Kin twom battery display

Question

my kin twom battery sometimes show low battery, but after a while, it comes back some level, without even charging. Is that normal?

Answer 1

Yes, and no. To say that your battery has problems, it possibly could, but it could also be completely fine. Battery life indicators themselves aren't the most accurate things, but there are a few things that you could do to help them. Try cycling your battery a few times; that means fully charging, and then fully discharging it. Note, that this does not mean overcharging, and by fully discharging, i mean by going till it gives the low  battery warning, or 10% left.
Here's a quick article regarding rechargeable batteries:
http://www.puremobile.com/cell-phone-batteries.asp
One more article regarding batteries, specifically the section 'prolong your battery life'
http://www.wikihow.com/Make-Your-Cell-Phone-Battery-Last-Longer
Just a heads, Lithium batteries and nickel batteries behave in very different ways; so don't take all this advice for all batteries, make sure you know what kind of rechargeable battery you are dealing with. Most newer cell phones, including the kin, have lithium-ion batteries (whereas, most rechargeable AA/AAA batteries are Ni-MH). They're not going to be directly 'damaged' by not fully discharging and fully charging (in fact, read the article below, you will actually see they benefit from not fully discharging), but that doesn't go to say that the indicator might be a little off (as in your case). Theoretically, if you cycle it, it will be able to 'zero' out the indicator. On the 2nd link i provided, you will read that it says lithium-ion batteries don't require cycling of the battery, and that is true in that it doesn't damage the chemicals to not completely cycle them. However, i probably just do it out of habit from time to time. And regarding the indicator effect, that is more aimed towards nickel-based batteries but it still could be prevalent in lithium-ion batteries.
You will also notice in the 2nd article that it says not to completely discharge a lithium battery, and that is true. However, with the Kin batteries, they automatically will shut off and just not turn on when their battery is below set level, my guess is ~8%, so that is a fail-safe against significant damage to the battery. I would still recommend charging them no lower than the region where it has the low battery indicator (the diagonal-lined low battery) and not use the phone much longer after it has the critical battery warning (where the indicator is completely empty); mainly, don't make it a habit of going down there on a consistent basis. from my experience, the phone just shuts off very soon after you get the pop-up of 10% battery left, and that is a good thing in terms of preserving the battery life.
One last more in-depth article regarding the batteries:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
The biggest thing to get out of this one:
"Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The smaller the depth of discharge, the longer the battery will last. If at all possible, avoid frequent full discharges and charge more often between uses. If full discharges cannot be avoided, try utilizing a larger battery. Partial discharge on Li-ion is fine; there is no memory and the battery does not need periodic full discharge cycles other than to calibrate the fuel gauge on a smart battery."
So yes, the periodic full discharge could help your battery gauge re-zero/calibrate itself. Naturally, you aren't going to charge your phone at the exact same level, every single time; but say you do, just by dumb luck, then the indicator could slowly begin to think that was the capacity of hte battery, which it isn't. In your case, it sounds like the indicator is indeed off, so give it a try, only one or 2 cycles should do it.
Regarding battery life, in this article, there is a chart of experiments regarding the depth of discharge and charge cycles before the battery wears. Do the math if you want (simply multiply the percentage by the # cycles to get the equivalent time of 'full cycles' of battery life), but it comes out that completely cycling the battery consistently has a lower battery life, but at the same time, charging the battery when it is nearly full (10% discharged) continually actually has just as poor of performance. The optimal battery life from their experiments is somewhere in between 25% and 50%; but that is hard to tell if they are talking about 'time' cycle, or by total capacitance of the battery left. Batteries discharge logarithmically (in simpler terms, not in a straight line).
And one of the simplest solutions, at times, it could simply be that your phone isn't recognizing it correctly, so just turn off the phone, pull the battery, and put it back in. I don't have any solid 'evidence' as to if this helps or not, but it sure doesn't hurt and lots of times the simple reset does wonders.
I'm just giving you the data, and my opinion and what i do. There comes a point of balancing a good battery and convenience. I know i don't base my life around when i need to charge my phone; sometimes charge it when it goes down to the low battery indicator, others i charge after a day or 2, when it is still around half full. Thinking about it, i really don't care too much if my battery lasts as long as it did when i got it new, or if it has some wear and a reduced capacity, as long as it lasts ~2 days. I like charging at night, so that is when i do it. If you spend so much effort trying to preserve your battery life by charging it at 50% every single time, you might as well pretend your battery only has 50% capacity, cause you never use it past that point. I'll take the little bit of cycle wear that comes along with charging it by convenience; worst case, i am so dissatisfied with my battery i have to buy a new one for $30. But you look at the charts from the 3rd link, and it only varies from ~90% capacity to ~70%. I can live with that. That gets me through my 2 days, and chances are in 2 years, i'll be getting a new free phone to replace this one.
Sorry for the super long post, but the answer to your question is located within the first paragraph. The rest is just extra information about the batteries.