Most importantly, these lithium based batteries are far more damaging to the environment and they get thrown away faster (overall) than nickel-cadmium hybrid (=Nimh) batteries.
The latter not only offered me bigger autonomy, but also last much longer and are quite universal and easy to find, whilst those lithium-based batteries used to cost a lot and not easy to find, especially after 5 or so years when they were outdated but too low on their energy to offer their full autonomy.
Back then, replacing a set of 4 AA Nimh batteries was about 12-25 € depending on quality, capacity, and shipping fees (as I live in France). In contrast, Li-ion for the models I had researched were 40 € ! (these prices may have changed now down the years and progressive availability).
Nimh, or Ni-mh batteries have two basic types :
- the most common are the old technology, with a fast rate of discharge, even when not used and laying on your shelf.
- The second type is called Low self-discharge, allowing to keep the electrical charges afloat much longer - up to 5 years for some models.
Batteries capacity is expressed in mAH, or amp-hour. I'll let you read about this on wiki.
The more the mAH's the more capacity, but also the longer they will need to charge.
In lab conditions (as in : the lab of the maker), batteries are supposed to have a certain number of cycles of use, charge & discharge, after which the chemicals won't be able to offer their nominal capacity, and eventually die-out. These conditions are seldom met in a person's life, and thus it's important to learn about proper charging methods, and use better chargers than those basic ones you'll find at most stores for very attractive prices, but damaging effects.
The best way to charge your batteries is to first make sure you fully discharge them before charging them back up again, at the slowest pace you can - overnight preferably. I've learned to discharge at least once every 6 months all my batteries is usually enough.
Also, it's best to use what is called a smart-charger, which usually offers more functions, including a discharge program but also discharges and charges in individual channels, so each battery is treated as a unique unit, instead of 2 or 4 or 8 batteries together.
My first chargers were designed for both ni-mh and the now almost never heard of Ni-Cd batteries, which had tiny capacities, discharged very fast, and became obsolete due the fact they were so useless in most cases.
On the other hand, ni-mh offer capacities up to 5X those of Ni-Cd, discharge at much slower rates, especially with those low self-discharge types, and although they cost more, have a much longer life-span, and are far more useful.
Before I knew better, I had bought a Sony fast charger, thinking it'd be useful to gain time when I needed batteries under 15 minutes, but this turned out to be a very bad idea. Charging batteries this way is equivalent to poring a huge jug of water into a tiny cup really fast, expecting all the water to be contained in the cup and not to spill over...
In electrical currents, this is bad. Battery shelf-life is shortened when you charge in this fashion too often, as their capacity goes down due to the memory effect, especially that this particular model treated the 4 batteries as 1 unit. As soon as 1 battery was detected as full, the charger stops, out of a security measure to prevent overheating. The problem is that the other 3 batteries may not be full yet, and each time you charge them in this fashion, their capacity lowers.
Upon careful research, I chose my current 2 chargers, allowing slower paced charging times. I do have to remember to pre-charge what I need, but this is a small concession to regained capacity and longer shelf-life.
The Tensai TS- 2800 EUF which is easy to transport, weighs only 170gr (just under 6oz), but presents a few design flaws, and the Maha MH-C9000 which can also be transported, but not as easily. (the link is to Maha's user manual in PDF. I cannot find one for the Tensai)
Both allows AA & AAA Ni-Cd or Nimh batteries, and 100-240V currents (at 50-60Hz), to use all over the world (but you may need an adaptor to plug it... I know in the UK this results in further imbalance and I'd discourage using this particular model with adaptors unless you can secure their stability).
The Tensai has those collapsible wall-connectors which sometimes collapse back on themselves. You must make sure that you balanced it well on the wall or power bar, as it tends to topple, and may get disconnected.
Each battery is charged or discharged individually ; you can charge 1-4 batteries, and you can see their progress on the LCD screen with bars going from top to bottom (discharge) or bottom to up (charge).
You cannot decide the rate with this model.
