Battery Charger Knowhow


It has been a long time that I didn't update my resources page. I received many enquiries and constantly receiving emails and messages asking about charger compatibility with a certain type of batteries. I myself have spent quite a fortune buying many different types of charger, some are good and mostly are just so so...hence I decided to write something on the charger and batteries mystery (apply to all AA / AAA / D / C size charger) so that users can buy the RIGHT charger on the first time.

(You don't really need more than one charger, Get the RIGHT ONE Get the Best!) nor the writer (KOH KHO KING) takes no responsibility to the accuracy or damage to readers with the content of this article.




Types of Charger

In general, battery chargers can be grouped into two:


        1. Smart / Intelligent Charger

        2. Timer based Charger


The characteristics of the two chargers are:


Smart / Intelligent Charger

Timer based Charger

Voltage detector

~ the charger is constantly measuring the voltage in the battery. Once the charger detecting a preset voltage in the charger, it will stop charging.


Resistance Detector

~ some better smart charger will detect/measure the resistance when charging. A battery when about full (95%) will have high resistance in receiving further current. A better smart charger will then switch its charging current to a lower one to continuously topping up the battery to 99.9% full.

Non-voltage/resistance detector

~ the charger will continuously pumping in current into the batteries for a preset duration of time. Eg. 8 hours for most timer based charger.

~ If the power current to the charger has been cut off during charging, the charger will start counting its time/duration again from the beginning.

~ Timer based charger is meant for a specific capacity of battery. If you use a timer based charger to charge a battery that is larger capacity than what it is original designed for, then you will not get full charge.

(eg. If the charger is meant for 2000mAh batteries, then you will not be able to charge a 2500mAh batteries full with the charger, unless you overcharge it by doubling the time/duration of charging)





Which type of charger is yours?

A simple test can be performed to check if your charger is timer based or smart type.


1. Fully charge your batteries overnight using your current charger. Wait till the indicator on the charger that shows FULL (you should dump your charger if it doesn't have a FULL indicator)

2. Switch OFF the power of the charger with the batteries still inside the charger (that you have just charged to FULL)

3. Switch the charger back ON

4. Let the charger continue charging the batteries for 10 to 15 minutes



1. A smart type charger will show FULL sign within the 15 mins time, since the batteries have just been charged full overnight

2. A timer based charger will continuous charge the batteries for many hours as preset in the charger


Advantages / Disadvantages

Which is a better charger? Timer based or Smart type? The answer to is no brain, of course the smart type, but why?

Continuous pumping current to the batteries even after it is full is doing harm to the batteries. This will shorten the life-span of the batteries. Using a battery that isn't fully charge is wasting the actual capacity that the battery is capable of delivering. You will not want to buy a 2500mAh battery and charge it only upto 2000mAh right? Spending long hours charging is dreadful...especially if you are in a rush. Most timer-based charger are slow type (which is also known as slow charger), and takes hours (5 to 10 hours normally) to fully charge the batteries it is intended to.


The only reason to buy a timer-based charger is due to its low price. With the simple design and features that it offers (nothing besides charging for a long period), manufacturer is capable of producing timer based charger at a very affordable price. However, as a are actually paying more for it in long run, as it shorten the life of your batteries and the frustration of not knowing the condition (Full, Half-Full, Empty?) of your batteries. So, you will end up buying another charger (smart type this time) and wasting on the first timer based charger. I know this because the first charger that I bought after entering into photography is a timer-based one (more than 12 hours...), dumb it within one month and spent double the price for a smart type later, well worth it! Should have bought a smart one in the first place.


Charging Current

Timer Based Charger

A timer based charger is also known as a low cost charger, hence most of this charger will only have one constant charging current to the battery. Most timer based chargers are using 200mA/hr as their standard charging current.


Smart Charger

There are various types of smart charger in the market. Most smart charger will have high charging current which are also known as Fast Charger or 1 Hour Charger or Quick/Super Quick Charger. These chargers normally uses charging current from 800mA to 2000mAh to super quick charge the battery. Side effect to this is high temperature to the battery. Some batteries might yield very high temperature that endanger the user/surrounding. Hence, buy a reliable smart charger that has a temperature cut off detector (auto cut off the power when detecting high temperature on the battery).


~ Maha C204W one hour worldwide charger is using 2000mA as the initial charging current with temperature cut off feature. When the charger detects the batteries to be 98% full, it will switch to Top-Off Charger and then Maintenance Charge (also known as trickle charge) mode that continuous pumping in current to the battery at 50mA. This charger is also known as the best charger in the world that is able to charge the batteries to 99% full with its FOUR STAGES CHARGING PROCESS. More more review of the charger, click me...


~ Maha C801D Eight Batteries One Hour Charger is also using 2000mA current when charging. It also features the same trickle charge mode at 50mA charging current when the batteries is at 95% full.


