# Formula Questions

4 posts / 0 new
Offline
Last seen: 12 years 3 days ago
Joined: Saturday, May 26, 2007 - 22:41
Points: 135
Formula Questions

Formula Question

Amp hr capacity multiply by the voltage of the pack gives me the watt hrs of the pack.
That tells me how many watt hours a given pack has.
Now if the pack was drained completely I would need to put back in that amount of wattage correct? So if I have a 36 volt 23ah pack I need to put back in 823 watt hrs of juice right? Now how do I calculate how long it would take to put back 823 watt hrs?

Matt

echuckj5
Offline
Last seen: 11 years 9 months ago
Joined: Wednesday, November 29, 2006 - 07:13
Points: 394
Re: Formula Questions

Amp

watts = volts x amps, volts = amps x resistance. amp hours is a capacity measurement of the battery. watt/hours = volts x amp/hours.. Most chargers are constant current for agm batteries. If you are using a 36 volt charger that is 3 amps it will fill your battery at the rate of 36volts x 3 amps/hr = 108 watts/hour.. It will take this charger about 8 hours to charge a 828 watt pack,, 828 watts divided by 108 watts/hour = 7.66 hours

[b]AGM BATTERIES[/b]

Offline
Last seen: 12 years 3 days ago
Joined: Saturday, May 26, 2007 - 22:41
Points: 135
Re: Formula Questions

THANK YOU!!!!!!!!!!!!!!
THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!
THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

chas_stevenson
Offline
Last seen: 10 years 1 week ago
Joined: Wednesday, December 6, 2006 - 17:14
Points: 1309
Re: Formula Questions

The calculations are correct but they leave out the loses. There is normally some loses in the form of heat when transferring energy from one source to another. I don't know what the lose would be in this case but I would make an educated guess of 20 to 30 %. These looses would add to the charge time so the 7.66 hours would be more like 7.66 x 20 to 30%. I will use an average of 25% and the new time would be 1.25 x 7.66 = 9.579 hours.

Chas S.
My Bicycle Pages

## Who's online

There is currently 1 user online.

• flapjacksbestof

## Who's new

• wildbeas
• lkonings
• Kenechukwuezegbulem
• Paguilar
• simplyeric