I've a Nikon P330. Its USB charger is 5V/550mA and the manual says the following about charging the battery inserted in the camera through USB:
About 4 hours and 30 minutes are required to charge a fully exhausted battery.
Will it be faster if I buy and use a 5V/2A USB charger?
The Nikon P330 camera uses a Nikon EN-EL12 1050 mAh battery.
EN-EL12 battery capacity is nominally 1050 mAh as supplied.
After market batteries may claim higher capacities and, regardless of label, may have lower capacities.
If the charge rate is not limited by the camera itself when in-camera charging, or when externally charging the battery, maximum charge rate is achieved when charger mA capability is >= battery mAh rating. Chargers above that capacity will charge no faster.
Nikon sell an MH-65 charger.
Nikon genuine MH-65 $37.95
"ebay genuine" MH-65 $5.88
The Nikon P330 manual
advises on page 97 that charge time with a MH-65 charger is 2 hours-30 minutes.
Charging via USB in-camera may limit charge rate regardless of charger capacity.
See users' manual and notes below.
The maximum charge rate you can achieve with most LiIon / LiPo batteries is about
70 to 80% in one hour
Full capacity in about 2.5 to 3 hours
The battery charges to about 70% to 80% at max allowed current
(usually mA max is numerically equal to mAh rating )
and then the battery is charged at constant voltage and the current tails off under control of the battery chemistry. One factor in total charge time is how low the charger allows the current to fall before terminating charging. Charging termination at high currents eg 50% of I_charge_max enhances battery life,enhances whole-of_life mAh capacity and shortens charging time, at the expense of capacity per cycle. Low charge terminatiuon currents will increase capacity per cycle (perhaps by 10% in extreme cases) but will shorten battery life and increase charging time. The termination current % varies among manufacturers.
A Nikon P330- battery is typically rated at 1050 mAh. Some after market version may claim or be labelled with higher capacities, but unknown brands are just as likely to provide LESS capacity than originally while claiming to have more.
A charger of up to 1050 mA output will provide faster results than your 550 mA charger provided that the camera does not limit the charge current when charged in-camera via USB - which it may or may not.
Charging the battery in an external charger of 1050 or higher mA charge rate will increase the charge rate compared to using a 550 mA charger.
As a rough guesstimate, I would expect a 550 mA charger to take about
1050 mAh x 80% / 550 mA + (2 to 3) hours to fully charge
=~~ 3.5 to 4.5 hours
This figure is approximate as the "tail" period depends somewhat on battery chemistry and on the % of max current used for end of charge determination.
SOME manufacturers specs vary, but almost all LiIon camera batteries charge at a maximum of the C/1 rate = the same mA as the mAh capacity.
IF you could charge the whole way at this rate the battery would charge in about one hour, but LiIon / LiPo does not work quite like that. The battery is charged at constant (usually max allowed) current until max allowed charge voltage is reached and then at constant voltage until the current decreases to a preselected % of full current. The "tail" is what takes the most time.
Charging strategies:
(1) If you have a number of fully discharged batteries and want max charge input in a given time, charge each for about 45 to 50 minutes in turn.
(2) If you have a number of batteries and you do not know the degree of charge in each and want max input in a given time then "round robin" sequential cycling them is liable to give best results. Say change every 10 minutes or so - more often won't hurt but you get diminishing returns for the extra work.
(3) "About enough time:" If you had say 9 hours and 3 batteries of unknown charge state and a highly capable charger (C/1 or higher) then you have long enough for all to charge fully and can leave a battery in place until the sooner of "charged" indicator lights or 3 hours. If the battery does not show as fully charged by then it must be very close and swapping to the next one at that stage makes little difference.
(4) If you have a number of batteries and you DO know the degree of charge in each (it's sometimes shown by the camera) and want max input in a given time then.
PC = percent charge in battery.
Tcharge for ~= (80 - PC) / 80 * 45 minutes
Do each battery in turn as above
Then go back and do longer of full charge on each.
This will charge each battery at max allowed C/1 rate until they are probably slightly below the CC/CV changeover point where charge rate starts to drop off
eg for a battery with 20% charge, charge for (80-20)/80 x 45 =~ 33 minutes.
If batteries are above the CC/CV changeover point and capacity in each is unknown then charging them "round robin" still gives best results.
(5) Super user: If your camera shows the amount of charge in each battery then you can "calibrate the charger and find out where the changeover point from max rate / CI to tapering rate CV occurs. Do this by noting the charge say every 5 minutes and noting when it changes from a linear increase with time. You can check this with several batteries and are then in a position to decide how long to charge a battery of given charge-state for before swapping.
I've never got as far as doing (5) above :-).
A less frenetic alternative is to have enough fully charged batteries to get you through the longest photo session and enough charging capacity to always get all batteries back to 100% before the next occasion that they are needed. I have 6 x 1600 mAh NP-500H batteries for my Sony A77. I have 3 mains chargers but usually use 2 max. When I travel I usually take 2 chargers. Worst case* I need then to roll out of bed once in the night to swap batteries and the 2nd charger provides protection against you-just-try-and-buy-an-xxx-charger-in-eg-Shijiazhuang-when-they-are-picking-you-up-at-8am itis. (Ask me how I know :-))
[[* eg 6 hours at eg the Terracotta Warriors in Xian methodically (obsessively?) working along the rows of figures (when most tourists come and go in an hour or two) does make demands on batteries]].
Batteries will not be harmed by any of the above methods.
Maximising battery life:
If you use your batteries reasonably often, then charging them from empty for 1 hour only with a full capacity charger (eg >= 1050 mA external in this case) will significantly improve battery cycle life and total mAh delivered by battery in a lifetime.
If storing LiIon batteries unused for long periods then charging from fully empty for say 45 minutes before storage will make them last longer.
Storing LiIon in a cool but not "freezing cold" place will improve lifetime - say 10C or above. Maybe slightly cooler if essential but never as low as 0C.
If batteries are "freezing cold" (a few degrees C or sub zero) then warming them gently before use to say 10C or better will improve available capacity significantly and als9o will improve lifetime. Warming by placing in a pocket or elsewhere in clothing works well for warming.
When carrying batteries of ANY type in clothing be CERTAIN not to short the terminals. Large amounts of heat can be produced rapidly (ask me how I know :-) ). With LiIon and LiPo batteries, shorting the terminals COULD cause fire and significant injury.
Battery University pages:
Prolonging LiIon battery loife
I have not read this page recently, but my above simple method will hopefully be a simple-to-do subset of what they say.
Waking up a sleeping LiIon battery
Try hard to not need to do this.
It's possible, but unlikely.
The USB 2.0 (maybe 2.1?) standard specifies 500 mA max standard current. If the camera came with a 500 mA charger (the extra 50 mA is likely just a bit of available overhead), then the in-camera charging-circuitry is most likely set to max out at 500 mA, as per the standard.
There are a few types of higher-current USB sockets around.
Apple have their own implementation (supporting 1A and 2A) which tie one of the data lines to a specific voltage to indicate the ability to negotiate/draw higher currents.
Android (actually its more common than just them) have another, which I believe ties the data lines together, indicating higher charge available.
And some USB3 ports offers up to 900 mA (the USB3.0 standard allows negotiation up to 900 rather than the old 500 mA limit of USB2).
Now, not all ports will deliver even what the standard says (some laptops especially fail to deliver 500 mA on USB2 ports), but my advice would be to look around your computers or other devices (especially if you have a tablet of some kind) for USB chargers or USB ports that exceed 500 mA. iPhone chargers are 1A, iPad chargers are 2A, USB3 ports are often 900 mA, Android and other USB phone chargers for new phones are also likely >= 1A.
Try a few of them out first. Even if it doesn't work with one (say an Apple one) it might work with another (say an Android one).
Most likely though, you'll be stuck at 500 mA because that's what the camera was designed for, especially if it's a USB2 port (not USB3).
