I have purchased a Canon 1200D and am wondering how long I should charge the battery when it arrives. I've heard people say that we need to charge a battery for one day to prevent battery "memory".
Do I actually need to charge the battery for that long, or will two hours be sufficient?
In general I'd recommend charging the battery fully before 'playing'. However this probably isn't necessary with modern lithium ion batteries, which don't suffer from memory effects.
The idea of battery memory and long first charges is a hangover from the day's of NiCd batteries.
When in doubt though read the manual.
The battery charger that comes with your camera indicates when the battery is fully charged. After this point is reached, it will stop charging the battery, so leaving the battery in the charger any longer than this will have no effect.
My recommendation is to simply charge the battery until the charger indicates that it is fully charged before using it for the first time. The manual should give you an estimate on how long this will take. For instance, the battery for my EOS 750D takes about 2 hours to fully charge.
The memory effect of lithium-ion batteries is negligible. The software in your camera may however do some battery calibration, so it may be a good idea to completely discharge and then fully recharge the battery every once in a while.
You don't need to do this when purchasing a DSLR.
When you get the DSLR, it has probably around 40% charge because that's the optimal charge for long-term storage. If that partial 40% charge doesn't annoy you, you can start shooting immediately. Or, you can charge it immediately if you want to.
DSLR lithium-ion batteries are unlike car lead-acid batteries, they like operation at partial charge. So, actually charging the battery to full reduces its lifetime! So, you get slightly better battery lifetime if you start using it immediately and then charge when the red low charge indicator blinks. But you get only 40% of an additional cycle for free, with battery lifetimes being around 500 cycles, so the benefit in starting to use it immediately without charging are minimal.
To avoid battery problems, you should avoid elevated temperatures at 100% charge. Most laptop batteries spend most of their time at elevated temperatures and at near 100% charge, and they last only a few years. DSLRs do not heat up naturally as much as laptops do, so the only thing you need to keep in mind is to not leave a 100% charged battery in a hot car. Try to avoid storing batteries in freezing temperatures as well. Electric cars have in-built battery heating systems, DSLRs don't.
Also, try to avoid charging obsession (charge to 100%, use until 90% charge left, charge to 100%, use until 90% charge left, ...). So, don't recharge all the time, recharge only when you have used a sizable fraction of the battery capacity (not necessarily draining it to completely empty, as partial cycling may have benefits). The reason is that charging damages batteries the most if it's nearly empty or nearly full*. Try to prefer charging whenever you see the red low charge indicator blinking, instead of using every last percent of the battery charge.
If you need to store a battery for a long amount of time, charge or deplete it to approximately 40% charge level, put it to a plastic sealed ziploc bag, and store it in a refrigerator.
The charging is fully automatic. It will show when it's full and there's no need to leave it in the charger for a longer amount of time. No damage either if you forget the battery in the charger.
With these tips, I'm sure you'll have many useful years of battery operation.
* sources / justifications:
The reason is that charging damages batteries the most if it's nearly empty or nearly full. Do you have a source for that? Every source I know of states that partially charging is the way to go - even to 100% if you don't plan to store the battery in this state for months. Also, the damage charging does depends on the current, not the battery level at the moment of recharging (again according to all sources I know of).
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Naturally, all batteries have somewhat different characteristics, but as a general rule Lithium-Ion (Li-Ion) batteries will last the longest if you never charge them above 80% and never discharge them below 20%. Should you be anal about that? Naaah, but here are some tips:
1) Don't be afraid to recharge your battery even though it's not depleted.
2) Don't leave your battery in the charger unnecessarily, especially not overnight.
3) Ignore the long first charge suggestion. It is valid, but not for this type of battery.
By the way: All this goes for your mobile phone as well.
Most rumours about "battery memory" are somewhat true for NiCD, NiMH and lead acid batteries. Even then, many of these effects are due to dodgy charger designs that take shortcuts on correct charging methods.
NiMH batteries are still commonly used for flashguns, however they haven't been used as a standard power source for DSLRs for at least 15 years. Some truly first generation DSLRs - think Kodak DCS series or the Nikon D1 series - used custom NiMH packs. Some semi-professional DSLRs in the 2000s could optionally take off the shelf NiMH cells in a battery grip. Some vintage gear lovers might still maintain some NiCD or Lead Acid based flashguns. None of this matters for a shrink wrapped DSLR bought today.
Lithium Ion batteries will fail- not degrade, usually FAIL and be unserviceable - if allowed to self discharge far below minimum voltage (due to abuse or being allowed to self discharge in long disuse). So charging any Lithium Ion battery you get as soon as you get it, and storing it charged, is prudent. Do not attempt to revive a Lithium Ion battery that a bona-fide charger refuses to charge at room temperature, there is a reason it refuses to charge it: Such a battery could be succesfully charged but at the same time turn physically unsafe.
A lithium battery that an intact charger announces as fully charged IS fully charged, there is nothing to be gained from leaving it in longer, the charger stopped charging it at that point, and if it tried to charge it more, the battery pack electronics would usually stop it from doing so - also for a reason. Lithium Ion batteries do not tolerate overcharging and will quickly fail from it, sometimes catastrophically and dangerously.
