A battery question

[Marine]

Hi guys.
How do you work out how long a battery will take to charge. What is the maths formula to work it out. Thanks.

[Tom C]

every battery is different. it will take as long as it takes in a normal situation with a normal charger you can use the amp hour rating of the battery and then use the current supplied by the charger in amps to give you a rough estimate, it also depends upon your charge termination voltage.

http://www.batteries-faq.com/activekb/questions.php?questionid=55

with a SG it depends upon many variables. a rough way to do it is to look at what your primary battery is supplying to your circuit in amps. use that number and your capacity in amps of your battery for a rough estimate. if your machine is drawing 500 milliamps and you have a 10 amp hour battery expect it to take 20 hours or more depending upon your battery, and your setup, this is a ROUGH ROUGH estimate not a rule, could vary by 20 or 30 percent . a really small single coil bifilar machine will have a hard time charging a large capacity battery, like a car starter battery. you have to size the battery for the coil

Tom C

[Marine]

Thanks Tom. I'll re read this several million times until my brain accepts it lol

[Marine]

How long should you wait before testing the standing charge in the battery after it's been charging? 5 minutes? And hour? Is there a rule of thumb?

[John_Koorn]

Rule of thumb is to wait until the battery voltage stabilizes, usually 30 minutes to an hour.

John K.

[Marine]

Thanks for that John.