Are batteries too light?

[Tyko]

It always struck me as odd that batteries were so light / low density. the 100 unit battery weighs as much as a thermometer and it's twice as big / 8 times the volume. Batteries in RL are heavy and dense...have others noticed this?

[Daveroski]

Make them heavier and people who enjoy the use of ion engines will NOT be happy.

D.

 

[klgraham1013]

I've noticed.  I should look at balancing them in my game while I'm looking at probes.

1 minute ago, Daveroski said:

Make them heavier and people who enjoy the use of ion engines will NOT be happy.

D.

Can't please everyone.  If anything was going to change, it would should have been done pre1.0.  I don't think you have anything to worry about.

[linuxgurugamer]

34 minutes ago, Tyko said:

It always struck me as odd that batteries were so light / low density. the 100 unit battery weighs as much as a thermometer and it's twice as big / 8 times the volume. Batteries in RL are heavy and dense...have others noticed this?

I would say that the thermometer was too heavy

[Tyko]

22 minutes ago, linuxgurugamer said:

I would say that the thermometer was too heavy

LOL....all the science experiments are that heavy...I guess I should have focused on the density. 

[Xurkitree]

Assuming 1kWh = 1 EC, i'd say Batteries are rather efficient

 

[Fearless Son]

I am assuming that Kerbin has a different ratio of metallic elements than Earth, and that is why their batteries tend to be lighter: easier access to different materials with which to store a charge.

I mean, the planet is about the same gravity as Earth while only a fraction of the size, it would have to be composed of different elements.

[Tyko]

The solution I'm using is to scale down the size of surface mount batteries by 50%. This makes them more dense which makes sense to me.

I didn't mess with the stack mount batteries because it's easy enough to hand-wave the extra volume away as "structural". Though I'm thinking about doubling the battery capacity and weight so they're twice as dense too. Not sure yet.

Edited January 16, 2019 by Tyko

[Rocket In My Pocket]

I've often thought about (and dreaded) making this suggestion because I know how complicated and nightmarish these sorts of things can get but; Does anyone think there is room for an unofficial "Community Balance Patch" mod?

Now the reason I said it's a nightmare is that these things can get really political; it's all well and good if we all agree a part needs changing but there is likely to be several "camps" of thought on this for any given part. Then there is the question of who get's to be on the "committee" of people making said balance patch? How do we decide who represents the "community?" Won't we invariably have a camp of people who outright hate it and decry it no matter what it is or how it's shaped/framed? You can't please everyone after all.

Anyways, I know of several other games that have community balance passes, or community ran versions of the game essentially. (Xenonauts comes to mind as a good example.) In many cases (as is the case with Xenonauts) the community "fork" of the game is actually better and has for the most part completely supplanted the base game. I think the entirety of the KSP parts line could really stand for a complete, comprehensive balance pass. Not an overhaul, not reinventing the wheel, but fixing anything that the majority of the community agrees is glaringly wrong. I'd love to see Squad to do it, and maybe they will eventually but it's easily within our power to do it for ourselves, if we could find enough common ground to base it on. Which is a major issue, KSP is like ice cream, you can have vanilla, sure; but there are thousands of different flavors. A large group of people wouldn't even be interested in a stock balance overhaul because they don't play stock in the first place lol. Then you have the stock purists who would refute anything mod based. Finally, those actually interested, most likely won't agree on what to change and how. So idk..bad idea or what?

[Tyko]

28 minutes ago, Rocket In My Pocket said:

I've often thought about (and dreaded) making this suggestion because I know how complicated and nightmarish these sorts of things can get but; Does anyone think there is room for an unofficial "Community Balance Patch" mod?

Tough question...I currently just tweak things I need to tweak as I go along. 

I like the way Community Database of MM Patches works - there are a bunch of patches that tweak various things and the player is free to pick and choose amongst them. This eliminates the need for a committee to decide what's in and what's out of some giant patch. It also solves a big issue of mine with "balance patches" from other games which is when I like 90% of what a patch does but can't stand the other 10% but have no way to filter out what I don't like.

Maybe they could pin it to the top of the Add-on Releases forum??

 

[klgraham1013]

3 hours ago, Rocket In My Pocket said:

Does anyone think there is room for an unofficial "Community Balance Patch" mod?

I do.

3 hours ago, Rocket In My Pocket said:

Then there is the question of who get's to be on the "committee" of people making said balance patch?

There in lies the question.  

3 hours ago, Rocket In My Pocket said:

You can't please everyone after all.

Nor should you try.

3 hours ago, Rocket In My Pocket said:

In many cases (as is the case with Xenonauts) the community "fork" of the game is actually better and has for the most part completely supplanted the base game.

Long War for XCOM also comes to mind as a sort of defacto balance / game changing mod.  It's certainly not for everyone, but is pretty well known and quite pervasive.

