A hypothetical question!

I was thinking something today, about batteries, and one question popped into my mind:
if the standard/classic car battery (lead-acid battery 12V 60Ah) would be made ​​on the same principle as 18650 batteries, out of lithium, how much volts and amps would it have?
:nerd_face:

This would be an energy density question.

the Wh of Li-ion batteries for a given volume is 2 to 2.5 times that of lead acid batteries, 3 times for a given weight.

The Volts and amps would depend of the configuration of your Li-ion pack (number of cells etc…).

Using a size 35 battery the dimensions are 230x175x225 mm. Divide that by 18x18x65 for a 18650 battery and you could get 430 18650’s in that volume. If you put 3 batteries in series to get 12V then that’s 143 sets of 3 18560’s times 2.6Ah each. That’s 372 Ah at 12V.

Realistically, it would be less than that because you would need room for wiring and holders for all of those batteries and I don’t know if 3 in series would really give you 12V. You might need 4 in series. And to have a good working range, you might only want to use half or even a third of the actual battery capacity to increase the number of cycles you could get.

electric cars are made with that principle(litio), buy one to support the research xD
actually acid batteries are durable safe and cheap on the other hand litios give up to 4x the capacity of leadacid at the same weight

wikipedia is your friend or take a look here

I guess it would work. As you'll have to make big parallel packs, things might get complicated (or you have a "buck" driver between battery and the rest). If you used parallel packs, you could use almost any cell available because in (for example) a 4S30P cell, no cell will see much load. Problem is: expensive as hell. Thats 120 cells and even if you could buy them for 2$ a piece, you could still buy 4 or more regular car batteries at that price.

Plus I tend to buy car batteries in the 700ah range (4 x 4 with a winch, I want capacity and current delivery) the above equation falls short of that.

700Ah car battery? That would be about the size of your engine..?

Nope, an 069 is 690…… Ah, I may mean cold cranking amps (cca) :8)

The size I use is definitely an 069 because I need an odd post arrangement and small case to fit in my zuk, hang on….

My mistake, 70ah, 610 cca :8) :zipper_mouth_face: :~ that counts as tonight’s stupid post, sorry.

Stupid? No. Funny? Yes! :P

If you use IMR cells for the battery, you could have about the same cca. 70Ah, 1.3Ah per cell, so 4S50P. Good IMR cells can deliver 20A -> 1000A. Should be enough. :)

But that would be 200 cells.. theres a reason we dont have LiIon starter batteries. And theres also a reason, electric cars are that expensive. You can rent an electric car in Germany for about 250$/month but have to add 60$ each month to rent the battery.

Buy a Porsche 911 GT3 RS and tick the li-Ion option :slight_smile:
http://www.greencarcongress.com/2009/11/porsche-liion-20091123.html

I see that this led you to thinking also :smiley:
This is primarily a theoretical question, i don’t plan to build something like this :slight_smile:
I know that lithium batteries are made by winding thin foil covered with lithium so we get round shape BUT, imagine for a moment that we can loaded powder lithium into car-battery-like housing and car lithium battery is born :slight_smile:
would we be able to calculate voltage and amperage based on the dimensions of that battery (its housing)?

Round shape aint a problem, just take a look at the batteries from optima, those are (imo) 6 round cells in a square container.

Maybe you can calculate something, flat lithium batteries exist, if you roll them.. :D

What would the battery be like if it were not composed of smaller batteries but the same size as a car battery but using lion chemistry?

would be too complex. li-ion need lots of battery management electronics. have to monitor each cell individually, or group in parallel

also under the hood temps are very high

Ultracapacitor car starters aren’t uncommon…. search youtube.

Nothing can beat Amps that can deliver. :slight_smile: