Running a 12V VHF Radio off a 24V system?

[Wotname]

Originally Posted by coopec43

OMG! I can't handle this anymore.

Did you bother reading my comment #30?

Yes, of course I read you post #30. In it, you quoted Jedi's post #5. You will notice I quoted Jedi's post #31.

You can do it like Jedi suggested in post #5 but that is a very second rate method. I mean, it is OK if you are trying to everything on a shoestring but what Jedi suggested in post #31 is way superior.

IMHO, the simplest way is often the best but also often expensive. In your instance, the simplest way is to buy a Furuno 24V VHF radio but yeah, they cost big bucks. Fit the radio, connect it to your 24V panel and connect the antenna - you are good to go.

Next best (IMO) is to follow the information in post #31. I.E. fit a one Victron Smart Orion Isolated 24 -> 12 converter and a small 12V AGM battery and then connect any 12V radio and other nav equipment to this 12V dedicated supply.

Or buy a shipload of no name el cheapo 24/12 convertors and stuff around with them at your hearts content.

At some point you have to make a trade off between dollars and quality / reliability. If you have a strong background in the electrical trades, then you can determine what risk is acceptable to you and buy accordingly.

[coopec43]

Originally Posted by Wotname

You might notice it says it has a 'build in DC DC convertor'. It is not possible for a user to make the GM8000 operate of 12 volts.

Now I dunno about being clever, I'm pretty sure I am not however I have managed over the years to repair all sorts of commercial, marine and aviation radios and whatnots to component level (back in the day when they had replaceable components) so I know my around a power supply. But don't take my word for it, ask Icom Australia, they are a friendly bunch and they will put you straight.

Well I suppose it is a matter of semantics then.

I think we'd both agree there are very few 24V VHF radios on the market that input 24V (without a DC to DC)

[goboatingnow]

Originally Posted by Wotname

Yes, of course I read you post #30. In it, you quoted Jedi's post #5. You will notice I quoted Jedi's post #31.

You can do it like Jedi suggested in post #5 but that is a very second rate method. I mean, it is OK if you are trying to everything on a shoestring but what Jedi suggested in post #31 is way superior.

IMHO, the simplest way is often the best but also often expensive. In your instance, the simplest way is to buy a Furuno 24V VHF radio but yeah, they cost big bucks. Fit the radio, connect it to your 24V panel and connect the antenna - you are good to go.

Next best (IMO) is to follow the information in post #31. I.E. fit a one Victron Smart Orion Isolated 24 -> 12 converter and a small 12V AGM battery and then connect any 12V radio and other nav equipment to this 12V dedicated supply.

Or buy a shipload of no name el cheapo 24/12 convertors and stuff around with them at your hearts content.

At some point you have to make a trade off between dollars and quality / reliability. If you have a strong background in the electrical trades, then you can determine what risk is acceptable to you and buy accordingly.

Indeed , both approaches are different , but under engineering evaluation each has merits , there’s no “ best “ solution

Don’t equate money with quality , in my lightening strike all the victron stuff failed , yet the cheap Chinese DCDC survived and there’s a reason why they did. ( way larger input voltage range )

Changing everything to 24v is futile , getting some of this stuff in 24v is difficult , centralised dc dc means reliance on one unit and a separate wiring loom

Hence if simplicity is what you value followed by cost effectiveness , the distribution of multiple low power dc dc is better then a single high power dc dc.

[coopec43]

Originally Posted by goboatingnow

It is , firstly it’s cost effective , doesn’t require separate 12v wiring runs from a centralised convertor and it’s redundant design, as a single failure doesn’t result in looking all 12v units.

It’s also easy to mount as the small dc dc unit converters can be often just mounted in the same enclosure as the 12v appliance or nearby.

Considering my lack of technical expertise I now think I should use dedicated no name el cheapo DC to DC converters. (I know other approaches may be less expensive(?)/more reliable and sophisticated etc)

[s/v Jedi]

Originally Posted by coopec43

Considering my lack of technical expertise I now think I should use dedicated no name el cheapo DC to DC converters. (I know other approaches may be less expensive(?)/more reliable and sophisticated etc)

The 20A one that is hermetically sealed and which I linked to earlier in the thread is a very reliable unit. Do not think of it as a cheap no-name unit, because when you look at the small Victron one you will find it is blue but otherwise exactly the same. Even the 50A and 100A (ah, Victron does have a 100A model!) are exactly the same but for the color (see attachment).
One would be okay to consider they are equal and most likely from the same factory.

That said, the second option I gave is far superior but that doesn’t mean it is more reliable, because like GBN says: if the one converter fails, you lose it all, so you need to carry a spare for this.

Now there is talk about surviving lightning strikes. I think we hold records for number of strikes that wiped stuff out aboard, and I can tell that selecting one brand over the other with this in mind is futile. The only thing that works is lightning strike avoidance as plan A, surge suppression as plan B, and spare inventory as plan C.

The best thing to add to the advanced setup is adding surge suppression to both the 24V system as well as the isolated 12V system. Something like: https://www.amazon.com/gp/product/B09KBRXXXR

Also, on coax cables you add surge suppression, like: https://www.amazon.com/Lightning-Pro.../dp/B089GL275H

[Baronkrak]

Originally Posted by coopec43

I am wondering how to run a 12V radio on a 24V system. Is this a possibility or am I completely confused?

For information.

Originally Posted by Baronkrak

A 12/24V battery management system. Do not requires DC/DC converters.

