Boat electrics help with 2x12v batteries

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#1946094 24-Jan-2018 15:51

MikeAqua: Good idea for weight distribution. For the heavy leads for you trolling motor ... when you know where you will mount the circuit breaker (some shelter is best) ...

Have an auto electrician make up and terminate any heavy duty cables. You are looking for tinned cable and a gasless crimp which is usually a hex or radial crimp. Not soldered and not a punch crimp. You then want adhesive heath shrink over top of the terminal and a few inches of the cable.

What is the thinking behind not soldering the cables? Reason I ask, Is that in my van. The alternator output was wired to a double crimp terminal on the starter motor, and from there to the battery. The alternator output current made the terminal get really hot, which then melted the plastic end cap on the starter solenoid, the B+ terminal then started migrating through the molten plastic. I was very lucky that it didn't touch the metal sides of the solenoid housing. Otherwise I would have had a direct short through the starter cables.

All because that connection wasn't soldered after it was crimped. Alternator is rated at 120A so even 0.1ohm can cause excessive heating at that current. And trigger thermal runaway. The other end of the alternator cable is soldered as well as crimped.

Hatch

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#1946095 24-Jan-2018 15:51

MikeAqua:

Ooops - I've edited out the offending spelling errors .

As you only have two devices I would connect them separately direct to the battery a via a Circuit Breaker or fuse.

It would be preferable to buy a battery with threaded stainless steel terminal posts. This will allow you to use 316 stainless nuts and lock washers to secure your leads. If threaded posts aren't an option look for the terminals posts with holes through them so you can fit stainless bolts, lock washers and nuts. Either allow you simply disconnect the leads at the battery when you remove it for charging and securely re-connect them. Fishfinders don't like the intermittent connections which can result form other types of battery terminals like clamps and wing-nuts.

I suggest a separate sealed in-line fuse holder (blade type) for each of the (+) the 12v leads. You only have two of them so this is the simplest option.

The power draw of the fishfinder will probably be trivial and suited to 2mm cable and a 5A fuse.

When you know the draw of the trim unit we can determine a suitable cable gauge.

For both I suggest doubled sheathed cable like this: https://www.burnsco.co.nz/productdisplay.aspx?categoryid=199&productid=12853&colour=

For wire-wire joins I suggest crimp joining sleeves - the kind with adhesive heat shrink insulation (http://www.narva.com.au/products/browse/heatshrink-terminals) At the battery ends of the leads use ring type terminals. In both cases over-lay with adhesive heat-shrink-tube. This gives a join that is double-sealed, glued and mechanically secured.

You can crimp those kinds of terminals yourself with hand-held ratchet crimping tool. I use this one from SCA
http://www.supercheapauto.co.nz/Product/SCA-Crimping-Tool-Heavy-Duty-Ratchet-Type/213236

I hope this helps.

Again Mike you are providing super-useful and what appears to me to be quite expert (or experienced) advice. If I was not able to get this type of advice here I would have sought it elsewhere from an equally suitably qualified person. Kind regards

MikeAqua

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#1946106 24-Jan-2018 16:29

Aredwood:
MikeAqua: You are looking for tinned cable and a gasless crimp which is usually a hex or radial crimp. Not soldered

What is the thinking behind not soldering the cables? Reason I ask, Is that in my van. The alternator output was wired to a double crimp terminal on the starter motor, and from there to the battery. The alternator output current made the terminal get really hot, which then melted the plastic end cap on the starter solenoid, the B+ terminal then started migrating through the molten plastic. I was very lucky that it didn't touch the metal sides of the solenoid housing. Otherwise I would have had a direct short through the starter cables.

All because that connection wasn't soldered after it was crimped. Alternator is rated at 120A so even 0.1ohm can cause excessive heating at that current. And trigger thermal runaway. The other end of the alternator cable is soldered as well as crimped.

Solder creates a stiff area in the cable. Under the forces experienced in small boats (vibration slamming etc),this can lead to a break at the end of the stiffened area. Crack a main cable and you have significant problems ... Under the ABYC standards, (which are legally binding in the US) it is illegal to have a solder as the only means of support for an electrical connection.

It sounds to me like in your case the cable/terminal was undersized or there was corrosion (increased resistance) or some other issue caused all that heat.

The type of crimp I'm referring to on heavy cables is evenly compressed around its circumference with a hydraulic press. The individual strand of wire are deformed against each other and against the inside of the crimp terminal. It's called gasless because there is theoretically no space within the crimp to hold gas. if you cut through one it looks like solid metal.

