Is it possible to charge a laptop from 12V,7Ah battery using a 75W power inverter?

[pradeep_k_b]

Hi,

I have a small power inverter with me(input voltage 11-15V dc,output voltage-220V ac,output power-75W,one that is used in car) and also have a small UPS battery(12V,7Ah-lead acid).Is it possible to charge a laptop with this?..Battery-inverter-laptop charger-laptop....Is this 12V,7Ah battery is enough to fully charge a laptop?

 

[faiza nasir]

no, this could damag ur laptop.the charger used in the car and that of the laptop are entirely different.perhaps it can charge ur laptop but it will do more harm then to charge ur laptop

 

[smijesh]

no, this could damag ur laptop.the charger used in the car and that of the laptop are entirely different.perhaps it can charge ur laptop but it will do more harm then to charge ur laptop

Laptop charger is designed for LI iron batteries only. But your configuration is

UPS Battery(7Ah ,12VDC)

Inverter (12V to 220VAC)(Should provide 500mA minimum)

Laptop Charger(220VAC to 19VDC@3.3A)

Laptop Battery(7.2Ah ,12VDC)

You can charge the laptop but not fully, each stage you may lose 15 to 25% of power loss. UPS Battery will fail first, because you drawing more current from UPS battery.

 

[pradeep_k_b]

Thanks for your reply.

@faiza..Please note,I am not charging the laptop directly from a 12V,7Ah battery..firstly I will convert the 12V DC to 22oVAC using an inverter...

@smijesh.....I think most of the laptop batteries are 11.1V,4400Mah,so its only 48Wh,but a 12v,7Ah battery can give 84Wh...Please note this...48 is just only 57% of 84....

 

[Audioguru]

When your laptop battery needs to be charged, the little lead-acid battery can power the inverter to operate the charger. It can fully charge the laptop battery only one time.

 

[pradeep_k_b]

@Audioguru...Thank you for your reply....Are you sure about this?..please let me ask you something,how much output power can be available from a fully charged lead acid lead acid battery?..or how much power can utilise from a fully charged lead acid battery before the deep discharge cut off ?...Do you know something about this

 

[faiza nasir]

@pradeep.....hmmm ok then u could recharge it but u can only charge it for one time

 

[nandhu015]

By Googling i got this one.. There are a lot of circuits like this. I am not sure about the working of this circuit.

There is no need to convert the voltage to 230 as the loss will be more and need a big transformer.

You can search with DC to DC converter

 

[Audioguru]

@Audioguru...Thank you for your reply....Are you sure about this?..please let me ask you something,how much output power can be available from a fully charged lead acid lead acid battery?..or how much power can utilise from a fully charged lead acid battery before the deep discharge cut off ?...Do you know something about this

Most 7Ah lead-acid batteries can supply 0.35A for 20 hours, 0.7A for about 8 hours or 1.4A for about 3.2 hours. It can provide 13V at 1.4A= 18.2W for 3.2 hours.

A laptop battery has lithium cells in parallel but has 4 sets of cells in series for a fully charged voltage of 16.8V that drops to about 12.8V when it shuts off and needs a charge. Maybe the battery is 4.4Ah. Its average voltage is 14.8V and it charges in 3.2 hours with 4.4Ah/3.2 hours= 1.4A. (1.4A x 14.8V=) 20.7W is needed so the little lead-acid battery can almost charge it one time. My calculations missed the inefficiency of the inverter and charger.

 

[smijesh]

Again I am saying it is not possible to completely charge the laptop. :lol:

We will start from laptop battery
1)4.4Ah
(It will hold 12Vx4.4A = 53W, but we have to charge 20% more, required power for charging 63W)

2)Laptop charger-19V@3A (19Vx2.5A = 47W, so 1.5 hours required to full charge the battery(63W)

3)Inverter (Should provide 50W(220Vx0.22A) output for 1.5 hours[Inverter efficiency 25% so required power 62W])

4)Lead Acid Battery-7Ah (Should provide 62W for 1.5hours [12Vx5.1A])
From 7Ah(12Vx7A =84W for 1 hour ) battery you can able to drain maximum of 80% of stored energy (67W=12Vx 5.6A for 1 hour)

But practically we can drain require current of 5.1A for 45 min only. But we need 5.1A for 1.5 hours. How the laptop charge completely?

 

[tanveerriaz]

dc2dc 12v to 18v 3a