Originally Posted by Baronkrak

Search Internet: 12/24V battery management system. cruisersforum

[goboatingnow]

Those sealed units nick mentioned are Chinese widely available on AliExpress I’ve used some.



Victron seem to oem them if you like expensive blue paint

I e used the cheaper open frame ones in the interior of my boat without issue either I have 3 open frames and two sealed on this boat for over a year

[AKA-None]

So what’s the purpose of a 24v system if you keep running around shuffling it down to 12v every where?
Color me a bit confused

[Uncle Bob]

Originally Posted by AKA-None

So what’s the purpose of a 24v system if you keep running around shuffling it down to 12v every where?
Color me a bit confused

You are not alone in your wonderings.

[coopec43]

Originally Posted by AKA-None

So what’s the purpose of a 24v system if you keep running around shuffling it down to 12v every where?
Color me a bit confused

Maybe you should read this to understand the advantages of 24V? (These days most manufacturers of larger boats (40ft+) have (or are) switching to 24V)
24-Volt Electrical Systems
What are the advantages of 24-volt electrical systems? Read what noted expert Chuck Hawley has to say.

https://www.westmarine.com/west-advi...l-Systems.html

This short video clip also explains why 24V is a better choice.

https://www.youtube.com/watch?v=VpCqXMnapIE

[s/v Jedi]

Originally Posted by AKA-None

So what’s the purpose of a 24v system if you keep running around shuffling it down to 12v every where?
Color me a bit confused

Define everywhere? For radios and most electronics, 13.8V is the norm. Same for the NMEA2000 bus.

So with a 24V boat, you can do this using something like a Victron Orion programmed as a 13.8V power supply, or, like I described before, using another small battery and the Orion set as charger, to create a backup and isolated supply.

Now for a 12V boat. Basically, you can use an Orion 12-12 converter and do the same, but almost nobody does and they just connect their electronics straight to the batteries. This is bad, because now you get 12V or 14V or with good ole FLA batteries, 11V etc. Also, you may get a big surge when you start the engine. I have encountered boats that must shutdown electronics when starting the engine.

So 24V boats have a stable, clean supply for their electronics, taking most of the experienced problems away.

Then there are countless other devices that you can upgrade to 24V. Big items are lights up in the mast or big consumers like windlass. Cable losses are slashed by a huge margin. Let me explain:

All critical circuits aboard should be sized for a maximum 3% voltage drop. For a 12V boat, this is 0.36V while a 24V boat can drop 0.72V before reaching that limit.

Now lets take the DC cabling between solar controller and battery. Assume solar produces 480W and the controller on a 12V boat will push 40A into the battery.
For a 24V boat with the same solar array and controller, you now only get 20A. So you only need a controller that is half the amps. Boats with 48V keep laughing as they only need a controller that is 25% rating compared to 12V boats. That is significant savings when buying these controllers.

Back to the comparison. Lets say we have a distance of 10’ between battery and controller, so that is 20’ of positive and negative cable added. Let me push this into my calculator…. and it tells me I need AWG 6 cable.

Now for 24V… I’m using the circuit wizard app… the answer is AWG 12!!

That is a huge difference from AWG 6 to not AWG 8, not to AWG 10 but all the way back to AWG 12. And it tells me it can do 31.5A over that cable instead of just the 20A.

Similar advantages are gained with wiring for a windlass or an anchor light, for an inverter etc.

So it’s not just that you have half the amperage… you can also drop twice the voltage before it becomes a problem, meaning the difference is a factor 4.

[coopec43]

s/v Jedi Thank you for taking the time to make that excellent post.

Right now I am finishing off the electrical work on the yacht which has been done along the lines you have suggested. (I'm glad I got an auto electrician's advice before starting)

When I tested the cabin fans/lighting the 12V oscillating fans sounded like Mustang aircraft readying for take-off. I had planned to replace the 12V fans with 24V versions (at $45 ea.) but I have decided to use the excess capacity of the DC to DC 24/12 converter and it will cost me nothing (AND no messing around installing the new fans either)

NOTE: the fans only draw .65A

[goboatingnow]

Originally Posted by coopec43

s/v Jedi Thank you for taking the time to make that excellent post.

Right now I am finishing off the electrical work on the yacht which has been done along the lines you have suggested. (I'm glad I got an auto electrician's advice before starting)

When I tested the cabin fans/lighting the 12V oscillating fans sounded like Mustang aircraft readying for take-off. I had planned to replace the 12V fans with 24V versions (at $45 ea.) but I have decided to use the excess capacity of the DC to DC 24/12 converter and it will cost me nothing (AND no messing around installing the new fans either)

NOTE: the fans only draw .65A

Having has 2 24v boats I’m glad to be back in 12v land. I found picking up 24v stuff in chandleries much harder and everything was special order etc.

[coopec43]

Originally Posted by goboatingnow

Having has 2 24v boats I’m glad to be back in 12v land. I found picking up 24v stuff in chandleries much harder and everything was special order etc.

Yes I agree.

No doubt some time down the track I will want to install some sort of gear such as sound equipment which won't be available in 24V. Having 12V available could save the day

[Colin Stone]

I use a couple Alfatronix - https://uk.farnell.com/alfatronix/pv...12a/dp/1182706
One runs all the 12v stuff - 2 VHF, Log/Sounder, Rudder Indicator etc etc.. 17 years no problem. Plus one spare.
£5 each at a boat jumble.
I also use a variety of ebay DC buck converters for laptops, 12v satellite receiver etc etc.