Wickes 18 volt battery pack, would not charge. Have investigated the cells and found what looks like a disintegrated resistor in the wire connectors, taped to the adjacent cell. Does anyone know the identity and rating of this component as a replacement would solve my problem.
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Re: Battery pack failure
The device you found isn't likely a resistor but a thermal fuse. These are incorporated to open at a fixed temperature to prevent cell explosions if the charger fails or cells are shorted exposing the remaining good cells to either too high of a current or overcharging.
These fuses do not heal, once open, they are finished.
If you are in the US, you can buy a low-cost digital multimeter that will let you check the individual cells; nominal for NiCad is ~ 1.25-1.4 volts after charge or about the same for NiMh cells. Any cell 10% more or less after charging is not normal.
It will also let you check the continuity of the thermal fuse and this should show up as a nearly dead short - 0 Ohms.
You can buy such meters at Radio Shack or auto parts stores for under $20 and under $10 if you have a Harbor Freight Tool store in your area.
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During the initial state of the charge, the charger operates in a fixed-current mode. This means that the current will be held at a constant rate until the battery is charged to a bit over 18 Volts. During this phase, the output of the charger will not be 18 Volts. This is done for safety and battery preservation; forcing 18 Volts on a battery discharged down to 15 Volts or less could cause the battery to overheat. If no battery is connected, the charge controller may hold the output low until a battery insertion is detected.
The exact behavior of the charger depends on the chemistry for which it is designed, whether Nickel-Cadmium, Nickel-Metal Hydride, or Lithium ion. If the output of a known-good battery is 18 Volts after charging, and it has normal capacity, the charger is working properly.
However, a bad cell in the battery changes things. If you run a Ni-Cd battery down too far, the weakest cell in the battery may begin to reverse charge from the current coming from the other cells. This usually causes an internal short circuit, and the cell will be stuck at 0 Volts. A battery pack with one shorted cell will read 16.7 -16.9 Volts when fully charged, and the drill will not have the peak power it should. The charger will give you a battery fault indication if it is equipped to do so.
If the power cells are operational and it will not start; then either the motor is dysfunctional or something is jammed in the intake module. A conduction test with instrumentation can indicate if the motor is the problem, the power cells are not fully charged, or you have a short circuit. Check Fuses.
A lot of ni-cad packs have one or two bad cells. to find the bad one(s); unscrew the cover on the battery pack and use a voltmeter set on dc volt 2v full scale and test the cells one at a time. they should each have at least 1.25 volts. The bad cells can be removed and replaced with good cells from other discarded packs. If they're not too old many ni-cad cells will still work. You can also revive some cells by unplugging the vent hole in the top of the cell so it can breathe (seriously). Also, I have zapped single cells by momentarily connecting them one by one (even in the pack) to a car battery. plus to plus,minus to minus. But only for about a half second. Also, heating ni-cads will kill them.
This is the info i found on WG250 battery . It says up to 50 min below in the features. Hope it helps
The WORX WG250 hedge trimmer incorporates an 18-volt 1.7 Ah Ni-Cd battery pack. You can use this battery pack with other WORX Ni-CD PowerShare tools. The included charger takes about an hour to restore a dead battery to full charge.
Probably the battery pack is worn out or has a "memory" problem. A worn out pack will have one or more cells shorted internally (one or more cells read 0 Volts, and an ohmmeter reads less than 1 Ohm when connected to the 0 Volt cell). If it is a memory problem, it is possible to recondition it, but not simple. You have to remove the pack, then connect a 150 Ohm resistor across each cell and let the battery sit until the cells are completely discharged. You can't just connect a resistor across the entire battery pack because the stronger cells will reverse-charge the weaker ones, which will cause them to short out.
Running the battery too far down will cause the reverse-charge problem, but not running it down at least occasionally will cause the memory problem. (Memory problem explained: the cadmium crystals grow when the battery is charged and shrink as it is discharged. However, the larger ones tend to remain intact on discharge and grow faster than the smaller ones. Eventually they block the ion flow through the battery, so the battery loses capacity. It's called a memory effect because the battery only "remembers" it has the capacity to go down as far as it is habitually used. Running the cell all the way down dissolves the over-sized crystals.)
It is possible you have a problem with the charger. Check for voltage on the charger plug. It should be about the rated output voltage printed on the charger box before messing with the battery.
If the battery pack is more than 2 years old its time for a replacement. The typical charge/discharge life cycle of a rechargeable cell is 500 - 700 times and the shelf life is about 3-4 years from the date of manufacture. If the charging indicator lights up when you dock the battery on to the base and still does not work after 5 hours - its due for a replacement.
The R1 resistor basically drops the 9V to around 5V for charging the battery pack. The resistor is a 10 ohm , 2 watt resistor. The other resistor is 220 ohm. This only limits the current to the LED.
The 10 ohm resistor burnt because the battery pack was left to sit too long without use and charging. So the cells shorted causing excessive current through the resistor when you attempted to charge the batteries.
After replacing the resistor, you will need to replace the battery pack before charging. Otherwise, you'll just burn the resistor again.
The problem was caused by the failure of 7 of the 1.2volt cells in the battery pack, the other problems were symptoms of the battery pack failure. Replaced the thermal cutout a 131 degree C component on the PCB in the docking station for the vacuum when recharging, I also had to change the LED which had also failed this is a Red 12 volt 5 mm dia component observe the correct polarity when replacing. Also make sure when replacing the thermal cutout that it is secured tightly to the resistor it sits along side, otherwise it will not respond quick enough if there is another failure.
2.7 volts is too low. Usually camcorders use battery at least 6 volts. Problems with rechargeables especially NiCds and NiMH, a cell will be shorted. for 6 volts pack, there are 5 cells in series (5 pcs x 1.2 volts with load , 1.35 no load). If you are measuring only 2.7 volts, it is highly possible that 3 cells are dead.
As for the charger, if the same charger is used to power the camcorder and you said the the camcorder operates using the adaptor, this means that the charger is OK.
You can ZAP the battery back to life but I will not recommend. It can be dangerous. If you can buy the battery, I suggest you do it since the old battery, even when zapped, will not provide enough juice anymore.