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Old 05-08-2015, 01:51   #16
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Re: Laptop charging

I'm starting to think that I should invest in a decent quality permanently installed inverter. I assume that even if I get a high output unit, if it's efficient it will still draw not much more than the Mac charger requires?

It would be kind of nice to be able to occasionally use my electric toaster for a special treat at anchor (750w @ 230v = 39A @ 12v?)
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Old 05-08-2015, 02:27   #17
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Re: Laptop charging

By the way Rapture40, iPads are easier than MacBooks. You can't charge a MacBook with 12 volts or with a standard 5 v USB as you can with Android or IOS devices. The only safe way to charge a MacBook is with the supplied mains charger on a sine wave AC of between 100 and 240 volts. I know this as I have iPhone, Android phone, iPad and MacBook Pro. I've just literally used 3X reading glasses and a magnifying glass to read the MacBook specs on the charger again.

It's output (that goes into the Mac) is DC 16.5 volts and up to 3.65 amps. That only makes 60 watts but we still need a sine wave inverter rated at +300 w to charge it. I think it's to do with impedance which is basically AC resistance and that applies to the inverter as well as the Mac charger. Someone else might advise.

I use the same MacBook charger either in NZ with 230v 50 cycle or in USA with 110v 60 cycle as lots of charging equipment is now designed. Would you believe my MacBook charger is made by Samsung Electronics?

The main reason you can't use 12 volts to charge is that you can't easily turn 12 volts DC into 16.5 v DC.
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Old 05-08-2015, 04:16   #18
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Re: Laptop charging

My inverter is a PITA.... even now with plenty of amps being pumped in from the solar and a 95% full battery, it squeals like a pig and then cuts out even when the volt meter is showing 12.9v. I would blame the cig lighter connection except it works fine when the motor is running.

I'm just glad I'll be in Kalamata marina on Friday and then in Stockholm for a few days. I will buy a decent inverter.
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Old 05-08-2015, 04:24   #19
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Re: Laptop charging

I bought a cig lighter to Macbook thingo a few years ago for ' a large sum of money'. Worked well until I used it when radios were on..... massive RFI. Still have the Macbook plug end but have that connected that to one of these Mini-Box - ,Power Supplies (mini),Micro-UPS Load Sharing Batteries which lives in the $10 enclosure they also sell.
Works good.....
Also have two of their 'dumb' 12v/12v jobbies.... regulates the 12v input so no brownouts when starting the engine or voltage spikes when ever.
One is inside my ship's PC that is used for sailmail/cmap stuff/etc, the other runs the lcd/led display at the chart table. All work well and with no fuss for some years now
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Old 05-08-2015, 04:42   #20
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Re: Laptop charging

Correction... 'it always worked well but produced a lot of RFI'.....

I see they now have an .au addy... I bought mine directo from the US... maybe they also have a European website as well these days.

Running a bloody great inverter to run a computer charger doesnt make sense to me... bin there done that...
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Old 05-08-2015, 05:18   #21
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Re: Laptop charging

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Originally Posted by El Pinguino View Post
Running a bloody great inverter to run a computer charger doesnt make sense to me... bin there done that...
I agree, it can be grossly inefficient, I certainly don't have that sort of power to burn on my little tub ;-) While my battery charger serves as a 1000W inverter in a pinch for something like a power tool or similar, pretty much nothing requiring electrical power comes aboard my boat unless it can be plugged into a 12V DC outlet...

I believe Maine Sail did the calculus awhile ago on the inefficiency of charging devices using an inverter, it was pretty significant as I recall...
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Old 05-08-2015, 06:24   #22
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Re: Laptop charging

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Originally Posted by GrahamHO View Post
By the way Rapture40, iPads are easier than MacBooks. You can't charge a MacBook with 12 volts or with a standard 5 v USB as you can with Android or IOS devices. The only safe way to charge a MacBook is with the supplied mains charger on a sine wave AC of between 100 and 240 volts.



The main reason you can't use 12 volts to charge is that you can't easily turn 12 volts DC into 16.5 v DC.

It is very easy to turn 12V into 16.5V and charge a MacBook directly from the house batteries. We do it all the time, and several here have stated the same.

