Charging NiMh batteries when not completely discharged

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
The aaa alkaline batteries went out on my tv remote.

I decided to use my NiMh UBL aaa batteries. 1100 mAh.

They are currently showing 1.31 volts.

And they work ok in the remote as is.

My charger is the manual type.

It charges that type at 150 mA.

I want them fully charged since they are 1.2 volts versus 1.50 for the alkaline.

I would like to know how much longer to charge them.

Thanks,
Andy

Re: Charging NiMh batteries when not completely discharged
AK wrote:
Quoted text here. Click to load it

** The correct procedure is to discharge the cells fully and then apply a full recharge cycle  -  8 hours in your case.  

If you must recharge partly discharged cells, then it takes whatever time needed until their temperate just starts to rise. Constant monitoring by you is needed.  
  


...   Phil  

Re: Charging NiMh batteries when not completely discharged
On Thursday, June 13, 2019 at 7:28:44 PM UTC-5, Phil Allison wrote:
Quoted text here. Click to load it

I have no way of monitoring temp.

How do I fully discharge the cells manually?

Andy

Re: Charging NiMh batteries when not completely discharged
On Thu, 13 Jun 2019 19:08:20 -0700 (PDT), AK

Quoted text here. Click to load it

If they are unused, it is best to charge low self-discharge NiMH every
nine to twelve months. Do NiMH batteries need to be completely
discharged before charging? No, NiMH batteries do not have a memory.
They can be charged without adverse effect at any point regardless of
their state of charge.

https://www.thomasdistributing.com/Battery-and-Charger-FAQs_ep_46-1.html

Get a quality charger that monitors each battery under charge
individually with an indicator for each cell to tell you when it is
recharged.

Monitoring temperature is over-kill IMO and not the best method.  It
is too dependent on ambient temperatures, air flow, etc..

By all means get the batteries that are low self-discharge types.
(sold as "pre-charged")

Old Nickel Cadmium cells required discharging to get the full capacity
out of them.

Re: Charging NiMh batteries when not completely discharged
On Friday, June 14, 2019 at 4:52:06 AM UTC-5, default wrote:
Quoted text here. Click to load it

Thanks default.

My EBLs were low self discharge.

Andy


Re: Charging NiMh batteries when not completely discharged
On Fri, 14 Jun 2019 20:02:22 -0700 (PDT), AK

Quoted text here. Click to load it

EBL is what I've been buying and get good results with them.  Eneloop
are excellent too but cost more.  I just bought some Amazon branded
batteries to see if they are any good (but the price wasn't that much
better than EBL).

Awhile back, after getting frustrated with rechargeable AA
performance, I rigged a dummy load across a battery holder and bought
a few cheap quartz clocks to see which of the odd collection of
batteries I had on hand still could hold a decent charge.  The clocks
stop working when the voltage gets down to ~.7V and records the hours
takes to get there.


Re: Charging NiMh batteries when not completely discharged
On Saturday, June 15, 2019 at 5:42:07 AM UTC-5, default wrote:
Quoted text here. Click to load it

Interesting results.

Andy

Re: Charging NiMh batteries when not completely discharged
On 15/06/19 11:42, default wrote:
Quoted text here. Click to load it


I thought the subject was batteries, not cells.

When considering discharging, there is a very significant
difference between cells and batteries.

Fully discharging a cell with a resistor is relatively safe,
whereas fully discharging a battery that way *will* cause
the weakest cell to be reverse charged - and damaged.

Re: Charging NiMh batteries when not completely discharged
On Sat, 15 Jun 2019 15:08:57 +0100, Tom Gardner

Quoted text here. Click to load it

Yeah, I conflate cell with battery, as do a lot of people.

AND that idea that the weakest cell suffers in a battery would also
hold true for the cheap chargers that charge cells by the pair.  No
charging takes place unless there are two cells and then they are
charged in series - that seems like a good way to screw up batteries.

Re: Charging NiMh batteries when not completely discharged
On 15/06/19 17:03, default wrote:
Quoted text here. Click to load it

No, not necessarily.

Different cells *will* have different capacities
due to manufacturing tolerances. Discharging them
in series *will* lead to the cell with the smaller
capacity becoming reverse charged - and damaged.

