Battery Wire gauge for distance

[Yakfishingfool]

HI everyone, thanks in advance for any info you can offer. This is a new to me motor and I have it on a J16 skiff. I want to put the starting battery forward so need to run new wires from battery to motor. Can I get away with 6gauge? It is about a 12 foot run maximum one direction. I believe the motor pulls 25 amps at start. I believe 6 will do it but was looking for some real application reports. Secondly has to do with the battery itself. If you know the j16 she is a small bot. I am fishing the everglades, back country shallow water. I am set up to tiller steer and want to move weight forward to balance. I also have a trlling motor and have been told a single battery for both is a real no-no. I get it. What is the smallest battery you can use as a starting battery. Can you get away with a 35aH 350CCA battery, like a motorcycle batter/tractor sized battery? 2 full-sized Lead acids are going to be way too much weight up in the bow. Any advice is greatly appreciated. Scott

[fairdeal]

I've re-read this several times, if there's an engine model mentioned I'm missing it.

But here is Yamaha recommended cranking battery minimums for smaller hp 4-strokes



I think you are going to want larger cable than 6 AWG for 12 feet each way.

[zenoahphobic]

You do have another choice: lithium battery.
Pro is they weigh nothing and you can use their full capacity.
Con is cost but somewhat offset by life. And require stricter charge control, and may become instantly dead and dangerous if discharged too far.

[Yakfishingfool]

Sorry guys, yes it is an F40LA. I was also thinking about 4 gauge. It is a big wire. But bigger is better. Looked at Lithium but still a bit temperamental and a bit out of my $$$ league. Thanks for the input. S

[zenoahphobic]

Sorry guys, yes it is an F40LA. I was also thinking about 4 gauge. It is a big wire. But bigger is better. Looked at Lithium but still a bit temperamental and a bit out of my $$$ league. Thanks for the input. S

If you are only need a battery for starting you can get away with a much smaller capacity lithium battery. You need to see what motorcyclist use, some those those engines like big v twins need a lot more than your 40hp.
These batteries (in Australia) are barely double the cost, but less because a smaller capacity is all that is required. And I would think the cost of the extra length of thick cable would add another half to the cost anyway.

[Yakfishingfool]

Zeno, I am seeing the 400 CCA Lithiums for the v-twins. Certainly at a price point I could live with. Have you seen anyone use one as a starting battery for an outboard? Also since so light would not require moving battery. Can put a big old lead acid variety upfront for the *****in motor. Thanks for the heads up.

[walleye1]

You guys are annel about thish shit, make it simple use the heaviest you can,.

[99yam40]

I am still trying to figure out how the OP came up with the starter only needing 25 amps

[zenoahphobic]

I've not seen, only read about lithium batteries for large capacity bikes. But I do have lithium (don't know the sizes but they are small) one in my WR250R and one in my XSR 700. The thing is they both start with a blip on the starter button. But what is noted, that if more sustained cranking is required the battery does it without showing any fading.

These are Life, I have a lot of experience with Lipo and found that they have incredible current giving capacity like Life (this is why they are far more dangerous than conventional leadacid) and this is why you need to rethink the size when changing from leadacid.
So the CCA rating comes into question. There is no way your outboard uses 400 amps to crank, or almost anything even car V8s! That spec of a leadacid battery I think is a sustained 400amps for a minute providing ADEQUATE voltage doing so.
With lithium they can sustain a much higher discharge at a higher voltage for a longer time. This is where actual capacity specification is the key. I do not know the current your 40hp needs but I suspect under 100 amp (not taking into account actual startup current that the lithium battery way way outperforms leadacid. Ie can deliver higher amp requiring a much shorter duration that actually uses less energy).
There is one more important superior difference that should be taken into account and that is the superior ability of lithium to take up charge, a flat lithium maybe 1 or 2 hours to full, a leadacid more like 10 hours and at appalling efficiency. This is why Leadacid batteries are specified "large", they need extra stored capacity as often when they are needed again they actually haven't recovered the loss from the previous cranking, affectively then being a smaller battery and so on. This is really the key in deciding the size required.
This is attested to the fact that often you here to go for the largest or heaviest battery, we seemed to need tons of reserve capacity, some sort of strange formula in our (and manufacturer recommend) heads.
Now if we maintain our engines properly, and why wouldn't we, we are going out to see; the engine should start quickly every time. So it is stupid logic that we would rather spend money on a bigger battery than on maintenance!
Of course I am only talking about a starter battery, for which it is widely accepted that it is common sense to have a dedicated battery for starting only.

