Inverter power consumption

  De Marcus™ 10:46 27 Jul 2006

This isn't a particulary computer related thread so thought fit to post here instead.

I've just dusted off and aired our tent out, we're off camping this weekend, a mini break if you will. I've copied some of our daughters favourite movies to the hard disk of our laptop so she doesn't get too bored out in the wilderness of Yorkshire. I will be taking a fully charged laptop that lasts around 2 full length movies in terms of battery life, I'll also be using it for serving up a little background music. I have a Halfords power inverter to charge it up, I've used this successfully in the past to charge ipods, camera batteries, etc. My question is, how long would a 14.8v 4400 mAh battery take to charge on the inverter? It's rated at:

DC input: 10-15v
AC output: 230v /50Hz
Battery Low Alarm: DC 10.5v +/- 0.5v
Battery Low Shutdown: DC 10v +/- 0.5v
Output Power: 120w Max

I'm asking because I've been caught out before, I left the inverter charging a lantern and when I returned the lantern was charged but there wasn't enough kick left in the battery to start the engine, no problem though, we bump started it. I've got a Grand Cherokee now which is automatic so if the same happens again, I'll be buggered and a long way from home and wanting to avoid calling the AA out.

  De Marcus™ 11:25 27 Jul 2006

The power brick:

Input: 100-240v~ 1.6a 50-60Hz
Output: 19v 3.42a


  oresome 12:10 27 Jul 2006

If I understand the question correctly, I think the answer will come from the laptop manual.

The car battery powers the inverter which in turn powers the power brick. The output from this feeds the laptop, but will be regulated further within the laptop to charge the internal battery and it all depends on the design of this circuitry.

The manual should give a time for fully charging the battery, I'd have thought.

  De Marcus™ 12:19 27 Jul 2006

I'll try to clarify,

Is there enough power in a car battery to charge the laptop fully without leaving me high n dry and unable to start the engine?

The manual only states a time of 24hrs for the initial charge, no guide on how long subsequent charges should take, on average though they take about 4-5 hours for a full charge.

  Steve- 12:19 27 Jul 2006

My laptop which has a similar rated PSU takes about 40 watts at 240 volts, assuming 50% efficiency in your inverter this could mean about 5 amps from the car battery. The charging time will depend on the Laptop circuits but will be the same as at home on the National Grid, I'd guess at about 1.5 Hours. A new fully charged Car battery should be able to deliver 5 amps for about 10 hours before going flat so charging the laptop should present no problem - just give the car a run now and then to top it up.

  De Marcus™ 12:23 27 Jul 2006

Thanks steve-, thats reassuring.

Do you think running the engine for 10-15 minutes every couple of hours is sufficient?

  Steve- 12:35 27 Jul 2006

Posssibly depending on the state of the battery, it would be better to take the vehicle for a run over a few miles. Your car manual should tell you the battery capacity in Ampere hours or Ah the battery should be able to deliver that number for 1 hour i.e 40 amps for 1 hour or 1 amp for 40 hours etc. I'd assume the 10 volt switch off on the inverter is designed to protect from a completely flat battery, the battery on your previous vehicle may have been faulty to have failed so fast.

  De Marcus™ 12:41 27 Jul 2006

Thanks steve-.

  David4637 15:16 27 Jul 2006

Try it at home after a good run in your car and see whether you can start the car after the laptop is fully charged. If not you could use a car battery charger. David

  oresome 17:06 27 Jul 2006

Re camping,

Before I got soft and used only sites with electric hook-up, I used a separate leisure battery to supply our electric needs which I put in the car every 2 or 3 days when we were travelling to re-charge.

The cigar lighter socket provides a suitable output current, although I had mine wired in the boot.

Much safer than depleting the car battery, especially on cold damp mornings with lots of dew about when the engine can be awkward to start.

I found that a split charge device is not required in the car as the added resistance of the wiring to the spare battery always ensures that the car battery gets the lions share of the alternator output.

  spargo 17:45 27 Jul 2006

De Marcus™

I,m not sure if your inverter can cope with the load the 'brick' is going to impose on it!
Max o/p 120W!

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