Providing that the current/voltage is within the
specified trickle charging limits, if you charge
in series then one cell will become fully charged
before the other but overcharging shouldn't
damage it.

Re: Charging NiMh batteries when not completely discharged
Tom Gardner wrote:

.......................
Quoted text here. Click to load it

.......................................

** When I was involved in electric car racing, the favourite way to discharge a 7.2V NiCd pak was to use a small, 12V lamp.  

When the lamp dimmed, time was up. Immediate recharge prevented the harm that sometime happens to a reversed cell.  

The risk is much greater with paks that contain many cells, the OP has a two cell pack so the risk is minimal.  

...   Phil


Re: Charging NiMh batteries when not completely discharged
On Thursday, June 13, 2019 at 4:26:13 PM UTC-7, AK wrote:
Quoted text here. Click to load it

Not a surprise; alkaline cells when fresh are 1.5V, but are useful down to about 1V.
NiCd and NiMH are 1.2 to 1.4V fresh-charged, useful down to about 1V.
Li nonrechargeables are 3.6V fresh, useful down to 3.0V (so can replace
a 4.5V alkaline clock battery, or two in series can replace a 9V which has 6 alkaline cells)


Quoted text here. Click to load it

Don't use rechargeables for best shelf life, but for best total life.

Mainly, your remote control is inert (it gets used in subsecond bursts when you press
a button).   The self-discharge when not in use (and higher purchase price) make  
rechargeables a questionable fit for that application.

Re: Charging NiMh batteries when not completely discharged
I would think in terms of overall costs, that nimh would be cheaper than buying alkaline aaa batteries. My "alkies" last about 6 months. I have charged the nimh ones about 3 times. My charger charges them separately.  

It would help me find relevant replies if so many were not littered with arguments and cussing. Thanks,Andy

Re: Charging NiMh batteries when not completely discharged
On Tue, 18 Jun 2019 05:11:41 -0700 (PDT), Andy

Quoted text here. Click to load it

I agree.  The price on rechargeables has come down, chargers have
gotten much better, and the low self-discharge make them hard to beat.
(and you aren't storing a lot of alkaline batteries so you have them
on-hand when you need them).  (I store batteries in the refrigerator
so space counts)

Amazon has their house-brand rechargeable for ~$12 for 12 AAA
batteries, and EBL $24 for 16 AAA and an eight station smart re
charger as a package deal.  Eneloop is $28/12 batteries.

Amazon house brand alkaline is $20/100 AAA size, and name-brand
~$40/100 (sounds like a 1-2 year supply for me)

Re: Charging NiMh batteries when not completely discharged
 Andy wrote:
Quoted text here. Click to load it

 ** Then you would be thinking wrong.  

It is ONLY in high usage and high current applications that re-chargeables come out the winner.  

For items like remotes, clocks, DMMs, rarely used torches and any low usage item - forget NiMH cells.  

  

Quoted text here. Click to load it


* It would help even more if the half witted, half baked trolls who think they own the NG would kindly piss off.  



....   Phil


Re: Charging NiMh batteries when not completely discharged
On Wed, 19 Jun 2019 02:08:20 -0700 (PDT), Phil Allison

Quoted text here. Click to load it

That it would, PHIL.

Re: Charging NiMh batteries when not completely discharged
On Wed, 19 Jun 2019 08:57:58 -0400, default wrote:

Quoted text here. Click to load it

Yeah, FUCK OFF PHIL.

Re: Charging NiMh batteries when not completely discharged
On 19/06/2019 12:11 AM, Andy wrote:
Quoted text here. Click to load it

I use Eneloop calls in my remotes and not just for the savings or reduced waste over using  
throw-away cells. I've had more than one remote damaged by leaking alkalines and am yet to see an  
Eneloop leak so there's that...

I use a Maha One charger / conditioner which is also great for matching cells if you need to run  
them in series.
--  
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy little classification  
We've slightly trimmed the long signature. Click to see the full one.
Re: Charging NiMh batteries when not completely discharged
On Tuesday, June 18, 2019 at 2:19:29 AM UTC-5, whit3rd wrote:
Quoted text here. Click to load it

I already had them, so decided to go ahead and use em.

Andy

Site Timeline