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Old 12-10-2019, 11:42   #1
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Electric setup dual 12V battery for 24V trolling motor

Hi all,

I've bought a 24V 160lb Haswing Protruar 5.0. This motor draws 100A max. The motor is powered by 2x 12V 180AH AGM batteries.

I want to be able to do the following:

Measure the voltage per battery to see the state of charge
Measue current draw of the system (https://s.click.aliexpress.com/e/DZ5Hp98k)
Disconnect the batteries without unplugging. For safety and convenience
Install one fuse per battery
Install a battery balancer/equalizer: 12V Lights and accesoiries will be installed later (https://s.click.aliexpress.com/e/sDveKfs4)
Convenient unplugging of the batteries, for charging and easily being able to take the batties out of the boat when necessary.

So...

I've made a scheme of all of the things above.. I'm not a trained electrician, so to make sure I'm not making a mistake somewhere and see the boat sink to the bottom in a flaming short circuited mess.. The grey rectangles are Anderson connectors. The charging connectors are not drawn in this picture.

Is there anyone here who can take a peek at my idea / scheme?

(attached)

Thanks!

Tonka
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Old 12-10-2019, 20:08   #2
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Re: Electric setup dual 12V battery for 24V trolling motor

Iíve thought about the concept, but with the 120lbs motor that draws 60 amps and LiFePO4 batteries. You better check that your AGMs will happily supply 100 amps. Also, those batteries are VERY heavy if you want to move them in and out every day... I donít quite follow your schematic so canít comment... I am very interested to hear more about the motor!
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Old 12-10-2019, 22:42   #3
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Re: Electric setup dual 12V battery for 24V trolling motor

The batteries weigh 48kgs each, so thats heavy enough :-) I just want to be able to disconnect them without any tools. But if itís not freezing or above 30 Celcius, Iíll leave them in the boat.

The batteries can supply 2700W constantly for max 15 mins. Thatís 225A at 12V. So 100A will be ok, I think?
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Old 12-10-2019, 22:48   #4
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Re: Electric setup dual 12V battery for 24V trolling motor

And what would you like to know about the motor?

It’s powerful, that’s for sure.

I purposely bought a bit overpowered motor. In the summer we will have the whole fam in the boat with kids in a rubberboat in tow and I want to get home with a bit of a chop and a headwind.
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Old 13-10-2019, 01:08   #5
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Re: Electric setup dual 12V battery for 24V trolling motor

Edit: I misread it at first.


It is a bit confusing because of the colours you have used. If you make the +ve on the lower battery through to the -ve on the top a grey line (same as the one to the equaliser) and the lower red line from the equaliser black it makes a lot more sense. Do I have that right?
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Old 13-10-2019, 01:48   #6
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Re: Electric setup dual 12V battery for 24V trolling motor

Is this right?
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Old 13-10-2019, 01:56   #7
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Re: Electric setup dual 12V battery for 24V trolling motor

Quote:
Originally Posted by TonkaNL View Post
And what would you like to know about the motor?

It’s powerful, that’s for sure.

I purposely bought a bit overpowered motor. In the summer we will have the whole fam in the boat with kids in a rubberboat in tow and I want to get home with a bit of a chop and a headwind.
100 A max @ 24 V = 2400 W = 3.2 HP flat out.

What size boat? That would probably drive the rubber boat with the kids in it OK , but family in boat + towing kids in rubber boat in chop and headwind? Dubious!


Quote:
The batteries can supply 2700W constantly for max 15 mins.

How long do you expect to take to get home in that chop and headwind at full throttle?
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Old 13-10-2019, 03:11   #8
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Re: Electric setup dual 12V battery for 24V trolling motor

Greetings and welcome aboard the CF, Tonka.
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Old 13-10-2019, 03:14   #9
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Re: Electric setup dual 12V battery for 24V trolling motor

Wellll..

