Jump to content

On board inverter, how small is too small?


Recommended Posts

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?

Link to post
Share on other sites

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.

Link to post
Share on other sites

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.

Link to post
Share on other sites
Guest 000

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.

Link to post
Share on other sites

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.

Link to post
Share on other sites

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.

Link to post
Share on other sites

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

Link to post
Share on other sites

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... ;)

Link to post
Share on other sites

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

Link to post
Share on other sites

Pure sign hands down. As IT stated the inverters aren't efficient apart from a somewhat narrow band, DC-DC's are good but limited. If you have a fairly good idea of what you want to run then size the inverter for this in it's peak band

 

https://www.victronenergy.com/upload/documents/Output-rating-operating-temperature-and-efficiency.pdf

 

In this document you can see that if you wanted 400-1600w of load and have 90%+ efficiency you'd be looking at the 3000va units. DC-DC converters top out at 98% for the expensive super duper ones

 

 

Really comes down to what exactly you are planning to power.

Link to post
Share on other sites

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.

Alternators won't start to produce power below 2000rpm so work out your pulley ratio. Wind gennys are great when a cyclone is about, all other times a lot of noise and nothing at the other end so SPs are the way to go and good storage for rainy days.

Link to post
Share on other sites

Most laptops require 19v DC to run (chip set and CPU power) and as others have stated, the best 12v DC conversion is to run a simple switch mode power supply to get 12v to 19v. Inverters be it pure since wave or square won't create a problem when using a laptops 240v power supply as the filtering is able to handle the ripple but if you are power conscious, go a direct DC to DC converter. Basically it's a oscillator stepping 12v up to 19v using a transformer so better conversion than inverter and converting down.

The Chinese are now producing laptops that are true 12v. However the wattage will probably be the same as a 19v unit (more amps) so no real gain.

We have gone down this road and there are now USB (5V) PCs available that have dual processors and capable of 1080p HD resolution. They have USB ports so mouse and keyboard can be plugged in and externally powered hard drives run OK. All you do is plug them directly into a HDMI port on a monitor and there are 12v monitors about that can run these. 2ah!

Link to post
Share on other sites

So, We've gone Jon's way, and got a smaller supply just for charging the myriad small devices and will get a larger one later. Reasoning is this: 

  • The macbook pro is a bugger to find a decent 12v charging solution for and I'm not upgrading my Mac because it's already kick arse and supposed to last me another 4-5y.
  • The small inverter, although less efficient, also allows me to charge a bunch of other different things with different voltages, that a fixed DC-DC converter doesn't. So I only have to buy one item, and not a number of items and given the state of the bank balances at this moment, that's a good thing.
  • The prospective wind generator is intended for longer voyages - yes I know they're noisy.
  • We will also get a 100W Solbian "flying" panel, to position optimally when the sun is out for additional power; weighs only 2kg.
  • I have battery powered power tools, that can be charged from it. 
  • It's small enough that I won't be tempted to try to run my big powertools from it. 
  • It's large enough that I can run this and save a bit on bottled gas.
  • bialetti_moka_electric_standard_1.jpg
Link to post
Share on other sites

The Dutch take their coffee very seriously which is why I am not letting Joke see the pic of your espresso pot. Have looked online for wattage info but without success. But producing heat takes mega amps from your battery - can your system afford it?

Link to post
Share on other sites

You’ll find, DrW, that 160amp hours is small. IMO. We use about 150amp hours every 24 hours on average. I know lithium is easier, faster charge rate etc, but you still have to put it back in!

What’s the engine?

Link to post
Share on other sites

Yea, I actually want to double it to 320, but had trouble convincing the yard and my bank balance Engine is d1 4. Standard alternator, so I’m still looking for more charging. At least with the Li a short period of higher current load won’t kill it.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...