Is there an app which will stress TEST a cellphone battery?

Jeff Liebermann wrote, on Sat, 26 Apr 2014 23:06:41 -0700:

Yikes. All sorts of things happen once the li-ion battery gets out of the range of the green temperature box!

the lithium plating seems to be sort of analogous to the typical insoluble sulphides of a lead acid battery, in so much as it permanently reduces the capacity of the battery.

These things are fragile!

Ahmed E. Souaiaia posted Sun, 27 Apr 2014 01:51:01 -0500

I suppose the embedded cell circuitry would cut off the cell sooner. At 2.5V it would be already damaged.

"a voltage cut-off below 3.2V can lead to chemical instability in the cell. The result being a reduced battery lifetime. For this reason, electronics manufacturers tend to use higher cut-off voltages, removing the need for consumers to buy battery replacements before other failure mechanisms in a device take effect."

Ahmed E. Souaiaia posted Sun, 27 Apr 2014 01:57:31 -0500

sulphates, not sulphides. :-)

Jeff Liebermann wrote, on Sat, 26 Apr 2014 23:06:41 -0700:

Wow. The conclusions of that article are highly intuitive!

Here's my take, on what the article tried to tell me:

1. These lithium batteries get weaker and weaker with every daily charge & use cycle.
2. Battery packs usually last about 3 to 5 years.
3. The worst thing to do is keeping a fully charged battery at elevated temperatures.
4. That means *using* a PC or iPad while charging all the time, is not a good idea.
5. It's OK to charge all the time though, because the charge cycle will shut off when the battery is full.
6. For storage, you do not want to store the battery dead; you want about a 40% charge for long-term storage.
7. No more than 70% of capacity is a good charging current.
8. Optimal longevity is achieved at 3.92V/cell charging levels; but that results in only about half capacity.

The outer + and - terminals are the battery connections. For cell phones, one of the remaining two terminals is probably an NTC 10K thermistor, so that the charge controller knows the battery temperature. The other is usually unused, although it might be a data pin for those vendors that are into protecting their profits by blocking the use of aftermarket batteries.

That's because it is easy. The problem is that it's not a constant current discharge, which is what the battery analyzer provides. However, as long as the voltage is fairly constant over the operating range, it's good enough since all you're interested in is the "knee" in the curve.

However, I goofed. The maximum draw on the Samsung Galaxy S3 is allegedly about 0.9A. Doing the discharge test at 2.1A seems like cruel and unusual punnishment for the battery. So, a more proper resistor should be: 3.7v / 0.9A = 4.1 ohms (4.7 ohms is close enough) 3.7v * 0.9A = 3.3 watts dissipation For 3.3 watts of heat, I would get a >20 watt resistor, or something that could be mounted on a heat sink. The heat sink on the CBA-II tester should have been a clue:

You may have a problem making a good connection to the battery terminals. I ended up making a fixture with brass screws in order to get a low contact resistance. Converting an aftermarket Samsung battery charger will make a fair holder.

Also, try to measure the battery voltage of your battery when it's charging. If it's over 4.2v, your charger or phone are killing the battery.

The author manufacturers high quality battery chargers and analyzers:

So does the cell phone and laptop. A of about a year ago, the average life of a commodity cell phone was 18 months. Smartphones are running about 30 months, mostly thanks to 2 year contracts. Laptop useful life is limited by law to 5 years (7 years in California): If the cell phone battery remains usable for 3-5 years, it's doing fine because the phone won't last that long.

The problem is that some devices, such as laptops, operate in the worst possible conditions for long battery life. They are left on full charge, 24x7, and in a rather warm environment. Cell phones on dashboard car kits get quite hot. That will kill Li-Ion batteries rather quickly. There's not much that can be done about the temperature, but todays laptops have a setting that limits the charge to 80% of full charge. That's good for a major increase in battery life, at the expense of about 20% in capacity. Cell phones should have a similar settings, but don't.

Oh, I could think of worse things. Overcharging the battery is probably the worst. In cell phones and laptops, the advertising value of having a longer operating time forces manufacturers to charge to absolute maximum safe value. That's great for the numbers on the sales literature, reviews, and comparisons, but not so great if you care about battery life. It also creates a market for replacement batteries. The technology to allow users to set their own charge threshold is present in every device with a built in Li-Ion charger, yet the best that the industry can offer is a single 80% set point.

Yep, that's about it.

Jeff Liebermann posted Sun, 27 Apr 2014 09:32:10 -0700

Important difference is if voltage is with circuit open or under charge. 4.2V voltage top is meant for open circuit voltage.

The way I understand it, the voltage across the terminals should not exceed 4.2v or things start to break down inside. Whether that's with or without charging or load, it's irrelevant. It's 4.2v maximum under any conditions. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2).

Of course, with Li-Ion, nothing is simple:

I beg to differ. You can run a Li-Ion battery down to about 3.0v and leave it there for a long time. 2.5v will also work, but recharge fairly soon.

You forgot to cite your source: That refers to the point where a cell phone or mobile phone declares the battery to be discharged, and turns itself off. That's the "cutoff voltage" in the title. Most police and fire vehicles have such a device on the 12v power line to the radios, in order to prevent the radio receiver from running the battery to zero. 3.2v is probably a good point to proclaim the battery discharged, if you don't mind using only 70% of the battery capacity. The problem is that with different loads, the battery discharge curve varies substantially. Trying to find the proper cutoff point is difficult. In my never humble opinion, the only way that works reliably is a coulomb counter (battery fuel gauge), that measures total charge (capacity) and discharge rate to determine SOC (state of charge). Another problem is that using the battery terminal voltage for SOC implies that the measurement is made as the open circuit voltage. That never happens in cell and smartphones, that rarely are turned off.