No gas = no corrosion and there is good conduction between the cable and the crimp terminal. The sticky heat shrink tube and subsequent liquid electrical tape offer further protection and the heat shrink tube stops the cable flexing to much right beside the terminal.

I did the heavy cables in my boat this way before my son was born. He is at high school now and they are still good.

Mike

MikeAqua

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#1946108 24-Jan-2018 16:34

Hatch:

Again Mike you are providing super-useful and what appears to me to be quite expert (or experienced) advice. If I was not able to get this type of advice here I would have sought it elsewhere from an equally suitably qualified person. Kind regards

I'm not an expert or qualified in anyway. I've learned from professionals and applied myself and found what works. Some of the work professional marine electricians do in the US is really nice. The legal standards (and litigation risks) are much tougher over there and you just know those guys don't want to re-do jobs.

Mike

Hatch

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#1947028 26-Jan-2018 10:30

Have just heard back from the manufacturer, the power draw for the tilt trim unit is 6.7 – 13.0 amps.

On the basis of this I am looking at a 25-30ah battery to power the tilt trim unit and the fish finder.

I want to keep it at this size in order to keep the weight down.

The tilt trim is only used for about 5-10mins max per boating excursion in my experience.

I may also look into the outboard charging circuit now.

MikeAqua

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#1948139 29-Jan-2018 13:58

Hatch:

Have just heard back from the manufacturer, the power draw for the tilt trim unit is 6.7 – 13.0 amps.

On the basis of this I am looking at a 25-30ah battery to power the tilt trim unit and the fish finder.

I want to keep it at this size in order to keep the weight down.

The tilt trim is only used for about 5-10mins max per boating excursion in my experience.

I may also look into the outboard charging circuit now.

For 13A I would power the trim unit with 2.5mm2 cable. It will tolerate almost 30A and if you protect it with a 20A fuse you can't overload it.

If you hook up the charging as well you will have three circuits. The simplest solution is still to use ring terminals on all six leads. Use standard-size waterproof in-line blade fuse holders (standard size) at the battery end of the (+) cables for the trim and fishfinder circuits.

I would consider a battery box with external terminals. Like this one from Burnsco. But: -

(1) Replace those useless wing-nuts with hex-nuts & lock washers (more secure);

(2) Replace the strap buckle on the webbing with a click-buckle like the type used on life jackets (faster).

When you get home you can quickly and easily unscrew the terminals, release the click-buckle and remove the whole box for charging.

What is the maximum charging current the engine can output?

Mike

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Aredwood

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#1948180 29-Jan-2018 15:01

Just check what kind of output the outboard charging circuit has. Some of them are actually a non regulated output. Meaning that you might overcharge your battery if you are going to be using the outboard for long periods of time.

Hatch

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#1948368 29-Jan-2018 22:16

MikeAqua:

For 13A I would power the trim unit with 2.5mm2 cable. It will tolerate almost 30A and if you protect it with a 20A fuse you can't overload it.

If you hook up the charging as well you will have three circuits. The simplest solution is still to use ring terminals on all six leads. Use standard-size waterproof in-line blade fuse holders (standard size) at the battery end of the (+) cables for the trim and fishfinder circuits.

I would consider a battery box with external terminals. Like this one from Burnsco. But: -

(1) Replace those useless wing-nuts with hex-nuts & lock washers (more secure);

(2) Replace the strap buckle on the webbing with a click-buckle like the type used on life jackets (faster).

When you get home you can quickly and easily unscrew the terminals, release the click-buckle and remove the whole box for charging.

What is the maximum charging current the engine can output?

Thanks, I have those battery boxes with external terminals already:)

According to the service manual, the output of the 25Hp Yammy is 12 v 80 watts.

Hatch

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#1948369 29-Jan-2018 22:18

Aredwood: Just check what kind of output the outboard charging circuit has. Some of them are actually a non regulated output. Meaning that you might overcharge your battery if you are going to be using the outboard for long periods of time.

I've done some research on it, and I'm not sure if my outboard has the rectifier required for charging. At the moment I'm still leaning towards not bothering with a charging circuit. All batteries will have to come out of the boat at the end of the day anyway.

kryptonjohn

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#1948409 30-Jan-2018 08:58

MikeAqua:

For wire-wire joins I suggest crimp joining sleeves - the kind with adhesive heat shrink insulation (http://www.narva.com.au/products/browse/heatshrink-terminals) At the battery ends of the leads use ring type terminals. In both cases over-lay with adhesive heat-shrink-tube. This gives a join that is double-sealed, glued and mechanically secured.

