What is the difference between single-use (primary) and rechargeable batteries?
Single use batteries (also known as primary batteries) are the same as disposable batteries, which are designed not to be recharged and have to be discarded when flat (or discharged). Common primary battery types include alkaline, carbon zinc, lithium, silver oxide and zinc air batteries.
Rechargeable batteries can be recharged and reused from 500 to 1000 times depending on usage. Common rechargeable battery types include nickel metal hydride (NiMH), nickel cadmium (NiCd) and lithium ion (Li-ion) batteries.
Can I use rechargeable batteries in devices that use single-use or alkaline batteries?
Yes. In most situations, nickel metal hydride (NiMH) batteries can replace (single-use) primary batteries, especially for high drain electronic devices. The main benefits are that after the initial investment they will save you money as you can reuse those batteries hundreds of times and they have the added benefit of helping the environment by saving raw materials and avoiding the waste of single-use batteries which may eventually end up in land-fill.
There may be some devices where rechargeable batteries may not be suitable, for example some brands of DAB radios where four or six batteries are used in series, and the voltage difference between NiMh rechargeable batteries and standard alkaline batteries can cause poor performance. See the FAQ on voltage for more information.
What is the difference in voltage between rechargeable batteries and single-use batteries?
Standard size single-use batteries usually have a nominal voltage of 1.5 volts whilst rechargeable batteries are 1.2 volts. The exception being PP3 9 volt block size battery, and some specialist security batteries, which can be higher depending on the size and type of battery.
As single-use batteries are consumed, the voltage reduces. So throughout the time the batteries are used, single-use batteries’ average output is 1.2 volts, similar to that of rechargeable NiMH batteries. The major difference is that single-use batteries output 1.5 volts when first used and end below 1.0 volts, whilst rechargeable NiMH batteries maintain an average of 1.2 volts for most of the time.
This means that in the vast majority of devices the voltage should not be an issue when replacing single-use batteries with rechargeable batteries. However there are some exceptions where the difference in voltage can cause poor performance. For example when using four or six batteries in series in some brands of DAB radio, the voltage difference between four alkaline batteries (4 x 1.5 volt = 6 volt total) and four rechargeable NiMH batteries (4 x 1.2 volt = 4.8 volt total) can lead to shorter battery lifespan. However there would be no detrimental effect on the radio, and the majority of DAB radios will work well using rechargeable batteries without any problems.
What does 'Stay-Charged' mean?
Stay-charged rechargeable batteries hold their charge much more effectively when not in use. Standard NiMH rechargeable batteries (those that do not have the Stay-Charged technology) will gradually lose their power over a period of weeks and months even when not in use (around 30% per month) in a process known as ‘self-discharge’. This occurs when the internal chemical reactions reduce the stored charge of the battery even when the battery is not in use. By comparison, Stay-charged batteries have a low self-discharge rate of around 2-3% per month, therefore retaining their charge and remaining ready to use.
In practical terms, using stay-charged batteries for everyday devices (that don’t drain the batteries completely in a short period of time) means they will retain their power when not in use and so will be ready to use and not need recharging as often. For high drain devices such as remote control toys or digital cameras using a flash, a higher capacity standard NiMH rechargeable may be more suitable, as they will have more power over the first few days before the benefits of a stay-charged battery are applied. However for devices such as smoke alarms, torches, or devices that are used a little less frequently but need a charge on demand, then stay-charged batteries may be a better option.
Can I use my rechargeable batteries straight from the pack?
If your rechargeable batteries state they are ‘Pre-Charged’ or ‘Ready to Use’ they can be used straight from the pack just like single-use batteries. However, standard rechargeable batteries do not have this feature so they will need an initial first charge before use.
What is ‘self-discharge’ of a rechargeable battery?
Self-discharge is an occurrence in rechargeable batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes i.e. when not in use in a device. Self-discharge decreases the shelf-life of batteries and causes them to initially have less than a full charge when actually put to use.
The rate at which self-discharge in a battery occurs is dependent on a range of factors such as the type of battery, state of charge, charging current and ambient temperature. Typically, among standard rechargeable batteries, lithium batteries suffer the least amount of self-discharge (around 2–3% discharge per month), while nickel-based batteries are more seriously affected (nickel cadmium, 15–20% per month; nickel metal hydride, 30% per month), with the exception of Low self-discharge (stay-charged) NiMH batteries (2-3% per month).
Storing batteries at lower temperatures thus reduces the rate of self-discharge and preserves the initial energy stored in the battery.
What is ‘Memory Effect’? Does it apply to rechargeable batteries?
Memory effect occurs when a rechargeable battery is charged before its’ capacity is completely drained. The battery may then ‘memorise’ the last discharge level and only accept that amount of charge in subsequent charges, therefore decreasing the capacity it will recharge to and reducing its service time. However with advances in rechargeable technology this problem has been virtually eradicated in modern NiMH rechargeable batteries.
