Soft start a 12V DC motor, max 250A, possible?

[Bidda]

Hi
I have a boat (20ft) with an bow thruster that is to big, I want to soft start motor, aprox 2-3 sec.
It is an 12V DC motor and in tecnical data it says max 245A.

Is i possible to find this soft starter in stock, enyhvere??

BR
Brede

[Benta]

Ah? Do you mean A? There's a hell of a difference.

[BILLPOD]

Even if it is A,(Amps), 245 is a lot.

[themadhippy]

245 is a lot.

Is it? T'is not even 3KW

[BrokenYugo]

What type of motor is this? Does it not already have a speed controller? I would think that would be where any soft start/limited ramp up rate would be implemented in such a system.

[johansen]

Find a 500 amp carbon pile battery load tester, with a knife switch to bypass it.

[BeBuLamar]

They make speed controller for bow thruster. A speed controller would be a soft start.

[Bidda]

Ah? Do you mean A? There's a hell of a difference.

Yes, A, my bad

[Bidda]

What type of motor is this? Does it not already have a speed controller? I would think that would be where any soft start/limited ramp up rate would be implemented in such a system.

No speed controll, only on/off

[Bidda]

They make speed controller for bow thruster. A speed controller would be a soft start.

Yes, Sleipner have a set I can buy, it is expensice (2500 EUR). A softstarter should be less costs and work.

[Bidda]

Find a 500 amp carbon pile battery load tester, with a knife switch to bypass it.

Thx, can you make me a drawing of how you think? Link to equipment?

[mikerj]

If it's a regular brushed motor you should be able to find something much less expensive e.g. https://www.4qd.co.uk/product/pro-160/

[Bidda]

THX, Yes it is a brushed motor, I will contact them to ask for a solution :-)

[johansen]

Find a 500 amp carbon pile battery load tester, with a knife switch to bypass it.

Thx, can you make me a drawing of how you think? Link to equipment?

carbon pile load testers are a stack of about 25, 1/8" thick carbon disks 3" diameter. flat plates on both ends connect to the battery terminals.

the adjustable knob tensions a spring which compresses the stack together. works from about 0-500 amps somewhat non linearly with time because as far as i remember, the carbon shrinks when it heats up.

you could make your own using two flat plates, spring tension etc.. but instead of carbon disks you could strip the copper off of arc gouging rods and cut them and lay them like cordwood in an alternating cross pattern.

or just buy 50$ worth of NTC resistors.

[WokeJordon]

Do you means Max 250mA?

[Tim S]

If it's too powerful, then elctronic PWM is one way to go, but you could always change the propellor for a smaller diameter or a finer pitch one. PWM and marine are not good bedfellows!
Essentially the thruster  motor is a DC starter motor and will easily pull hundreds of amps. In a yacht there is often a load battery next to the motor, long cable runs cause voltage drop when trying to pull 200A. If you have a battery next to the motor, try disconnecting the battery - the long cable run from the engine battery will act as a ballast resistor. Beware - the cables will get hot! If this is too much, then a delayed switching in of the load battery could work. When you press the 'thrust' switch, the motor can start on the long cable then a relay/solenoid can switch in the load battery after - say 2 seconds to save overheating the cables.

Tim.

[Bidda]

Do you means Max 250mA?

No, 250A is max