Charge your battery as often as possible-revolutionary, comparative, numeric results!

[Menneisyys]

I’ve, in all Windows Mobile forums, very often posted on the fact that Lithium-Ion / Polymer batteries should always be recharged whenever possible. That is, you should put your handheld / handset on the charger whenever possible. NEVER EVER wait before the handheld shuts down because even after only 4 months, your battery will only hold about a third (!) of its original charge holding capacity and, as opposed to what several people say, putting the device on the charger only once a day (or two-three days with devices with better battery life – mostly, TI OMAP-based handsets) on a regular basis (not waiting for the battery to completely deplete) will also have an adverse effect on the battery life.

Now, Groucho's pretty cool Nokia N95 blog (http://www.blogn95.blogspot.com/) has published a remarkable article (http://blogn95.blogspot.com/2007/07/gentlemen-charge-your-batteries.html), which is of extreme interest to anyone having a device with a Lithium Ion or Polymer-based rechargeable battery (not only Nokia N95 users – again, this info applies to ALL current Windows Mobile handsets, and a lot more other gadgets like digital cameras etc.). The figures he shows certainly prove I’ve been right when I recommended recharging your device whenever possible.

Groucho has purchased three N95’s (again and again, don’t think this discussion only applies to the N95 – it does apply to ANY device out there!) at the same time and used them in a pretty similar way. He, however, made absolutely sure he charged the device in three consistent (not mixing up the devices) and radically different ways: the first was charged only once a day (every night), not during the day; the second was charged when it has completely shut down because of the battery’s going flat and the third was almost always on charger whenever possible. The difference in the battery capacity, based on the different ways of recharging, turned out to be astonishing: the second battery (which was always let go flat, and only after that was it put on a charger) could only hold slightly more than a third of the battery that was always on charger whenever possible. The latter battery, in addition, fared considerably (about 16%) better than the battery only regularly (every night) recharged.

Note that the blog post has a mistake (which has no effect on the credibility of the results): it states they will have exactly the same charge holding capabilities throughout their life, and, suddenly, they die (“They have a finite shelf life which starts from the day they are manufactured and their condition from then degrades to the point where they fail! This is not to be confused with their charge holding abilities which are very good for their full life! When they go they just go!”). This is, of course, incorrect: their capacity will degrade over time. Just an example: my HP iPAQ 2210, which I bought right after it was released in Europe, at first, shut down at 2-3% battery level. After about two years, this raised to about 20% and, after three years, this was already around 35-38%. This also shows – along with a multitude of other examples – that these batteries do lose capacity over time. Also note that, as I’ve also recommended several times, Battery University has a decent article (http://batteryuniversity.com/partone-12.htm) on all these questions – except for, of course, real-world results like the above.

Verdict: ignore if somebody says the opposite. Recharge your handheld whenever possible.

[JonnoB]

I think most people who say these things (charge only at night or when fully drained) are confusing battery technology with the old 'memory' stricken NiCad type batteries.

[Menneisyys]

I think most people who say these things (charge only at night or when fully drained) are confusing battery technology with the old 'memory' stricken NiCad type batteries.


Yup. Too bad even resellers and mobile phone companies do this.

[Menneisyys]

There is some really interesting discussion of this article at MoDaCo (http://www.modaco.com/content/Smartphone-General-Discussion/261360/Charge-your-battery-as-often-as-possible-revolutionary-comparative-numeric-results/), HowardForums (http://www.howardforums.com/showthread.php?p=10164684#post10164684), FirstLoox (http://www.firstloox.org/forums/showthread.php?p=72596#post72596), PPCT (http://www.pocketpcthoughts.com/forums/viewtopic.php?p=444900#444900), XDA-Developers (http://forum.xda-developers.com/showthread.php?p=1638551#post1638551) - well worth checking out for more info / discussion.

[thierryb]

One more complex question: is it better to have rapid charger {high voltage) or slow charger (low voltage)?
Because sometime I charge my pda in my car with a slow charger 5A 1V, and sometimes at home 5A 2V.

[Menneisyys]

One more complex question: is it better to have rapid charger {high voltage) or slow charger (low voltage)?
Because sometime I charge my pda in my car with a slow charger 5A 1V, and sometimes at home 5A 2V.

Some state ( at XDA-Dev - see link above) it's better to use a slow(er) charger.

I'll just post there an answer to this, pointing out the dangers / pitfalls of this approach.

[deanhatescoffee]

Just to be clear, it's not necessary (with Li-Ion batteries, anyway) to do the full charge before first use, right? Wasn't that just a NiCad issue, or is that still a best practice?

