FYI: using an power supply adapter to go from big plug to small plug throttles Dell laptops

[JEDI]

Over the years I have bought a few Dell laptops.
They all used the same size power supply plug (90w).

Well, last year I got a refurbished Dell Latitude (i5-6xxx) and came with a small plug power supply.

I bought adapters from eBay for $1 shipped because I have all these old power supplies and I don't want to buy new power supplies. (Home, travel bag, mom's place)

the Dell laptop didn't like the adapter and gave an error msg saying it won't charge the battery but will power the laptop.

Fine I thought. I rarely run the battery anyway.
Then I noticed my laptop was running really sluggish.

Ran task mgr and saw the cpu speed was throttled to 400mhz!

Unplugging the power supply, the cpu speed went up to 2.5 ghz.

I went into bios and turned off the Intel speed step option so the cpu always runs at max speed.

Nope. Still 400mhz.

400mhz is no problem for email and websurfing.
But installing programs and windows updates took forever.

Why did Dell switch to the small size power plugs?

 

[Fardringle]

Dell actually only used those small power plugs on a few super-thin laptops. Most still use the standard larger one.

However, it sounds like maybe you have a bad adapter if it's not letting the laptop get power properly.

 

[JEDI]

Dell actually only used those small power plugs on a few super-thin laptops. Most still use the standard larger one.

However, it sounds like maybe you have a bad adapter if it's not letting the laptop get power properly.

was going to order another one. saw the adapter on ebay 2 for $4 shipped.

then saw a dell compatible power supply (small plug) for $11 shipped.
ordered the power supply.

it arrived today.
worked. charged the battery.

if 3rd party can made good Dell power supplies, then why cant 3rd party make good power supply adapters (big plug to small plug)?

 

[ElFenix]

is the adapter actual dell OEM or is it an ebay knockoff?

edit: looks like knockoff. i assume the adapter from dell itself works properly.

 

[SamMaster]

From my actual experience as an on site Dell repair tech: Dell gas a tiny pin on the adapter to let the system know what the wattage of the AC adapter is. If it is not detected properly, the laptop will put itself in low power mode and won't charge the battery to protect itself (like in case you plugged an HP adapter instead). The problem with 3rd party adapters is that they have a higher chance to have that part not work, thus seeing the issues you had.

A big advantage of USB-C laptop chargers IMO.

 

[Lanyap]

I learned a long time ago if I need a laptop power adapter for Dell (especially), HP, Lenovo, etc. I always purchase a new genuine PA from eBay, Amazon, etc. it costs more but a lot less hassle.

 

[mindless1]

My understanding of it is that it is similar to what SamMaster stated, except that the center pin just reads a PROM value as valid, or invalid/missing, and will only run the laptop at full speed and charge batteries if the valid prom value is detected.

So this has nothing to do with smaller connector, just that whatever PSU you use, has to have the right chip (programmed ID) in it that the laptop bios is programmed to recognize, and this pin must pass-through to the laptop instead of the connector only having +/- contacts.

 

[JEDI]

My understanding of it is that it is similar to what SamMaster stated, except that the center pin just reads a PROM value as valid, or invalid/missing, and will only run the laptop at full speed and charge batteries if the valid prom value is detected.

So this has nothing to do with smaller connector, just that whatever PSU you use, has to have the right chip in it that the laptop bios is programmed to recognize, and this pin must pass-through to the laptop instead of the connector only having +/- contacts.

For some reason, big connector to small connector adapters aren't passing this info through.
Thus no charging and I'm limited to the bare minimal speeds ( .4ghz in my case)