I've just got a set of NiMH AA batteries and a charger. What's the best way to care for them - to keep them charged, or to keep them discharged?
They're reading 1.13V out of the packet. Should I charge them before the first use?
Finally, do the chargers just have a timer, or do they actually measure the voltage on the batteries?
Thanks,
Daniele
=============================================== Leaving them in a discharged state is not wise.
As there already charged from new it's not wise to charge them now.
Some chargers have a timing circuit built in others don't.
[T] For NiMH I believe *some* charge and regular re-charge due to their self discharge rate. [T] You might need to 'cycle' them a few times to get full capacity. Put them in something that you can keep an eye (or ear) on and run them low (not flat). Recharge and repeat a few times. [T] How long is a piece of string! If you could imagine all the different things a charger can do and you can probably get one to do it!
As a general rule, an 'expensive' charger is less likely to damage your cells than a cheap (especially 'rapid') charger. I have a variable current / automatic charger designed for the Radio Model field and that will charge various combinations of cells and rates vie the use of external battery clips. Probably cost +AKM-40 all in but a very good solution (for me).
The lower the charge current the longer time it will take to charge and the less chance of damage.
Most types of rechargable don't like getting too hot, being over charged or over discharged.
Regular gentle use and they will last for years.
All the best ..
T i m
Charged, but they will self discharge in a week or so anyway IME.
Bloody useless things NiMh.
Charge em. They should be nearer 1.3v fully charged.
Depends on teh charger.
But sadly, thats how they end up if left anyway.
They are not already charged. All Nicad NiMh are shipped pretty much flat.
That at least is true.
I have a Uniross 'Turbo Charger' and a bucket load of 2300mAh AA's, this charger is pretty much as cheap as they come and the majority of my batteries were unbranded eBay purchases.
That said, I use them and abuse them, drain them flat, leave them in the charger for over 48 hours, etc. They were mostly used in my old Digital Camera and CD Walkman.
Over the past couple of years that I've had them, not a single one has died on me nor displayed reduced charge capacity.
Just to make sure I'm talking about the right battery type, these are NiMH
2300mA AA batteries.Don't know if this helps at all.
Seri
On 27/02/2004 D.M. Procida opined:-
Some chargers work on charging for a preset time interval and this type of charger really should only be used with the design and capacity of cell they were designed for.
Some work on a DeltaV (voltage) principle where the cells are charged until they acheive a certain critical voltage change.
Others work on a DeltaT (temperature) principle where the cells are charged until they demonstrate a sudden rise in temperature which is used to terminate the charge.
Either DeltaV or T is the best charging method and allows a variety of cell capacities to be accomodated in one charger and a rapid charge without damage, providing all the cells in the charger are matched. Even better is a charger which applies DeltaV or T on an individual cell basis, which allows any mix of cells to be charged simultaneously.
All cells exibit a sudden rise in temperature as they approach a fully charged condition, as used for the DeltaT sensing. All cells exibit a tiny rise in voltage then a slight decline as the approach a fully charged condition, as used for DeltaV sensing.
You should never over discharge cells which are used together as a battery, because over discharge might mean that the lower capacity cells in the battery might actually become reverse charged. Reverse charging will quickly ruin the cells.
=============================== Well his ain't. I have these type of batteries in My phone from new/straight out the packet. The Phone is a Caller display/With Number storage Digital. Been in there 3 Months now.
On 27/02/2004 The Natural Philosopher opined:-
There has been a major improvement in all cells recently in respect of self discharge. I have had some NiMh cells in my camera which were lat charged in June. They have been in regular use since then and I used the camera about an hour ago, but are still not showing any need for charging.
Should be just about flat then. Self-discharge for NiMh cells is in the region of about 1%/day (and yours were presumably sold within days of being packaged for sale).
Charge them and store in a 'fridge (but warm up before use) - they'll hold their charge longer this way. I don't do this myself because I charge batteries on a daily basis. I've been using Ni-MH for years and must have saved thousands of pounds.
Terry D.
"... must have saved thousands of pounds." compared with what?
Other rechargeables
Dry cells(what sort?)
Alternative power sources (you, mains, petrol, ??)
and goes back into a charger holder each night no doubt.
I'd like to see teh voltage fall off as soon as a bit of load is applied to them. I doubt that they have any charge in them at all. Measuring with a voltmeter draws no current (well in theory anyway) and so you will measure TPD which will probably be 1.1V even when flat
Yeah, pretty useless in the construction of battleship hulls and pianos
In article , D.M. Procida writes
Ensure your charger monitors voltage over time To indicate whether your charger does this it will tell you it uses "DV/Dt" technology on the charger or in the manual. Use them cyclically. When they do not perform the job recharge them. The chemistry will only take so many charge cycles so get the most out of these charge cycles by running the batteries over as much of a discharge cycle as you can i.e. until low not completely flat. When they are discharged charge them as soon as possible and you may store them charged.
You are lucky. Mostly they fallten thesmlves in teh pack within 6 nmonths. His quited voltage of 1.13v is pretty much halfway down fromn 'charged to 'flat. Its about 1.25 fully charged, and about 1v more or less flat.
Give me Nicads for abuse, or Lithium polymers for far higher energy density, any day.
NiMh are cheap and cheerful crap IMHO. Useful for low current appliacations where weight is not hugely critical, and don't contain cadmium, which as everyone knows is worse than Uranium or Ricin, but thats about it.
>
Interestingly, I just bought an Olympus 350 camera which will take "conventional" or lithium batteries
I have 3 portable RDS radios and I seem to be always putting new batteries into them (4XAA). I'll be getting a portable DAB radio soon and have heard that they are even more power hungry.
So - question - would it be possible to use rechargeable batteries in portable radios? I've heard that rechargeables are only of any use in high powered devices like digital cameras but wondered given development, would they now be of any use for my purpose?
TIA.
You'll probably get away with it, although they won't last long without re-charging. 4 rechargeables will start out at under 5 volts instead of over 6 with alkalines - and are of much lower capacity as well.
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