Boat electrics help with 2x12v batteries

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#1945916 24-Jan-2018 10:59

Aredwood: Any idea what the normal running current of the trolling motor is? As if it is 42A continuously, then those batteries will be flat after just 1 hour.

Note that normally you don't discharge lead acid batteries below 50% charge, unless it is a standby type application where the batteries will only rarely get used. And below 50% the output voltage typically starts to reduce quickly anyway.

Any reason why you can't just get a little 2.5HP or so outboard for trolling use? As it avoids the need for big and heavy batteries, and you will then have a backup to your main outboard as well.

Your electric trolling motor has a max output of around 1KW not allowing for motor efficiency losses. For comparison.

The trolling motor runs maximum 42A (according to specs), which would I assume would be at highest speed setting. There are 10 speed settings. I haven't checked its general running current. The trolling motor a Watersnake GPSmart 80, is really designed for a much larger boat, so typically it is only run at very low speed settings for trolling purposes e.g. setting 2-4.

Would prefer to stick with this setup, even with the hassle of batteries, due to the GPS function and quietness. Also this motor is forward mounted which frees up space on an already small dingy. Btw the boat is a Smartwave 3500.

Hatch

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#1945922 24-Jan-2018 11:09

MikeAqua:

I suggest sticking with the 24v for the trolling motor. This will be 2 x 12v batteries connected in parallel. If you change from 24v to 12v supply then you double the amps and the wiring may not be set up to accommodate the increased current.

I would use a heavy duty resettable circuit breaker like this one from Burnsco. Position the breaker on the positive lead powering the trolling motor, as close to the batteries as possible. It will also function as an isolation switch when you are not using the boat. The instructions for the trolling motor should specify what amp rating circuit breaker to use. Whatever you do make sure you use marine rated components.

I would definitely install a separate small 12v battery for the fishfinder and power trim. (e.g. a jetski battery).

Do you know how many amps your power trims draws?

Is your outboard electric or manual start?

Thanks, your advice is super-useful, especially re the breaker. There are fuses in the circuit already but a resettable breaker makes much more sense.

Yes I now plan to install a separate battery for the power trim and FF. This will also cut down on wiring as I intend to house the 12v batteries at the front of the boat with the trolling motor for weight distribution.

I have no idea about the power requirements of the trim tilt bracket. I bought it used and the online documentation doesn't provide any details. I have messaged the manufacturer for the time being.

The outboard is pull start.

1101

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#1945923 24-Jan-2018 11:11

Dont try & overthink it.
none of this is critical equipment.
Just connect tilt trim unit to one of the batts . Dont run trim & motor at the same time .
Have some way of checking each batts voltage: run them too low & you ruin them

Some sort of high current kill switch is a must have for the batts .

Coil

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#1945924 24-Jan-2018 11:11

I've never understood the need for a separate Trawling propulsion device.

Can't you just idle the outboard? Seems like lipstick on a pig.

We trawl for Marlin on one engine at minimum RPM. Sits around 6-8 kts.
In terms of those batteries. its not going to be the most ideal setup if you are also starting the outboard off of those batteries.
You ideally would want to have a single 24V battery and a single 12V battery for this.

Hatch

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#1945926 24-Jan-2018 11:14

MikeAqua:

nickb800:

If you go for a separate small 12v battery for fish finder etc then you may find that the charge output from the outboard is sufficient to keep it topped up. Then have separate 2x12v for trolling motor that you charge on land

Good point ... do you have charge output from your outboard?

Yes, but I will be removing the batteries when storing the boat anyway.

Hatch

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#1945928 24-Jan-2018 11:16

Coil:

I've never understood the need for a separate Trawling propulsion device.

Can't you just idle the outboard? Seems like lipstick on a pig.

We trawl for Marlin on one engine at minimum RPM. Sits around 6-8 kts.
In terms of those batteries. its not going to be the most ideal setup if you are also starting the outboard off of those batteries.
You ideally would want to have a single 24V battery and a single 12V battery for this.

Probably on a big boat it seems pointless, but on a small dingy an electric trolling motor is quite nice. Not only is it quiet, but also trolling a 2 stroke is not ideal with the fumes.

I'm going to stick with what I have and will be just rerranging the battery placement and wiring configuration.

AliExpress

Shop now on AliExpress (affiliate link).

Hatch

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#1945929 24-Jan-2018 11:17

1101:

Dont try & overthink it.
none of this is critical equipment.
Just connect tilt trim unit to one of the batts . Dont run trim & motor at the same time .
Have some way of checking each batts voltage: run them too low & you ruin them

Some sort of high current kill switch is a must have for the batts .

I don't disagree about overthinking it. However, a third battery at the rear means I won't need to run wiring from the front (where I intend to house the 12v batteries).

trig42

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#1945931 24-Jan-2018 11:24

Those electric trolling motors are pretty cool. Drift fishing - hit a good spot, push the button on the trolling motor and it will park you over the spot and keep you there.