You can crimp those kinds of terminals yourself with hand-held ratchet crimping tool. I use this one from SCA
http://www.supercheapauto.co.nz/Product/SCA-Crimping-Tool-Heavy-Duty-Ratchet-Type/213236

I used these insulation displacement connectors for underground irrigation control cables:

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Scotchlok-Electrical-IDC-314-BOX-Pigtail-Self-Stripping-Moisture-Resistant-and-Flame-Retardant-Blue-22-14-AWG-50-per-carton-500-per-case/?N=5002385+3294772691&rt=rudhttps://www.amazon.com/gp/product/B00P1UENB6/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1

'moisture proof' ... so I plan to hang onto the leftovers and use them for various low-current boat wiring jobs - joining speaker and lighting wires etc.

Extremely quick and easy as no wire stripping required, inherently sealed and semitransparent so you can see the wires are inserted fully.

Fred99

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#1948419 30-Jan-2018 09:35

Be careful with rectified but unregulated charge circuits from many/most small outboards if used to charge batteries on boat circuits with electronics like VHF also connected.

The load from the battery usually keeps the voltage down and they're fine, but it's pretty common for people to have wires from the outboard and the wire to the boat switchboard on the screw terminal of a clamp type battery connector. If the connector comes loose from the battery terminal (ie from vibration) and the motor is at high RPM, then with no load from the battery, the charge circuits often outputs over 20v - and I've seen several VHFs fried this way.

For use for a trolling motor - though I don't use it for that - only as a outboard for a tender, I have a 2.5hp 4-stroke Suzuki. Unlike the small 2hp 4 stroke Hondas, the exhaust is submerged (not through-prop, but comes out under the cavitation plate). It's very quiet at low RPM, just a gentle "chuff-chuff" (the Hondas are much noisier). Has gearshift (fwd/neutral only - rotate to reverse) made in Thailand, quality seems okay, uses a tiny amount of fuel. Light enough (about 14kg) so that I can easily deal with it one-handed.

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Sounddude

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#1948432 30-Jan-2018 09:54

As a coastguard volunteer, I tend to do a lot of jumpstarts of people with flat batteries who can no longer start their engines.

If you can, I highly recommend keeping your starter motor battery separate from your house batteries (fish finder, radio etc).

That way you can always get yourself home, no matter how long you spend sitting and fishing.

MikeAqua

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#1948462 30-Jan-2018 10:02

Sounddude:

As a coastguard volunteer, I tend to do a lot of jumpstarts of people with flat batteries who can no longer start their engines.

If you can, I highly recommend keeping your starter motor battery separate from your house batteries (fish finder, radio etc).

That way you can always get yourself home, no matter how long you spend sitting and fishing.

Good advice for bigger boats. OP has a small boat with a 25 HP outboard which he can pull start.

Mike

MikeAqua

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#1948504 30-Jan-2018 10:23

kryptonjohn:

I used these insulation displacement connectors for underground irrigation control cables:

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Scotchlok-Electrical-IDC-314-BOX-Pigtail-Self-Stripping-Moisture-Resistant-and-Flame-Retardant-Blue-22-14-AWG-50-per-carton-500-per-case/?N=5002385+3294772691&rt=rudhttps://www.amazon.com/gp/product/B00P1UENB6/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1

'moisture proof' ... so I plan to hang onto the leftovers and use them for various low-current boat wiring jobs - joining speaker and lighting wires etc.

Extremely quick and easy as no wire stripping required, inherently sealed and semitransparent so you can see the wires are inserted fully.

I've seen good reports for scotch locks in low amperage applications like LED lights or NMEA-0183 in sheltered locations and they are quick and easy, l especially for fiddly little wires.

Personally I wouldn't use them in an open boat situation. They are water-resistant as opposed to waterproof and I wonder how well they will cope with vibration.

For the OP's purposes 13A is getting toward the upper current limit of a scotch lock although the trim will only operate for short period of time, which mitigates.

Scotch locks require the wires to run parallel while a sleeve joiner will allow wires to be joined end to end, which may be an advantage or disadvantage depending on your layout.

Mike

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#1948665 30-Jan-2018 15:32

Sounddude:

As a coastguard volunteer, I tend to do a lot of jumpstarts of people with flat batteries who can no longer start their engines.

If you can, I highly recommend keeping your starter motor battery separate from your house batteries (fish finder, radio etc).

That way you can always get yourself home, no matter how long you spend sitting and fishing.

Regardless of their membership status, there should be a surcharge for this sort of blatant "she'll be right" stupidity. It's not exactly unforeseen.

When Coastguard started offering unlimited assists I ceased being a member. In my mind it simply encourages the irresponsible at the expense of the responsible. I feel that's reflected in the membership cost rising from IIRC $35 p.a. to $115 p.a. since.

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