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Battery Memory Effect - What it is and what you can do about it
Almost anyone who uses rechargeable batteries has heard of the memory
For those who have not heard of this problem it is commonly believed
that when rechargeable batteries are not fully discharged between charge
cycles that they remember the shortened cycle and are thus reduced in
capacity (length of use per charge).
This problem was very common with rechargeable batteries up until about
5 years ago. With improvements in batteries and charging technology this
'memory effect' is becoming a thing of the past.
'Memory Effect' is the common term used to replace the more accurate
term 'Voltage Depression.'
Voltage Depression is more a problem with incorrect charging than a
Voltage Depression does not necessarily permanently damage a battery.
It can most likely be corrected by fully charging and discharging the
Voltage Depression ('Memory Effect') is often incorrectly used to explain
low battery capacity that should be attributed to other problems, such
as inadequate charging, overcharge, or exposure to high temperatures.
Voltage Depression can be affected by the discharge rate of a battery.
Generally speaking, the depth of discharge will be less on discharges
at the higher rates. This increases the capacity loss as less of the
active material in the battery is cycled.
Voltage Depression occurs primarily in NiCad batteries. NiMH batteries
are almost never affected and Li-Ion batteries are NEVER affected.
So how can you maximize the use of your rechargeable batteries?
Here are a few steps to take to get the most use out of your batteries:
1. Invest in a good charger. NiMH batteries should not
be charged in a NiCad charger, unless the charger is specifically made
for both chemistries. There are cheap chargers and there are expensive
chargers. Make sure the charger you get has good reviews and
is well made. Chargers with micro-controller chips are usually the best
2. When charging your batteries occasionally discharge
them fully before recharging them. This is especially helpful to NiCad
batteries. Be careful not to discharge too deeply. (Less
than 1v per cell for NiCad and NiMH. E.g., a 3.6v pack to no less than
3v.) Discharging to absolute zero will make your battery useless. It's
best if you have a charger with a conditioner that will cycle the battery
3. Be sure to store your batteries properly.
Do not leave your batteries in a hot car, or in humid conditions. The
best storage conditions are a cool, dry place. The refrigerator is fine
if you stick in a packet of silica gel with your batteries in a sealed
bag to keep them dry. It is a good idea to charge your NiCad or NiMH
batteries fully before use if they have been in storage.
4. Most cordless phones use NiCad batteries. To maximize
your cordless phone battery life, make sure to leave your phone off
the base every once in a while until it is dead. Then leave it on
the base until it is fully charged. You should leave your phone on the
base for at least 24 hours to charge it fully.
There is no need to avoid rechargeable batteries. They can save you
significant amounts of money over time. Don't be scared
off by the 'memory effect'. It is easily manageable if it ever occurs.
- Zbattery.com - www.zbattery.com
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