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Author Topic: NiCad Storage  (Read 1610 times)

wullie/mk2

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NiCad Storage
« on: August 19, 2011, 03:12:05 PM »

I have a 7.2v 2000mAh NiCad powering an airboat. What is the best thing to do after a sailing session? Leave it fully / partially discharged, or recharge.
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unbuiltnautilus

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Re: NiCad Storage
« Reply #1 on: August 19, 2011, 05:09:33 PM »

NiCads, if I remember correctly :-) Discharge and then recharge fully. The buggy boys used to discharge to flat, then store them with a piece of piano wire across the terminals, dead flat until next needed, mind you they were animals :}
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Peter Fitness

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Re: NiCad Storage
« Reply #2 on: August 20, 2011, 12:01:52 AM »

In my RC flying days, I was always told that allowing NiCds to go completely flat risked reversing the polarity, is that true??

Peter.
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JB

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Re: NiCad Storage
« Reply #3 on: August 20, 2011, 12:53:35 AM »

In my RC flying days, I was always told that allowing NiCds to go completely flat risked reversing the polarity, is that true??

Peter.

I think I remember hearing that too.


when I flew with Ni-Cad's and also ran R/C cars with my son, i understood that discharging to 1.1v per cell was considered good practise, 1.1v X 6 cell pack  = 6.6v minimum, charge just before use was also the usual method, a freshly charged 7.2 v pack would give a voltage of 1.4v X 6 = 8.4v straight off the charger dropping slightly after a short time.

When digital meters began to appear on transmitters...replacing the old needle type, a freshly charged 8 cell Ni-Cad would read 10.4v off the trickle charger according to the digi meter.

If I remember correctly that is...! it has been a few years since I had a Ni-Cad to charge.

JB.
    
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unbuiltnautilus

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Re: NiCad Storage
« Reply #4 on: August 20, 2011, 09:33:52 AM »

In my RC flying days, I was always told that allowing NiCds to go completely flat risked reversing the polarity, is that true??

Peter.

The buggy boys were aware of this, the 'shorting out' of a dead flat cell 'apparently' ensured that it would not wander around the zero volts range, as it would if just flattened to nothing and left there without the shorting wire. You would immediately recharge as soon as you removed this wire. Just telling it how it was, I have never used this method and dont intend to start any time soon...
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Timo2

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Re: NiCad Storage
« Reply #5 on: August 20, 2011, 09:53:28 AM »

Hi All

    Some Battery INFO from          http://www.powerstream.com/SLA.htm

Hope this will help you all

Timo2    :-))


    NiMH (Nickel Metal Hydride) Battery Storage

Duracell NiMH Battery Storage

Ni-MH batteries can give years of safe and reliable service if they are used in accordance with recommended procedures and are not abused. Batteries should be kept clean and dry both during use and storage. They can be stored for many months in a charged or discharged state without any detrimental effects as long as they are not exposed to extreme temperatures for any long period of time. After periods during which the battery has not been used, the battery should be charged before being placed in service. Extended overcharging or overheating of the battery should always be avoided.

Varta NiMH: Battery storage in any state of charge is possible. Storage temperatures between -20 and +35 are recommended, relative humidity approximately 50%. In case of long term storage cells must be recharged once a year.

Sanyo NiMH: Under the recommended storage conditions (-20 C to +35 C) the Twicel can be stored indefinitely in either a charged or uncharged state. Recovery may take several cycles. If a battery is stored for a prolonged time connected to a load, electrolyte fluid will leak, the battery will begin to deteriorate, and capacity will be impaired after storage. During long time storage battery deactivation may tend to occur, and for this reason charging may stop early during recharging after storage. This problem can be solved by charging and discharging the battery several times.

Sanyo NiMh Battery Storage: Generally speaking, a loss of voltage and capacity of batteries due to self-discharge during storage is unavoidable. The factors inducing this self-discharge of Nickel-Metal Hydride batteries is listed below:

    The inside of the cell is a hydrogen atmosphere at low pressure, which gradually reduces the active materials at the positive electrode, resulting in a drop of cell capacity. Accompanied by this, the negative electrode which is thermodynamically unstable in its charged state gradually gives off hydrogen gas, thus reducing cell capacity.
    The active materials at the positive electrode in its charged state self-decompose, causing the cell capacity to decrease.
    Impurities within the cell, especially nitric ions, are reduced at the negative electrode and diffuse to the positive electrode where they are oxidized. This results in a lowered cell capacity.

The factors (2) and (3) also apply to Nickel-Cadmium Batteries. As discussed above, the self-discharge of Nickel-Metal-Hydride Batteries during battery storage causes a loss in stored energy. However, once recharged, this lost portion of the capacity will be almost completely restored. The self-discharge characteristics of Nickel Metal Hydride batteries is affected by storage temperature. . . If the battery is stored at high temperatures, the self-discharge will be accelerated. Also, the longer the storage period, the more the cell capacity decreases. As mentioned above, since the capacity of Nickel Metal Hydride batteries lost by self-discharge can be restored by recharging, there are virtually no noticeable adverse effects of battery storage. However, prolonged storage at high temperatures may deteriorate or deform the gasket or the separator, and should be avoided. Either fully charged or discharged, Nickel Metal Hydride ( NiMH ) batteries may be stored indefinitely. . . In either cased (charged or discharged) the capacity is recovered within two or three charge / discharge cycles.

Panasonic NiMH Battery Storage

Because long term storage can accelerate battery self-discharge, and lead to the deactivation of reactants, locations where the temperature ranges between +10C and +30C are suitable for long term storage.

When charging for the first time after long term storage, the deactivation of reactants may lead to increased battery voltage, and decreased battery capacity. Restore such batteries to orginal performance by repeating several cycles of charging and discharging.

When storing batteries for more than one year, charge at least once a year to prevent leakage and deterioration of performancedue to self-discharging.

Nickel Cadmium

Linden: Handbook of Batteries and Fuel Cells

The sealed nickel-cadmium cell can be stored in the charged or discharged state without damage. It can be restored for service by recharging (one or two charge/discharge cycles). [Ed. note: or three charge/discharge cycles].

Panasonic NiCad Battery Storage

Store NiCad batteries in a dry location with low humidity, no corrosive gasses, and at temperature range of -20C to +45C. Storing batteries where humidity is extremely high, or where temperatures fall below -20C or above +45C

Because long term storage can accelerate battery self-discharge, and lead to the deactivation of reactants, locations where the temperature ranges between +10C and +30C are suitable for long term storage.

When storing batteries for more than one year, charge at least once a year to prevent leakage and deterioration of performancedue to self-discharging. When using a rapid voltage detection charger carry out charge and discharge at least once ever 6 months.
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Timo2

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Re: NiCad Storage
« Reply #6 on: August 20, 2011, 09:56:05 AM »

Hi All

    Lots more Battery and Power Pack info at


        http://batteryuniversity.com/learn/article/how_to_store_batteries



     Timo2      :-))
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wullie/mk2

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Re: NiCad Storage
« Reply #7 on: August 21, 2011, 06:51:12 PM »

Thanks Timo2, that was a very comprehensive answer.
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