Rechargeable batteries, inbuilt batteries and lifespan?

[canidoit]

Hi All

Does anyone know the general rule regarding brand new batteries. I have noticed that products are going in the direction of inbuilt batteries and wondered how the rule applies when it comes to their batteries. There are some stores/sellers that sell batteries or battery products over 6 months old and I am wondering whether there would be battery issues when purchasing products that may have gone to zero charge during that period?

At what point do Li-ion or nimh batteries start deteriorating if left flat for long periods and what are the possible damage caused of leaving it flat/zero charge for so long?

Are manufacturers considering these issues when designing their products with inbuilt batteries knowing that some products may sell when the product is discontinued which could be 2-5 years later.

Thank you.

 

[JohnRoberts]

Hi All

Does anyone know the general rule regarding brand new batteries. I have noticed that products are going in the direction of inbuilt batteries and wondered how the rule applies when it comes to their batteries. There are some stores/sellers that sell batteries or battery products over 6 months old and I am wondering whether there would be battery issues when purchasing products that may have gone to zero charge during that period?

At what point do Li-ion or nimh batteries start deteriorating if left flat for long periods and what are the possible damage caused of leaving it flat/zero charge for so long?

Are manufacturers considering these issues when designing their products with inbuilt batteries knowing that some products may sell when the product is discontinued which could be 2-5 years later.

Thank you.

They generally print dates on battery packages.

I don't think manufacturers speculate about their SKUs sitting unsold for years. Some battery powered SKUs ship with the batteries loose.

For my last battery powered design, I went to great lengths to extend useful battery life. I only needed 3.3V but used 4xAA cells. In fact I had too much voltage from fresh batteries for one of the ICs. My solution was to design a crude pre-regulator. With LDO regulators I can run down 0.9V per cell before dropping out of regulation. The processor will still run below that, but I blink a LED to warn about low battery voltage.

While I am far from a battery expert I have experimented with NIMH for my highly modified solar powered driveway lamps. I doubled up the solar panels (two in series), and changed the inductor in the charge pump for lower LED lamp current. These have been working for a few seasons since the modifications. The nicads delivered much shorter service life (maybe one year).

JR

 

[Tubetec]

Something like a laptop or phone battery which would be Lithium based gradually reduces its capacity over time ,  the charge controller reduces the charge it gives them for safety.
I think once its down to around 50% capacity its basically EOL and at some point the micro controlling it says 'no more' . I swapped out the Ni-cd cells from my DeWalt drill for a Li-on Rc three cell must be close on 10 years ago , Ive deep discharged that battery many many times , to the point where the RC style charger flags it as to low to charge , I simply set the charger to two cell mode , give it a few minutes to bring up the cells to what would be nominal discharged voltage , then put it back to three cell balanced mode and it charges away . In the 10 years Im using it the actuall cell capacity has only dropped less than 10% , so what was once 2200 mah is now only takes around 2000MAh . Computer and mobile phone batteries err on the side of caution as the companies dont want the bad press or lawsuits if someones house burns down , not to mention the built in obsolesence factor.  I had a laptop battery where one of the 6 cells (three pairs in series) went bad , I thought I could simply chop it out and replace it with a known good cell , but no, the moment I disconnected it the microcontroller never allowed it to charge again .  Never ever 'dumb' charge lithium cells in series  , the charge voltage has to be monitored and balanced across the cells or it can easily turn into an incendiary fire ball that no fire extinguisher can quell . 

I called into what once was a hifi,video and Tv repair shop I used work for around 25 years ago some time back , Any of the techs that were still employed were no longer repairing hifi , they were swapping internal batteries in smart phones and tablets and doing firmware/os upgrades , most of their time was taken up filling out paperwork for warranty claims ,they hadnt used a soldering iron in years , clerks  ;D