Not Charging to 100% -- What's Up?

[jodeg1945]

The last two times I charged my ZW3, using the Dash Charger as always, it would only charge to 97%. It also seems to be taking a bit longer.

I've had my watch since the end of November, and it's always charged to 100%.

What am I doing wrong?

Thanks!

 

[Rukbat]

How far are you allowing it to discharge? Anything lower than 40% can permanently damage the battery. (Down to 0% constantly can damage it in less than a month.)

 

[jodeg1945]

No, I only get it down to maybe 50% and then charge it. Never down below 40%. Thanks!

 

[jodeg1945]

I just charged my watch again, and it worked perfectly! Charged fast, charged to 100%. Don't know what went wrong the last couple of times, but seems fine now!

 

[wynand32]

I'm not sure about that "discharging below 40% can permanently damage the battery" thing. That would be exceedingly odd for a lithium ion battery. Really, a company would get in some deep trouble with its customers if it designed a device with a battery that could be permanently damaged merely by discharging it to less than 40 percent--which would be a common thing in normal use.

And letting it run down to 0% can reduce the battery's lifespan, but not within a month. That's merely a full cycle, and unless the battery in the ZW3 is of a very poor design, it should get a few hundred cycles before it loses more than 80% of its full charge.

 

[jodeg1945]

I agree, wynand32. I wondered about that post too. It charged up just fine the last time, so I'm not sure what happened before. Thanks for your comments!

 

[TabGuy]

Anything lower than 40% can permanently damage the battery. (Down to 0% constantly can damage it in less than a month.)

Can you tell me why you think that? Is there a link you can provide? As a former Electrical Engineering major I'm curious as this is the first I've heard of this.

I had a Moto 360 watch for two years and I ran the battery to almost zero every day with no ill effect. Are you implying that this problem is unique to the Zenwatch 3?

 

[Aquila]

Can you tell me why you think that? Is there a link you can provide? As a former Electrical Engineering major I'm curious as this is the first I've heard of this.

I had a Moto 360 watch for two years and I ran the battery to almost zero every day with no ill effect. Are you implying that this problem is unique to the Zenwatch 3?

Lithium batteries do better with more frequent shallow discharge and charge cycles, rather than deep cycles. Dropping to 0% invites the possibility of permanent damage and the device might never power on again. Dropping below the 40% or 20% mark, depending on your literature, doesn't directly harm the battery, but rather it causes the need for a longer and deeper charge cycle which causes much more wear and tear and ramps up the degradation to the life cycle. Infrequently doing so but keeping it above 0% is not ideal but is relatively safe. Frequently doing so can significantly degrade battery life in a noticeable timeframe, such as weeks or a couple of months.

 

[wynand32]

Lithium batteries do better with more frequent shallow discharge and charge cycles, rather than deep cycles. Dropping to 0% invites the possibility of permanent damage and the device might never power on again. Dropping below the 40% or 20% mark, depending on your literature, doesn't directly harm the battery, but rather it causes the need for a longer and deeper charge cycle which causes much more wear and tear and ramps up the degradation to the life cycle. Infrequently doing so but keeping it above 0% is not ideal but is relatively safe. Frequently doing so can significantly degrade battery life in a noticeable timeframe, such as weeks or a couple of months.

The best way to characterize things is that lithium ion batteries have a certain number of full cycles before they start to show reduced capacity. With modern batteries, it's a few hundred full cycles, which is discharging from 100% to 0% and charging back up to 100%. A particial discharge is just that--not a full discharge--and so an li-ion battery is going to last longer if it's not seeing a full discharge every day.

However, it's simply not true that an li-ion battery is "permanently damaged" when it's discharged to 0% and that it "might never power on again." Anybody who has routinely discharged their devices to 0% should know this. And, discharging below 40% just means that it's going to require more charge to get back to 100%. But it means nothing more than that.

Yes, it's a good idea to avoid deep discharges, because that means your battery will last longer before it starts to suffer from reduced capacity. So, sure, charge it when you can. But you're not risking destroying your battery or having your device never start up again just because you let it discharge to 0% on occasion.

 

[Aquila]

The best way to characterize things is that lithium ion batteries have a certain number of full cycles before they start to show reduced capacity. With modern batteries, it's a few hundred full cycles, which is discharging from 100% to 0% and charging back up to 100%. A particial discharge is just that--not a full discharge--and so an li-ion battery is going to last longer if it's not seeing a full discharge every day.

However, it's simply not true that an li-ion battery is "permanently damaged" when it's discharged to 0% and that it "might never power on again." Anybody who has routinely discharged their devices to 0% should know this. And, discharging below 40% just means that it's going to require more charge to get back to 100%. But it means nothing more than that.

Yes, it's a good idea to avoid deep discharges, because that means your battery will last longer before it starts to suffer from reduced capacity. So, sure, charge it when you can. But you're not risking destroying your battery or having your device never start up again just because you let it discharge to 0% on occasion.

I'm basing that statement of permanent damage upon several tablets that had an issue where discharging to "0" would result in it being unable to power on without 8-20 hours of charging and some would never power on again. Now it's entirely possible that was caused by a device issue rather than a battery issue, but it did cross many OEMs without much else in common.

 

[wynand32]

I'm basing that statement of permanent damage upon several tablets that had an issue where discharging to "0" would result in it being unable to power on without 8-20 hours of charging and some would never power on again. Now it's entirely possible that was caused by a device issue rather than a battery issue, but it did cross many OEMs without much else in common.

The bottom line is this: if discharging to 0% could actually damage a battery, then manufacturers would simply include code to shut the device down before it reached that state. Otherwise, they'd face massive problems with warranty claims, class action lawsuits, etc. It would be nearly impossible to avoid hitting 0% on occasion, and if you check you user guides you'll likely find not even a single reference to avoiding it.

I'd say your experience was just coincidence.

 

[Aquila]

The bottom line is this: if discharging to 0% could actually damage a battery, then manufacturers would simply include code to shut the device down before it reached that state. Otherwise, they'd face massive problems with warranty claims, class action lawsuits, etc. It would be nearly impossible to avoid hitting 0% on occasion, and if you check you user guides you'll likely find not even a single reference to avoiding it.

I'd say your experience was just coincidence.

They actually do that. 0% on the reading is not fully depleted. The issue is that they can still deplete while powered off, though that bleed is usually very minimal, it can accelerate based on extreme temperatures, etc.