The Naked Scientists

The Naked Scientists Forum

Author Topic: rechargable batteries, what exactly is one charging cycle?  (Read 2775 times)

paul.fr

  • Guest
batteries generally last 100 charges, but what is counted as a charge? If it is 99% full and i pop it on charge does that 1% count as one of my 1000 charges?
Are all types of batteries the same?


 

Offline techmind

  • Hero Member
  • *****
  • Posts: 934
  • Un-obfuscated
    • View Profile
    • techmind.org
rechargable batteries, what exactly is one charging cycle?
« Reply #1 on: 05/12/2007 17:42:18 »
I doubt you'll get a straight answer to that!
I understand batteries are usually rated for full/complete charge/discharge cycles, and the manufacturers typically indicate (for NiMH, at least) that you should get many more cycles if they're only partly discharged before recharging - or at least you don't run them absolutely right down to nothing.

In "Real World" use however my experience has been that rechargeables never seem to last more than 100-200 cycles.

However a really big killer of rechargeables (NiCd/NiMH) is overcharging.
Most modern chargers charge the battery in one to two hours at a "fast" rate until they determine that it is "done", then switch to a trickle-rate which is safe to leave on indefinitely. The point when the battery is charged can be determined by monitoring the battery temperature (it starts to rise quickly when the chemistry can no-longer absorb any more energy), or the cell-voltage "dV/dt" stops rising -or even falls slightly. If the charger "glitches" and doesn't cut the fast-charge when it should then the cell gets hot and vents hydrogen and rapidly looses future-capacity. The endpoint-sensing circuits can be confused by poor battery contacts, stopping and restarting the charge too often, externally-caused changes in battery temperature during charging ... or, it seems, just bad luck.
« Last Edit: 05/12/2007 17:44:54 by techmind »
 

lyner

  • Guest
rechargable batteries, what exactly is one charging cycle?
« Reply #2 on: 06/12/2007 13:42:00 »
Older re-chargeables used to exibit 'memory' and would treat a partial discharge more or less like a full discharge - only it was worse, because their capacity would be reduced, too.
The new ones are better behaved, though.
And what about the charger for duracell batteries? Did they work? I never bought one.
The biggest rip off seems to be the lead acid accumulator, which should not be discharged by more than about half its capacity or it deteriorates. So, a 100Ah battery is only, really, a 50 Ah battery.
Can someone tell me I'm wrong about this? I would be grateful if I was !
 

Offline Pumblechook

  • Hero Member
  • *****
  • Posts: 569
    • View Profile
rechargable batteries, what exactly is one charging cycle?
« Reply #3 on: 07/12/2007 15:40:17 »
Battery University..  Detailed info on each type of battery and prolonging life.


http://www.batteryuniversity.com/
 

The Naked Scientists Forum

rechargable batteries, what exactly is one charging cycle?
« Reply #3 on: 07/12/2007 15:40:17 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums