# How Long Does a Capacitor Hold a Charge?

The question as stated is a little hard to answer. Like "how high is up".However, yes. Capacitors cannot store a charge forever. Once charged a capacitor will slowly lose charge to leakage. How fast is a matter of what the dielectric is and other factors**. Caps like aluminum electrolytics lose charge relatively quickly while Teflon, polypropylene and polystyrene (rare these days) hold charge relatively well. Also, the circuitry the capacitor is connected to has to be considered. Even the circuit board can be a problem in some cases.I think that applications where charge holding is important are becoming rare. These would include memory backup using volatile memory and sample and hold circuits. How long? Depending on the application the capacitor might need to hold the charge (with varying amounts of allowed loss) for from microseconds to weeks.**Voltage of the charge relative to the rated voltage of the capacitor and specific design details

1. What's the difference between 2 A and 10 A charging options?

You are right that 10 amperes is faster, by a factor of 5x.Lead-acid batteries are charged in 3 stages, first by constant current (with voltage limit), then by constant voltage (with tapering current), then in the end during float charge the voltage is reduced to a float charge voltage level.The 2 ampere and 10 ampere options allow charging different capacity batteries. You would use 10 amperes on a car battery and 2 ampere on whatever small batteries you might want to charge that still use the same voltage. For example, a motorcycle battery could use the 2 ampere charging option. Many lead-acid batteries only allow 25% of the capacity per hour: 2 amperes could then be used to charge at least 8 amp-hour batteries, whereas 10 amperes could be used to charge at least 40 amp-hour batteries. I am not sure how good your charger is, but many these days are microprocessor controlled, so they have all of the 3 stages. The very best are temperature compensated.In the worst case, the charger does not have a sane voltage limit and thus requires you to observe the charging time and disconnect the charger when you expect the battery to be full of charge.

2. My charger's plugged in, but laptop not charging! Help!!?

Hi alexela, Your battery seems to be dead. When a battery starts doing this, it means that the battery is unable to retain charge anymore. If you try to run the laptop off the charger it should work, but if you try to run it off just the battery without the charger, it would not . Simply get a new battery. Good luck! I hoped I helped!

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