Laptop battery suddenly drop from 35 percent to 7 percent

Run a battery report:

Open a command prompt with administrator privileges and type

powercfg /batteryreport

What are the current and design charge capacities of the battery (NOT the current charge state, which is what the "health" relies on!)?

@ejn63​ full capacity is 31,260 mWh and charge capacity is 29,975

Depending on the battery you have, it should be 42, 51 or 68 WHr -- meaning it has lost at least 30% of its design capacity. Translation:  you need a new battery.

@ejn63​ thanks another thing if i may ask, 

Its design capacity is 31,200 mWh 

But in the official site and as you mentioned that my battery capacity should either be 42, 51 or 68 MWH 

Does it mean that my laptop has no original battery 

Thanks

Only you can answer that question.  If it was purchased from Dell as new, it has an OEM battery of one of the three capacities.  If it was purchased used, anything could have happened to the system, including replacement of the battery with something incompatible, lower in capacity, or third party.  Only your seller can tell you.

The system is four years or more old, so even with an OEM battery it's overdue for replacement if it's the original battery.

@ejn63​ i don't know the answer i asked the seller he said that its not the issue.

I don't know is he lying or not. I don't think its logical.

I value your advice, if my battery is not original and it provides low power then this laptop is designed for isn't this causing the sudden drop in battery,

And is this battery good for my laptop isn't this battery gonna disturb the performance of this laptop and harm it in the long run.

I have recently purchased it so i can return it 

Please let me know of your opinion 

Thanks in advance 

Regards

Fahad 

@ejn63​ thank you very much