could you make a universal car battery adapter, so that batteries could be reused between car types?

if not, why not? :slight_smile:

Probably a more precise version of this question would be, in the set of all car types with their unique batteries, could we identify several broad subsets such that batteries could be shared within the subset / equivalence group by using an adapter / interface / whatever gadget for this subset.

Incidentally, I have the same question about reusing batteries between different laptops.

Couple of points:

the wrong size battery may not be held securely enough and the vibration from driving will damage it.

there are some adapter post things at the auto parts store that might let you use the ‘wrong’ battery any how.
You can always put a smaller battery in place of a bigger one, usually it is not possible to put a bigger one in a spot for a smaller one.

I always thought most cars had batteries that were the same physical size. How many different sizes are there?

I don’t know of a car sold today that doesn’t have a 12 volt battery in it (unless you’re talking about hybrids- they’re a different story). Therefore, the differences among car batteries are physical size, capacity (cold cranking amps, for example), and connecting post style and orientation. There are adapters for post differences (side post to top post cables and vice versa). One can sometimes use a physically smaller battery than stock, but capacity is generally tied to size, and a smaller battery may not start a much larger engine than it’s made for.

There are brands of batteries that come with both side and top post connectivity. I think the several broad subsets of batteries that would satisfy your criteria are readily available. Just do a little research, open a store and stock the right ones.

I think this already happens. There isn’t a unique battery for every type of car. They almost all use 12volt, and require a minimal peak amperage, and then come in only a few shapes and sizes for that amperage.

ETA: Looks like everybody’s responding this way.

There are differing sizes (dimensions) and differing capacities. mainly in amper hours and cranking amps, some engines require more power to turn over when starting. Also there are a couple different terminal shapes (flat plates or round posts) Also the terminals are sometimes one way round or another…But assuming they are 12volt then you can fit a different battery to any car, If its lower capacity or lower cranking amps it will get hot and possibly die early or instantly. If its bigger in capacity or bigger in cranking amps, it will be fine, probably better. There is a theoretical risk in a bigger battery in that if its totally flat the alternator might try to charge it and overheat, but in practice all modern alternators have heat cut outs and its not a problem.

There have been many points in my life where I’ve had more cars than batteries. Most older cars were close enough-- as an extreme example, for a while I had to pull the battery out of my little '74 Corolla and drop it in my Chevy truck if I needed to get some wood or run to the dump. You usually can’t get away with that on modern cars, since the engine compartments are so cramped there’s only one size battery that will fit, not to mention the two cable types.

The battery relocation kits they sell are similar from what you describe. These are often used when you’re building a race car from a car where the stock battery location is inside the cabin. That’s often against the rules, so you you need to relocate the battery to the trunk (usually), so you get something like this: A happy side-effect is that your car now takes a standard sized battery instead of one that had to be weirdly shaped to fit under your back seat.

I think prior to 1980 it was pretty much one size fits all.


there are a few different sizes, but the key difference is in the terminals. for top post batteries, there are normal and reverse (positive and negative are swapped.) then, there are side post batteries, mainly used by GM cars in the 80s and 90s.

I think side post batteries have become standard. Oh, my 02 Cavalier has them. Many replacement batteries come with both top and side terminals. Yes, every size and style of battery ever made can be found, but I think most cars now use one of only a few type.

Even if every vehicle used the same battery rating, the design of the car itself requires different sizes and shapes. It’s kinda like flashlight batteries, the shape of the flashlight dictates what will fit.

FWIW, Intserstate batteries lists 41 batteries for passenger cars (only 5 side posts and 2 dual posts, and I bet that last one is a lawnmower battery or something)

For GM, yes. For cars as a whole, not even close.

Again nope

Since everyone else is commenting on cars, I’ll take this one.

Nope. :frowning: The problem is not the batteries, per se, but rather the casing. It will be custom designed for every laptop, to fit into whatever holding slot the thing was designed with. There may be some standardization within a single manufacturer’s lines (made up example: Compusludge’s x, y and z models all use the same battery, but their a and b models use something different), but there is no standardization at all between manufacturers.

Actually it’s worse than that. The voltage used across laptops is not universal. I’ve seen a range of at least 14 to 18v.

Universality in car batteries is much easier because 12v is essentially a given, and all you need to worry about is cranking amps and total amp/hours. Both the latter only matter if they are too low, so you could just have a battery with high cranking amps and total amp/hours and it would do the job for most cars. You only then have to fit worry about finding a space to fit it under the hood and attaching it. The latter is a question of just having some sort of connector and a few adapters albeit very heavy duty. The former depends on whether you can find room and tie the battery down securely, which is going to depend on the car. At least a rough looking solution is going to be hidden under the hood.