Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Why do they tell you to leave the unit being charged all the time?  Ni-Cad batteries die early if not drained & recharged.
Document: Nickel metal hydride batteries can be, realistically, charged around 500 times before their capacity drops off. We have had our vacuum two years and it has been great but you can definitely tell that the power is beginning to decline. I would definitely spring for the lithium ion version of this vac.
The vacuum works great - for a while. As you will read from others here the batteries last from a few weeks to a year or so then die. You can't replace the batteries.I find it unacceptable that such an expensive product is essentially a throw-away. It does have a 2yr warranty - so keep your receipt - you WILL need it. Hopefully they will replace the unit.
Which brings me to the one strong drawback: the battery doesn't last very long - we get about 15 minutes of powerful vacuuming (at the most) and then it quickly starts to die, and also unfortunate - it takes a long time to charge back; not exactly sure how long to charge - but when we are house cleaning it still isn't charged enough to work after an hour. It also is really only good on hard floors.
A faster charging battery unit would be welcome (I tend to have to leave it overnight) and operating time could be longer =(. Loses suction as battery runs down (unlike dysons that shines here but I just do not like handling dysons)  If you have new woollen carpets that typically sheds a little initially, you'll be running to the bin every other minute.5 stars if used for just a quick whirr around the home for the quick spot clean. Not suitable for wet patches or large areas.
It is not construction orange, it is a classier color. It's not at all a coral, but in my opinion, it would not clash harshly with the coral color group. It has all shiny silver accents or dark grey. There are only those 3 colors on the entire unit.I am delighted with my vacuum. I've had it a few days, but I have used it quite a bit, for about 10 minutes each time. I charged it overnight the first night, but not since then.
We have been using this vacuum for the past few weeks and it does a fine job both on our tile floors and as a hand vacuum. It is too early to tell how well the battery will last.
I loved this little beauty when it worked but just as it passed its second birthday (and the end of the warranty), the batteries began to fail - at first just less suction, then less time and finally they just won't hold a charge at all (unit is about 2.5 years old now).
Really a disappointing product from such a prestigious manufacturer as Electrolux. The battery life is abysmally short for such an expensive unit, and I don't mean normal run-time (which was originally about 5 minutes continuous). I'm talking about the product life of the batteries over time. They started going weak at about three months and now at a year they won't even turn the motor more than a few RPM.
It did work well for about 6 months. After 6 months battery would last less than 5 minutes. I also noticed that the motor seemed to be running at "low" speed.A year later decided to have a look inside of the unit as it was useless sitting in the cradle not working anymore / not getting a charge.I opened it up and found 3 of 8 batteries had burst.I decided to try to replace all of the 8 batteries with new one.It was a bit time consuming.
(it took my vacuum about 8 months to die and not hold a charge, I used it everyday, sometimes twice a day)Luckily my husband is an electrical engineer and knew how to replace the batteries. If you have a handy man that knows about this stuff then the vacuum will work for you. The Vacuum has 10 batteries inside it that need to be soldered and rewired. It took my husband about 1.5 hrs to replace the batteries.
Answer: First off, the batteries used in this unit are NiMH, not NiCad, which normally is a good thing (less toxic, better memory etc). Regardless, the problem is the batteries are junk. There was a recall for bursting batteries early on, but most of the newer units don't fall under their coverage. Check your serial # against the recall just to make sure. The best repair short of throwing it away (which is feasible according to many of the reviewers) is to replace them with upgraded batteries. There are ten batteries at 1.2V each (yes it's actually a 12 volt unit). and I upgraded the MAh to 2000 ea vs the 1200 of the stock batteries. It's a tricky operation to solder in the new tabbed batteries, so only someone who is very handy with a soldering iron should attempt it. It's worth the hassle if nothing else just because it's a fun project that made the wife very happy. And we all know how much better life can be if the wife is happy...Anyway, you can Google around for the batteries and related info. Cost me about 35 bucks total.