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Battery discharges on Evo N400c/Also when on battery, the power controls say it is on AC Power

reyeuro asked
Medium Priority
Last Modified: 2008-01-09
Battery discharges on Evo N400c/Also when on battery, the power controls say it is on AC Power....I have a couple of these Compaq Evo N400c notebooks with expansion bases.  Oddly enough this particular one runs great in the base, and out of the base while it has the AC Adapter plugged in, when I put a perfectly good battery in the laptop and unplug the AC Adapter the icons and the power meter both say the laptop is still plugged in to the AC Adapter.  Also a battery which when fully charged in another laptop, same model and configuration, which lasts two hours, when that same battery fully charged is used in this laptop it discharges within 15 minutes and the laptop hibernates.  HELP!
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Top Expert 2005

It sounds like something is wrong with the motherboard.

  Is the system under warranty?


Unfortunately no...

Does it do the same thing regardless of which battery bay is filled?

It sounds like the charging circuit (a.k.a. "power board") is bad.
Unfortunatly yours in built into the motherboard.


"Does it do the same thing regardless of which battery bay is filled?" <- Skip that.

You have two connector locations for one battery.
I confused that to mean you had an optional second battery capability.
Most Valuable Expert 2015

Open the control panel, open the power options, and make sure you have set up the power schemes correctly for your notebook. You may need to install the utilities and drivers for your notebook from the homepage of HP.


I do have an optional second battery, it is called the "Handle" battery, which provides a "Handle" that you can prop the laptop up on for better keyboard access, so it is an optional battery, and I have not checked to see if it does it with or without the optional battery, perhaps I could disconnect the internal battery and no longer have this problem?  Is that your suggestion?

If the power board (circuit) is bad to the main battery that does not necessarily mean it is bad to the optional battery as well. - So long as they don't connect to the same contacts.

When you use the normal battery it discharges very fast. That is a bad bad thing. You have excessive current going somewhere and draining the battery. Bad for the battery and something is getting hot when that happens.
I would not use a battery in the normal bay at all and if the 'handle battery" discharges very fast too I wouldn't use that one either. Your options at that point would be to replace the mainboard or just use AC only on that laptop.


Sometimes the battery metering circuitry is out of whack and yells about battery low, whan in fact the cells are well charged. Some laptops have a BIOS function that can calibrate the metering function. If applicable try this.


Thanks, I was able to calibrate the Main Battery or Internal Battery but the "Handle" battery went through the entire process and when finished it came back "NOT CALIBRATED" wherein the "Main" battery at the end of the process came back "CALIBRATED" and now seems to be holding a charge.

Check the AC power in plug on the laptop. With the power brick unplugged from the wall and the unit turned off, insert the power brick jack into the power plug on the laptop. Slightly wiggle it. If you get excessive play in the plug it is braking loose from the mobo. Intermittant power to the power board from a loose power jack will give you the symptoms you have listed. The off/on power from the loose jack to the power board confuses it and it can drain a battery quickly if there is also a short in the jack. With a short, the power brick will not charge but become a load.
That's why it runs great in the base, different power connection.

If thats the problem, here is a link to the jack you need. You can always just resolder the old jack but I don't recommend it as the leads are weak if they have been shorting.


I have found that this does not work with either battery at all, no matter how good the battery is, the laptop runs perfectly without any battery and only under the powe of the ac adapter...there is something wrong with the motherboard I think, because even unplugged with the a fully charged battery or a discharged battery the laptop boots up says it is on ac power and shuts down within minutes after it discharges the battery, yet the same battery performs perfectly when inserted into another laptop.
I'm sure now that the charging/battery circuit (power board section) of your motherboard is bad.

If you can live with AC power just leave the battery out (to prevent more damage) and run on AC.
If you want backup power for power outs plug the AC adapter into a battery backup as with a desktop computer.

If AC isn't acceptable you need to replace the motherboard or the laptop.

Sometimes a good route (especially since you seem to have more than one of this model laptop) to replace a laptop motherboard is to find a known good and working laptop on eBay with a damaged screen. Probably less expensive than buying a motherboard outright and you could possibly end up with other spare parts for later. (Keyboard, touch-pad, drives, screws, CPU, memory....)

Alternately you could buy a stripped one. Good mainboard but no keyboard, drives, or memory. Some of those have good screens (for a spare) and some don't.


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Thanks, that is exactly what I am going to do, I have some others, just have never changed a motherboard or really changed much of anything in a laptop before except for RAM and Hard Drives, I once installed a mini-pci card in an omnibook...but thanks for the info.
Top Expert 2005

I have plenty of points, however, I think splitting points is what you should have done considering I told you there was a problem with the mothertboard in my firts post.
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