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June 8th, 2025 16:22
Latitude 7490 without power supply, only with battery extremely slow
Hello,
i bought two Latitude 7490 (refurbished), perfect optical condition about 2 weeks ago, run flawlessly on the power supplies,
but only with the existing built -in battery (immediately after pulling the charger) are both extremely slow at the moment.
Short history, which I had checked so far:
All energy options in Win, BIOS and Delll Power monitor are "for battery operation" for top performance.
BIOS is the latest at the moment (which hopefully was not a mistake ...).
It's not just about a few percent slower (as well with most notebooks only by battery),
But the performance falls on a quarter (and far below), in contrast to performance with power supply.
What I could still observe: CPU-Z (clock window) shows all four cores with multiplier up to 36 (3.6 GHz) with a power supply unit with a power supply
And even with a bench, the multiplier only goes back to 22-26 after about 30 seconds.
The same scenario with a pulled out power supply; All four kernels go immediately! on multiplier 4, which means a core clock of only 400 MHz.
This cannot be correct that the CPU of a notebook in battery operation drives back so far ...
In both NB's there was / is a small variant of the 4 cell battery (not original, replica) with only 5800 mAh / 44 Wh (instead of 7490 7500-8500 mAh 60-62 Wh as with 4 cells).
I think that the smaller battery may not deliver the current electricity that the board/CPU would need for the higher clock!?
But that's just a guess. Unfortunately, I have not been able to read the problem on the Internet so far ...
Maybe you can think of something else?
It would be grateful for any indication of what it could be that you could do.
ejn63
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June 8th, 2025 16:56
Does the system perform normally when on AC power with a recognized, OEM Dell AC adapter?
langer650
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June 8th, 2025 21:57
Yes, if the power supply is connected, the speed is flawless to the maximum.
I have researched what an i5 8350U in power at Max Core tact, converted in current at this 7.6 V voltage of the battery.
This no name 5800 mAh battery does not even deliver a quarter of it, breaks down from 7.6 v to less than 5 V at just a little over 3 A.
ejn63
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June 8th, 2025 21:59
That would be the problem -- replace the battery (if you can find a new, OEM unit that would be the best option).
langer650
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June 8th, 2025 23:21
A new "good" battery is already on the way to me.
Interesting that in the company (I assume that these two notebooks come from a company)
had installed new batteries (since they are newer than the computers themselves),
it should be cheap batteries and you bought such bad ones.
These bad ones are still available, but they are not really cheaper than good batteries...
langer650
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June 9th, 2025 14:30
Good news, with the better battery the CPU clocks up again.
This battery has LG cells. No manufacturer of the cells were displayed in the bad battery. The field was empty.
There were still a few small problems, all my energy settings in the BIOS were gone
But that was to be expected because CMOS had to be reset, otherwise the battery was not loaded and it initially only refused to run with a battery without a power supply.
After that everything was fine, but after a restart he lost the CPU Max Power Sets for battery.
That was strange, everything corrected again and from this point on he really saves everything.
Another good point.
Dell Power Manager finally keeps the settings for the loading mode (in my case mainly network operation)
and no longer forgets that.
With the cheap battery, this had always been set to default after every start.
langer650
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June 12th, 2025 07:02
Happy too early ...
The performance with the new battery is now as quick (can be just as fast ...) as with a power supply,
But ... there is still something software.
Because when I start the notebook with a power supply, everything is ok, the power supply can then cut off and it stays fast, even if you only work with battery for a long time.
But now it comes.
He must have briefly "seen" the power supply. It is enough if you put it on for a second and immediately put it out.
Then it is and remains quick. Without that, he stays slow.
It is and remains slowly started without a power supply. If you put it in briefly and out again = quickly and stay fast,
ok so far so bad but even if the power supply is enough in the state
only the first second after printing on the on button until the BIOS logo appears in it.
If you pull it there again, that's enough and he starts and only runs quickly with battery.
It seems that the BIOS already decided whether it will be quick or slow.
But what option ensures that it recognizes that the power supply is or not
And why or what decides the further run?
I have everything in the BIOS a dozen times. I can't think of anything anymore ...
(edited)
ejn63
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June 12th, 2025 10:52
If you have a warranty on the recent purchase, return the system for a refund. It may be perfect cosmetically, but it isn't functionally.