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300w Inverter - Does the device itself draw much from batteries?


Jim Batty

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I've been having trouble finding a 12v cigarette lighter type charger for an old-ish MacBook Pro.

 

What I'd like to be able to do is charge the laptop in the evenings after the solar panels have done their thing and topped up the leisure battery bank.

 

Wandered into Maplin where they have a deal on a 300w inverter. Now I know inverting 12v to 240v then dropping it down to 18v (?) again via the standard computer adaptor can't be the most efficient way of going about this. But I was wondering how much a 300w inverter draws just being hooked up to the battery bank.

 

(We have a 1500w inverter/charger, but it seems over-the-top to run that at night just to recharge a laptop.)

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12V to e.g. 18V converters are commonly available on Ebay, if the power rating is greater then the maximum power demanded by the laptop it should work on some older Macbooks (there is information on the web listing the MacBooks that will work from a simple DC supply). The problem is obtaining the correct power connector for the laptop. Maplin have a range of leads and adapters; if your MacBook has the 'mag' connector you may not find a solution.

 

I have a Maplin 300W MSW invertor. It powers my HP laptop but refuses to work with my HP printer. I guess it draws ~0.8 to 1A on standby and is unlikely to be more efficient than your existing 1500W invertor.

 

It would be more efficient to recharge the laptop when the solar panels are active or the engine is running. Ideally, remove the fully charged laptop battery (may not be possible with a MacBook) and run it from a 12V or 240V invertor. Li-Ion batteries have a limited cycle life and are much more expensive per Kw/h than any lead/acid battery. They particularly do not tolerate being discharged to 95% then topped up to 100% which is what many laptops do when permanently connected to external power.

 

HTH, Alan

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I have a 300w Maplin special and when I try to charge the mac pro book the mac power supply switches off after a few seconds and won't come back on..

Works ok off the main inverter.

 

Terrible device...

 

Bob

My 300W Maplin (Nikkai) invertor has served me well for ten years. It always had a problem with a small inductive loads like an electric drill but the second operation of the trigger usually allowed me to drill a hole. More recently it has developed a fault; leave it switched on for a few hours and it works fine but after being switched off for a while it pulses the 240V at ~80Hz. dropping to 60Hz and then permanent 240V with a small load applied. Dirt cheap on their annual offer, it has paid for itself but I can only reccomend it as your only invertor for small power applications or a backup (e.g.for 'fridge) if your main invertor fails.

 

HTH, Alan

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12V to e.g. 18V converters are commonly available on Ebay, if the power rating is greater then the maximum power demanded by the laptop it should work on some older Macbooks (there is information on the web listing the MacBooks that will work from a simple DC supply). The problem is obtaining the correct power connector for the laptop. Maplin have a range of leads and adapters; if your MacBook has the 'mag' connector you may not find a solution.

 

I have a Maplin 300W MSW invertor. It powers my HP laptop but refuses to work with my HP printer. I guess it draws ~0.8 to 1A on standby and is unlikely to be more efficient than your existing 1500W invertor.

 

It would be more efficient to recharge the laptop when the solar panels are active or the engine is running. Ideally, remove the fully charged laptop battery (may not be possible with a MacBook) and run it from a 12V or 240V invertor. Li-Ion batteries have a limited cycle life and are much more expensive per Kw/h than any lead/acid battery. They particularly do not tolerate being discharged to 95% then topped up to 100% which is what many laptops do when permanently connected to external power.

 

HTH, Alan

 

Exactly correct.

 

That is what I would have said but Iwas a sleep. smile.png

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I have a 300w Maplin special and when I try to charge the mac pro book the mac power supply switches off after a few seconds and won't come back on..

Works ok off the main inverter.

 

Terrible device...

 

Bob

 

We have made use of a 300W Maplin Inverter on "Chalice" for many years as the only source of 230V.

 

It has worked reliably, and powered everything I would expect it to, from small twin tub through to many types of laptop power supply.

 

I have measured the current it draws when not powering anything, but can't remember exactly what it is. No0t a lot, I know, possibly an amp or two.

 

That said we are very frugal power users, and generally turn it off when it isn't actually needed.

 

It has been good enough that I bought a second one for ad-hoc use on "Sickle".

 

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I've been having trouble finding a 12v cigarette lighter type charger for an old-ish MacBook Pro.

 

What I'd like to be able to do is charge the laptop in the evenings after the solar panels have done their thing and topped up the leisure battery bank.

 

Wandered into Maplin where they have a deal on a 300w inverter. Now I know inverting 12v to 240v then dropping it down to 18v (?) again via the standard computer adaptor can't be the most efficient way of going about this. But I was wondering how much a 300w inverter draws just being hooked up to the battery bank.

 

(We have a 1500w inverter/charger, but it seems over-the-top to run that at night just to recharge a laptop.)

 

Hi Jim

 

My twopenneth is that rather than buy a cheapo device that for similar money top quality stuff in good nick is often on fleabay or gumtree second hand. In the past 3 years I have purchased 2 mastervolt inverters a 1200 and an 800 fo 150 pounds each and both giving great service. The 1200 draws 0.4 of an amp when switched on but nothing running, mastervolt are sooooooo much bettter in every way.

