DC - DC Converter

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Ammonite

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Can anyone recommend a reasonably priced isolated dc to dc converter that will supply a constant 12v, ideally rated around 4A - 6A? Ive tried a few of the non-isolated types readily available on eBay etc and they have all interferred with the VHF. Thanks
 
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Chaktoura said:
Can anyone recommend a reasonably priced isolated dc to dc convertor that will supply a constant 12v, ideally rated around 4A - 6A? Ive tried a few of the non-isolated types readily available on eBay etc and they have all interferred with the VHF. Thanks
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What input voltage ?
 
Sorry if not clear. Stable 12v output from circa 12.5v - 14.8v input. Loads on eBay that do this but the three Ive experimented with over the last few years all interfere with the VHF
 
What sort of VHF do you have?
A marine VHFs rated for 12V might be a bit fussy about the DC oscillation (lack of, that is), but it should work perfectly with a slightly higher voltage.

My boat is 24V DC, so I have several converters onboard, for some of the instruments and car stereo, for instance.
But while these converters (at least mine, which are all AlfaTronix) do provide a stable output, it's actually 13.6V, not 12V.
And that's true regardless of how stable the 24V input is, since the converter can take anywhere from 17V to 32V.
 
MapisM said:
What sort of VHF do you have?
A marine VHFs rated for 12V might be a bit fussy about the DC oscillation (lack of, that is), but it should work perfectly with a slightly higher voltage.

My boat is 24V DC, so I have several converters onboard, for some of the instruments and car stereo, for instance.
But while these converters (at least mine, which are all AlfaTronix) do provide a stable output, it's actually 13.6V, not 12V.
And that's true regardless of how stable the 24V input is, since the converter can take anywhere from 17V to 32V.
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Raymarine Ray54E. Nominal 12v. Working range 10.5 - 16v. I haven't tried installing a convertor alongside this as yet but was basing my comments on a 12v Cobra on my other boat
 
What is it you want to run off a buck/boost converter?
I've a few ebay offerings which seem OK, though mounted well away from radios and the ripple they put back out on the voltage is negligible as is airborne, though putting the input/output through ferrite rings wouldn't do any harm.
An RTL usb tv dongle can work as a spectrum analyser for the cost of a london beer which is a handy way to see what's going on.
Spektrum SV Mod: RTL-SDR Spectrum Analyzer Software Now with Improved UI
 
Led lighting and potentially a TV. Ive also had problems with various bits of kit triggering low voltage alarms / shutdowns (notably a Garmin plotter) when starting the engine on my last boat despite renewing the batteries, cabling etc so just good to have on board. The other route is to buy leds rated for 10-30v but they are a lot more expensive and i need loads of them. I know several people on here run 12v leds without regulation with seemingly no problem but ive also heard a few horror stories
 
Chaktoura said:
Raymarine Ray54E. Nominal 12v. Working range 10.5 - 16v.
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If your boat is 12V, I'd try connecting it with no converter at all first.
Then check if it works fine with battery current alone (i.e., neither charger nor engines running).
You know, just to check that there isn't any problem with the wiring that has nothing to see with the "quality" of the DC supply.
If it works fine when battery-only powered, test it also with the battery charger on, and then with the engines on.
My bet is that it'll work just fine in all conditions.
Fwiw, my old VHF (Raymarine 230E) works perfectly with the 13.6V supplied by the 24/12 DC/DC converter.
 
Chaktoura said:
Led lighting and potentially a TV. Ive also had problems with various bits of kit triggering low voltage alarms / shutdowns (notably a Garmin plotter) when starting the engine on my last boat despite renewing the batteries, cabling etc so just good to have on board. The other route is to buy leds rated for 10-30v but they are a lot more expensive and i need loads of them. I know several people on here run 12v leds without regulation with seemingly no problem but ive also heard a few horror stories
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Good quality LED lighting isn't a problem, some cheap ones and the LED strips can have issues with raised voltages when the batteries are on charge. Any half decent TV will not be a problem. Your Garmin plotter will happily work over voltage range.

The Victron DC-DC converter that Vic posted a link to would happily run your lights, plus the TV and the plotter, but as i said, they should not need a DC-DC converter, so all you really need is something reasonable to run the lights. But, your main issue is the engine causing low voltages on the domestic circuits, this isn't good news for anything that's switched on when you start the engine. You need to address this, i suspect you have a 1-2-Both switch and possibly a battery that's either under sized or on its last legs, or you have some wiring issues.
 
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MapisM said:
If your boat is 12V, I'd try connecting it with no converter at all first.
Then check if it works fine with battery current alone (i.e., neither charger nor engines running).
You know, just to check that there isn't any problem with the wiring that has nothing to see with the "quality" of the DC supply.
If it works fine when battery-only powered, test it also with the battery charger on, and then with the engines on.
My bet is that it'll work just fine in all conditions.
Fwiw, my old VHF (Raymarine 230E) works perfectly with the 13.6V supplied by the 24/12 DC/DC converter.
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Thanks for this but the VHF isnt the problem. Its designed to cope with the voltage fluctuation. Its when I use a convertor to power something else closeby that it interferes with the VHF signal.
 
Chaktoura said:
Thanks for this but the VHF isnt the problem. Its designed to cope with the voltage fluctuation. Its when I use a convertor to power something else closeby that it interferes with the VHF signal.
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Is it the converter that is interfering with the VHF or is it the "somthing else"?
 
VicS said:
Is it the converter that is interfering with the VHF or is it the "somthing else"?
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The convertor. Without it there was no interference but the plotter low voltage shut off would trigger when starting the engine. I replaced the battery and instrument cables etc but couldnt find the fault and all other instruments were fine, so gave up and stuck in the converter. Anyway that was the old boat and this time its a means of regulating the leds im after without replicating the VHF issue. I just need to work out whether to go with something along the lines youve suggested or upgrade the leds to the 10-30v variety. Moneywise there doesnt seem a lot in it!
 
Chaktoura said:
Thanks for this but the VHF isnt the problem. Its designed to cope with the voltage fluctuation. Its when I use a convertor to power something else closeby that it interferes with the VHF signal.
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The interference is most likely due to radiated emissions from the high frequency switching of the power converter which is why I suggest you put it in an earthed cheap metal 'project box' to act as a Faraday Cage.
 
Chaktoura said:
The convertor. Without it there was no interference but the plotter low voltage shut off would trigger when starting the engine. I replaced the battery and instrument cables etc but couldnt find the fault and all other instruments were fine, so gave up and stuck in the converter. Anyway that was the old boat and this time its a means of regulating the leds im after without replicating the VHF issue. I just need to work out whether to go with something along the lines youve suggested or upgrade the leds to the 10-30v variety. Moneywise there doesnt seem a lot in it!
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Which DC/DC converters have you tried ?

I have some onboard that look the same as these and they don't cause any issues with my VHF, or anything else: 400W 15A DC-DC Power Converter Boost Module Step-up Constant Power Supply | eBay
 
They were very similar but I suspect they were lower rated as they only had one heatsink. Given the cost I may as well give one of these a try though - thanks
 
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