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Old 24-05-2020, 06:30   #1
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weight savings for 24v vs 12v in performance oriented design

Given that 24v theoretically results in higher power density than 12v, I'm wondering what actual weights can be saved in a real world implementation by using 24v systems over 12v.

I'm really looking for data rather than opinion here if anyone had something available about actual weights of 12 vs 24 of various items such as.
  • Cable runs
  • Anchor windlass
  • powered winches
  • autohelm
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Old 24-05-2020, 06:43   #2
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Re: weight savings for 24v vs 12v in performance oriented design

24 v is the way to go

Over time it will be more expensive

At a small marine store 24 v equipment is never in stock

Special order, come back next week

Also remember the ac side

110 v is goofy
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Old 24-05-2020, 06:53   #3
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Re: weight savings for 24v vs 12v in performance oriented design

Quote:
Originally Posted by barrymac View Post
Given that 24v theoretically results in higher power density than 12v, I'm wondering what actual weights can be saved in a real world implementation by using 24v systems over 12v.

I'm really looking for data rather than opinion here if anyone had something available about actual weights of 12 vs 24 of various items such as.
  • Cable runs
  • Anchor windlass
  • powered winches
  • autohelm
The main reason for having a higher voltage is the size of your boat. We're 36', but for anything bigger 24v is probably the way to go, or the wire gauge is going to get expensive. I don't think any weight savings are significant enough to make a difference.
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Old 24-05-2020, 07:37   #4
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Re: weight savings for 24v vs 12v in performance oriented design

Nobody I have ever talked to has used a 24 volt system because of weight savings, so I suspect the "data" will be hard to come by. But... it is easy to calculate. If you size the wires using the same procedure, the wires will have 1/2 the cross sectional area, and therefor 1/2 the weight. Wire weight per length specs are easily found, and I assume you know the length of the wire runs that you are concerned about.

Windlass, winches, autopilot, etc. will NOT have significant (if any) weight reductions for motors of the same HP. Yes, the wires in the coils are smaller, but there are more turns, so net-net no real change. If you consider that "opinion" and not data, you could just go look up DC motor specifications for yourself and see.

I am not sure what kind of "performance oriented design" uses powered winches, but you'll save more weight switching to manual sheet winches than a 24 volt conversion will get you. Of course you'll need bigger, stronger crew, but they are moveable ballast so are good for performance!
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Old 24-05-2020, 07:41   #5
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Re: weight savings for 24v vs 12v in performance oriented design

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I am not sure what kind of "performance oriented design" uses powered winches, but you'll save more weight switching to manual sheet winches than a 24 volt conversion will get you. Of course you'll need bigger, stronger crew, but they are moveable ballast so are good for performance!
Work saving equipment = waistline expanding equipment

Although seriously, from a cruisers perspective, the more complicated it is the more likely it will be unfixable in remote locations. Go manual if practical.
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Old 24-05-2020, 13:06   #6
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Re: weight savings for 24v vs 12v in performance oriented design

Minimal, you will be able to save some weight on heavy power cables but for all the small stuff 16g is a minimum to provide strength not power handling. Even with LED lights don't go below this or the system will get unreliable. If by 'performance you mean out and out racing and you are cutting the handles of the toothbrushes I could see the point but not for any form of cruising. Also given that nav gear runs at 12v unless it is made for commercial craft going 24v means in addition to the 12v system and any weight saving will likely be lost in extra kit such as needing both 12&24v batteries.
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Old 24-05-2020, 13:11   #7
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Re: weight savings for 24v vs 12v in performance oriented design

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Minimal, you will be able to save some weight on heavy power cables but for all the small stuff 16g is a minimum to provide strength not power handling. Even with LED lights don't go below this or the system will get unreliable. If by 'performance you mean out and out racing and you are cutting the handles of the toothbrushes I could see the point but not for any form of cruising. Also given that nav gear runs at 12v unless it is made for commercial craft going 24v means in addition to the 12v system and any weight saving will likely be lost in extra kit such as needing both 12&24v batteries.
Yea, additionally many other appliances and equipment are difficult to find in 24v, but not in 12v.
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Old 24-05-2020, 13:28   #8
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Re: weight savings for 24v vs 12v in performance oriented design

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Yea, additionally many other appliances and equipment are difficult to find in 24v, but not in 12v.
This was the case a decade or more ago, but these days virtually everything is available in 24v models. A lot of equipment will even accept either 12v or 24v.


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Originally Posted by roland stockham View Post
Also given that nav gear runs at 12v unless it is made for commercial craft going 24v m
The only pieces of equipment we have on 12v are the NMEA 2000 bus and the VHF. Our chartplotter, radar, autopilot computer, AIS, navigational lights, USB plugs, solar regulators etc etc will all run on either 12v or 24v. You donít even need to make any changes, they automatically select the input voltage.

