laptop not running on battery, new battery, tried with two different batteries

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Srijib

Commendable
Nov 1, 2016
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1,520
my Acer 4736z laptop is not starting up on battery. I have tried replacing the battery no luck. power LED and CPU fan spins. but no display nor it boots. it runs perfectly fine when connected to mains, boots well. once the laptop boots with AC power adapter, when I keep it in sleep mode and disconnect the main AC supply the sleep indicator remains blinking on battery.

on resuming on battery alone it shuts down. battery is 100% charged. any answer will be helpful. am an electronic hobbiest I HV multimeter and understand PSU pleas feel free to use technical terms.

 
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Solandri

Solandri

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Jan 4, 2012
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Li-ion batteries have a very flat voltage discharge curve. Their voltage does not drop as much as NiMH or NiCd (or even alkaline) batteries as charge level decreases. So it's relatively easy for battery protection circuits to mistake the voltage depression due to the sudden application of load for a battery with no charge.

What happens when you power up on AC, then unplug AC forcing it to run on battery? If it stays powered on, my first guess would be a HDD or fan whose bearing is going and thus draws an unusually large amount of power when spinning up. If it shuts off, my guess would be a fault in the battery charge level detection (calculation) circuit, although it too could be caused by something drawing excessive power.

Was the second battery you tried newly manufactured (check the manufacture date)? Or had it been in storage for several years (either at your house or at the store warehouse)? Excessively long storage times will kill a Li-ion battery due to self discharge. A Li-ion battery which has been overdischarge is prone to catch fire or explode if recharged. So the protection circuitry built into the battery will kill it if it ever senses an overdischarge state, preventing it from being charged or used again. The symptoms you're seeing may be how a killed battery behaves in this particular laptop. If you're storing Li-ion batteries (or NiMH), it's recommended to pop them back into the device every 6-12 months to check their charge state and recharge if necessary. (1-3 months for NiMH, and charge those only to about 50%-70% before storage.)
 
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S

Srijib

Commendable
Nov 1, 2016
22
0
1,520
both batteries are new, and looks like they have recently manufactured. I tried removing the hard-disk and DVD player and turning it on with battery still no change. power LED are on but laptop not showing bios screen.

even when laptop runs on power and force it to run on battery it shuts down immediately.
 
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