Pretty cool. Just don't get your braided line wound around the prop (been there, done that :( )

MikeAqua

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#1945977 24-Jan-2018 12:21

Coil:

I've never understood the need for a separate Trawling propulsion device.

Can't you just idle the outboard? Seems like lipstick on a pig.

Stealth - which works well for trout or if you are stalking shallows for snapper or something like that.

It's also not good for some outboards to idle for long periods.

Also some electric trolling motors will function as virtual anchor holding you over a mark like groper-hole.

Mike

Coil

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#1945980 24-Jan-2018 12:23

trig42:

Those electric trolling motors are pretty cool. Drift fishing - hit a good spot, push the button on the trolling motor and it will park you over the spot and keep you there.

Pretty cool. Just don't get your braided line wound around the prop (been there, done that :( )

On the launch we got auto pilot that will hold positions and a large drogue that we can let out as well.
I now see the requirement for one, easy to hold a position in a small boat that is easily blown around or moved with the tide.

MikeAqua

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#1945999 24-Jan-2018 12:55

Hatch:

Yes I now plan to install a separate battery for the power trim and FF. This will also cut down on wiring as I intend to house the 12v batteries at the front of the boat with the trolling motor for weight distribution.

I have no idea about the power requirements of the trim tilt bracket. I bought it used and the online documentation doesn't provide any details. I have messaged the manufacturer for the time being.

The outboard is pull start.

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. I then overcoat mine in liquid electrical tape.

For your 12v system how many device do/will you have?

- Power trim

- Fishfinder

- Any others installed or planned?

I think you will find that your power trim draws around 25 amps meaning you can get away with something like AWG-10 wire if the 12v battery is housed in the stern. I can't comment on whether your outboard will charge your 12v battery. It depends on the type of outboard and how it is set-up.

Mike

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Hatch

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Ultimate Geek
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#1946005 24-Jan-2018 13:06

MikeAqua:

Good idea for weight distribution. Fir the hevay leads for you trolling motor ... whne you kniow whre you will kunt the circuit breaker (some shelter is best).

Have an auto electrician make up and terminate further 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. I then overcoat mine in liquid electrical tape.

For your 12v system how many device do/will you have?

- Power trim

- Fishfinder

- Any others installed or planned?

I think you will find that your power trim draws around 25 amps meaning you can get away with something like AWG-10 wire if the 12v battery is housed in the stern. I can't comment on whether your outboard will charge your 12v battery. It depends on the type of outboard and how it is set-up.

Some colourful language there Mike...

But very good advice about cables and connections. Previous owner did an ok job but connections were not waterproof and I need to replace. 12v system will only power trim and tilt bracket and fishfinder.

Outboard does have ability to charge battery, but as I will take batteries out at the end of the day, so long is the battery has sufficient capacity I can probably avoid an extra charging circuit just to keep it simple.

MikeAqua

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#1946061 24-Jan-2018 14:52

Hatch:

Some colourful language there Mike...

But very good advice about cables and connections. Previous owner did an ok job but connections were not waterproof and I need to replace. 12v system will only power trim and tilt bracket and fishfinder.

Outboard does have ability to charge battery, but as I will take batteries out at the end of the day, so long is the battery has sufficient capacity I can probably avoid an extra charging circuit just to keep it simple.

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.

Mike

cadman

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#1946075 24-Jan-2018 15:22

Hatch:

Thanks, good advice. I am completely confident that I can do this myself, with some assistance.

Unfortunately, Confidence ≠ Ability, despite what they're teaching in schools these days. We're suffering a over abundance of confidence that is rarely backed up by ability.

1101:none of this is critical equipment.

But an electrical fire in a boat is a critical situation you really should do everything you possibly can to avoid.

Aredwood: Any idea what the normal running current of the trolling motor is? As if it is 42A continuously, then those batteries will be flat after just 1 hour.

What's more, the Ah rating is based on a 20-hour use. A 80Ah battery can deliver 80/20= 4A for 20 hours. Increase that draw and their capacity is significantly derated.

Using them for significant durations at 5x their rated capacity, as in this 24V scenario, and they won't live long.

Hatch

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#1946090 24-Jan-2018 15:46

cadman:

Hatch:

Thanks, good advice. I am completely confident that I can do this myself, with some assistance.

Unfortunately, Confidence ≠ Ability, despite what they're teaching in schools these days. We're suffering a over abundance of confidence that is rarely backed up by ability.

1101:none of this is critical equipment.

But an electrical fire in a boat is a critical situation you really should do everything you possibly can to avoid.

I'm not rewiring my house for gods sake. What we are talking about here is a couple of very simple circuits with appropriate gauge wiring, circuit breakers and connectors.

What I said is that I have confidence, that with assistance (i.e. learning from and utilizing the abilities of others) this will be easy to do.

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