How do I charge my rechargeable batteries?
Rechargeable batteries will generally need a separate, suitable battery charger to recharge them.
There are a wide range of battery chargers available for different battery sizes, from fast, intelligent chargers, to overnight chargers – all with different features and benefits. For full details please see our Guide to Chargers.
There are some exceptions such as in DECT cordless phone, baby monitors or solar lights where the batteries are recharged via the contacts in the device when it is placed in the base charging unit or dock. Please check the instructions to ensure you choose the correct type of rechargeable battery for your device.
What is the difference between a high capacity and a low capacity rechargeable battery?
Rechargeable batteries come in a range of sizes and each size will be available in a range of capacities. The capacity of a rechargeable battery relates to the amount of energy the battery will hold. The higher the capacity, the greater amount of energy the battery will provide. Capacity is measured in mAh (milli ampere per hour) which is a unit of electric charge. The higher the capacity of the battery, the longer it will take to charge. A simple analogy would be to think of the capacity of a battery being a bucket – and electric charge being water. The bigger the bucket, the more water it can hold, but the longer the bucket will take to fill.
The capacity doesn’t reflect the physical dimensions of a battery (for example AA or AAA batteries are standard dimensions) but there are different capacities available for each size of battery. On our individual product details we aim to provide guidance for common uses for batteries, but if you are not sure, you can always contact our customer service team for more advice.
Which capacity battery is best for me?
Different devices will require different capacity batteries. For example cordless phones are frequently charged, so don’t usually get a chance to run completely flat, therefore a low to mid capacity battery would be suitable (see our Cordless Phone FAQ for more details). Other devices which can use a low capacity battery include garden solar lights or remote controls.
Typical low–mid range capacity batteries are:
AA size batteries: 800 – 1300 mAh
AAA size batteries: 400 – 800 mAh
Typical high capacity batteries are:
AA size batteries: 1950 - 2700 mAh
AAA size batteries: 950 - 1100 mAh
Devices which require high capacity batteries include remote control cars, digital cameras and some electronic toys. If you find you are replacing batteries frequently, a high capacity battery will provide longer lasting power.
If your device requires batteries which hold their charge in between uses and perhaps are not used for a period of time you may wish to choose a rechargeable battery with stay-charge technology which means the batteries retain their charge between uses.
What is the best type of battery for my cordless phone? (Including DECT phones)
We would recommend a low-mid range capacity rechargeable battery for cordless phones (for AAA size batteries a capacity of around 400 mAh to 800 mAh). The capacity of a rechargeable battery in a cordless phone does not need to be high as it only effects the time between charges and usually cordless phones are replaced in the charger when not in use. If the cordless phone is used for long periods of time choose a rechargeable battery with a higher capacity and if the phone is used for frequent short calls then replaced in the charger, a low capacity battery (400 – 600 mAh) will be sufficient. If you require the battery to hold its charge when not in use (perhaps as you have a single charging base and two phones) you may wish consider a stay-charged battery.
What is the best type of battery for my solar garden lights?
With solar garden lights the amount of charge they can receive in a typical day is quite low, therefore it isn’t necessary to buy a high capacity battery as they wouldn’t be able to fully charge in an average day. Most solar light batteries are in the capacity range from 400 to 800 mAh, with 600 mAh being common (typical for AAA size batteries). For more information see our FAQ on battery capacities.
One consideration for solar garden lights may be to choose a battery with stay-charged technology. This means they can retain their charge when not in use, therefore holding the charge they receive on sunnier days, which is useful as the amount of solar charge they would receive can vary from day to day.
What is the best type of battery for my smoke alarm?
Smoke alarms use a small amount of power over a long period of time, and often are used as a back-up for mains powered smoke alarms. For this reason we would recommend using either single use alkaline batteries, such as Duracell Ultra or Plus Power or for rechargeable version we would recommend a stay-charged type 9 volt battery such as the GP ReCyko or Unrioss Hyrbio as they will retain their charge for up to a year when not in use. We would not recommend standard rechargeable batteries as the power in these batteries slowly discharges over time even when not in use.
What is the difference between a battery code that starts with a HR (such as HR6) and LR?
The battery codes LR6 and HR6 both refer to AA size battery sizes – with LR6 being single use (alkaline) AA size battery and HR6 being rechargeable AA size battery. The prefix LR can be applied to most alkaline batteries whilst the prefix HR relates to rechargeable batteries. The physical dimensions of both types are identical therefore a AA size HR6 rechargeable battery can replace an LR6 alkaline battery, a AAA size HR03 battery can replace a LR03 battery and so on.