Do I really have to discarge the batteries manually?

I have my 25W 15 ohm resistor lying beside me... before I hook it up to drain the battery, is there a way I can discharge with my standard "300D" charger?

I don't want to fiddle with the connections if I don't have to.

Thanks

Any particular reason you'd want to discharge the battery? not sure what the options are for a 300D but if I needed to do this, I'd turn camera sleep mode off - then leave it switched on untll battery went flat.

With multicell batteries (any battery over 1.2 to 1.5 volts, depending on the type of battery), shorting out the whole battery to take it down to a totally discharged condition is a BAD thing to do. The reason is simple. The cells in a battery are never of identical capacity. As soon as the first cell is totally depleted, the rest of the battery's current will be attempting to reverse charge the dead cell. This can - particularly in Ni-Cad batteries - cause all sorts of havoc with the weak cell.

SkipD wrote in post #2583804
With multicell batteries (any battery over 1.2 to 1.5 volts, depending on the type of battery), shorting out the whole battery to take it down to a totally discharged condition is a BAD thing to do. The reason is simple. The cells in a battery are never of identical capacity. As soon as the first cell is totally depleted, the rest of the battery's current will be attempting to reverse charge the dead cell. This can - particularly in Ni-Cad batteries - cause all sorts of havoc with the weak cell.

Ok... but I'm only concerned about my 300D battery. BP 511 and I think it's a 2 cell battery? (Just from the shape). I want to discharge it because the battery indicator is way off at the moment.

Are the lithium batteries prone to this phenomenon too?

If I discharge it in the camera, won't reverse charging occur the same?

It's old and the charge in the battery is not what it used to be. This, by the virtue of their design makes the battery indicator give false readings.

DocFrankenstein wrote in post #2584011
Ok... but I'm only concerned about my 300D battery. BP 511 and I think it's a 2 cell battery? (Just from the shape). I want to discharge it because the battery indicator is way off at the moment.

Are the lithium batteries prone to this phenomenon too?

If I discharge it in the camera, won't reverse charging occur the same?

The camera should not let the battery go totally flat. The camera should shut down when the voltage provided by the battery is below a critical threshold.

Lithium batteries lose their capacity over time, but they don't take on a "memory" like ni-cads do. However, I would strongly suspect that you can damage a multi-cell (any more than one cell) battery by taking it down to zero charge.

This article could be good reading.

I've been reading this:

Batteries with fuel gauge (laptops) should be calibrated by applying a deliberate full discharge once every 30 charges. Running the pack down in the equipment does this. If ignored, the fuel gauge will become increasingly less accurate and in some cases cut off the device prematurely.

The BP-511s do have the gauge afaik.

DocFrankenstein wrote in post #2584115
I've been reading this:

Batteries with fuel gauge (laptops) should be calibrated by applying a deliberate full discharge once every 30 charges. Running the pack down in the equipment does this. If ignored, the fuel gauge will become increasingly less accurate and in some cases cut off the device prematurely.

The BP-511s do have the gauge afaik.

I believe they are talking about the fancy little windows gizmo that tells you that the battery is low. To my knowledge, Canon cameras do not have such a meter.

DocFrankenstein wrote in post #2584115
I've been reading this:

Batteries with fuel gauge (laptops) should be calibrated by applying a deliberate full discharge once every 30 charges. Running the pack down in the equipment does this. If ignored, the fuel gauge will become increasingly less accurate and in some cases cut off the device prematurely.

The equipment will not totally discharge a battery like shorting it through a current-limiting resistor will do. The equipment will usually stop discharging the battery (by turning itself off) before the battery is dragged down below a critical level.

gjl711 wrote in post #2584159
I believe they are talking about the fancy little windows gizmo that tells you that the battery is low. To my knowledge, Canon cameras do not have such a meter.

My rebel shows full and then low battery.

It runs on low battery for 400 shots.

SkipD wrote in post #2584177
The equipment will not totally discharge a battery like shorting it through a current-limiting resistor will do. The equipment will usually stop discharging the battery (by turning itself off) before the battery is dragged down below a critical level.

My problem is that it doesn't seem to solve the indicator problem.

DocFrankenstein wrote in post #2584178
My rebel shows full and then low battery.

It runs on low battery for 400 shots.

So it sounds like the battery is getting old and it's internal resistance is getting high. But since the camera is suck a low current device, it still has enough capacity to take pics because of the small current draw. How old is the battery?

DocFrankenstein wrote in post #2584182
My problem is that it doesn't seem to change the battery's capacity.

I haven't studied lithium-ion battery technology thoroughly, but I do not think that you can expect to restore capacity.

Proper maintenance throughout a battery's life can lengthen the life, but that does not necessarily mean that a battery's capacity can be restored after it is used in a less-than-optimum way for a long time.

gjl711 wrote in post #2584202
How old is the battery?

Soon to be 3 years... in my use. The other one is 2 years.

SkipD wrote in post #2584205
I haven't studied lithium-ion battery technology thoroughly, but I do not think that you can expect to restore capacity.

Proper maintenance throughout a battery's life can lengthen the life, but that does not necessarily mean that a battery's capacity can be restored after it is used in a less-than-optimum way for a long time.

Sorry, mistypes make I.

Please refer to my edited post.

DocFrankenstein wrote in post #2584219
Sorry, mistypes make I.

Please refer to my edited post.

Same answer, though....