[Menneisyys]

Just to be clear, it's not necessary (with Li-Ion batteries, anyway) to do the full charge before first use, right? Wasn't that just a NiCad issue, or is that still a best practice?


It depends on what you mean by fulll charge. Sure, it's worth waiting some 1-2 hours AFTER the charger has finished work (LED stopped blinking, its color changed etc. to show this). However, you do NOT need the sometimes 12-16-24-hour first charges many manuals advise. It's no longer needed with Li-Ion batteries and is another common myth no longer grounded.

[Sven Johannsen]

One more complex question: is it better to have rapid charger {high voltage) or slow charger (low voltage)?
Because sometime I charge my pda in my car with a slow charger 5A 1V, and sometimes at home 5A 2V.

My lord, I hope not. PPCs are 5V devices. You wouldn't be able to charge them with a 1 or 2 V device no matter how much current was available.

Here's the deal. To charge a battery you have to drive current through it backwards. To do that you need to apply voltage higher than the batteries rated voltage. Look at the batteries themselves, they do not say 5 volts. OK. Current is a regulated by a voltage applied across a resistance. Batteries have some fairly fixed resistance, so the greater the voltage applied across them, the greater the current that will go through them. The device draws current, the charger does not drive current. Think about your car battery. Isn't it rated at well over 100Amps. When you hook your car radio across it, it doesn't get 100A shoved into it, it draws what it needs. As the battery charges, it's voltage gets higher, making the charger voltage to battery voltage smaller, lowering the charge current, which slows down charging as the battery gets 'fuller'.

Now, the more current you shove backwards through a battery, by raising the charger voltage, the more current flows, charging faster....and heating it up. Even more and you can destroy the battery. For that reason there are charge regulating circuits in devices that have rechargeable batteries. They limit the amount of current the battery draws, by regulating the voltage that is actually applied across the battery. What ever is left between what is given to the battery, and what the charger actually provides, has to go somewhere, and typically it heats up the regulating circuitry...and can burn it up.

OK, lets look at a device charging, and it is drawing current from a charger. We said the voltage difference is what defines the current drawn, regulated by circuitry that won't let it get too much to hurt the chargee. But what about the charger? That current goes through it too. The rating on the charger is how much current it can deliver without overheating, not how much it is going to push. So what if the device wants, and can accept, 2A going through it, and the charger can only deliver 500ma (.5A). If the charger is built right, it regulates the current it is allowed to deliver, doesn't burn up, and the device just charges more slowly. The charger can do a couple of things. It can just shut down the output, which is what some cheaper USB ports do, or it can lower the charging voltage to a point that the voltage difference now results in a charge current that can be supported safely.

So take this for what it's worth. If you over voltage the charger, and it can handle the current thus drawn, the device circuitry will have to compensate for that drastically, and you will not get faster charging, just a hotter device. Get the right voltage charger. For current capacity, you will get faster charging, the more current the charger can deliver, up to what the device can safely draw. That max is a function of the device, not the charger. Current capacity beyond that is useless. Current capacity in the charger below what the device wants can result, in slow charging, no charging, a hot charger, or a damaged charger, depending on the engineering of the charger. Devices that can be charged via USB port, can reasonably expect to get 500ma (.5A) from the port, so they are designed with that in mind. If you try to charge it with something that only delivers 300ma, you can expect charging to be slow and the charger to get hot, at a minumum.

There you go. Hope some of this makes sense.

[thierryb]

One more complex question: is it better to have rapid charger {high voltage) or slow charger (low voltage)?
Because sometime I charge my pda in my car with a slow charger 5A 1V, and sometimes at home 5A 2V.
Obviously you have all understood 5V 1A and 5V 2A.

[Sven Johannsen]

One more complex question: is it better to have rapid charger {high voltage) or slow charger (low voltage)?
Because sometime I charge my pda in my car with a slow charger 5A 1V, and sometimes at home 5A 2V.
Obviously you have all understood 5V 1A and 5V 2A.
Yea, I took advantage of your typo to pontificate a bit. :wink: Fast and slow charge aren't entirely based on what the charger max safety rating is, which is what that Amp figure is printed on it. Really doesn't matter whether you charge fast or slow as long as you don't exceed the charging parameters of the device. If you stick with the right voltage, and the device is suitable engineered, you shouldn't have an issue.

[thierryb]

So that means that if I stay at 5V, there is no risk for my battery or my pda even if I use a 3A charger, because as I have understood my pda will get what he wants and no more than 3A.
So when I use a 5V 0.5A charger, like an usb port, my pda charges slowly because he does not get what he wants.
Now again. my question because I am not sure to have understood all your answer:
Is it better for the battery to give a low level of A, so the battery will charge slowly. Or give to the battery what it wants, and will charge normally.

