Resolved No Power to HP G71-340US

I recently replaced the screen, lcd video cable had the notebook computer running for a few hours with out any problems. Shut it down for the night. When I turned on the machine the next day there was no power when I pushed the Power on/off switch. So I plugged in the AC adapter still no power but I did notice the power and HDD indicator lights were very dim and the battery indicator light is very bright. Any Ideas. If you want the specs the P/N is VM114UA#ABA. S/N CNF9460CK3

 

Replaced the HP power on off switch with HP SPS Power On Off Switch Button Board HP 531860-001 with no luck.

 

Try running on just the power supply - with the battery removed and see what happens. If the battery has developed a short, it may be drawing too much current while still in circuit.

 

Tried without the battery. Didn't get any power to anything not even the dim power, hdd indicator lights or bright battery lights. When I put the battery back in and plugged in the ac adaptor all three lights blinked 9 times. Could it be the mainboard might be shot.

 

And did your notebook allow running without the battery with no problems before (some notebooks require the battery be in the circuit at all times)?

If so, then yeah, it does not sound good.

I found this procedure on HP that helped with some folks with similar issues:

1. Power off notebook,

2. Remove battery,

3. Remove charger,

4. Press and hold the power button for 30 seconds to fully discharge circuits,

5. Insert charger only (no battery yet),

6. Press power button and [fingers crossed!] boot into Windows,

7. Shut down Windows and power off the computer,

8. Insert battery, press power button, and with a bit of luck, problem solved. ​

If still no go, the next suggestion was to update the BIOS - but I don't know how you can do that if it does not boot.

 

That procedure was the first thing I tried, but, I tried it again hey you never know . No power unless the Battery and the A/C Adaptor are connected. When I received the machine to work on, I could only get to work with both the battery and ac adaptor. I only installed a new LED Screen and the lcd connector cable. It was up and running for a few hours. Then I shut it down for the night . When I tried to start it the next day no power. So I installed a new Power On Off Switch Button Board HP 531860-001 which I ordered from HP Parts Direct.

 

Ah, I thought this was your system. So you don't really know the complete history here, I assume? For example, we don't know if it used to run on charger only (without battery installed).

Frankly, I don't like working on notebooks because they are too proprietary. All the makers do power distribution and management differently - but I digress and stall.

If me, I would want to know the condition of that battery and unfortunately, about the only way to conclusively determine that is to try a different battery - which most folks don't have laying around. And is that the original charger? You can measure the charger's output, but to do it properly, (like all power supplies/batteries/motors) you MUST measure while in circuit and/or under a realistic load. So, if you can measure the voltage on the battery contacts with the charger connected, the voltage should be at (or slightly above actually) the charger's rated voltage. If less than the rated voltage, then either the charger is failing, or the battery is faulty.

Beyond that, I am sorry, I have no more to suggest.

 

I have two batteries that goes with HP G71. It is the same exact battery that came with my HP Pavilion dv4-2167sb. I also have an HP 9 cell that's the replacement battery for both machines. Both charge but I still get no power when pressing the power on button just the dim power and HDD indicator lights and a bright battery light, which goes off when the my two spare batteries are charged. The battery that is in the machine when it was brought to me doesn't charge but the owner knew that. The history with this person is to run the machine on AC power with the battery installed. As many times as I told the owner not to do this my advice always falls on deaf ears. So it may have finally come back to bite them.

 

My two cents:

Well, I don't hear as well as I used to but I do hear you. That said, there is not a consensus suggesting removing the battery is necessary. Notebook charging circuits are not dumb, but highly "intelligent" devices - so are the batteries. Even on budget notebooks - notebook fires due to battery failures is NOT good publicity!

And more importantly, not all batteries or charging circuits are designed the same - therefore one rule does not fit all.

Plus, the very nature (Laws of Physics) of how batteries work means when fully charged the batteries stop accepting a charge from the charger. That is, UNLESS FAULTY, the battery will not "overcharge" and Li Ion batteries don't suffer from "memory effect" like older NiCads. When fully charged, a battery just shunts (bypasses) the excess charging voltage along to the notebook's power/regular circuits and not into the battery.

Bottom line, IF everything is functioning properly, there is no real evidence leaving a notebook battery inserted full time is harmful, or that it shortens the battery's life.

That said, even today's sophisticated Li Ion batteries need to be "deep-cycled" every so often.

I leave the battery in my nearly 5 year-old 17" Toshiba full time and I still get well over 2 hours of run time, same as when new. About once a month, I unplug the charger and run the battery down until the system yells at me that it is about to shut down on its own.

Perhaps surprising and counter to popular belief, the greater threat to batteries is heat. For example, most folks think starting your car in 0° weather is harder on the battery than in 100° weather. Not so! Cold simply slows down the chemical reaction in the battery. While the CCA (cold-cranking amps) of the battery are greatly reduced when cold, and certainly the oil thickens when cold, it is not hard on the battery to crank when cold.

