BlackBerry® PlayBook™

[jerryg50]

Batteries work on the principle of current stored at the desogned voltage. It is difficult for most people to understand. The current source of a battery is the determination of its internal resistance.

If the voltage reads low this is because the cells are over discharged. As the battery is used it is normal to have a slight voltage drop. Then after some time the voltage will drop rapidly. Before this sudden drop takes place the battery would have been depleted.

Chargeable batteries arr not very easy to understand.

Jerry G.

[peter9477]

jerryg50, I just wish you could post stuff that didn't simultaneously appear to insult lots of intelligent people ("difficult for most people to understand") while simultaneously containing misinformation.

Batteries do NOT store current, they store charge. Current is the flow of charge per unit time... there's no "flow" when the charge is merely stored. I know you understand this, but the way you say it adds more confusion than it removes, I believe.

[jerryg50]

I did not mean to insult anyone... When. Battery discharges there is current flow. Charge is equivalent to current when applied. Devices use current flow to operate when giving load to a battery.

Tell me in your own words how you would define charge, and what is the affect of charge under load if I am not correct!

Please don't take this as an argument or a showdown. The idea here is to be educational and exchange information and opinions.

Jerry G.

[peter9477]

I'll take you at your word that you're not trying to insult.  I think there's merely a language issue.  If I find your phrasing about the technical stuff, um, "imprecise" then perhaps I shouldn't also take you to task for what might just be the same imprecision in your other words, so my apologies for "jumping down your throat" again. :-)

I don't really want to use my own words, when this stuff is well defined technical material.  I prefer just pointing people to Wikipedia and similar online references, where they can learn more for themselves.

In this case, charge is something measured in coulombs, or sometimes amp-hours, and Wikipedia's got lots to say about it.  It is directly related to current, but it's not the same thing any more than distance is the same as velocity, and in fact the relationship between the two dimensions in each of those pairs is the same: charge is to current, as distance is to velocity.  In each case, one represents "something", and the other the amount of something moving/changing per unit time.

I can't say what the "effect of charge under load" is, since the concept doesn't parse for me... I find it semantically meaningless, or perhaps just confusingly worded.  If I had to guess at what you mean by it, I'd say that since batteries store charge, applying a load (causing current flow, i.e. charge to flow out of the battery) results in a reduction in the charge over a period of time.  That reduction can be measured as the difference between the voltage (which measures the "pressure" of that charge) at the start and end of that period.  There, in my own words, that should say exactly what the wikipedia pages on charge, current, voltage, and such should say...

[Xandrex]

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peter9477 wrote:
Okay, that helps. So we could say that when the battery has reached the maximum voltage (during charging), it's not "fully charged", and the controllers have to monitor the current to determine when they've shoved enough extra energy in that they can stop charging.

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Not really. The voltage you see is the voltage the charger sees around the battery ; it does not materialize the SoC (state of charge). Chargers for Li-Ion batteries can work with constant Voltage (the graphic above shows that) or constant current. Here, the phase 1 is the first phase (where the battery receives a lot of energy), phase 2 is usually said to happen when the battery is charged at around 80% of its capacity, and the battery is considered fully charged when entering phase 3. at that point, the charger should not charge, except from time to time (phase 4) to bump a bit of energy into the battery (the top charging).

About the advise to top charge a battery, I am sorry I am not going to read all the pages of the website just for you

[peter9477]

Sorry, I've lost track now what the point of the discussion was.

As for the top-charge advice, you're the one who mentioned it, without a link. If you think there's a conflict between two pieces of information, and you're posting about it here, I would think it would help you if you provided enough information for people to find that conflict and read about it themselves, rather than making them go on a wild goose chase. I don't have any problem ignoring the whole thing though...

By the way, if there's one point I've been trying to make, and I don't think the graph or your "Not really" paragraph contradicts it, it's that measuring the voltage is the only measurement we have on the battery after it's charged, yet that voltage by itself does NOT give us the "state of charge" as in a percentage value. Only by monitoring voltage and current over time can the system actually give us that *estimated* value.

[jerryg50]

To actually know the condition of a chargeable battery it would have to be discharged using a known calibtated load that is in the range spec for the battery. While being discharged the Voltage must be monitored.

With most manufactures, when the voltage drops 10% below nominal for the battery spec, thje battery is considered discharged. Some manufactures allow slightly different percentages as their standard.

With most manufactures, when a 12.5 Volt battery voltage reading under load reads below 11.4 Volts the battery would be considered discharged. A nominal 12.5 Volt battery would read 13.8 Volts when removerd from the charger.

In devices that show battery condition, this is a prescaled reading done by a computer type circuit. It estimates the battery level according to the average current pulled in relation to the voltage change over accumulative time during discharge and charge time cycles. It is possible for this type of pre-scaler circuit to lose proper reference. The fix is to let the device discharge the battery until near or at a zero indication, and then fully recharge the battery. This should be repeated to average out the calibration.

I hope nobody is getting upset over this discussion, as per some of the comments I read. If you do some search on the net there is available information. Also, you could try to contact a battery manufacture yourself.


Jerry G.

[JSanders Resident Expert · Accepted solution]

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peter9477 wrote:
Sorry, I've lost track now what the point of the discussion was.

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Well put, Peter.

[MiataMike]

you all lost me multiple posts ago..... I wish the PB had a replaceable battery, because I have yet to see ANY rechargeable system that the storage battery didn't eventually fail. Just for my own interest I use an app called POWER GURU to look at how the battery charges and discharges under various conditions. I will ask if anyone can figure out if battery life (my definition = ability to reach at least 95 percent of charge that it had when new) is improved by different charging methods such as low current long time, high current shorter time, under load ie use it when charging, vs sleep, vs off. Maybe it is the heat that matters? Dont think powerguru monitors battery temp.

[peter9477]

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MiataMike wrote:
Maybe it is the heat that matters? Dont think powerguru monitors battery temp.

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MiataMike, it does record the temperature, but it's available only in the export file of historical readings, and not shown live onscreen at the moment.