Ensuring Stable 12v DC

[GordMay]

Greetings and welcome aboard the CF, BlueLagoon.

Originally Posted by smac999

that is what a battery is for.... it goes between the AC charger and the DC loads...

Indeed.

[Blue Lagoon SV]

Thanks everyone for your knowledge and experience. I don't have a radar, radio, chart plotter and so on so I will become familiar with power requirements before purchase. Thanks again for the info - Cheers!!

[roland stockham]

If you are looking at high power 'dirty loads' eg big pumps, fridges etc they can create interference on the DC line. Problems are noise and dropout due to spikes and dips when things turn on and off. Fitting a separate battery for the electronics gear solves the problem and gives a backup for critical equipment like nav light and radio. You do need some form of isolating splitter on the chargers. Before I did this I would find the GPS dropped out when the fridge turned on if the battery was low.

[fdr14127]

Best investment I ever made was to purchase a Freedom inverter. Functions as isolation between the 110v on the dock and the boat. Charges the batteries appropriately no matter if flooded or AGM, powers the microwave for soup/coffee while at sea, has a rudimentary led panel which keeps me informed as to the status of the system. Worth the price of admission.....

[john61ct]

Different functionality.

___
Split banks are very inefficient and expensive over time.

Yes sometimes necessary, but other ways to deal with "noisy" loads vs sensitive electronics should be tried first.

Voltage drop is entirely different and easy to solve at the root cause, again best to think systemically, not patching symptoms.

[dksail]

By having a voltage regulator it might help with some of the unregulated LED's that come and go on the market. It will extend their lifetime and avoid annoying shutoffs. Otherwise you are pretty much forced to get regulated bulbs (as far as I can tell). They don't seem to be very expensive.

[Locquatious]

On our boat we use computers a lot. And they take significant power. We set up a ~12V to 16.5V DC-DC boost converter to charge a Mac and use the USB to charge an iPad. 16.5V may charge the Mac a little slower than the 18.5V from the AC charger, but we are having excellent performance from our 6 year old battery since it never overcooks.

If you are using a Bullet wifi (or a repackaged Bullet- like a Bad Boy, or and power over ethernet devices) the extra voltage helps power the unit, at lower current, via the small ethernet (POE) wires. Putting a wifi POE radio and antenna atop a 40ft mast means you are sending transmission power over 80+ feet of 22ga wires. There will be a voltage drop, so it's better to boost it first.

Modern DC-DC converters are 95-98% efficient. AC inverters are power slurpers. Either one you can turn off by switch when not in use. The DC-DC converters use milliamps when quiescent (idling or not powering anything). AC inverters can be set with a low power idle delay, but some modern power tools (electric drills) won't start if they don't see power right away. Appliances may not draw enough power to trigger the inverter delay circuit. For example, our microwave only runs LED lights when not in use and didn't trigger the inverter delay circuit on. The lights aren't on during inverter idle and it doesn't start because there is no power to the start button.

When developing the Kiss Extractor™, I needed the ship's batteries to have a uniform voltage. So when the Kiss wind generator was putting out power, I had a circuit that would automatically turn on the AC inverter, to prevent the batteries from going over the test voltage. The inverter alone usually soaked up the excess energy. Sometimes, in higher winds, an AC compact fluorescent was needed to keep the voltage uniform.

[john61ct]

Originally Posted by dksail

By having a voltage regulator it might help with some of the unregulated LED's that come and go on the market

A voltage stabilizer/converter is very commonly part of the LED setup, on their own dedicated circuit.

Even better, buy the LEDs to match your infrastructure, don't let the tail wag the dog.

Investing in a much higher ampacity than what you specifically need for specialized consumers like that would quickly get very expensive.

But certainly better than maintaining a dedicated batt separate from the main House bank.

99% of devices designed for low DC voltages accommodate a wide enough range no worries.

[TreblePlink]

Originally Posted by Locquatious

[...]

Modern DC-DC converters are 95-98% efficient. AC inverters are power slurpers.
[...]

I agree that 12 volt AC inverters are inefficient "power slurpers" but how can a 12 volt DC-DC converter be 95 to 98% efficient? The required rectifier diodes have a minimum of 0.4 volt forward drop - or more with higher currents. Add that to the switching and inductor losses ... and you get to 90% pretty fast.

Please correct me if I'm wrong.

[john61ct]

The spec on the marketing materials is only for the most optimum power point.

But way better than inversion to AC, same point applies.

Combination of Killawatt for AC and AH counters for DC will show the truth, very useful gadgets

[S/V Illusion]

Originally Posted by hellosailor

" If unregulated, they behave poorly below 13 volts."
And you are basing that on what?

The radios I have worked with, documented by their manuals, usually say 13.8 volts plus or minus either 10% or a more generous 15%.

So for the one it is 12.42 volts minimum, for the other 11.73 volts. And if the ship' s battery is down to 11.73 volts, that's effectively a dead battery anyway. Some, like the old Drake radios, were actually quite happy at twelve and below. Others, including some popular Icom's, are notorious for misbehaving at "twelve". (Which is still a 60% discharged 12-volt battery.)
.

Based on decades of experience.

According to your manuals, 90% of 13.8v is 12.4V minimum. The result of voltages lower than recommended include increased IMD, spurious emissions, lowering screen voltages on tube rigs, increased gridlate voltages on the 'boatanchor' radios you mentioned, instability, etc..., all of which negatively affect performance both on transmit and receive not to mention potentially reduced output power.

This isn't a matter of opinion or conjecture.

[geoffr]

Found this a while back.. might be of interest on this thread...

Automatic Buck-Boost Converter DC 8-30V to 2-16V Constant voltage Current solar Regulator battery charger car power supply

link naming is weird - should point to:
Automatic Buck-Boost Converter DC 8-30V to 2-16V Constant voltage Current solar Regulator battery charger car power supply

[john61ct]

60-80w limit.

That kind of size is perfect **for devices that need it**.

Now look at pricing on whole-boat level ampacities.

My point being that would be very wasteful, especially since completely unnecessary.

I have the same opinion about inverters, usually grossly overused, just because they're easy.

[Paul Elliott]

Originally Posted by TreblePlink

I agree that 12 volt AC inverters are inefficient "power slurpers" but how can a 12 volt DC-DC converter be 95 to 98% efficient? The required rectifier diodes have a minimum of 0.4 volt forward drop - or more with higher currents. Add that to the switching and inductor losses ... and you get to 90% pretty fast.

Please correct me if I'm wrong.

The efficient ones use switched FET transistors in a switched rectifier bridge arrangement. The forward drop is in the low millivolt range -- much better than with diodes.

FWIW, I've not found a need for a secondary regulator on my 12V boat. I run SSB, nav electronics, LED lighting, laptop and "brick" computers, etc, all connected to my battery distribution / breaker panel. I use 12V/USB adaptors for the gadgets that want USB charging, and in-line 12V switchers for computers that need other than 12V. My windlass and electric winches are also connected to the main battery via breakers.

But I've got a fairly massive 12V AGM bank -- four 8D batteries totalling almost 1000 Ah capacity, and the wiring is top-notch. A system with a smaller bank might show unacceptable sag under similar heavy loads.

[john61ct]

Amazon links don't work.

https://www.ebay.com/i/272069213958

Use the same keywords to search for higher ampacity units.