Rechargeable NiMH battery storage question

[n2stitch]

I finally purchased my first set of rechargeables, Powerex 2700's and the Maha C401FS charger to go with it.

 

I have 4-AA batteries, and my 60 CSx only uses two at a time. I know to swap between my sets, but is it better to keep the batteries in the charger all the time when not in the unit, set to slow charge? (There is no conditioning setting, just fast and slow.)

 

Also, is it better to top off the batteries after every use, or drain fully before recharging?

 

Thanks in advance!

 

PS I am keeping a couple of sets of alkalines as spares.

[+fratermus]

I finally purchased my first set of rechargeables, Powerex 2700's and the Maha C401FS charger to go with it.

 

I have 4-AA batteries, and my 60 CSx only uses two at a time. I know to swap between my sets, but is it better to keep the batteries in the charger all the time when not in the unit, set to slow charge? (There is no conditioning setting, just fast and slow.)

 

Maha makes exceptional chargers in the price range most mortals can handle. I downloaded the manual for this charger and it says that (similar to other Mahas) :

 

"When the lights turn green, the batteries are ready to be used.

If left inside the charger, the batteries will be trickle charged"

 

Trickle or maintenance modes are theoretically safe for very long times. So leave them in there if you like. Fast or slow mode does not alter the trickle rate, but slow is always preferable when possible because of the lower heat buildup during charging.

[n2stitch]

 

Maha makes exceptional chargers in the price range most mortals can handle. I downloaded the manual for this charger and it says that (similar to other Mahas) :

 

"When the lights turn green, the batteries are ready to be used.

If left inside the charger, the batteries will be trickle charged"

 

Trickle or maintenance modes are theoretically safe for very long times. So leave them in there if you like. Fast or slow mode does not alter the trickle rate, but slow is always preferable when possible because of the lower heat buildup during charging.

 

Thanks for the reply!

 

Now all I need to know is whether it's better to top off the rechargeables after each use, or drain them down before re-charging?

[+admo1972]

NiMH are quite hardy, so top off as needed, they don't generally suffer from memory effect. As with other rechargables that are okay to top off, it is still a good idea to run them down completely once in a while, then do a full recharge.

[n2stitch]

NiMH are quite hardy, so top off as needed, they don't generally suffer from memory effect. As with other rechargables that are okay to top off, it is still a good idea to run them down completely once in a while, then do a full recharge.

 

Thanks very much!

[+EScout]

I have had the same charger as you, the Maha C401FS for several years and it works very well. I also agree that you should use it on the slow setting when possible. Use it with the cover up to let the heat out.

 

I have been using the Rayovac Hybrid AAs and I will never go back to regular NiMH. They hold their charge much longer, and the reported superior voltage curve seems to be true. Search past topics for info on these.

[Brian_d]

I finally purchased my first set of rechargeables, Powerex 2700's and the Maha C401FS charger to go with it.

 

I have 4-AA batteries, and my 60 CSx only uses two at a time. I know to swap between my sets, but is it better to keep the batteries in the charger all the time when not in the unit, set to slow charge? (There is no conditioning setting, just fast and slow.)

 

Also, is it better to top off the batteries after every use, or drain fully before recharging?

 

Thanks in advance!

 

PS I am keeping a couple of sets of alkalines as spares.

 

I have the c401fs also & if I remember right, it does put out a small trickle charge after charging completes - just enough to maintain battery charge. It's my understanding that that you do not want to completly discharge nihm's. I have 2300 powerex's & I love 'em! Last almost as long as alkalines!

[+Indotguy]

After buying my last set of NiMH batteries, I did a little reading on the subject. I learned the best way to take care of your NiMH cells is to keep them fully charged and stored in a sealed container in the freezer until needed. They will hold a full charge for quite some time that way. Take them out of the freezer and let them warm up to room temperature before installing them in your device. After use, recharge them and put them back in the freezer. It's working well for me.

[+NightPilot]

Most, if not all, manufacturers recommend NOT fully discharging NiMH batteries. Run them down, but don't fully discharge them. They're not like NiCd, which do require occasional full discharging to prevent memory setting. I charge mine to a full charge, then put them in a Pelican case for storage. They do discharge over time, but it's not worth the effort to freeze them, at least for me. I'm not often near my freezer when I need batteries. I am often relatively near my truck, though, and that's where I keep most of my batteries. Convenience trumps keeping a full charge. The newer hybrid batteries, which will soon be all you can buy, I predict, mostly eliminate the problem of discharging over time anyway.

Edited June 7, 2007 by NightPilot

[+DonB]

I finally purchased my first set of rechargeables, Powerex 2700's and the Maha C401FS charger to go with it.

