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laptop car charger

Kal_B

Member
Hello,

I've tried a couple of those small300-400W inverters from Canadian Tire and Walmart to power up my laptop and they didn't work at all.
Does anyone have good experience with one that you can recommend?
How about those ones I see online that plug right into the laptop, so 12VDC to whatever laptop voltage, are these any better?

Thanks
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Definitely go for a purpose made car charger, they are far more efficient that going via an inverter & less likely to have problems.

The Lind ones are excellent; not cheap but very high quality. They often appear on ebay.

Examples from the makers site:
 

Diver300

Well-Known Member
Most Helpful Member
I agree that it's inefficient and needs lots of components to go via 120 V ac. It's better to have a dedicated 12 V to laptop charger. The Lind ones are good but are quite big. You can get very small chargers for Dell laptops, and probably other makes.

https://www.ebay.co.uk/itm/GENUINE-...759175&hash=item5dc6c68508:g:iAsAAOSwwRpgXvDv

I've used those quite a lot. You need to get the one that fits your laptop.
 

Diver300

Well-Known Member
Most Helpful Member
As to why the inverter didn't work with the laptop charger, I have seen that happen.

A lot of inverters are sold as "modified sinewave", which is more like a square wave with every second pulse negative. The waveform has about the right RMS voltage, about the right peak voltage, and about the right Volts-seconds so that conventional transformers don't saturate. As a result, most loads will work fine.

However I've seen a laptop power supply that simply did not turn on when connected to one modified sinewave inverter. I think that the power supply detected the periods of zero voltage between the pulses as power interruptions.

For that, I bypassed the problem by connecting the laptop charger input to the DC voltage that the inverter produces, before it is chopped into the modified sine wave. That meant opening the inverter, messing around with lethal voltages, and having an IEC lead with DC on it, what would have damaged quite a lot of loads, but it did run that laptop.

I would go for a direct 12 V input laptop charger if I did it again.
 

Kal_B

Member
Thanks everyone. Lots of great information.
With regard to power consumption, my AC adapter is rated for 120w and I have found a car adapter one locally ( store is closed, will buy it tomorrow) also rated for 120w and I will assume that should do. But I am curious if there's considerable difference in consumption when charging and when not. Two scenarios, one the battery is fully charged and two is the battery is removed, does either of both of those situations consume less?

Thanks
 

Diver300

Well-Known Member
Most Helpful Member
Laptops and their charging are complicated.

Most laptops adaptors can signal to the laptop how much power is available, so the laptop won't take more than that. If you connect a laptop to a lower-rated adaptor, the laptop will limit the rate of charging of the battery so that the adaptor isn't overloaded.

A laptop will usually take much more power when it's charging its battery.

The computing part of the laptop will take more power if the display is brighter, or if the processor is doing more work. If the power that the computing part is taking is more than the rating of the adaptor, then the battery will be discharging rather than charging. That can happen briefly as programs, or the whole laptop, are started up or shut down. If large amounts of computation are happening, that will increase the power, so running a game with lots of graphics can often make the laptop use more power.

If the laptop is connected to a low-power charger, the processor may be slowed to reduce power consumption. Also, it may be impossible to turn the laptop on with a low power charger connected, and no battery fitted.
 

Kal_B

Member
One more silly question just out of curiosity, I purchased a DC one and set it to output 19.6VDC (actually it insisted on the 0.6 by itself) and it works great.
hypothatically speaking how long would it take to drain the car battery (DieHard Gold- Group Size 34, 800 CCA)?

Thanks
 

MacIntoshCZ

Active Member
One more silly question just out of curiosity, I purchased a DC one and set it to output 19.6VDC (actually it insisted on the 0.6 by itself) and it works great.
hypothatically speaking how long would it take to drain the car battery (DieHard Gold- Group Size 34, 800 CCA)?

Thanks
lower than
Amper-hour rating on battery/ Load current of invertor in Amps.
for example
70Ah/6A
 

Pommie

Well-Known Member
Most Helpful Member
Just looked at my laptop, it says 19V @ 3.5A which is around 70W which will be laptop on and battery charging. At that rate a 12V 80Ah battery will be completely flat in ~14 hours. Note, cold cranking amps (CCA) mean nothing in this case - just the Amp Hours.

Mike.
 

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