12V step to 24V - possible?

[rogerthebodger]

Don't forget, the OP only has motors for davits Roger, could well be more than those converters can handle, but doubt they'll be 40-50A @24V

Yes it does depend on the current draw of the davit motors which could be less that the maximum possible

My Davits that are partook my solar arch I use my cockpit which's to lift my rigid GRP dingy.

We do need more InfoMation to make proper recommendations.

What I am quoting is the motors I have to setup and the current is the maximum as shown on the motor and the actual current draw depends on the actual load on the motor so we can only use maximums as shown on the motor which we don't know

 

[PaulRainbow]

Yes it does depend on the current draw of the davit motors which could be less that the maximum possible

My Davits that are partook my solar arch I use my cockpit which's to lift my rigid GRP dingy.

We do need more InfoMation to make proper recommendations.

What I am quoting is the motors I have to setup and the current is the maximum as shown on the motor and the actual current draw depends on the actual load on the motor so we can only use maximums as shown on the motor which we don't know

I found a manual for Simpson electric davits Roger, the motors are much more powerful than i thought they might be, being fitted with 50A fuses on the 24V models !

http://webarchiv.sailtec.de/pic/upload/cooney_serie-7_electric_davits_owners_manual.pdf

 

[rogerthebodger]

I found a manual for Simpson electric davits Roger, the motors are much more powerful than i thought they might be, being fitted with 50A fuses on the 24V models !

http://webarchiv.sailtec.de/pic/upload/cooney_serie-7_electric_davits_owners_manual.pdf

Interesting the link does show a 50 Amp fuse for the 24Vdc motor and 80 Amps for a 12 Volt motor

I does also depend on the controls that would stop the motor fully up and down if any or it could be just stall the motor and usse the stall current draw to stop the motor

I think a bit more research needed to give a proper answer

In any case it looks like a low current DC DC converter would nt provide the current required which is the conclusion came to when looking t my 24 Vdc winch setup

 

[ianc1200]

Thanks for all the replies but feel not going to resolve this until the Autumn - boat was launched last week & we had a look at getting the covering plates off to reveal the electric motors, but as these are outboard of the swim platform it wouldn't be easy/safe. So will leave until she comes out again. Will have a closer look to the two solenoids which do have reference numbers - perhaps they will be a clue to amps draw.

 

[Refueler]

Thanks for all the replies but feel not going to resolve this until the Autumn - boat was launched last week & we had a look at getting the covering plates off to reveal the electric motors, but as these are outboard of the swim platform it wouldn't be easy/safe. So will leave until she comes out again. Will have a closer look to the two solenoids which do have reference numbers - perhaps they will be a clue to amps draw.

Solenoids will have a max rating .. not 'draw'. The 'draw' will be what the motors demand to work.

I would not be surprised - if the dinghy weight is well below the davits max rating .. you may be able to swap out the solenoids (if they don't work with 12v) to 12v versions .... motors won't care ... they will use whatever power is given .. question will be if enough to lift the dinghy.

 

[Alex_Blackwood]

Solenoids will have a max rating .. not 'draw'. The 'draw' will be what the motors demand to work.

I would not be surprised - if the dinghy weight is well below the davits max rating .. you may be able to swap out the solenoids (if they don't work with 12v) to 12v versions .... motors won't care ... they will use whatever power is given .. question will be if enough to lift the dinghy.

Sorry, the motors will care. They will run, yes, but at reduced speed, power and torque and are likely to overheat. Bottom line is that the davits and associated equipment are designed for 24 volt operation, not 12 volts. Why faff about changing solenoids and trying to run a motor designed for a 24volt application on 12 volts?? Why try and run a 24volt unit on 12 v.??
By the way just to clarify relays. When we say 12 volt relays, we are referring to the coil voltage. the contact rating will be in amps with an associated ac or dc voltage max. rating. Some relay contacts are rated for ac only as dc arcing is much heavier. Be aware.

 

[PaulRainbow]

Thanks for all the replies but feel not going to resolve this until the Autumn - boat was launched last week & we had a look at getting the covering plates off to reveal the electric motors, but as these are outboard of the swim platform it wouldn't be easy/safe. So will leave until she comes out again. Will have a closer look to the two solenoids which do have reference numbers - perhaps they will be a clue to amps draw.

