Frequently asked Questions
Most Quality power tools on sale now, including DEWALT, BOSCH, MAKITA etc use Lithium cells. Equipment bought over 10 years ago was mainly NICAD and NIMH, Capacities 1.3 to 2 Ah (1300 to 2000 mAh) NICAD in their cheaper ranges with NiMH up to 3.5Ah battery packs for top of the range models. Lithium Ion batteries account for about 90% of new power tools and this is increasing.
Battery Care - What is the best way to look after my battery?
The worst thing you can do to a NICAD or to some extent NIMH battery is not use it. Even if a charged battery is stored for extended periods they have a tendency to "Die". Once this has happened, they can be revived but will lose the ability to store a charge for long periods, ie fine after a charge will be good for a few days but will be totally discharged in a few weeks.
If not required for long periods (a month or more), run a discharge/charge cycle if you have a smart charger. If not, run down in a drill etc, then give a full charge and repeat once a month. This will also condition the cells to the same charge level as they discharge at slightly different rates. This is the same as Reconditioning explained below.
They also do suffer from MEMORY EFFECT This can be reduced by a charge/discharge cycle on the charger if it has one. If not the best way is to run it down completely on the drill or similar equipment, then re-charge. This is called RECONDITIONING which will help to increase the capacity of the battery.
The prime reason is to ensure all the cells start from a discharged state; instead of some cells with a charge and some without any charge, causing an imbalance.
Same applies to this type but they are less likely to "Die" than NICAD's. They also require conditioning cycles but not so frequently as NICAD's. For this reason they are better suited for the "occasional" handyman jobs.
For frequent everyday use, either is good but NIMH usually have a higher capacity than Nicad's.
Never leave any power tool battery in a shed or unheated outhouse during the winter months. Most Winters cold spell kill many batteries of all types as the electrolyte freeze causing the cells to rupture.
NICAD or NIMH, what is the difference?
There is quite a bit of confusion about the difference. As far as Power tools are concerned - very little. It's the chemical makeup that's different.
NICAD and NIMH cells can be interchangeable (as a set) and most chargers will work the same with either type, as they are Delta T type. These chargers are designed to terminate with an increased temperature at the end of charge and will work on both types. Older type Delta V peak detection NICAD chargers may not work properly with NIMH as the Voltage drop at the end of charge is more subtle and may not be detected, resulting in overcharge. Slow or trickle chargers will work on both but as most NIMH batteries are higher capacity, they need much longer to charge and if left at the same charge time can under-charge the battery.
NIMH batteries should not be charged greater than half the capacity (C) at a constant rate. ie, If the capacity is 3Ah the charge current should not be more than 1.5Amps (in some cases up to C -3A is possible but needs to be tested first). This is because NIMH cells produce heat when charged, unlike NICAD cells, which produce less heat. This can cause the cells to overheat if the current is too high, or terminate prematurely if controlled by a temperature sensing devise.
However most SMART chargers will use a pulsing charge, which will allow a high current with less heat, or fast charge (say at 5 to 10 Amps) for the first stage, then 0.5C for the last stage - or a combination of both.
To find out what your charger type is, check how many connections there are from the charger to the battery. This may involve removing the cover to the charger. If it's only a 2 wire connection, it's either a slow/trickle charger or a Delta V type. If 3 or more connections it's a Delta T type. Nearly all power tool batteries have 3 or more connections, as they are fitted either with a Thermistor or temperature switch (or both). This is to suit most types of charger.
Higher capacities are possible with NIMH type but their disadvantage is leakage. They lose up to twice as much charge in a given time as NICAD batteries. NICAD batteries are more harmful to the environment but not if disposed of properly (recycled). NICAD's can be charged up to 4C but their life is reduced. NICAD vs NIMH
Lithium Ion - Advantages, disadvantages
Advantages are no memory effect, much greater capacity for same weight as Nimh or Nicad. Ability to hold full charge for long periods. Disposal is non toxic.
Disadvantages include - liable to explode if overcharged, or damage if cell voltage drops too low. For power tools this can be an abrupt stop as sensors detect this. Generally not as good power output as Nicad or Nimh (tends to die under heavy loads). Complicated charging circuits with circuit boards inside the battery.
What equipment should I buy - NICAD, NIMH or Li-ION?
Lithium batteries are improving all the time and for the average DIY use are perfectly adequate, however they are not easily repaired due to the onboard elecronics; so you are at the mercy of the manufactures for replacements.
For buiders and heavy everyday use I still think the simplicity and ruggedness of NICAD, and mainly NIMH batteries are the best option as they can be repaired easily.
The latest NIMH cells are now superior to the originally produced NIMH cells and can take up to C in constant charging current, ie a 3.3Ah NIMH cell can be charged at 3.3 Amps. The originals would only take 0.5C (1.6 Amps)......These are my sole supply now, I don't use NICAD any more.