AA Battery charger and re-chargeable battery

Question

I have a Canon digital camera that requires a 3.2V battery.

I'm trying to figure out what would be the impact if i use a re-chargeable battery that has 1.2V capacity. For a similar reason, I need to know, if I buy a new battery of capacity 3.2V then what should the charger specification be?

I don't understand the concept of "Volts" as applied to battery specifications. Can you explain how I could determine from the specifications whether or not a slightly different battery is compatible with a device?

Answer 1

The impact of running a 3.2V device on a 1.2V battery would be that the battery would go flat very rapidly, and the device won't function.

There are two values you need to consider: The voltage and the amperage (or current). The voltage is measured in volts (V) and the current is measured in amps (A or mA - 1A = 1,000mA)

The voltage of the device and the power source (battery) have to match. Too much voltage from the power source and you will destroy (or seriously damage) the device. Too little and it just won't operate.

The power source has to provide at least as much current as the device requires. The device will never draw more current than it needs, so it is perfectly safe to use a power source with a higher current rating without damaging the device. However, using a power source with a lower current rating that the device could risk damaging the power source - in the case of a battery it could cause the battery to rupture and a fire could be caused.

Batteries can be connected together in series to increase the voltage (+ of one battery connected to - of the next; + of that one to the - of the next etc), or in parallel to increase the current (all the + linked together and all the - linked together) or you can do a combination of the two to increase both the current and the voltage.

So, three batteries at 1.2V each connected in series would give 3.6V - a little over the rated voltage of the device, but it may be allowable - you should check the manual or data sheet for the device.

Batteries don't have a current rating as such, but instead have a "mAh" rating. That's *milliamp-hours" or the amount of current that can be given out in an hour.

So, an 800mAh battery can give 800mA over the course of an hour before it goes flat. Or it could give 400mA over 2 hours, or 200mA over 4 hours, etc. The more current that is drawn the quicker it will go flat.

To better understand voltage and current I like to try and get people to visualize a pipe with water flowing through it

• The voltage is akin to the diameter of the pipe. The wider the pipe the more water can flow through it at once.

• The current is akin to the speed of the water flowing through the pipe. The faster it flows the more kick it has as it squirts out the end.

• The water pressure is akin to the power or wattage (which is the current multiplied by the voltage), which is like the number of liters per hour that flow through the pipe.

As far as chargers are concerned that depends on the chemistry of the battery you buy.

There are three major chemistries that fall into two groups:

1. Ni-MH - Nickle Metal Hydride. These are the run-of-the-mill AA and AAA rechargeable batteries you buy in the shop. Your normal AA or AAA battery charger charges these easily. Most will have a charge current and time on them, such as "16hr at 220 mA".

2. Li-Ion and Li-Pol - Lithium Ion and Lithium Polymer. These are the kind you get in things like your mobile phone. They are much harder to charge up and require special electronics to manage them. They must not be allowed to go completely flat or you won't be able to charge them up again. However, they are much more powerful than the Ni-MH ones.

Answer 2

The 1.2V battery won't work in something designed to take 3.2V. The voltage needs to be within a working range likely specified in your camera manual. Too low and nothing will happen (probably), too high and you risk damage of the camera.

The charger should be specified to charge that battery chemistry and capacity. Being a camera battery it is likely Li-Ion, which can be explosive if charged incorrectly, so it is important to use the right charger. I would use whatever the manufacturer recommends (battery and charger)

Answer 3

The question is about a Canon digital camera that takes 2 x AA cells. For discussion purposes we can look at a recent Canon model, the PowerShot SX150 IS. This camera takes 2 x AA cells also, and recommends using either alkaline (non-rechargeable) or NiMH (rechargeable), both of which would run somewhere around 2.4V most of the time during use.

However if we look at the Specifications web page for this model, we see:
Flash Recycling Time: 12 seconds or less (battery voltage: 3.0 V)

This is not saying the camera requires a battery with 3.0V output in order to function well. It's trying to quantify how long the flash capacitor takes to recharge, but they've shaded the spec to look as good as possible by measuring the between-flashes time with a battery (or possibly a power supply if the measurement was taken in a lab) set at 3.0V. It's likely that with half-discharged alkaline or NiMH cells the flash-to-flash time would be noticeably longer than 12 seconds, BUT not so much longer as to render the camera unusable, only enough to possibly lose a "spec war" relative to some other brand's camera.

Stating the specification as such is nearly cheating, in that you'd have to install new lithium primary AA cells (Energizer Ultimate Lithium or comparable) to get such a battery voltage, while a real-life scenario would typically be a bit different. A shady practice, but not worse than a cookie maker calling a "serving size" two cookies.

To answer the question: You can buy any AA batteries and they'll probably work in your camera. If you want longer runtime, Canon suggests you buy their NiMH AA cells and charger, but other brands such as Sanyo Eneloop will work fine. For the longest runtime you can consider lithium non-rechargeable such as Energizer Ultimate Lithium, but in the long run they'll cost a lot more than buying a 4-pack of NiMH and keeping two sets of 2 cells recharged and ready to swap out.

Reference: http://usa.canon.com/cusa/consumer/products/cameras/digital_cameras/powershot_sx150_is?selectedName=Specifications