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[Richard230]

I was wondering if the KWH capacity of a battery pack can be calculated if you know the voltage and the amp hour rating for the pack? 

[Starpower]

V x Ah = Wh, Wh/1000 = kWh.

[MVetter]

V x Ah = Wh, Wh/1000 = kWh.

Correct. Remember to use nominal voltage instead of max.

Also know that manufacturers may add soft caps to the top and bottom of the charge cycle to reduce stress on the cells.

[Fran K]

Sure you can calculate the kwh but to get the real kwh available you need to know if the manufacturers numbers are "badge" numbers or something honest.  I took a picture of my Ktm battery label and the one for an outdoor power equipment Husqvarna one.  Ktm uses the terms rated and Husqvarna and Makita use that symbol of a solid line with a broken into three parts line right after the printed voltage.

I remember with an incoming hurricand Tesla did some over the air mod so folks could draw their battery down a bit farther in an emergency.

Edit and the ktm charger draws 10.8 amps on regular and 12.8 amps on fast so their own charger would seem to put out more than what the label calls for when in the fast switch position.  They even put capacity in the row with amp hours.

[TheRan]

That symbol just means it's a DC voltage, AC has a wavy line instead of the dotted one

[Richard230]

Thanks, everyone. I thought it might be something like that, but I just wanted to be sure. And I hear you regarding manufacturer's claims. Always take them with a nice dose of salt. 

[Specter]

Look at the C rate they tested it on as well.

Batteries do much better when you draw them very slowly .vs. the way most people use them.  With this, some shady manu's will give you a really good looking number.  Then you see they drew the battery down over a 100 hour period to get to that point.

If they tested the battery at a 20 hr or  100 hr rate, that's not helping much in the real world.

The broken line basically is just telling you it's DC, or pulsating DC,  versus AC as a sine /square wave.

At best, Id take their numbers, and then multiply that by 0.75 or 0.8 tops, to get a more realistic number.  Drawing ANY battery down 100 to zero SOC will shorten it's life drastically.  With a lead acid, as few as 10 or 15   100 percent DOD's and you can clearly see the hit in capacity remaining on subsequent cycles.

Aaron

[jotjotde]

The manufacturer's nameplate numbers are for bragging when you sit in the bar with your friends 

Look at Energica's battery which has 21.5 kWh printed on it. That might be the number you get when you really wrangle every electron out of it, at ideal conditions and chemistry be damned.

But as Aaron recommended you multiply this by .75 and get 16.1 kWh which is pretty much the real life capacity you can expect.
I charge my Ribelle with a counter and allowing for charge losses, I get about 16.5 kWh into the battery at around 20 degC. It's about 5 % less at 5 degC.