Battery Draining/Charging

[tim_l_012]

Hi All,

I purchased a wireless optical mouse a few months ago, and I haven't really treated the batteries 100% as it said to in the book. As soon as performance started getting laggy, I charged the batteries back up again.

Now, I get to use the mouse for about 20 mins after it says its fully charged before I lose the X-Axis. I can only move up or down, so I need some way of draining my batteries, so that I can have a good set in the mouse, and a set being fully drained so I'm not tempted to charge them up again

If anyone could provide a circuit diagram that will fully drain the batteries, in the minimal amount of time.

Thanks in advance,

Tim.

 

[Dean Huster]

You didn't mention what package the batteries were in. "AA"? "AAA"? Some form of button cell? If they're "AA" batteries, just slip them into a penlight and run them down. Recharge for the recommended time, then put them in the penlight and run them down again. Do this for three or four cycles, and they should be back up to par. Be careful and remove the batteries from the penlight when the lamp drops to a yellow glow so that you don't reverse-charge one of the cells.

If a smaller battery, connect them in series into a similar penlight circuit with a #222 lamp for a load to discharge them.

The worst thing you can do with NiCd batteries is to leave them on the charger all the time. Wait until they're about ready to cash it in, and then recharge. NiCds that are constantly on charge and then used for a little bit and put back on charge will only give you a little bit of usage as they acquire a "memory".

If the mouse came with NiCd cells, consider replacing them with NiMH cells if you can find them. Wal-Mart is now carrying several brands of NiMH in both "AA" and "AAA" now. NiMH cells are compatible with NiCd chargers.

Dean

 

[ante]

Hi Tim, I always discharge the cells one by one, this way I don’t have to monitor them. They can be left over night and there will still be 0.5-0.55 Volts left in them. It requires one resistor and one diode for each cell. The value of the resistor depends on the decided discharge rate and the Ah of the cell, from 10R to 100R. The cells are more equal after this and will be more equally charged after this procedure.

Ante :roll:

 

[tim_l_012]

Hi All,

The batteries are AAA, and are the Ni-MH version. I know I could leave them in a light to run them down, but this would take quite some time. I need a schematic that will put a huge drain on the battery, so I can pop the battery in, and take it out ASAP.

I'm gonna have to get new batteries anyway, but the thing is I won't be running them all the way down without a circuit like this, becuase as soon as I lose the X-Axis on my mouse its therefore useless, so I charge the batteries up again. I would get 2 sets and have Set #1 fully charged, when Set #2 goes bad, I'll put Set #1 in my mouse, and use this circuit to discharge Set #2, so I can charge them up fully again.

If anyone could provide a circuit which would drain my batteries asap, that would be great.

Thanks in advance,

 

[tim_l_012]

So does anyone know how to quickly discharge a battery?

 

[Sebi]

I also have a wireless mouse from A4tech, it designed for battery operation with two AAA cells (3V). The fully charged two cell NiMH or NiCd battery only 2.5V same as low batt. Unfortunately i can't use the mouse with accus....

 

[Nigel Goodwin]

So does anyone know how to quickly discharge a battery?

A piece of thick wire straight across it :lol:

No, but seriously, as you are wanting to extend your battery life, you don't want to be abusing them by discharging them quickly.

The scheme suggested using a diode and a resistor sounds as good as any simple scheme, just pick the resistor value for the discharge current you want.

If you want to do it 'better', things get much more complicated. You could use a micro-controller with an A2D input to monitor the battery voltage while discharging it into a dummy load (another resistor), or do it using comparators, so it turns the discharge load off at a certain low battery point. In the same way, you could also arrange smart charging of the batteries, in fact better quality chargers would probably do this anyway.

 

[tim_l_012]

OK, well assuming that my batteries, if I were to discharge them one at a time, they are 800mAh Ni-Mh batteries, I would also be hooking up an LED which obviously would get more dim as the power level decreased, and a switch

What are the resistor and diodes that I am after?

Thanks in advance,

Tim.