[99yam40]

I would be thinking about the proper charging of the LIPO batteries.
I am not sure the regular charging system would be the proper way to do that or not.
the regular battery charges are not used on Lipo battery operated drill batteries

[zenoahphobic]

I would be thinking about the proper charging of the LIPO batteries.
I am not sure the regular charging system would be the proper way to do that or not.
the regular battery charges are not used on Lipo battery operated drill batteries

Correct.
I'm relatively new to these used as automotive batteries and am relying on what is said out there.
Yes they all say you need a different home charger, that is one that plugs into the wall. But when it comes to what changes need to be made to the automotive charging system, information becomes scant, and little recommendations are given, often sighting that "provided it is a newer vehicle just swap them over"!
I have difficulty in accepting that because automotive charging is far more aggressive and damaging to batteries because they try to charge the battery in the shortest time, whereas home charging is slower and gentler on the battery making it last longer?!
I think that is driven by marketing, as with leadacid batteries they only care if they only last a couple of years. We have all accepted that (we don't like it though, as they lasted longer in the past). So a battery maker and seller is not going to sell as many batteries if modifications are required, so long as it will last a "reasonable time".
It stands to reason that LiFe batteries have a different voltage, just coincidently and very conveniently, the series voltage of four of these cells just happen to almost equal six cells in Leadacid but not quite.
That is one thing that should be changed.
I suspect the detection of "fully" charged needs more careful electronics, as Lithium batteries cannot tolerate overcharging, they tend to need the "exact" quantity of electricity.
Having said that, these are differences that need attention near the fully charged state. Therefore less so important when the batteries have been or remain in a partial state of charge.
So in the OPs case that outboard probably puts out feeble charge but at probably too high a voltage under little load, "con*****ing" it may also be less important as it is with Leadacid at the moment. However because Lithium would be charged quicker that no load high voltage (maybe 17 18 volts) must be held down to the precise voltage specified by the lithium, so it would be prudent to add a little electronics there.

[Yakfishingfool]

So I was mistaken on the 25 amps. Yamaha says somewhere between 380 and up. I am probably not going to go with lithium, I love the idea, but I would need some form of management of the charging system coming out. So I am probably going to go with a motorcycle battery, something in the 20 pound range. Lots of good discussion.

[zenoahphobic]

You guys are annel about thish shit, make it simple use the heaviest you can,.

And sink the boat.

[zenoahphobic]

So I was mistaken on the 25 amps. Yamaha says somewhere between 380 and up. I am probably not going to go with lithium, I love the idea, but I would need some form of management of the charging system coming out. So I am probably going to go with a motorcycle battery, something in the 20 pound range. Lots of good discussion.

I raised this because of my knowledge in motorcycling.
And I have Yamaha motorcycles and Yamaha outboards and there is not much differences between the two simple charging systems - using permanent magnets in the flywheel and simple regulators that bleed to earth excess output. The motorcycles don't seem to have a problem in changing over the batteries; improved "oomph" starting, longer Life, and less weight and size. No downside accept perhaps cost that may even be neutralised in the long run.
Lead acid is being phased out, and soon lithium will be the standard and not an option.
I wish I had' ve known more when I replaced my Can Am Spyder battery last year🙂🙂🙂

[zenoahphobic]

And I like to add we trust figures given by the industry, and accept what they say how these figures are derived. We believe what is written on these batteries etc.sometimes to our detriment.
As another example in this electricity stuff.
Why do we get more cynical as we age? I'm 68. I've just bought (another) solar panel.... they are all the go, everybody is getting into these. Mine is a 160 watt meant for mobile 12volt battery charging (RVs, camper trailers, boats). So what should I expect it will do? We in Melbourne, Australia are told we have some of the best sun in the world. So on the sunniest, and cleanest sky, aiming it exactly perpendicular at the sun on midday, I connected it to a good three quarter charged deep cycle 12volt leadacid battery (typical state of charge not flat not full).....everything perfect.
What do I get: 4 amps!.... I calculated what I should get (160watts at 16volts equals 10 amps I thought), did it again... doubted that I knew how to multiply, so I rang and harassed my primary school arithmetic teacher accusing him of malpractice in that he must not have taught me how to multiply and divide. I wonder whether these solar panels work differently in the northern hemisphere where it was made (German approved it even says on the label).
My conclusion is they tend to be grossly overrated and the figures can't be relied upon in any calculations you may want to make. At peak, appear only 50%.... and what they may produce over a sunny day just count on a few percent. I know.... if I took them into outer space onto my private orbiting satellite, it is guaranteed to produce that output☹