[Menneisyys]

So that means that if I stay at 5V, there is no risk for my battery or my pda even if I use a 3A charger, because as I have understood my pda will get what he wants and no more than 3A.

Absolutely no risk.

[VulcanTourist]

I have an iPAQ hx4700... is it safe to apply 6VDC to the charging input, say, from a lead-acid gel cell like a PowerSonic? Does it need to be stepped-down to 5V and/or regulated otherwise? Would 6V overheat or fry internal circuits or the iPAQ battery?

I had always intended to make a "portable recharger" for it, using a 6V 4AH PowerSonic battery, as I had done for my digital camera, making a hip pack out of it, to keep both the iPAQ and GPS charged on backpacking trips, for instance. I tried to find out from HP what the input tolerances were, but either I was speaking with idiots or they wouldn't tell me. I knew the data had to be available, because third parties were making similar but much more limited (read: useless) devices.

If I need a step-down circuit, would it be feasible?

BTW, this news about Lithium batteries isn't so shocking, really; much the same is true of good old-fashioned lead-acid cells, which are happier in a near constant charging state. The bizarre behavior of NiCad batteries has poisoned average folks' minds and they now assume all batteries behave like NiCads. I wish they made AA-sized lead cells, because I would have retrofitted my Norelco razor and Braun toothbrush with 'em years ago!

[Menneisyys]

I have an iPAQ hx4700... is it safe to apply 6VDC to the charging input, say, from a lead-acid gel cell like a PowerSonic? Does it need to be stepped-down to 5V and/or regulated otherwise? Would 6V overheat or fry internal circuits or the iPAQ battery?

I had always intended to make a "portable recharger" for it, using a 6V 4AH PowerSonic battery, as I had done for my digital camera, making a hip pack out of it, to keep both the iPAQ and GPS charged on backpacking trips, for instance. I tried to find out from HP what the input tolerances were, but either I was speaking with idiots or they wouldn't tell me. I knew the data had to be available, because third parties were making similar but much more limited (read: useless) devices.


You can give it a try. I'd, however, only do it if I still had warranty on the iPAQ ;-)

[Nurhisham Hussein]

You can give it a try. I'd, however, only do it if I still had warranty on the iPAQ ;-)

I've given this a try before - it's usually possible, but as with higher amperage, you will heat up the charge circuit and battery. So only do this if you have no other choice, and in a cool, well ventilated area.

[VulcanTourist]

I just had a thought whilst reading your replies: what if I were to yank apart a spare cigarette lighter charger and use the circuit outta that? Could that become my stepdown and regulator circuit? I don't know if it would correctly step down from 6V to 5V as well as it does 12V to 5V, but it might be worth trying. I suppose I can just rig up a Powersonic battery to it unmangled first and then measure the output voltage and amps....

Anybody care how that turns out?

[Sven Johannsen]

I just had a thought whilst reading your replies: what if I were to yank apart a spare cigarette lighter charger and use the circuit outta that? Could that become my stepdown and regulator circuit? I don't know if it would correctly step down from 6V to 5V as well as it does 12V to 5V, but it might be worth trying. I suppose I can just rig up a Powersonic battery to it unmangled first and then measure the output voltage and amps....

Anybody care how that turns out?
Probably wouldn't work right. There is actually engineering that goes into these things. That enginerring is different if you are expecting to step 12v DC down to 5vDC than it is to go from 6v to 5v. May not be enough difference in potential to operate. If you want to sacrifice one to try, go for it. Probably would be good to breadboard this with some volt and ammeters to see if you are actually getting any benefit. Could be you tear one apart and can adequatly step down a lantern battery, but only get 500ma because of the reduced potential difference. You'd get that lower current for a loooong time though ;) Could welll be enough to run the device tethered to the battery brick, even if it doesn't speed up charges.

If yoiu try it and get some reproducable results, I'm sure others would want to know. My solution was to buy a Socket external battery. maybe a little pricey, but well built, safe, and very flexible. 'Bout anything that can charge from USB can be handled, as its output is a USB socket.

As far as using 6v directly, that is potentially dangerous as it does rely on circuitry IN the PPC to dissipate the extra energy, and that has no place to go but heat generated IN the device. To keep size small mobile devices aren't typically over-speced much. You can't push them much before they shut themselves down. It is much easier to dissipate that heat in ciruitry outside the PPC since you are likely dealing with a bigger unit because of the battery size in the first place, so some componenets with gonzo heat sinks aren't a big issue.