn...not working output hp of your motor.

FYI
80Amp draw at 12v 3% v-drop @ 40' would give you 1/0
100Amp draw at 12v 3%v-drop @ 40'  would give you 2/0
125Amp draw at 12v 3%v-drop @ 40' would give you  3/0

It's hard for me to tell your exact draw but you would be in the range of 80 to 125A. Do you know anyone who has a clamp on Ammeter?

Dev


« Last Edit: August 20, 2017, 08:16:21 PM by DevMah »
2015 21' Sea Ranger
2015 Yamaha F150
2013 Mercury 9.9 Bigfoot 4 blade
2012 Lund 1650SS  w 2012 60HP Mercury-Sold

Offline Neal

Re: Battery cable size
« Reply #9 on: August 20, 2017, 08:12:17 PM »
Thanks


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Offline Neal

Re: Battery cable size
« Reply #10 on: August 20, 2017, 08:14:54 PM »
I have a 100 amp fuse on engine so would I be safe to put in 100 amps. And then I should get a 2/0. Now leaning towards 2/0.  Getting expensive.  I already started so cannot stop now and I already bought two optimum blue top batteries.  Thanks for your help.


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Offline DevMah

Re: Battery cable size
« Reply #11 on: August 20, 2017, 08:17:06 PM »
No problem
if you are fused at 100 then that's the max draw 2/0 would me my recommendation based on your 40' length.

Dev
2015 21' Sea Ranger
2015 Yamaha F150
2013 Mercury 9.9 Bigfoot 4 blade
2012 Lund 1650SS  w 2012 60HP Mercury-Sold

Offline Neal

Re: Battery cable size
« Reply #12 on: August 20, 2017, 08:25:17 PM »
Thx


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Offline Cannon

Re: Battery cable size
« Reply #13 on: August 22, 2017, 07:00:14 PM »
Process of buying cables for battery move to cuddy.  I need 20 feet to and from. So 40 feet total length.  I have a Honda 135 with a 51 amp alternator.  So I went to blue sea chart and it says #2 wire.  Did I calculate right?  What size cable did most of use for battery Change to cuddy?   Thanks


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If you go with AWG 2, your voltage drop will be 8.03%
If you go with AWG 1 your voltage drop would be 6.37%
If you go with AWG 1/0 percentage of voltage drop will be 5.5%
Less than 5% is good, especially when you are starting your OB!
You should use tinned wire when you change it out, and it ain't cheap, but if you fish the salt it will stand up to the corrosion. I bought all of my wire from http://www.genuinedealz.com/ and I was very happy with the prices compared to local prices. The also provide free shipping which makes it apples to apples!
Remember, the ark was built by amateurs; while the Titanic was built by professionals.

Offline Cannon

Re: Battery cable size
« Reply #14 on: August 23, 2017, 08:20:27 AM »
I have a 100 amp fuse on engine so would I be safe to put in 100 amps. And then I should get a 2/0. Now leaning towards 2/0.  Getting expensive.  I already started so cannot stop now and I already bought two optimum blue top batteries.  Thanks for your help.


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You won't be sorry! I went with 3/0 and it made a world of difference!
Remember, the ark was built by amateurs; while the Titanic was built by professionals.

Offline wedocq

Re: Battery cable size
« Reply #15 on: August 23, 2017, 08:56:39 AM »
Neal,
Please post a picture of your "post" you are planning on putting in the back of the boat. I am having a hard time picturing what you are talking about. I think some of the guys here will be able to steer you in the right direction with this.
-Shawn
2002 21' Arima Sea Ranger HT  Suzuki DF175 4-stroke.
WEDOCQ= WE DO SEKIU! It pays homage to my Uncle Jay who died of cancer.