 

I have 4-AA batteries, and my 60 CSx only uses two at a time. I know to swap between my sets, but is it better to keep the batteries in the charger all the time when not in the unit, set to slow charge? (There is no conditioning setting, just fast and slow.)

 

Also, is it better to top off the batteries after every use, or drain fully before recharging?

 

Thanks in advance!

 

PS I am keeping a couple of sets of alkalines as spares.

Check out a set of the new Sanyo eneloops, I've been using them in several different electronic devices and love em.

[n2stitch]

Thanks for all the information, it's very helpful!

[+Seedillume]

Most things you would want to know about batteries can be found at Battery University. Here are a couple of quotes:

 

The recommended storage temperature for most batteries is 15°C (59°F). While lead-acid batteries must always be kept at full charge, nickel and lithium-based chemistries should be stored at 40% state-of-charge (SoC). This level minimizes age-related capacity loss, yet keeps the battery in operating condition even with some self-discharge. While the open terminal voltage of nickel-based batteries cannot be used to determine the SoC accurately, voltage fuel gauging works well for lithium-ion cells. However, differences in the electrochemistry of the electrodes and electrolyte between manufacturers vary the voltage profile slightly. A SoC of 50% reads about 3.8V; 40% is 3.75V. Store lithium-ion at an open terminal voltage of 3.75-3.80V. Allow the battery to rest 90 minutes after charge before taking the voltage reading.

 

Nickel-metal-hydride can be stored for about three years. The capacity drop that occurs during storage is permanent and cannot be reversed. Cool temperatures and a partial charge slows aging. Nickel-cadmium stores reasonably well. Field test reveled that NiCd batteries stored for five years still performed well after priming cycles. Alkaline and lithium batteries (primary) can be stored for up to 10 years. The capacity loss is minimal.

 

While capacity loss during a battery's life cannot be eliminated, simple guidelines minimize the effect:

 

Keep batteries in a cool and dry storage area. Refrigeration is recommended but freezers should be avoided. When refrigerated, the battery should be placed in a plastic bag to protect against condensation

 

Do not fully charge lithium and nickel-based batteries before storage. Keep them partially charged and apply a full charge before use. Store lithium-ion at about 40% state-of-charge (3.75-3.80V/cell open terminal). Lead-acid batteries must be stored fully charged.

 

Do not store lithium-ion fully depleted. If empty, charge for about 30 minutes before storage. Self-discharge on a depleted battery may cause the protection circuit to trip, preventing a recharge.

 

Do not stockpile lithium-ion batteries; avoid buying dated stock, even if offered at a reduced price. Observe the manufacturing date, if available.

 

Never leave a nickel-based battery sitting on a charger for more than a few days. Prolonged trickle charge causes crystalline formation (memory).

 

Always store a lead acid battery in full-charge condition. Observe the open terminal voltage and recharge the battery every 6 months or as recommended by the manufacturer.

 

Here is a summary of the advantages and limitations of nickel-metal hydride batteries.

 

Advantages

 

30-40% higher capacity than standard nickel-cadmium. Nickel-metal-hydride has potential for yet higher energy densities.

 

Less prone to memory than nickel-cadmium - fewer exercise cycles are required.

 

Simple storage and transportation - transport is not subject to regulatory control.

 

Environmentally friendly - contains only mild toxins; profitable for recycling.

 

Limitations

 

Limited service life - the performance starts to deteriorate after 200-300 cycles if repeatedly deeply cycled.

 

Relatively short storage of three years. Cool temperature and a partial charge slows aging.

 

Limited discharge current - although nickel-metal-hydride is capable of delivering high discharge currents, heavy load reduces the battery's cycle life.

 

More complex charge algorithm needed - nickel-metal-hydride generates more heat during charge and requires slightly longer charge times than nickel-cadmium. Trickle charge settings are critical because the battery cannot absorb overcharge.

 

High self-discharge - typically 50% higher than nickel-cadmium.

 

Performance degrades if stored at elevated temperatures - nickel-metal-hydride should be stored in a cool place at 40% state-of-charge.

 

High maintenance - nickel-metal hydride requires regular full discharge to prevent crystalline formation. nickel-cadmium should be exercised once a month, nickel-metal-hydride once in every 3 months.

Edited June 21, 2007 by Seedillume

[hyflyt]

I know to swap between my sets, but is it better to keep the batteries in the charger all the time when not in the unit, set to slow charge? (There is no conditioning setting, just fast and slow.)

 

Also, is it better to top off the batteries after every use, or drain fully before recharging?

 

Thanks in advance!

 

PS I am keeping a couple of sets of alkalines as spares.

 

http://www.greenbatteries.com/index.html Most everything you want to know about batteries. Haven't looked at the site for awhile, so info may be out of date.