 

Tim

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(We have a 1500w inverter/charger, but it seems over-the-top to run that at night just to recharge a laptop.)

Why do you think it seems over the top? In all probability the power taken from the battery by a 300 watt inverter will be almost exactly the same as would be taken by your 1500w inverter, in fact if it's a cheap 300w inverter it may even take more.

 

And remember that even the 12v to 18v converters are just an inverter in disguise, so they can be quite inefficient too.

 

My advice would be to use your existing inverter and spend the cash on some beer instead.

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I think there are 12v to 18v ( variable ) DC to DC powers supplies available ...... they take your variable 12v battery power supply and can be tuned as it were to produce a stable 18v or 19v supply for a laptop. As has been said, you may have to be creative to connect the laptop input plug.

 

Serenity Malc.

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I read the OP's request as 'how much does an inverter draw when on standby'

My answer - based on recent measurements is:-

(Not 42) but between .3 to .75 amps ('depending' on the actual machine). That seems an awful lot for a device just waiting for your needs.

Whether or not that current draw is in addition to the power needed to deliver mains voltage when running - I know not.

 

The answer of course is to switch the inverter off when not in use - but then you're asleep...

 

An of these devices 12 to 18V converters included will have some standby penalty.

I have a 24 to 12v converter for my radios and found that it draws 300mA in standby.

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I have a 300w Maplin special and when I try to charge the mac pro book the mac power supply switches off after a few seconds and won't come back on..

Works ok off the main inverter.

 

Terrible device...

 

Bob

Probably the mac power supply wants a true sinewave and won't work on a Modified Sine Wave inverter.

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Thanks everyone for your input.

 

I have a 300w Maplin special and when I try to charge the mac pro book the mac power supply switches off after a few seconds and won't come back on..

Works ok off the main inverter.

 

Terrible device...

 

Bob

 

Hi Bob, is yours a modified sine wave one or a pure sine wave? I'm wondering if the Mac would prefer the latter? The fairly knowledgeable fellow at Maplin, who seemed to know Macs, suggested that the modified sine wave one (300w @ about £49) would be fine. He said only video/tv type equipment demanded pure sine wave.

 

... if your MacBook has the 'mag' connector you may not find a solution.

 

I have a Maplin 300W MSW invertor. It powers my HP laptop but refuses to work with my HP printer. I guess it draws ~0.8 to 1A on standby and is unlikely to be more efficient than your existing 1500W invertor.

 

It would be more efficient to recharge the laptop when the solar panels are active or the engine is running.

 

Hi Alan, yes my Mac has the old 90-degree mag connector. I am massively surprised that Apple haven't designed their own 12v charger. Surely there must be tens of thousands of people who want to charge their laptops in cars. The only third party charger I can find online for this connector has been discontinued.

 

Yes, I know it would be ideal to charge the laptop straight off the 1500w inverter during the day when the solar panels are humming away and putting out 6 amps. Due to other commitments though I can't always be on board during the day! And I'd like to be able to sometimes just plug the laptop in to fully charge it up for later (evening) use.

 

The efficiency of the 300w Maplin inverter was what I didn't understand. I suppose I thought it might draw 1/5 the amount of the larger 1500w inverter ... so could be flicked on for, say, 2 hours to recharge the laptop and draw next to nothing over and above what the laptop battery needed.

 

 

Why do you think it seems over the top? In all probability the power taken from the battery by a 300 watt inverter will be almost exactly the same as would be taken by your 1500w inverter, in fact if it's a cheap 300w inverter it may even take more.

And remember that even the 12v to 18v converters are just an inverter in disguise, so they can be quite inefficient too.

My advice would be to use your existing inverter and spend the cash on some beer instead.

 

Ho ho! I think this is probably going to be the way to go. Save myself £49.

 

I suppose that if there's enough sun the following day the solar panels will fully charge the leisure batteries and what does it matter.

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Why do you think it seems over the top? In all probability the power taken from the battery by a 300 watt inverter will be almost exactly the same as would be taken by your 1500w inverter, in fact if it's a cheap 300w inverter it may even take more.

 

And remember that even the 12v to 18v converters are just an inverter in disguise, so they can be quite inefficient too.

 

My advice would be to use your existing inverter and spend the cash on some beer instead.

Today we have found out just the same.

 

Our new 2000 watt inverter when turned on with no load applied uses less power than our old El cheapo 300 watt unit did.

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We have made use of a 300W Maplin Inverter on "Chalice" for many years as the only source of 230V.

 

It has worked reliably, and powered everything I would expect it to, from small twin tub through to many types of laptop power supply.

 

I have measured the current it draws when not powering anything, but can't remember exactly what it is. No0t a lot, I know, possibly an amp or two.

 

That said we are very frugal power users, and generally turn it off when it isn't actually needed.

 

It has been good enough that I bought a second one for ad-hoc use on "Sickle".

 

 

I agree is is a good piece of kit but it dosn't work with Mac power supplies.

One pother thing is if you use it through a lighter socket its only rated to 150w

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