The clue to the motor max current is in the schematic i posted Ian, if they are the same/similar davits. 50A fuses suggest a significant current and the type of DC-DC converter previously posted would go up in smoke as soon as you pressed a button on the davit. The cost of a suitable converter would be significant. An alternative would be a pair of modest 12V batteries in series, with a DC-DC charger to charge them. Or, as they would only be for occasional use you might get away with a small solar panel and a inexpensive solar controller.

 

[Refueler]

Sorry, the motors will care. They will run, yes, but at reduced speed, power and torque and are likely to overheat. Bottom line is that the davits and associated equipment are designed for 24 volt operation, not 12 volts. Why faff about changing solenoids and trying to run a motor designed for a 24volt application on 12 volts?? Why try and run a 24volt unit on 12 v.??
By the way just to clarify relays. When we say 12 volt relays, we are referring to the coil voltage. the contact rating will be in amps with an associated ac or dc voltage max. rating. Some relay contacts are rated for ac only as dc arcing is much heavier. Be aware.

Maybe read my post again ....

" motors won't care ... they will use whatever power is given .. question will be if enough to lift the dinghy."

The guy has a set of davits ... ideal would be to have a bank of batterys supplying 24V ... but then he has to sort out charging as his boat as I understand it is a 12V only job at present.
As Paul says - a DC-DC converter is going to be a serious bit of kit ... and the load on a 12V system could be too much.

It will be unusual if the motor will not run on 12V ... the factor that will decide success - is the weight and whether the 12v to the motor will lift the dinghy. Of course the ampage will a serious factor.

Its actually not necessary to swap out the solenoids to test 12V working ... jumping the 12V to the OUTPUT terminals of the solenoids will power the davit motors ... if that works - then great - if not - nothing lost.
If it does work - then if the solenoids fail to operate on 12V ... why not swap them to 12V versions ???

There is another way of course - but then its only a temporary measure and not one I would suggest for more than a few times while more permanent solution found ... and it would require a charger .................. A decent capacity 6S LiPo ... which at full charge would be 6 x 4.2 = 25.2V. A 3000 mAh with a reasonable C rate of 30+ would be able to thump out more amps than the davit would ask .... Charger for it runs of 12V and cost about 30 euros for a basic user programmable smart unit. But as a modeller who has such items - of course it would be possible for me.
You would be amazed what some of us modellers do with our LiPo's !!

 

[rogerthebodger]

My 24 Vdc winch motors do work on 12 vdc but as Alex says will be a lower power but you also need to look at the duty cycle as one way to increase the power of both AC and DC motors is to increase the voltage above the designed voltage.

This is how the power tool motor gets the torque / power from a small motor. These motors will overheat if run to longer than the duty cycle.

As the davit motors would only run long enough to lift the dingy and then stop and would cool down so the other info that would be needed is to look at the duty cycle, but that info is not generally available.

It all about suck it and see.

Relay / solenoids coils also have a duty cycle.

I have some 24 Vdc solenoid valves that I run at 18 Vdc as they overheat if run at 24 Vdc continuous.

I would fit the davits and connect it up to a 12Vdc system and see how it works, does it lift the dingy and do the relay work powering the motor.

If not then consider uprating the supply to the motor and/or the relay. If either does not lift the dingy change the supply to either just the motor and or the relay depending on which does not work

 

[Alex_Blackwood]

My 24 Vdc winch motors do work on 12 vdc but as Alex says will be a lower power but you also need to look at the duty cycle as one way to increase the power of both AC and DC motors is to increase the voltage above the designed voltage.

This is how the power tool motor gets the torque / power from a small motor. These motors will overheat if run to longer than the duty cycle.

As the davit motors would only run long enough to lift the dingy and then stop and would cool down so the other info that would be needed is to look at the duty cycle, but that info is not generally available.

It all about suck it and see.

Relay / solenoids coils also have a duty cycle.

I have some 24 Vdc solenoid valves that I run at 18 Vdc as they overheat if run at 24 Vdc continuous.

I would fit the davits and connect it up to a 12Vdc system and see how it works, does it lift the dingy and do the relay work powering the motor.

If not then consider uprating the supply to the motor and/or the relay. If either does not lift the dingy change the supply to either just the motor and or the relay depending on which does not work

A 20 minute duty cycle is about the norm for that sort of use. But that is at 24 volts not 12 v. where it will be at least half that.
Run the thing off 24v. and never mind all the bodging and faffing about.

 

[rogerthebodger]

A 20 minute duty cycle is about the norm for that sort of use. But that is at 24 volts not 12 v. where it will be at least half that.
Run the thing off 24v. and never mind all the bodging and faffing about.