This is why batteries are often stored in cooled environments - to slow down or even suspend the chemical reactions going on internally to extend their "shelf life ".

"Heat is the bane of all electronics" - including batteries. So the real danger of leaving a battery installed and connected to the charger full time is possible exposure to constant high temps. This is made worse in notebooks because notebooks are notorious for heat related issues, lack of easy access to clean out heat-trapping dust, and poor cooling.

Unlike a PC (which receives the necessary +12, +5 and +3.3 from the PC's power supply), a notebook's power distribution circuit typically gets 16 - 19VDC from the supply (or battery) which it must then break down into the necessary 12, 5, and 3.3V voltages - a process that can generate a lot of heat inside the notebook.

So when I am asked if the battery should be removed, I say, "it depends ". If your notebook stays fairly warm to the touch after the battery fully charges and the notebook is not being used, you might consider pulling the battery. If your notebook cools and stays cool once the battery is fully charged, then I have no qualms leaving it in.

Regardless if you leave it in or out, you still must fully "deep cycle" the battery every so often (once a month is good).

Okay, that was more than 2 cents worth - consider it the "nickel" tour!
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The fact you are having the same symptoms with multiple batteries suggests the notebook's charging/power circuits has developed a fault (assuming the charger is the correct one and working properly). And yes, on most notebooks, those circuits are integrated into the motherboard. So from here, it does not look good.

 

Thanks Bill. That was the premium tour and very interesting. Then why is it that all there notebooks do not function unless both the battery and ac adaptor are plugged in. If you remove either one from the equation = no power.

 

"All" their notebooks? I see only reference to one notebook (2 if you count your notebook). How many of "their" notebooks are we talking about? Same models? Age?

This is another reason why I said above, "it depends ". In this case, it might depend on the notebook design. Some require the battery to be in circuit to "complete" the circuit so the power supply/charger "sees" a proper load. A quick look in the user manual should reveal if a notebook needs the battery inserted, or not.

However, any notebook "should" (obviously) run fine with just (a properly charged) battery installed.

Sadly, there is no ATX Form Factor standard for notebooks as there is for PCs. If there was, there would not be this guessing game with every notebook - they would all work the same way. But because there is such competition to make the lightest and thinnest, notebooks are very proprietary - which of course adds to their costs, and makes it harder (and more expensive) to repair.

While certainly possible multiple notebooks could develop similar problems at the same time, it seems unlikely. It is more likely multiple batteries (if of similar age) reached the end of their lives at about the same time. Another possibility is a power hit damaged the power supply/charger or chargers, which in turn, damaged the batteries. This is more likely if multiple batteries were charged with the same [faulty] charger.

A notebook with a "weak ", old battery should still operate with the charger connected. However, if the battery has been damaged due to excessive heat, power anomalies, bad charger, etc. it could have a blown fusible link creating an "open" in the circuit, blocking power, or it could have developed a "short" in one or two of its cells, sucking "all" the power from the power supply. The latter scenario is potentially more dangerous. A "short" (drop in resistance to 0 or near 0 Ohms), as defined by Ohm's Law (one of the many "Laws of Physics ") results in current (amperage) in the circuit to increase. And when current increases, heat goes up - and if excessively, thermal damage may result.

If you have a multimeter, I would test the battery with no load. The voltage on a charged battery should be slightly higher than the battery's voltage rating. A good, fully charged 12VDC battery will read, for example, somewhere around 13.8 - 14VDC. And if you leave the battery out of circuit and check the voltage again in an hour or two, it should still read around 13.8 VDC.

If the battery's voltage drops significantly while not in circuit in relatively short period of time, it is a bad battery. If it never charges to a little over the rated voltage, it is a bad battery. A charging battery will get pretty warm, it should never get hot.

If the battery stays charged while NOT in circuit after a few hours, then I would put it back in circuit (and back under a "proper" load) and measure voltages again. It will likely drop a little just being in circuit, but still stay a bit above 12VDC (again, using a 12V battery to illustrate). If the charge drops rapidly once in circuit, you probably have a problem with the notebook's (motherboard's) power and regulator circuits.

 

They have 3 dells and one hp. the hp is the one im working on. my original assessment was leaning toward a possible short somewhere on the mainboard. thanks Bill

 

My guess would be an open, rather than a short (or both) - mainly because a short often results in too much current elsewhere in the circuit, or in an adjacent circuit. This typically results in hot spots, if not smoke and that smell - at least until the hot component fries "open ".

But at any rate, if you are sure the charger and battery are good, then I agree with your assessment that the motherboard has gone.

 

I charged up the battery with ac adaptor. Took the battery and put it in my HP dv4-2167sb and started it up with just the battery. Like you posted something must either fried open, shorted, or both. I marked this resolved but I'll continue to tear down to the mainboard. Thanx for your input Bill it's greatly appreciated.

 

Thanks though sorry we did not get your problem resolved. Good luck.