Battery--Battery Cable to the center console question: Can I splice the battery cables to get more length?

T

TMan

Well-Known Member
Or.....is this just a bad/unsafe idea?
I am trying to figure out where to put the battery in my 16.5' aluminum center console. There isn't much room in the back, and I thought I might need or want to run two batteries at some time in the future. So I am thinking of tucking it all up under the console.
The cable that came with my engine is 8' (from the outside of the engine) to the terminal ends. Engine is a Tohatsu MFS 60, (21A alternator) and the cables from the factory are 000.
If I want the battery under the console, can I just use butt connectors (soldered and heat shrunk) to extend the cables? Total length once connected would be 15'.

The alternative is to just leave the cables alone, put the battery at the back, with the switch, and run power wires up to the console for the switches and nav lights and all the rest of it. Here's a pic of what I'm working with.
Any thoughts? I appreciate any advice given.
20210205_124351.jpg
 
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our battery in our 16’ center console is at the back i would talk to a marine mechanic but i believe our , riggers, bilge and Vhf are wired to a panel at the back directly off the battery , in the event of wiring trouble you can retrieve your cannonballs, bilge and VHF still work so you can stay afloat and call for help without needing to diagnose wiring troubles at sea.
 
If you can splice those cables, I would definitely get your battery (or batteries in the future) forward and under the console for 2 reasons. First, it’s better to have the weight forward in most boats, as it makes for a better ride. Second, it’s better to keep the batteries and as much wiring as possible away from the back of the boat, which is usually a lot wetter than under the console. Moisture equals corrosion. And if you take a wave over the back, your less likely to have an electrical failure.
 
Doesn't look like you have much protection under those gunnels... but, if you ran your existing wires from the back (starting) battery - to a battery switch in a waterproof box - say under the starboard gunnel - then you could run from there to the second (house) battery in the console.
 
TMan said:
Or.....is this just a bad/unsafe idea?
I am trying to figure out where to put the battery in my 16.5' aluminum center console. There isn't much room in the back, and I thought I might need or want to run two batteries at some time in the future. So I am thinking of tucking it all up under the console.
The cable that came with my engine is 8' (from the outside of the engine) to the terminal ends. Engine is a Tohatsu MFS 60, (21A alternator) and the cables from the factory are 000.
If I want the battery under the console, can I just use butt connectors (soldered and heat shrunk) to extend the cables? Total length once connected would be 15'.
Click to expand...
Yes, move the batteries ahead. Your cable guage is fine. I'd forget the solder and use the appropriate crimp ferrules and 2 ply shrink tubing to make the splice. Hammer crimpers are cheap and for occasional use they do a fine job.
 
Thanks folks. All good ideas. I'll have to think about it. I've flip flopped on where to put the battery more that a fish in a bucket. If I put the battery at the back I have to make that space for it and the switch. But for a couple of bucks I could spring for a full length starter cable and pit them in the console- which was the original idea.
I'll let you know how it goes.

Thanks again.

Trevor
 
Battery in the console would be the best option, it will keep it dry and easy to access, and keep the rest of the wiring in a more centralized location.

as far as splicing goes I would not recommend it, you would be surprised how much that will compromise the run. save yourself the headache and get a solid run. keep in mind even the plastic sheathing is permeable, I’ve seen 4/0 cable rot out completely mid run because it had a drip from cooling water hitting it, a splice is even more susceptible, and really needs to be done with a solderable type butt connector and also needs to be crimped with a proper crimping tool if attempted, but is far from ideal.

FYI those splice kits are not for marine use, not worth the insurance risk.
 
If you increase the length, increase the wire thickness. You get voltage drop on starts and it will make it harder to crank. Maybe not a big deal with a healthy battery but over time it may become harder to start.


300 amp starting - 3m 1 gauge.
Voltage drop: 0.73
Voltage drop percentage: 6.10%
Voltage at the end: 11.27

300amp starting - 6 m 1 gauge
Voltage drop: 1.46
Voltage drop percentage: 12.20%
Voltage at the end: 10.54

300 amp starting - 6 meter 3/0 awg
Voltage drop: 0.73
Voltage drop percentage: 6.08%
Voltage at the end: 11.27

I dont know your motors starting current, but a good example all the same. Find a calculator and size it appropriately. A splice, even a good one would also add resistance and voltage drop, along with as others stated, an potential source of failure.

This is why most batteries are very close to the motors. Starting currents are very high, and once you have long distances, you need very thick copper.

For me there would be piece of mind knowing it was done right.
 
As Marco stated voltage drop is a big consideration, remember when your looking at the wire size calculators you need to understand 12v is a round trip so if your battery is 15' away you need to calculate for 30' ( +/- runs) and solder is a no no in high current connections, a proper crimp is all that's needed.

While a splice can be done for the peace of mind I wouldn't suggest it with out the proper equipment.

I would go to your local welding supply or somewhere that sells welding cable and buy 2 lengths you need and have them crimp on the appropriate ends if you don't have a crimper.
 
Sr SQ said:
As Marco stated voltage drop is a big consideration, remember when your looking at the wire size calculators you need to understand 12v is a round trip so if your battery is 15' away you need to calculate for 30' ( +/- runs) and solder is a no no in high current connections, a proper crimp is all that's needed.

While a splice can be done for the peace of mind I wouldn't suggest it with out the proper equipment.

I would go to your local welding supply or somewhere that sells welding cable and buy 2 lengths you need and have them crimp on the appropriate ends if you don't have a crimper.
Click to expand...
Don’t use welding cable, it is not rated for marine use, the flexible sheathing is not as tough and its more permeable than marine grade cable, also more flexible makes it more likely to move around/chafe and wear through the housing. It also generally only comes in black, meaning you will have to differentiate the cables with color coded shrink wrap ends, this is always advised against as the risk of accidentially reversing connections is not worth it. Just get standard marine grade DC red/black or the new safety Red/Yellow wire colors as these are the accepted color codes that cannot be easily mistaken.

also while yes simple solder connections are not used in high current applications as the risk of heat causing the solder to melt and the connection to fail are too high, but this will only happen if the wiring is undersized or not protected as standards dictate, and this would also assume they are not crimped. I did state that it was to be crimped and soldered, this is very common in high amperage connections like large electric drive motors in ships, I have actually gone inside these motors (9000hp ones) to replace brushes and had to make new connections to windings in this manner, this is also the reason you can buy pre tinned lugs and connectors.

regardless, there should not be a crimp in a main starting circuit in a marine environment.
 
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Hey everyone! Thanks for all the replies. I hadn't looked at the thread sinc
All good stuff, and I learned a lot.
On Monday I ended up calling the folks who are going to run my engine in (I just mounted it myself this weekend!) and asked about putting the batteries in the console, and they said they could run a cable up there for me. They have some and they do it all the time. Whew! So now I'm not running around trying to find cable anymore. I feel much more comfortable with that now.
Hey Howzer, Yes I could fit two batteries in the console. Will take up a bunch of space, but will have room left over. I can sit in it while bolting in the gauges. (legs sticking out of course)

Trevor
 
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