Question Dell laptop charging issue

[SSS1999]

Latitude E5570.
original battery and charger.
Just got is used
it charger normally at first but around 30 percent it really slows down and then suddenly shoots up to 90 %s.
I let it drain to 0 % but the issues persists

 

[punkncat]

Almost every refurb I have purchased in the laptop dept needed a battery, unless stated that it was replaced. I would start there with a good quality replacement.

 

[SSS1999]

Almost every refurb I have purchased in the laptop dept needed a battery, unless stated that it was replaced. I would start there with a good quality replacement.

Yeah I am thinking about that but maybe the it is a software issue?
why would it slow down mid charge and then shoot up? Aida shows 30 percent wear level

 

[SSS1999]

Can i somehow force this laptop to charge fast, like normally?
voltage is fine. up to 8v
wear level 30%
10 000 - 20 000 mW charge rate. but the actual capacity goes up by 20s and 10s like - 40637 mW to 40652 mW and so on.
Device - Dell 7v69y53 original e5570 battery

 

[SSS1999]

OK so it charged from 5% to 50% in 1 hour.
now charge rate dropped to 6000 mW. 2 and a half hour estimate before full charge.

 

[SSS1999]

just checked on it,
now it is at 100. 35 minutes later...

 

[SSS1999]

watched a video for an hour. max brightness, highest performance. went down to 62 or something and then in an instant it went down to 6 percent with battery low warning. didn't connect the charger. soon it hibernated, opened dell bios. for an hour it has been on, screen is on and i am in the bios. it has been saying 1 percent battery for an hour.
This has got to be some kind of calibration issue right?