How to resurrect a nicad battery

WHAT DO YOU WANT TO DO? resurrect a nicad battery ???

1

Read the manufacturer's specifications for your NiCad batteries. Most NiCad batteries are intended for slow (trickle) to moderately fast charging. Some are specially designed to take a very quick charge (in as little as an hour). The recommended charging time will be listed as C(1), C(5) or some other number. The number tells you how long the battery needs in order to recharge properly. Most NiCad batteries have a range of C(5) to C(15) or so (five to 15 hours).

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  Step 2
  Select the right kind of battery charger for your NiCad batteries. Very slow chargers are less efficient and so more expensive to use. With some, only about 50 percent of the electricity ends up in the battery. A fast-charge system with a C(5) rating can be up to 83 percent efficient. That works out to 40 percent less electricity used to recharge a NiCad battery.
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  Step 3
  Avoid draining a NiCad battery completely. Completely discharging a NiCad battery shortens its useful life. It's even more important to avoid overcharging. If you do get an inexpensive charger, make sure it has a timer you can set to halt the charging. The best battery chargers use the "delta-V" technique. When a NiCad battery is fully charged, there is a tiny but detectable drop in voltage. A good delta-V charger has a sensor that detects this drop in voltage and turns the charger off. Ideally, the charger will have an LED readout of the charge on the battery. That's handy for checking to see if the charge is getting low so you don't deplete the battery completely.
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  Step 4
  Place the battery in the charger according to the instructions that come with the particular model. Don't forget to plug in the battery charger. Set the timer if there is one, and make sure the charger is placed in a secure spot where it won't be knocked over accidentally.
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  Step 5
  Allow the batteries to cool before returning them to the device they power. When charging properly, a NiCad battery will have a temperature of about 104 F (40 C). The battery will function better (and last longer) if you allow it to cool completely before reinstalling it.

a) First, check the charger to assure it is actually providing voltage. The only proper way to do that would be to place the meter across while charging to assure it was holding a reasonable float voltage (should be a fair bit above rated battery voltage). Ideally, you'd want to measure current with an ammeter in series, but that's not as easy to put together in most cases. If nothing can be readily measured with the battery in place, at least take a meter to the charger to see if you can pick up float voltage. There's no assurance with that measurement alone (could be being pulled down to zip even under a slight load) but it's better than nothing.

b) You say "battery" and not "cell". If it's a battery pack of some sort, it may well have internal charging circuitry (some contain "intelligent" electronics) -- or at a minimum, should have a temperature cut-off device (thermal breaker) to avoid any dangerous overcurrent conditions during charging or use. The charging circuit or internal breaker *may* have failed. Further, if it is a true "battery", the cells are internally bonded together. It's not common that these bond straps break (they're usually spot welded to the cells), but hey -- anything is possible.

c) Don't assume it's the battery itself that has failed (again, assuming it's not just a single cell). You may have lost an internal connection or may be dealing with a loose external connection. If it's one of those packs that come in a portable phone or R/C car (just as examples), a tiny tug on the wiring between the battery and connector may provide a surprise, and that'd give you zero in a hurry.

Some producers argue charger incredibly reduced charging times of 30 minutes or less. Cells with well-balanced and operating at moderate temperature, nickel-cadmium Dell Inspiron 1525 Batteries designed for fast charging can indeed be applied in a very short time. This is done simply dumped in a high charge current during the first 70% of the charge cycle.

In the second phase of the charge cycle, the charge current should be lowered. The absorption efficiency of the Asus M6000N battery charge is reduced gradually shifts to a higher charge state. If the charge current is still too high in the later part of the charging cycle, the excess energy is transformed into heat and high pressure cell. Eventually, the ventilation will occur, releasing oxygen and hydrogen. Not only reduce the gases escaping the electrolyte is highly flammable! A white powdery substance accumulating in the mouth area indicates the previous outburst.

NiCd tool batteries can be fixed. No matter what brand or volt battery you have.

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It's rare to see a *true* ZERO (even a little voltage disqualifies it from the following explanation, so I'm trusting you here!) due to a cell failure in a battery pack. If the charger is working, you either have an internal open circuit or other charging circuit problem in the hp compaq 8510p battery or one sorry battery that isn't going to be "resurrected". If the charger works, only checking of wires or cutting into the battery pack can tell you if it can be "fixed". a) First, check the charger to assure it is actually providing voltage. The only proper way to do that would be to place the meter across while charging to assure it was holding a reasonable float voltage (should be a fair bit above rated battery voltage). Ideally, you'd want to measure current with an ammeter in series, but that's not as easy to put together in most cases. If nothing can be readily measured with the hp compaq 8710p battery in place, at least take a meter to the charger to see if you can pick up float voltage. There's no assurance with that measurement alone (could be being pulled down to zip even under a slight load) but it's better than nothing. b) You say "battery" and not "cell". If it's a hp pavilion tx1000 battery pack of some sort, it may well have internal charging circuitry (some contain "intelligent" electronics) -- or at a minimum, should have a temperature cut-off device (thermal breaker) to avoid any dangerous overcurrent conditions during charging or use. The charging circuit or internal breaker *may* have failed. Further, if it is a true "battery", the cells are internally bonded together. It's not common that these bond straps break (they're usually spot welded to the cells), but hey -- anything is possible. c) Don't assume it's the battery itself that has failed (again, assuming it's not just a single cell). You may have lost an internal connection or may be dealing with a loose external connection. If it's one of those packs that come in a portable phone or R/C car (just as examples), a tiny tug on the wiring between the hp pavilion dv6 battery and connector may provide a surprise, and that'd give you zero in a hurry. If the charger is good, and you can't sort out the problem, and it's some sort of battery pack that's a bugger to replace, you can take it to a place like Batteries Plus to have it rebuilt with new cells. While you're at it, you might also consider switching them to NiMH for better capacity and lack of the "memory effect" that is a problem for NiCd cells.

I have done this many times. Take a voltmeter and put it across the cell (don't do cells in series, do them one at a time). Get a current limited power supply (bench power supply), set it to about 3 to 5V, and limit the current to something between 3 and 20 amps (yes, I have used as high as 20A and not hurt the sony vgp-bps8 battery). BRIEFLY (one second or less) touch the power supply wires across the battery. Watch the voltage. It should come up. If it reaches 1.2 V, stop, and charge it immediately. Be careful not to overheat the battery - it may explode.