Re-cabling batteries

Had a problem last Tuesday out at sea. Couldn't start my Suzuki DF250 motor.

Managed to start easily back home with a different battery connected directly to the motor, and then started easily on the existing battery/ies connected directly.

Pulled out the old cables and found severe corrosion on the lugs particularly on the earth cables so I have decided to replace all cables from the batteries

Question would you use 25mm2 (3 B&S) tinned cable or 2 B&S (32mm2) not tinned.

I believe both can handle the approx starting current of about 100 amps. I intend to solder the cable, crimp with an hydraulic crimper and then solder the open end of the lug to exclude moisture and will also seal over the sleeve of the lugs with glue lined heat shrink.

Also have a 180 watt solar panel which is currently connected in parallel on a 2nd battery switch. Can anyone advise if this is the correct way to connect a solar panel

Thanks in advance for any answers



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Posts: 11

Date Joined: 17/09/15

 I wouldn’t solder the cable

Tue, 2018-06-05 10:09

 I wouldn’t solder the cable first, it will compress the solder in the lug and create a loose connection over time (if you can even get a decent crimp on it after soldering) Crimp only, then solder the open end of the crimp if you like, the glue backed heat shrink will be beneficial also.

Rob H's picture

Posts: 5055

Date Joined: 18/01/12

 Sounds as though you dont

Tue, 2018-06-05 10:28

 Sounds as though you dont have a dual battery setup, probably a wise investment on an outboard of that size?

Johns right though, solder after crimping.

If the cable is tinned its easy, not tinned then tin it first (solder end and shake solder off while still molten.

100 amps-I would have maybe expected a bit higher than 100 amps peak, but its only very short duration.
When it was starting ok, did you get electronics dropping out/beeping when starting?
If so thats a warning sign something may not be 100%, say dodgy cable/earth/battery condition, cable size etc


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Posts: 252

Date Joined: 13/08/11

In a wet and salt water

Tue, 2018-06-05 13:35

In a wet and salt water environment tinned wire is the only way to go, copper wire is always going to be temporary.

Posts: 482

Date Joined: 21/05/12

 on a run on most boats under

Tue, 2018-06-05 16:25

 on a run on most boats under 2m 3b&S is fine

Gotta be tinned

I always thought im the bloke - crimped then soldering

seems i was wrong, young  bloke comes onto the boat im engineer on 12 years ago and show me articles on testing done

solder wicks into the wire - then also because of annealing action of heat softens and weakens copper makes it bend more -right next to where the crimp is - which leadsto a weakspot right next to connection where u also cut open the wire insulation sure u getting where this is going

that with the flux in the solder  leads to a very high rate of oxidisation in the copper makes for a weak connection -whre there is no insulation either to protect against salt spray or stop it bending


solder is out in both the marine and automotive market low voltage and aerials- just looks at your car wiring/ factory outboard fittings its not crimped to only  save money


crimp - crimp only and get a  good crimper - the $7.50 special with some crimp on connectors included  aint it!

decent crimpers mostly  look a bit like boltcutters 

ericl i have crimpers and some others odds - probably some lugs  i buy em in quantity , i then use a good water inhibiting grease - rocol product-not specifically made for it but boy it works and a waterproofing tape over it

theresa north sea oil rig where we did "exposed connections to a crane starter motor like this - 7 years on the rest has rusted but the bolted straight onto our connectors when they rpelaced the motor 

if u need to borrow pm me 

put money on it- if u cut of the first 7- 15cm of the existing cables they will work might even be less, the factory cable on the suzis is good cable imo



Ericl's picture

Posts: 233

Date Joined: 02/05/11

Cheers for that

Fri, 2018-06-08 12:01

Hi and thanks for the advice / replies.
I did do a response post, but unfortunately it didn't save properly. Not sure what I did wrong so doing again.
Firstly, I am now pretty sure it was a bad earth. The earth cable at the lug was green and the wires pretty black and corroded. Also, the fact that neither battery 1 or 2 or both made any difference makes me believe that the common factor to all 3 of these scenarios is the earth (negative battery connection)
From the advice given, I have ordered some tinned cable and will replace completely. I wont solder before crimping, but will solder the end closed to prevent any moisture getting in from the front. I will also use heavy glue lined heat shrink that will cover both the sleeve of the lug and extend some way up the cable to ensure water tightness.
Re dual batteries, I do have a dual battery setup but as the fault now seems not to have been batteries but the earth, dual batteries didn't help in this instance. I will be keeping high quality jump leads with lugs and not crocodile clips on board so I can totally bypass the cables / battery switch in the event of any future problems. I have a 36 volt Minn Kota and can use one of the 130 Amp Hour batteries if necessary ( This is the first time I have had an electrical problem in my 40 or so years of boating so hopefully will never happen again)
Shark1, thanks for the offer of tools. I do have a decent hydraulic crimper with crimp dies up to 70mm so will be OK on that. Also some lugs knocking about so all good. Re grease, I see there is a product from Wurth which is advertised as a battery terminal grease. Available on ebay for about $23.00. I believe some people simply use vaseline ?
Thanks again all for the info - Eric


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Ericl's picture

Posts: 233

Date Joined: 02/05/11

Cables replaced

Mon, 2018-06-18 20:54

Hi again

Quick update. Replaced both postive cables and the negative cable. All works great.

Starts on battery one, starts on battery 2 and starts on both. All with no sluggishness on the starter.

Also had instruments and radio on and none lost power during start, so pretty sure all is now good

Cheers - Eric


Don't spend all your money on beer, boats, and fishing. Save some to spend foolishly