I wouldn't have any problem with 3.0V but, at least with modern cells, there isn't much useful energy below ~3.2V. IMO, so it's not worth the risk operating below 3.0V.

I stand corrected. Looking at a typical curve: I would guess(tm) about 5% capacity left at 3.0V. Ok, so stop charging at 3.0V.

(snip)

and the same happens to GPS systems mounted on/above the dash. (Practical alternative locations are probably worse for the GPS.) They also seem to like a matt black finish case to minimise reflections into the windscreen, further helping the solar uptake.

But only very gradually provided you don't abuse them or subject them to high temperatures or long periods of total discharge or overcharging.

It is about the fastest way to kill a laptop battery since it gets cooked by the waste heat from the CPU/GPU. It was particularly bad back in the days of Pentium III portables which were noted for also causing painful skin burns to anyone daft enough to use one on their lap.

Allowing one to stay flat for far too long will also kill it.

Don't bet on it. There are some pretty dumb chargers out there. Keeping a lithium ion battery at full charge for extended periods is one way that guarantees loss of overall capacity when you need it. The battery will ultimately protect itself and refuse to take charge ever again if you abuse it sufficiently - there is a built in thermal failsafe in all properly designed consumer device battery packs. Although this hasn't prevented some Sony and Dell units from going haywire with smoke.

A reasonable tactic is to let it run down to 10% or so at least every month and perhaps every fortnight and then recharge. Even though theory says they don't have memory problems the only bomb proof battery technology I have ever encountered was the ancient NiFe wet plates. They truly were indestructible even under pretty severe military abuse.

Unless I need it in a hurry I prefer to slow charge any rechargeable even if the maker insists that they are OK for rapid recharging. It has to be more stressful to the battery to be charged at C/2 than C/10.

Around 4v/cell is probably a decent compromise and 80% capacity. I know the text says only half for 3.92v but the table says about 75%.

That isn't what it says. Products do not spontaneously fail 7 years after they are sold. The company no longer holds spares to repair them after that date. My cast off laptop before one is still going strong and it is a Pentium III. Its original battery no longer holds more than

The phone might be replaced on that time scale but a decent mobile phone that is looked after is good for 5-10 years. I still have an original early Nokia in good condition. I destroyed my favourite 6303i by dunking it in water accidentally. I prefer my mobile phones to have a very long life on standby and respectable talk times.

I don't give two hoots about txting and find browsing or gaming on a screen the size of a postage stamp an exercise in frustration. YMMV.

I do have a 7" tablet that is acceptable for internet browsing and I can tether to a MiFi or mobile phone as needed.

That is because many of the present generation of smart phones struggle to make it through the whole day on a single overnight charge!

You make a very good point. Trading better long term utility against battery capacity would be helpful - especially for docked laptops.

Many Android devices can be persuaded to show you a discharge curve and you can switch things on and off to see how they affect the gradient.

My guess(tm) is that we're going to see some hybrid battery conglomerations. Li-Ion for long term operation and supercap/ultracap for very fast charging. The latest ultracaps (theoretically) have about 1/4th the energy density (by volume) of Li-Ion cells. Therefore, an ultracap battery, equal in capacity to a commodity Li-Ion battery, will be 4 times larger. Or, if the same volume as a Li-Ion battery, will have 1/4th the capacity and therefore 1/4th the runtime.

There are big advantages to using an ultracap battery in a cell phone or laptop. They can be charged very quickly and they can safely be discharged to zero. They can also be left at full charge without damaging the battery. You might complain about the 1/4th runtime on your phone or laptop, but where re-charging takes literally seconds, its might not be so horrible. It's much like an all electric car, where long trips are difficult, but short trips are not a problem. For extended operating time, the Li-Ion battery takes over after the ultracap is discharged.

Of course, there are problems. To fully charge an ultracap equivalent battery in seconds requires LOTS of current, probably more than the existing battery contacts and flimsy charger connectors can handle. Probably also not suitable for wireless (transformer action) charging. Instead of C/2 or C/10 charge, I'm talking about 10C or maybe higher. Higher voltage (48V?) will help but then safety becomes an issue.

Batacitors, IOW. (See Philip Jose Farmer, "To your scattered bodies go".)

;)

Cheers

Phil Hobbs

Yep. I found a discussion on the topic from 2008: Roll forward 6 years and we now have some fairly good ultracaps. As the volumetric energy density of ultracaps approach that of Li-Ion batteries, a hybrid battery looks better. It's much like the hybrid hard disk drive, which conglomerates rotating and solid state storage. The combination doesn't solve every problem found in the individual technologies, but the few problems that the hybrid disk drive does solve, make it well worth the effort. Same with the hybrid battery. It's not going to be the ultimate power source, but it will be better than either individual technology.

Incidentally, I once had great hopes for a small gasoline engine driving a small alternator as a laptop power source. I soon discovered that neither the engine or the alternator scaled downward very well. So, I settled for an external gasoline powered battery charger. Unfortunately, nobody was interested in making or selling it. (not mine)

Jeff Liebermann posted Sun, 27 Apr 2014 15:43:50 -0700

There is electrochemical diference between open and charging voltage.

Pure voltage put on half cells is decreaced by term R . I, where I is charging current and R internal resistence of electrolyte, electrode materials and phase borders.

The same external voltage with smaller current causes by paradox bigger damage by higher internal voltage, causing destructive electrode reactions.