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Old 05-08-2015, 07:31   #23
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Re: Laptop charging

How about this?

http://www.technomadia.com/2009/05/t...ower-supplies/
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Old 05-08-2015, 07:38   #24
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Re: Laptop charging

i dono thave a mac anyhting, but i do have netbooks and a chromebook i occasionally use with a 12v cigarette type plug invertor. works great. i usually feel my cords as i already know about shipboard fires, having experienced 2 on this boat BRFORE it was mine.... oops fun beginning.....
the cords and plugs thet heat up i ditch,as they are potentially firestarters. the connections inside are toasting selves. quit early, when warm.
i also have 400 wtt invertor which was installed strangely, and i wont use until it is reinstalled correctly.
i prefer the lil lower wattage cig lightr kind, as they donot use as much juice to use.
and ALWAYS make sure your invertor can handle the wattage of the machine you plug into it.. there are more than one kind of these..90 wtt, 120 wtt, 200 wtt... i us 120 wtt, as 90 is too small and heats up hard.
i tried using the special universal 12v computer cords--they lasted 3 months with constant usage. oops...
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Old 05-08-2015, 13:41   #25
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Re: Laptop charging

I would very much like one of those 12v MacBook chargers that don't use an inverter. Nothing like that available here in NZ. I'll be visiting Canada and U.S. for a month from next week. Where do you think I could pick one up from a shop rather than on line. I don't think Apple stores sell them?
I wonder if they fully charge the MacBook or just up to 12v?

I don't need to run my motor for my hard wired inverter to charge the MacBook.
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Old 05-08-2015, 13:58   #26
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Re: Laptop charging

The Apple magsafe power adapter pulls a maximum of 85w and 1.5 amps. I'd be really surprised if it were the culprit in your problem except if it is defective. The mikegyver version should operate with the same specs, I believe.
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Old 05-08-2015, 14:01   #27
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Re: Laptop charging

After hours of frustration trying to charge on the inverter without the motor, I decided to run a cable directly from the 12V bypassing the electric panel to the car charger (the melted plug was removed) but with a 10A fuse in line. The cable I used is the same diameter as on the charger, probably 1.5m2

I checked occasionally and the cabling did not get hot.

I will either find myself a better quality set of car plugs or failing that, some other plug that will make a good connection and be rated for a decent amount of amps. I think I will also look for a better inverter as well.
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Old 05-08-2015, 18:51   #28
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Re: Laptop charging

Suijin, my Magsafe charger (made by Samsung Electronics) is not faulty. It is rated at 16.5 v / 3.65 a, output which is a fraction over 60 watts.

A good quality sine wave inverter of just under 300 w BUT with a lighter plug DC input lead will not charge my 13" MacBook Pro. The overload signal goes off signalling low voltage input to the inverter. That happens on my boat with heavy wiring to the cig socket. It also happened in a couple of cars even with the motors running. When I returned it for exchange to Jaycar the supplier, we did those and other tests. Jaycar is one of the biggest retail electronic parts suppliers in Aus / NZ

The 60 w of the charger is only its output. The charger itself consumes power and an inverter is not 100% efficient. So there is more power being consumed and even the best boat DC wiring has some voltage drop. Then the connection of the lighter plug / socket and the plug's built in glass fuse drops the voltage a bit more with its spring contacts.

I believe the main culprit is the attached lighter type plug. The inside of even the best quality lighter plug is so confined that a decent heavy input cable is impossible.

We have a good range of inverters available but the lowest wattage of sine wave inverter I could find with heavy DC input terminals is over 300w. It may be possible to hack into a smaller sine wave cigarette lighter type and install heavier cables but if you try and it doesn't work you can't return the inverter.

Some have run their engine to make it work where they are inputting maybe 14 v but maybe less if the charge is floating. My solar was providing around 13v / 14 v when I tried in the boat several times during a few weeks away.

There is no problem with my replacement hard wired 350 w inverter even while occasionally using an Elgato / MacBook UHF tuner to watch TV at night when the MacBook naturally heats up a bit. Don't want to run the engine then and don't want to flatten the MacBook battery.

There are 12 v adapters that some people have reported to charge OK but they report RF interference. That naturally suggests to me oscillation in the circuit.

Now I'm going to speculate that perhaps they work by rapidly charging and discharging a capacitor producing a pulsing DC of 16.5 v.(much like a camera flash charges a capacitor and discharges a very high voltage flash) A pulsing DC current, like that could be smoothed with old fashioned chokes but it would still be pulsing. I wonder why Apple don't seem to sell them as far as I'm aware. But lots of people think that manufactures in general don't know very much. It may or may not be that they could void the warranty. But I don't know.
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Old 05-08-2015, 20:44   #29
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Re: Laptop charging

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There are 12 v adapters that some people have reported to charge OK but they report RF interference. That naturally suggests to me oscillation in the circuit.
Most laptops require more than 12v in to charge, so the "12v adaptors" for computers contain DC to DC converters that step up the voltage to what's needed (eg 20v for the Lenovo laptop I'm using now). So yes there's oscillation, and inductors and caps to achieve the conversion efficiently. They often produce RF hash.
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Old 05-08-2015, 21:41   #30
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Re: Laptop charging

In the past I've had problems with my Mac's touch pad not working properly when when using the inverter. Although it has not been a problem this time around, so I'm not sure if it is my Macbook Air that suffered. However I am having problem with the touchscreen on my Raymarine e7 when the inverter is running

Stupid inverters
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