You are looking at the same power consumption at 12 Vdc

Well, I am a bodger but its just a suggestion.


Or just a way of suggesting how the OP can proceed.

I have done sonthing similar and posted a way to overcome the OP problem for both 24 vdc motor and 24vdc relay on his 12 Vdc boat

 

[ianc1200]

As noted above, I'm going to leave until the Autumn now - planning extensive works, coppercoating, deck painting, stern & bow thrusters. And am wondering whether dedicated batteries to the stern (& bow) thruster could also be used for davits & thruster if all 24V.

 

[PaulRainbow]

As noted above, I'm going to leave until the Autumn now - planning extensive works, coppercoating, deck painting, stern & bow thrusters. And am wondering whether dedicated batteries to the stern (& bow) thruster could also be used for davits & thruster if all 24V.

No reason not to use 24V for the thrusters, as long as you can charge them. DC-DC chargers could do that. Where are you keeping the boat Ian ?

 

[Alex_Blackwood]

You are looking at the same power consumption at 12 Vdc

Well, I am a bodger but its just a suggestion.


Or just a way of suggesting how the OP can proceed.

I have done sonthing similar and posted a way to overcome the OP problem for both 24 vdc motor and 24vdc relay on his 12 Vdc boat

Roger, Your installation was designed and built with 12volts for the relays and 24 for the motors. the OP's is a full 24v design. All I am saying is, If I was confronted with that unit I would consider it proper to run it from 24V and not, IMO, bodge and muck about with the designed parameters of the unit.
Each to his own. Think maybe we should leave it there

 

[ianc1200]

No reason not to use 24V for the thrusters, as long as you can charge them. DC-DC chargers could do that. Where are you keeping the boat Ian ?

She's at Titchmarsh, hope to come to Ipswich early season so will hopefully pop by and say hello. It's an Aquastar 38 called "Arabesque".

 

[rogerthebodger]

Roger, Your installation was designed and built with 12volts for the relays and 24 for the motors. the OP's is a full 24v design. All I am saying is, If I was confronted with that unit I would consider it proper to run it from 24V and not, IMO, bodge and muck about with the designed parameters of the unit.
Each to his own. Think maybe we should leave it there

All I was trying to do was to give the OP some alternatives.

If you don't like that is your issue no mine.

As the OP said in his last post, he has some other mods to do which could affect the installation of his davits

 

[Refueler]

All I was trying to do was to give the OP some alternatives.

If you don't like that is your issue no mine.

As the OP said in his last post, he has some other mods to do which could affect the installation of his davits

As you can see on posts - I'm in same camp as you ... why start installing / changing things if will run on 12v ??

 

[PaulRainbow]

No reason not to use 24V for the thrusters, as long as you can charge them. DC-DC chargers could do that. Where are you keeping the boat Ian ?

She's at Titchmarsh, hope to come to Ipswich early season so will hopefully pop by and say hello. It's an Aquastar 38 called "Arabesque".

Would be nice to catch up Ian, give me a call when you come, the kettle is usually on. We're coming to Titchmarsh for Easter weekend, so if you're there will see you then.

 

[rogerthebodger]

As you can see on posts - I'm in same camp as you ... why start installing / changing things if will run on 12v ??

Its all about the enjunity of the boat owner and how much need to be paid for a "professional job Paid For" or a job that will do the job.

As can be sean I am in the camp of make it such that it can be used.

I use wiper motors for all types of actuators. My engine shutdown lever is operated with a wiper motor with relays and limit switches

I posted a use of wiper motors as a winch drive motors as

When I purchased my current boat, it came with some electric winches that were 24 Vdc but the engine is 12 Vdc so I had to find a way to use then and I found one as I posted.

I am lucky as been in engineering manufacturer and design for more years I wish to remember. I have an Engineering workshop at home and the skills in fitting, turning, fabrication and welding. I also have local companies who do laser cutting, bending and rolling and any work I cannot do I can get done.

I am lucky I dont have to work and refuse to do work for others as payment is always an issue

I have been involved in small boats since in 1978 in the UK when I cruised the canals and inland waterways, including fitting engines and hot and cold-water systems in my 20 ft cabin cruiser.

It tends to be the "professions" who call me a Bodger as they will always use the items that have no come back and charge lots of money for what they provide.

I look for easy and cost-effective solutions even adaptingused /preowned items