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On board inverter, how small is too small?


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#1 DrWatson

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Posted 09 May 2019 - 08:14 PM

So as we're checking things off lists for the final handover, equipping and victualing the boat is in its final planning stages.

 

Trying to think of everything you need that you normally build up and refine over years, but without adding crap tonnes of weight. 

 

Last night i realised I have no way to charge the laptop on board. Heaps of USB plugs but no 240V. So I decide an inverter is the way.

 

And here the fun starts. 

 

Modified or pure sinewave (price difference x3).

 

How small is too small? Mac charger will suck 1.8A at 110-240AC, apparently, so worst case the charger sucks 440watts or thereabouts. So a 500W pure should cover that, but i can get 800 for an additional €150, or go further to 1200 but then we're looking at nearly €500 all up, or more if I get the "Phoenix compact". THis is all Victron stuff I'm talking about.

 

Will we need (as opposed to want) extra power?

 

Thoughts?


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#2 Island Time

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Posted 09 May 2019 - 08:49 PM

If all you want it to charge the laptop, it's much more efficient to simply buy an automotive dc-dc power supply for it.
Inverters are not as efficient.
However, you may like to install one large enough to run any power tools you may have in case of emergency.
I'd suggest 1500w true since wave with 3000w max.
Jaycar have them, not too expensive.
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#3 Island Time

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Posted 09 May 2019 - 08:51 PM

If all you want it to charge the laptop, it's much more efficient to simply buy an automotive dc-dc power supply for it.
Inverters are not as efficient.
However, you may like to install one large enough to run any power tools you may have in case of emergency.
I'd suggest 1500w true since wave with 3000w max.
Jaycar have them, not too expensive, about 700 nzd.
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#4 Chrisc

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Posted 09 May 2019 - 08:53 PM

I would go big on the inverter. We have a Victron 2 kw and a Victron 1 kw.
The 1 kw is ok for charging phones and tablets and it will run the fridge but it trips out at startup where i assume there is a bit of a spike so not much use. But good to have a little reserve capacity for whatever you may want to power in the future. We now have a small vacuum cleaner.
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#5 wheels

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Posted 10 May 2019 - 05:35 AM

To start with, pure sine wave. They have been around for so long now, they are not as expensive as they used to be. Plus everything will work on them and you do not get the electronic buzz some gear can put out with the modified wave.
Most gear draws max at start up. So to avoid tripping out, work on a rule of thumb of having bigger than needed. It is hard to put an exact figure on size, but for instance(an example only) it takes 3x the normal current draw to start a microwave running.
Many Boat Inverters double as Chargers as well and many also have internal auto change over switches to switch between shore/gen or battery supply. It makes everything seamless. For instance, I might be on the laptop or watching TV and wife starts the Genset to run the Microwave. The Inverter switches to the Generator supply and the inverter switches from supplying to charging. She stops the Genset and the thing switches back to supplying power and all the time, I have not noticed a thing.


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#6 mattm

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Posted 10 May 2019 - 08:22 AM

What’s the battery / charging system like? Genset or just main engine as main charge source? All good having a big inverter, but you need to be able to power it. Have you got the battery capacity to realistically run it engine off? Or would 1500w be engine in only? If engine on, 1500w could draw 130A+, can the alternator hack that, or would 5 mins of 1500w mean 30 mins of engine run to recharge the difference used. Is that what you want? What would you need to run that would make you ok with that? Does the boat have a smart (3 step) alternator regulator - great upgrade if thinking of heavy 12v loads / long trips.
IT has a good point re power tools, but I’ve seen a couple of boats who have brought 12v power tools, removed the batteries and put a lead and cig plug on them and run off 12v also. Seemed to work well.
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#7 Cazzate

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Posted 10 May 2019 - 08:30 AM

Dunno if you are planning on having a microwave or a 240v fridge or a genset but I guess not if it’s a pogo !

IT mentioned power tools , we live off grid and have a substantial solar system now but while we were building I only had a single 80w panel and a marine deep cycle battery in the shed . This charged the batteries for all my makita power tools for two years and tablets phones etc through a 1500w inverter . Makita fast charger draws 65w and takes about an hour to charge a 4amp battery . I reckon IT is on the money don’t go huge and use it wisely when the sun is out or the engine is running
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#8 DrWatson

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Posted 10 May 2019 - 08:47 AM

What’s the battery / charging system like? Genset or just main engine as main charge source? All good having a big inverter, but you need to be able to power it. Have you got the battery capacity to realistically run it engine off? Or would 1500w be engine in only? If engine on, 1500w could draw 130A+, can the alternator hack that, or would 5 mins of 1500w mean 30 mins of engine run to recharge the difference used. Is that what you want? What would you need to run that would make you ok with that? Does the boat have a smart (3 step) alternator regulator - great upgrade if thinking of heavy 12v loads / long trips.
IT has a good point re power tools, but I’ve seen a couple of boats who have brought 12v power tools, removed the batteries and put a lead and cig plug on them and run off 12v also. Seemed to work well.


Yea we have 115A alternate and a small solar panel circa 70W. Battery is 160Ah lithium. So it’ll deliver the current, but running the engine for bigger loads would be imperative. I’ll like get a wind gen for longer trips.

No idea on the actual charge setup. The start is still lead acid, and the alt also charges the Li so im interested to find out how they’ve set it up. I know they did have to get a diff charge controller, at least for the solar part. Let’s see....

I’ve got a few Ryobi batt tools which seem to do ok, and a couple 5Ah batteries. Charger draws 50 w or something.

Correct Cazzy, no 240v whiteware aboard... ;)
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#9 Jon

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Posted 10 May 2019 - 08:50 AM

I’ve got two cheap 400w inverters that are wired to there own power point
One is for the laptop and under chart table with label “laptop only”
The other is under TV which we use for movies charging phones, tablets, recharged power tools and torches.
I like the redundancy of having two and you can pickup a replacement anywhere around the world for very little.
If I was running a computer based primary nav system I’d go more serious however but it’s great to be able to plug in anything small from electric toothbrush to god only knows what
However we do have a 170w alternator on main engine and 7.5kw genset
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#10 Steve Pope

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Posted 10 May 2019 - 08:54 AM

A couple of extra solar panels are much quieter than a wind gen, no moving parts either. Another way is to have a belt driven alternator running off your prop shaft.


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