~ La Crosse BC-900 is the only smart charger that I know of in the world that has the ability to user selectable charging current from 200mA to 1000mA. You can select your desired charging current depending on your need/speed/time have. It also features trickle charge mode to top off the remaining capacity of the battery and keep the battery full at all time.


* cool charging of batteries means charging at 200mA or lower. Your batteries will not have significant temperature increment during charging

* trickle charge means charging batteries at a very small current. Different manufacturers use different trickle charge current, but normally is around 20mA. Trickle charge mode will do no harm to the batteries, in fact it keeps the batteries full at all time. Users can leave the batteries in the charger for an extended period and remove the batteries from the charger right before using. As NiMh batteries looses out the power over time, thus it is advisable to get a smart charger with trickle charge mode and keep a set of batteries constantly in the charger charging to remain the constant full charge.



Independent Circuit

Timer Based Charger

Most timer based charger has only one charging circuit, meaning that you need to insert all two / four batteries into the charger in order to start charging. There is no detector built into the charger, and the charger will continuous charging the batteries on the preset time/duration as long as it detects the complete circuit of the batteries.


Smart Charger

Smart charger nowadays varies from 1 to 8 independent charging circuits when charging (Maha C801D is having 8 independent circuits for each and every one of the batteries that it is charging). A better smart charger will have independent charging circuit for every single battery that it is charging. Independent circuit means that the charger is monitoring the condition of every battery that it is charging with different circuit/voltage/resistance detector. For example, Maha C801D with 8 independent circuits will charge every single batteries FULL by measuring the voltage and resistance of the batteries individually. It will not be affected by the condition of the batteries next to it. One can mix different capacity of NiMh batteries in the charger (eg. 2000mAh mixed with 2300mAh and 2500mAh or even 2700mAh in future) and the Maha C801D charger will charge every single one of the batteries full at its own time, and trickle charge it afterwards.


Maha C204W is having 2 independent circuits for the 4 pieces of AA batteries that it is charging. It uses one circuit to monitor the charging condition of two pieces of batteries. It is fine for those who uses the same capacity of batteries (eg. 4pcs or 2 pcs of PowerEx 2500mAH), but it is not recommendable if you were to mix 4 different capacity of batteries (eg. 2100mAh + 2300mah + 2500mAh + 2700mAh). The reason is because the the circuit will detect the smaller capacity battery (2100mAh) full earlier than the other batteries and switch to trickle charge mode. However, if user were to charge two 2300mAh batteries + two 2500mAh batteries, place the same capacities batteries on side by side onto the charger and the Maha C204W will still be able to charge both to FULL, and trickle charge to top up the remaining capacity.


 La Crosse BC-900 charger is using 4 independent charging circuits for every piece of batteries that it is charging. User can mix any capacity of NiMh batteries charging through the BC-900 at one time (eg. 2100mAh + 2300mah + 2500mAh + 2700mAh). La Crosse BC-900 charger will charger every single battery FULL and switch to trickle charge mode after that. User can even set/select different charging current on the 4 different circuit (eg. 200mAh 500mAh 300mAh 1000mAh).


Discharge/Deep Cycle/Revive Batteries

Timer Based Charger

I have not known of any timer based charger that has the discharge mode, as most timer based chargers are meant for low cost production...hence making the charger as simple/low cost as possible.


Smart Charger

Not all Smart Charger will have Discharge/Deep Cycle/Revive Batteries mode.


In theory, NiMh battery has no memory effect. It means that once can charge the NiMh battery regardless of how much power is remaining inside the battery. The battery that is charged full will deliver every drop of juice till it is completely depleted. In THEORY (theory is something that can never be achieved in real life but only on paper).


In real life, there is still very small memory effect built up in NiMh battery. Most NiMh batteries will have around 500 cycles life. It means you can charge the NiMh battery upto 500 times. After its life, current is hardly able to pump into the battery and vice versa. (NiCd batteries is well-known to have large memory effect, thus not popular among photographers in the world)


A better smart charger will have the capability to discharge your battery before charging it. It is recommended to discharge your batteries completely after every 10 ~ 20 cycles. This will keep your batteries in top performance. I will write another article on batteries in future.


Deep cycle is the ability of the charger to charge / discharge the batteries automatically for 3 cycles without user's interruption. Just press the deep cycle mode and the charge will discharge the batteries till empty, then charge them till full, then discharge, then charge, then discharge, then charge...Different charger will have different number of discharge / charge cycles, depending on the manufacturer.


Revive battery mode is the unique offering by the latest Maha chargers.

Maha designed a special "ramp-up" charge that "jolts" the batteries if needed to revive old batteries. This happens in the first two minutes after the battery insertion. This "jolting" is a series of carefully timed high current pulses that can activate both new and inactive batteries. From the customer's point of view, they can put batteries of different health levels and rely on the charger to give them a complete charge.