# Charing current

#### da-outcast

Charging current

I am total stumped on the following to questions so if someone could show me how to get started that would be good thanks.

1) A storage battery rated at 120 ampere-hours is to be fully charged at constant current in 8 hours. Calculate the charging current.

2) A lead-acid battery is designed to give continuous discharge of 180 amperes for 5 hours. Calculate the time it will be discharged by a steady current of 220 amperes.

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#### dduardo

Staff Emeritus
Why don't you use the RC equations for charging and discharging? I would assume you can treat a rechargable battery like a capacity in series with a resistor.

#### Doc

Hint: ampere-hours is a product.

#### HallsofIvy

Homework Helper
DDuardo, were you teasing?

1) A storage battery rated at 120 ampere-hours is to be fully charged at constant current in 8 hours. Calculate the charging current.
A current is measured in amperes. To go from ampere-hours to amperes, you divide by hours! Think about it.

2) A lead-acid battery is designed to give continuous discharge of 180 amperes for 5 hours. Calculate the time it will be discharged by a steady current of 220 amperes.
This is really a "proportion" problem. Let t be the time required by the 220 ampere current. Then x is to 220 as 5 is to 180.
Or, in more modern terms, x/220= 5/180.

#### dduardo

Staff Emeritus
Thank you, HallsofIvy. Yes, it was a joke. I was trying to make the poor guy complicate the problem even further seeing how you just have to multiple a couple of numbers to get the solution.

#### HallsofIvy

Homework Helper
Gosh, you're evil!

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