| |
In lugnet.robotics.handyboard, Aaron Dwyer <AaronD@nulec.com.au> writes:
> hi all
> the batteries are from mobile radios. motorola. 7.5V. 1200mAh.
> Nickel-Cadmium.
> can someone enlighten me on the best method to rejuvenate and charge these
> type of batteries are.
>
> motorola have a quick desktop charger available for $110, but i want to try
> it myself first.
You will need some good equipment, or you will need lots of patience and a
good DVM.
Here are the steps to rejuvinating old NiCds IF they can be recovered. If they
have suffered the effects of overcharging (common) then they may not be
recoverable.
1. Discharge the pack completely at a C/10 or C/20 rate (60-120ma in this case)
Complete discharge is considered to be .9V per cell. In a 6 cell (7.2V)
pack, this is 5.4V. WAIT FOR THE PACK TO COOL TO ROOM TEMP.
2. Charge them gently with a C/20 charger (C=1200mah in this case,
so C/20 is 60ma) until they are full. This is roughly 20 hours. The pack
should be just slightly warm. Check on it from time to time, if it gets
hot before 20 hours are up (at 60ma) then you have a dead pack, recycle it.
3. Do a high current discharge of 5 to 10Amps. A 1200mah pack is sub-c cells
and they can handle that current easily. Discharge until the pack reaches
.9V per cell, for a 6-cell pack, this is 5.4V. WAIT FOR THE PACK TO COOL
TO ROOM TEMP.
4. Do a high current charge of the pack until peaked. This is where you need
the good equipment. You want to charge the pack at 3C at least (3.6Amps).
This will take about 20+ minutes. You want a delta-peak detecting charger
to do this - RC car chargers are designed to do this. If you decide to
do it by hand, then you have to put a volt meter on the pack. The voltage
of a NiCd pack will rise as it is charging, so you need to provide a
constant current source to handle this. The pack is peaked when the voltage
starts to drop. I use a peak charger, but I know that about .1V dropoff is
not uncommon. An analog charger is best for this, watching the needle and
noting its location is easier than tracking a digital readout. WAIT FOR THE
PACK TO COOL TO ROOM TEMP. It will get a little warm during this process,
if the pack gets hot, then then reduce the charge rate, and repeat steps
1-4, if it still gets hot, recycle the pack.
5. Repeat Step 3.
If the pack is recoverable, you should now have a decent NiCd battery pack.
Yeah, its complicated and a mistake at any point in this process can result
in a fire or explosion - I use a discharger that detects the proper cutoff
point and a delta-peak detecting charger that I can set the charge rate on and
it tracks peak voltage and capacity. If your 6-cell pack has a peak voltage
over about 10.5V its a pretty crappy pack and not very good for high current
duties. You will need a power supply that is at least 12V to do this kind
of charging, and it has to handle about 5Amps to boot. Heat is the enemy,
NiCd's hate high temperatures.
have fun!
DLC
|
|
Message is in Reply To:
 | | recharging battery
|
| hi all i have come across some old batteries and want to know the best way to charge them. the batteries are from mobile radios. motorola. 7.5V. 1200mAh. Nickel-Cadmium. can someone enlighten me on the best method to rejuvenate and charge these type (...) (25 years ago, 22-Mar-00, to lugnet.robotics.handyboard)
|
2 Messages in This Thread:
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
