Battery Cable Size

[sailingjupiter]

This years winter jobs will include fitting a second battery and a BEP Marine VSR.

So I need to have some battery cables made up for this. Will also replace the existing engine start cables as well. The engine has always been reluctant to start in the cold so this may (would it?) help with this as well. Upon reading the old survey for my boat it noted that the cables looked "a little thin". But I never did anything about it at the time and forgot all about it.

The engine is only a Yanmar 1GM10. Maximum length of cable is around 1.5 metres. The VSR will be by the batteries.

Also can anyone recommend a suitable supplier that will make these up with the terminal rings on? Is normal automotive start cable OK?

Many thanks.

 

[vyv_cox]

Last winter I embarked on a similar project, increasing my domestic batteries to three and adding a Red Flash AGM starter battery. I had seen various cable sizes quoted for yacht auxiliary starter use, including quite often 35 mm2. I visited my local automotive factor to enquire about purchasing the end fittings and cable. I found that 35 mm2 is very large, the size used by trucks and the like. When I looked at the starter cable for my camper van, a 2.8 litre Fiat, I found it to be considerably smaller. I then visited my local car parts shop, who only stock 20 mm2, that looks very like my camper van stuff. It also looks very like the cable I bought for my windlass, which runs the length of the boat. So I bought the 20 mm2 in red and black, with the crimp ends.

It performs well and is clearly sufficient for a Yanmar 3GM.

So far as crimping the ends is concerned, any decent automotive electrical factor will do it.

 

[KenMcCulloch]

Vyv's is good advice, I think. I rewired my 1GM10 2 years ago with 25 sqmm cable and it seems well up to the currents involved, doesn't get detectably warm at all even when the engine is reluctant to start and more prolonged starter operation is involved.

If you are looking fopr a mail order supplier http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php are good, will make up cables to your specification and can supply all sorts of other bits and bobs.

 

[neale]

This years winter jobs will include fitting a second battery and a BEP Marine VSR.

So I need to have some battery cables made up for this. Will also replace the existing engine start cables as well. The engine has always been reluctant to start in the cold so this may (would it?) help with this as well. Upon reading the old survey for my boat it noted that the cables looked "a little thin". But I never did anything about it at the time and forgot all about it.

The engine is only a Yanmar 1GM10. Maximum length of cable is around 1.5 metres. The VSR will be by the batteries.

Also can anyone recommend a suitable supplier that will make these up with the terminal rings on? Is normal automotive start cable OK?

Many thanks.

Personally I wouldn't be happy to size the cable by what looks about right. I would find out what load is going to be on them, measure the exact length of cable run and taking voltage drops into account, buy the right size. You may even get away with smaller than you think!

The biggest problem will be voltage drop if you undersize the cables, or fire risk if you seriously undersize them. Buying bigger cables than you need will unnecessarily lighten your wallet.

 

[Pete7]

Tony Brooks web pages are worth a read:

http://www.tb-training.co.uk/SYES.html

Pete

 

[snowleopard]

You say 'battery cables' but we're really talking about 3 things

Starter
Charging
Loads

You will need separate cables for each so you need to know the maximum load and the length of each. The load on the starter cable is the CCA (cold cranking amps) of the starter, on the charge circuit the max capacity of the alternator - 35 or 55 A. For the load, the total of everything you're likely to have running at once.

Here is a wire sizing table - it's in AWG so here's a conversion table to get you to sq mm.

Using 3% voltage drop is good practice but can make for some massive cables.

As for crimping eyes, you may find it cheaper to buy a selection of fittings and get your own crimper. A ratchet crimper for 6-10 mm dia will set you back around £20 from an electician's wholesaler like WFGrant.

 

[misterg]

...The engine is only a Yanmar 1GM10. Maximum length of cable is around 1.5 metres...

The GM series operating manual that I have has starter battery cable size recommendations in the key to the wiring diagrams.


1+2+3 <2.5m 20mm^2
1+2+3 <5m 40mm^2

(1+2+3 is the wiring from starter motor terminal through battery isolator(*) and battery and back to engine ground)

You can get ready crimped lengths from a decent motor factor, or Halfords, even.

* The wiring diagram shows an isolator in the starter circuit.

HTH

Andy

 

[vyv_cox]

A ratchet crimper for 6-10 mm dia will set you back around £20 from an electician's wholesaler like WFGrant.

Really? I was looking for one at the beginning of this year and couldn't find one anywhere for less than about £60. It is possible to pay £1000 for one! Finally I managed to buy a very old but good one from a forumite for £30.

I've tried searching WFGrant websites but they don't seem to be searchable.

 

[KRG]

Having chased poor charging and starting with lots of investigation and overhauling of alternator and regulator etc. I was still unhappy with the charge voltages and sluggish engine starts so I bit the bullet and ripped out all the heavy cable and replaced it with tinned AWG 1 cable; I used proper crimped ends which I made up using a hydraulic crimper I borrowed from a local electrical store and heat shrink covers for added protection.

I know the cable sounds a bit overkill but the engine spins fast and charging is at 14.8V, it has transformed my electric setup, there must have been lots of losses in the cables and connections so very worthwhile. I would highly recommend using the tinned very flexible marine cable even if you don't go as far as AWG 1.

Volvo 2002 with 50amp alternator, 147 AH vetus house battery, 85 AH starter battery

I got all the cable etc. here http://www.power-store.com/view-item.asp?itemid=1313&id=217&

 

[savageseadog]

Really? I was looking for one at the beginning of this year and couldn't find one anywhere for less than about £60. It is possible to pay £1000 for one! Finally I managed to buy a very old but good one from a forumite for £30.

I've tried searching WFGrant websites but they don't seem to be searchable.

I was the forumite in question, glad it's done the job for you.

You have to remember that a vehicle electrics is usually much shorter than a boat's and there are other issues like starting on flattened batteries which you don't normally get on a road vehicle. I would try to go for at least 25mmsq whatever the length or 35mm sq preferably.

 

[snowleopard]

Really? I was looking for one at the beginning of this year and couldn't find one anywhere for less than about £60. It is possible to pay £1000 for one! Finally I managed to buy a very old but good one from a forumite for £30.

I've tried searching WFGrant websites but they don't seem to be searchable.

I bought mine from WFGrant around 1999. It cost £16. It has a rounded pin about 5mm dia that it drives into the side of the fitting. Apart from the shape of the jaws it looks just like the type you use for red, blue & yellow fittings.

Here's one

 

[vyv_cox]

I was the forumite in question, glad it's done the job for you.

You have to remember that a vehicle electrics is usually much shorter than a boat's and there are other issues like starting on flattened batteries which you don't normally get on a road vehicle. I would try to go for at least 25mmsq whatever the length or 35mm sq preferably.

Yes, it's been great, thanks. Several others have borrowed it and all happy. After I bought yours I told my son who said 'Oh, I've got one, you could have borrowed it!'

My replacement cable matched the diameter originally fitted by Sadler, so I had no concerns as they have lasted 25 years.

 

[Pete7]

Picked up one of these from Barden couple of weeks ago, bit expensive but they are only round the corner so convenient. Will just crimp 25mm with two hands. Discount for some clubs and associations.

http://www.barden-ukshop.com/ext011-1257-p.asp