3.2 hp in a regular outboard is perhaps not all that much. But most of the time people compare it with the speed a IC outboard can push a heavy boat forward with.

But that is not a fair comparison to make, I think.

HP is work in a period of time. So if you lower the speed required,, the amount of work per unit of time can go up. As you know, trollers are configured for heavy loads at relative slow speed. Big props, moderate rpm and relatively little pitch. so a large column of water can be pushed backwards at once.

The boat is 5m long (16ft?) and max weight fully loaded is 2300 lbs.

A single 12V battery (180Ah 10h) can deliver 225A for 15 mins. The max draw the motor asks is 100A. So I’m assuming that won’t be a problem.

Max travelling time is 30mins full throttle if needed.

I reckon this setup will suffice?
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Old 13-10-2019, 03:19   #10
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Re: Electric setup dual 12V battery for 24V trolling motor

Quote:
Originally Posted by StuM View Post
Is this right?
Yes it is!
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Old 13-10-2019, 03:56   #11
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Re: Electric setup dual 12V battery for 24V trolling motor

Quote:
Originally Posted by TonkaNL View Post
The boat is 5m long (16ft?) and max weight fully loaded is 2300 lbs.

A single 12V battery (180Ah 10h) can deliver 225A for 15 mins. The max draw the motor asks is 100A. So Iím assuming that wonít be a problem.

Max travelling time is 30mins full throttle if needed.

I reckon this setup will suffice?

OK, a small light boat, so not so bad.


But you need to rethink your capacity


A 12V battery can delivery 225A @ 12V (2700 W) for 1/4 of an hour at which point it is completely drained. i.e a totally capacity of 675 Wh. Two will provide 1350 Wh



The motor draws 100 A @ 24V (2400 W)



Your 30 minutes at 100 A at 24 V will draw 1200 Wh, almost completely draining the two batteries. Running AGMs down that far is not good for longevity



The above assumes your batteries are still fully charged when you start your run for home. If you've used them at all to motor out or to power anything while out there, you will have even less run time left.
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Old 13-10-2019, 06:03   #12
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Re: Electric setup dual 12V battery for 24V trolling motor

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Originally Posted by StuM View Post
A 12V battery can delivery 225A @ 12V (2700 W) for 1/4 of an hour at which point it is completely drained. i.e a totally capacity of 675 Wh. Two will provide 1350 Wh
Well, yes. but the height of the current draw will influence the Wh capacity..
It's a bit difficult to calculate, because it's a curve, no? (Peukart effect?)
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Old 13-10-2019, 10:46   #13
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Re: Electric setup dual 12V battery for 24V trolling motor

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Originally Posted by StuM View Post
Your 30 minutes at 100 A at 24 V will draw 1200 Wh, almost completely draining the two batteries. Running AGMs down that far is not good for longevity

The above assumes your batteries are still fully charged when you start your run for home. If you've used them at all to motor out or to power anything while out there, you will have even less run time left.
I found this excel sheet online, which can calculate the Ah value of a battery at a certain draw.

https://centurionbattery.nl/files/peukert.xls

My battery at 100A has a capacity of 86Ah. That's about 50 mins of full power. I don't know yet the draw at regular use, we'll have to see.

This is going to be a nice experiment.
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Old 13-10-2019, 11:51   #14
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Re: Electric setup dual 12V battery for 24V trolling motor

What is the stop thing? A battery switch? It goes on the pos wire.
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Old 14-10-2019, 02:24   #15
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Re: Electric setup dual 12V battery for 24V trolling motor

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What is the stop thing? A battery switch? It goes on the pos wire.
It depends on what you want to isolate, no? This setup is to prevent drain and should to my experience be put on the neg wire. In this particular situation it also works to cut the power from the motor to stop it from operating. The motor killswitch also does that btw. Thereís a fuse on the pos wire to take care of shorting.

If Iím wrong, let me know. Thatís why is posted it here 😊
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