High draw devices such as anchor windlasses, bow thrusters, autopilot drives, inverters and battery chargers (to name a few) are available in either 12v or 24v versions. The higher voltage actually provides a greater range of more powerful models that are not available in 12v.
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Old 24-05-2020, 14:02   #9
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Re: weight savings for 24v vs 12v in performance oriented design

Way back in the 80'S i meet a couple sailing a 50 Ft. Wooden Ketch in Singapore, they had 10, 8 d battery's [110 volt's] to power pretty much everything onboard,light's, ect., a generator kept them topped up, an amazing library was onboard, all leather bound, George was a Chef [French], on ocean passage's they would heave too for dinner, interesting couple, don't make them like that anymore.
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Old 24-05-2020, 15:10   #10
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Re: weight savings for 24v vs 12v in performance oriented design

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Way back in the 80'S i meet a couple sailing a 50 Ft. Wooden Ketch in Singapore, they had 10, 8 d battery's [110 volt's] to power pretty much everything onboard,light's, ect., a generator kept them topped up, an amazing library was onboard, all leather bound, George was a Chef [French], on ocean passage's they would heave too for dinner, interesting couple, don't make them like that anymore.
High voltage dc was common in the past
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Old 24-05-2020, 15:21   #11
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Re: weight savings for 24v vs 12v in performance oriented design

The only real weight saving I imagine is changing lead for lithium ! I know there are a lot of light boats out there but i prefer 25ton full keel that doesn't mind an extra couple of tons thrown onboard . 3 biggest draws are refrigeration windlass and autopilot ... Unless you come from that AC dependant place LOL.
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Old 24-05-2020, 16:39   #12
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Re: weight savings for 24v vs 12v in performance oriented design

Quote:
Originally Posted by barrymac View Post
Given that 24v theoretically results in higher power density than 12v, I'm wondering what actual weights can be saved in a real world implementation by using 24v systems over 12v.

I'm really looking for data rather than opinion here if anyone had something available about actual weights of 12 vs 24 of various items such as.
  • Cable runs
  • Anchor windlass
  • powered winches
  • autohelm



I am breaking with longstanding CF tradition by actually answering the question you are asking. I am also breaking my own tradition by replying to a post related to electrical matters.


Data on cable weight and resistance is available here:


https://www.gerrie.com/ASSETS/DOCUME...ductordata.pdf


Marine wiring practices select the wire size for large loads based mainly on percent voltage drop over the length of the run. 24 volt systems can tolerate twice the voltage drop of 12 volt systems. They also carry half the current. Using ohm's law we can see that the acceptable resistance for a load of the same wattage for 24 volt can tolerate 4x the resistance as 12 volt. You can use this to look through the table and make comparisons.


Boats with bow thrusters will have more cable weight in the cabling to the bow thruster than any other single run. For 12 volts, perhaps 50 pounds of cable depending on the details of the installation for around 80 feet of 4/0 copper. For 24 volt, the same performance could be obtained with #3 copper which, at 80 feet, weighs around 12 pounds. So that's a savings of 28 pounds.


But it would be unusual for a large bow thruster at 24 volts to be wired with #3 cable. Ampacity of the cable -- how many amps it can carry without overheating -- becomes limiting because smaller cables cannot dissipate heat as readily, even if the voltage drop is acceptable. And the cost difference in going up a couple of sizes from #3 isn't that great (for the 24v installation), in comparison to the costs of going up a couple of sizes from 4/0 (for the 12v installation). So in practice the weight differential would be less.


Generally there is no difference in weight for the motorized components you specify because the power they draw is not large enough for 12v to be unmanageable.


Typically there is no weight difference between 12v and 24v motors because they are built using the same armature and frame. There is a difference in performance, however, around 10-15% in delivered horsepower, torque, and efficiency. Bow thruster manufacturers will call this out in the specifications in some cases.


The benefit of 24v shows up in the equipment that handles very large power levels, and the wiring that serves it:
  • Alternator
  • Inverter/Charger
  • Bow thruster
  • Battery cabling
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Old 24-05-2020, 17:11   #13
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Re: weight savings for 24v vs 12v in performance oriented design

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I am breaking with longstanding CF tradition by actually answering the question you are asking. [/LIST]


Priceless!!!
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Old 25-05-2020, 09:28   #14
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Re: weight savings for 24v vs 12v in performance oriented design [SOLVED]

Quote:
Originally Posted by Jammer View Post
I am breaking with longstanding CF tradition by actually answering the question you are asking. I am also breaking my own tradition by replying to a post related to electrical matters.


Data on cable weight and resistance is available here:


https://www.gerrie.com/ASSETS/DOCUME...ductordata.pdf

Really appreciate your radicalism in providing some really useful information!
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