# AA batteries

Hello,

I have done a comparison of the big car batteries and I am not an physics expert (if I was I wouldn’t probably ask questions here) but based on my calculations, connecting a bunch of AA batteries would end up being cheaper and lighter than connecting the large betteries. Here is my comparison:

[B]Car battery:[/B]
Amper-hour: 40Ah
Voltage: 12V
Energy: 12V*40Ah = 48Wh
mass: 1.6kg
Energy/mass: 30Wh/kg
price: \$80

To store 12kWh:
batterries needed: 12000Wh/48Wh = 250
price: \$80 * 250 = [B]\$20000[/B]
mass: 1.6kg * 250 = [B]400kg[/B]

Therefore, to store 12kWh we need to pay \$20,000 and our vehicle will weigh 400kg more.

Now, if we used a bunch of AA NiMH betteries:
[B]AA battery:[/B]
Amper-hour: 2.5Ah
Voltage: 1.2V
Energy: 1.2V*2.5Ah = 3Wh
mass: 31g = 0.031kg
Energy/mass: 3Wh/0.031kg = 97Wh/kg
price: \$1

To store 12kWh:
batterries needed: 12000Wh / 3Wh = 4000
price: \$1 * 4000 = [B]\$4000[/B]
mass: 0.031kg * 4000 = [B]124kg[/B]

Therefore, based on my calculations (tell me if I’m wrong), by connecting 4000 AA batteries together, we would be able to store 12kWh of energy by just paying \$4000 and our vehicle will weigh only 124kg more.

Please let me know why AA batteries are not being used (whether I have some error in my calculations or there is some other reason for this)

Thank you

You calculated wrong… 12*40=480Wh… not 480, that would make your pack cost \$2,000, and not 20,000. Cost for 25 batteries.

Another reason we don’t use em, is because of connection loss for each welded tab.

By the way, where’d you find a 1.6kg 40Ah 12V battery?

I see my mistake. I would need 25 batteries. The weigh I provided is wrong too. A single 40Ah, 12V battery weighs 12 kg. Therefore, the total weight would be 25 * 12kg = 300kg.

Thank you for enlightening me.

no prob, i make math mistakes a ton, and end up eating my words

there’s an electric land racer that broke electric land speed records with C batteries… lots of them, in tubes.

Yes, that’s what I was thinking about too. If the batteries were connected in a string, you could get a pretty high voltage (1.2V * 4000 = 4800V), which would give a nice kick I think (tell me if I’m wrong).

I also just read news about an electric vehicle for 150,000 GBP that is about to come on market with 700 horsepower:

http://www.lightningcarcompany.co.uk/