What is the condition of the lead acid battery? Is it in good condition? Is the low voltage wiring connections to the battery using appropriately large wire and oxidation free connections? The inverter surely includes an input undervoltage lockout feature of some kind. If the battery is quite weak and is in need of charging or replacement (or the wiring/connection resistance is too high), then the inverter will quite possibly cycle like you suggest.
A 1500W surge rated inverter hooked up to a good battery with low resistance connections should have no trouble juicing up a little laptop power adapter.
Hmm... Brand new equipment eh'? Good electrical connections (not connected through something like a cigarette lighter socket or anything like that)?
How does the inverter behave when you hook up other loads such as incandescent lightbulbs, compact fluorescent lamps, motors/powertools, large transformers, other electronic equipment?
Modern laptop powersupplies do have input capacitors which are fairly large (but some form of inrush limiting is already included in the supply, likely an NTC or simple resistor), but the inverter should still have no problem with it. It if can't even drive this then it can't drive a whole lot of equipment, and if that is the case it is of a very poor design. I find it hard to believe it is really that bad. Something else is not right. I suppose it is possible the laptop powersupply might have a high power factor input stage that expects to see a sinewave voltage source. If this is true, and the inverter produces a squarewave, then it is conceivable the laptop supply might behave badly, but still...
Hi All, Ok, this is my problem. I need to run 2 laptops from a 12v 'leisure' battery via an inverter. The battery is a 12v 110Amh item and the inverter is a 600W continuous/ 1500W surge item.
The trouble starts when plugging in the laptop AC/DC adaptor into the inverter output. Even without the laptop connected, this trips out the inverter, which then starts to click (sounds like a relay switching) in and out. During this period of about 20 seconds or so it appears that the inverter is trying to supply enough current but fails and retries. The LED on the laptop adaptor gets increasingly bright, and then (say after 20 seconds), the inverter stops clicking and works correctly. I can then plug the adaptor into the laptop and then all is well.
Whilst this gets me running, I'm not happy with this. It appears that the adapter is pulling a lot of current when power is applied. Once the laptop is up and running the current load is much less. Does anybody have any cheap suggestion as to how I might get round this?.
I can think of 2 approaches:
1). Try to limit the current to the adapter. This would have to be done in the 240V AC part of the system and frankily I'm a bit scared of playing around with this!.
2). Alternatively, I could replace the 19v laptop adaptor with something else which doesn't require such a large start-up current.
adapter. The simplest way to limit the maximum current, is to add a thermistor in series in the power line. The input of a laptop switching supply, in it's simplest form, can often present very large currents during startup, but most should have their own current limiting circuit to prevent this being too 'silly'. However the current could easily be perhaps 5A (at the mains voltage) during the starting phase. I'd be inclined to think that the most likely reason (like the poster above), is that something is preventing the invertor from working as it should. It is worth realising that the '600W continuous' rating will require over 50A from the battery, while the 'surge' rating, will hit over
125A. I'd suspect that if this is driven from a 'cigar lighter' connection on a 'leisure' battery, the supply is just drooping too far...
All of the equipment is brand new. The battery has been fully charged and is outputing well over 12volts (over 13volts whilst charging). I'm pretty sure the kit is in good condition.
resistance
adapter.
Yes, that's what I would have thought. 1500W at 240V should provide a surge current of 6Amps!. However, the inverter documentation doesn't say for how long this power can be maintained. The laptop adaptors appear to have a large capacitance - when power is removed from them, the LED remains lit for
30-40 seconds before fading. I suspect that there's a sillllmount of capacitance in the laptop adaptors and that when it is connected, it draws a large current for a significant time before reaching a'steady state' situation. If I could limit the current for this period then I think I could avoid the inverter shutting down. Trouble is, I don't know how to do this.
Lower-powered adapters are cost critical, and there is a tendency to drop such expensive features as inrush limiters. As the input capacitor is typically less than 100uF, and the CM choke has series resistance, the peak surge for 110V/60Hz applications can still be under 30A. At 240V, the economy would be misplaced.
As this isn't a feature required by safety agencies, however, it could conceivably have been neglected in your model. It should be specified in the product's literature, somewhere.
These units are often sealed, with instructions refering the end user to qualified service personnel with a threat of a voided warranty if opened. Any fiddling or modification will obviously be at your own risk - which could be considerable.
I know it sounds lame, but the best way to tackle this is to complain to both manufacturers (inverter and adapter) and vendors, with pertinent details and model/serial numbers. Replacing the cheapest part, in the mean time, preferably with a different model/mfr might make the problem go away while the system grinds towards whatever conclusion is possible.
You might also consider listing the incompatible model numbers here, for a start, (and where you purchased them) until the problem is resolved to your satisfaction. They might ring a bell with other readers.
No cigarette lighter sockets here. It's literally about 1metre of cable from the inverter straight onto the terminals of the battery. I've put an AVO on the battery and it always reads > 12v at all times. I've run a radio from the inverter and that works fine. The inverter comes from Maplin (UK electronics reseller) model
NIKKAI N66AU 'ideal for applications such as notebooks, camcorders, modbile phone chargers...etc.. etc...'
and only cost about £40 but which fullfills the required specification on paper at least. The annoying thing is that once it's up and running it works fine. It's just getting it running that's the problem.
I read in sci.electronics.design that Dave Moore wrote (in ) about 'inverter problem and current limiting', on Tue, 7 Dec 2004:
So, either it is faulty or it won't, by design, cope with the inrush current of a laptop. Either way, you take it back to Maplin and complain.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
I run my Siemens laptop direct from the 12 rec battery in my camper, even though it is supposed to run off 19V. Seemed to work. I did try a Maplins "grade" inverter (QM81)) with the laptop mains adaptor, but that would cut out after 10 mins, even though load is only 90 watts or so. Shit inverter, but it will still run my soldering iron, scope, quantum solar nullifier, autodynamic toothbrush( without de-thrutcher), badger debristoller, toe nail curler etc.
martin
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