It discharges invariably at 0.2 A (= 200mAh) either AA or AAA batteries, but charges AAA at 0.8-1.2A and AA at 1.2-2.0A. Which is the maximum speed you should ever use...
If you start a discharge, it'll swap to charge as soon as it detects the lowest possible level of current, so you don't have to come back to it too often.
On the other hand, you cannot discharge some batteries while charging others at the same time. This only occurs when the Tensai swaps programs, but you cannot manually select them.
I therefore seldom use this model, only when I need more than 4 batteries and fast.
The battery capacity is = 1C.
In discharge, you shouldn't exceed 1C rates, whilst for charging, it's recommended to avoid lower than 0.3 and above 1C.
This means that if your battery is 2000 mAh, you shouldn't discharge it faster than 2000 mAh rate (thus never discharge faster than 1 hour). Choose speeds that allow a slow enough discharge, for example 300 mAh will fully discharge a fully charged 2000 mAh in 6 hours 40 minutes, and less according to the current charge level, off course.
As I said earlier, it's good to fully discharge your batteries at least once every 6 months.
When your camera doesn't have sufficient energy left from the batteries, it shuts down, but this doesn't mean all your batteries are empty. This is why you have to remember to fully discharge before recharging, to have as much as possible batteries on equal footing.
If you charge the same 2000mAh battery, choose slow speeds between 0.3C (= 600 mAh) and max 1C (2000 mAh). Charging times from 0 to 2000 in these cases would be 3 hours 20, and 1 hour, respectively.
In total, the maha offers
10 selectable discharge currents between 0.1 & 1.0 A
19 selectable charge currents between 0.2 & 2 A
(I repeat here, A, as in 1A= 1000 mAh, not measured in C's as that depends on your batteries)
Also, if you can, it is recommended to group your batteries with +/- 5% of capacity from each other (but remaining with the same brand, off course), as your camera's (and any other device's) performance is limited by the worst battery. This means that if your set has a nominal capacity of 2000 but 1 of them has lost part of it and only has 1800, this is the one that will shut your camera off, a full 10% before the official capacity would have ended.
The maha doesn't stop with these functions, however. It offers 3 other modes!
Break-in, which is great when you buy a new set of batteries
Refresh & analyse to determine a set's capacity
Cycle which performs discharge & charge cycles at an amount you specify.
I suggest reading all about these functions on the user manual, which is 4 pages long and more detailed than I could give you here.
To do anything with it, you have to plug, off course, you'll see the options cycling, before the screen will stop and let you decide what to do. You set 1-4 batteries in their slots, select the slot you want from the slot button, and program with the up/down buttons ; then you select the speed, and enter to validate your choice, and do that for each slot (they pass from one to the next in order as well, once you have entered everything). It immediately starts the chosen program, and lets you see the progress in current voltage and mAh speed (it can slightly vary from the rounded figures you decided).
Always remember to use AA or AAA, Ni-Cd or Nimh, but no alkaline or any other type and insert respecting the polarities, even though there is a detector for all those possible mistakes.
Also, stay a bit with your charger. You may get an error message, saying the battery cannot be charged (either it's a different type, or it has arrived to the end of its life, or some other reason. You may need to run a cycle or refresh program, or may have to get occasionally rid of your battery, by bringing to a collection point. Here in France, all supermarkets and malls seem to be equipped for that). Because, indeed, batteries do come to an end, eventually... their chemicals have no more possible charge.
The only complaint I have about this maha is the LCD screen : it is far too bright. I tend to use it in daytime, or set a small post-it on the screen, not to disturb our hamster (and never where we sleep, it'd still be too bright). I'd seen this video on youtube which shows how to unplug the light cable within the charger, but I'm not manual enough to risk this, nor the other video which explains how to set an adjustable backlight...
As those models aren't always easy to find anymore, and your own location may have different functions, I suggest you look at PDF user manuals before buying.
You need to determine not only your budget, but also which programs you need most. I suggest at minimum discharge & charge, with programmable speeds, and individual bays (= operating each battery on its own merit).
If you can, it'd be good to get a model that is similar to my maha, in the sense that it can perform more things.
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