3 hours ago, Rocket In My Pocket said:

I think the entirety of the KSP parts line could really stand for a complete, comprehensive balance pass. Not an overhaul, not reinventing the wheel, but fixing anything that the majority of the community agrees is glaringly wrong.

Completely agree.

3 hours ago, Rocket In My Pocket said:

So idk..bad idea or what?

Not at all.  It's been done for other games.  Why not ours?  You and I have both been around long enough to think of examples that the community near unanimously agreed upon.  Pod weight comes to mind.  Nothing would have to be an extreme change, but little tweaks here and there could go a long way.

[Superfluous J]

8 hours ago, Daveroski said:

Make them heavier and people who enjoy the use of ion engines will NOT be happy.

There are people that enjoy ion engines?

I mean USE, sure.

[Rocket In My Pocket]

2 minutes ago, 5thHorseman said:

There are people that enjoy ion engines?

I mean USE, sure.

Yeah, "enjoy" is a strong word.

Tolerate? Put up with? Accept? Sure.

Lol.

[klgraham1013]

13 minutes ago, 5thHorseman said:

There are people that enjoy ion engines?

I mean USE, sure.

I hypothetically enjoy them.

Still not enough evidence to confirm.

[Tyko]

Okay...I think it's pretty clear it would be too confusing to actually change the weight/EC since it's arbitrary anyway.

I DO THINK, that they aren't dense enough. Batteries are just about the densest thing that should be on the vehicle, so should be as small or smaller for a given weight than anything else. This I can work with.

Making batteries smaller without messing with the weight would keep the Ion lovers happy and not change the game balance, but it would still make them a bit more "realistic"  (love using that term in KSP)

[AngrybobH]

5 hours ago, Rocket In My Pocket said:

Does anyone think there is room for an unofficial "Community Balance Patch" mod?

I think this wouldn't be too bad of a job considering most, if not all, adjustments can be made with a  MM patch. MM patches are easily modified to suit the end users needs/wants. I would be interested in a community agreed (or roughly agreed) upon balance pass.

As for batteries and their weight, I don't know how KSP batteries compare to real ones in actual electrical terms and real density. But, these are the specs of a real lithium ion battery in use on a nissan leaf

403V
24kWh
140Wh/kg
2.5kW/kg
192cells
294kg(648lbs)

The newer leaf (2019) has a better battery(supposedly) but nissan hasn't even given the full specs to the EV specialists yet (me).

Since KSP uses nerfed values for tanks and engines(RS-25D vs KSPs SSME), I don't know what would be appropriate for the game.

[Taylanian]

I think this wouldn't be too bad

[Xavven]

11 hours ago, AngrybobH said:

I think this wouldn't be too bad of a job considering most, if not all, adjustments can be made with a  MM patch. MM patches are easily modified to suit the end users needs/wants. I would be interested in a community agreed (or roughly agreed) upon balance pass.

As for batteries and their weight, I don't know how KSP batteries compare to real ones in actual electrical terms and real density. But, these are the specs of a real lithium ion battery in use on a nissan leaf

403V
24kWh
140Wh/kg
2.5kW/kg
192cells
294kg(648lbs)

The newer leaf (2019) has a better battery(supposedly) but nissan hasn't even given the full specs to the EV specialists yet (me).

Since KSP uses nerfed values for tanks and engines(RS-25D vs KSPs SSME), I don't know what would be appropriate for the game.

Nice stats! Its dimensions are 61.8 x 46.8 x 10.4 in. (1570.5 x 1188 x 264.9 mm) and it's fairly rectangular (see https://qnovo.com/inside-the-battery-of-a-nissan-leaf/)

Feel free to double-check my math, everyone.

So with its structure it has a volume of ~ 0.494 m³ . It therefore has a density of 294 kg / 0.494 m³ = 595 kg/m³ . Side note: Water has a density of 1000 kg/m³ at STP.

We can use the known radial size of cylindrical batteries in KSP to estimate density. The Z-200 battery pack is a cylinder that fits in the 0.625 m stack of rockets. If I stack three of them high, they roughly equal the diameter of the battery in the VAB, so going off of these numbers, we have a height of 0.208 m. This would make its volume π(0.625/2)² x 0.208 =  0.0638 m³ . With a weight of 0.01 t, or 10kg, that's a density of 10 kg / 0.0638 m³ = 156 kg/m³ , which is about one quarter the density it should be. Maybe we should make this battery's weight 0.04 t

BUT remember KSP has a scaling factor in it? IIRC that scaling factor is 1.25x. If you look at a Z-4K battery pack the effect is quite noticeable. There's a "1m" bar for scale in the part's picture, and if you hold up an object to your screen on that scale bar, you can use it as a measuring stick and see it equals the radius of the battery. The battery is 2m in size but fits in a 2.5m rocket stack? What? That's the 1.25x scale I'm talking about!

So let's recalculate the Z-200 battery pack with this 1.25x scale applied. Its diameter becomes 0.625m/1.25 = 0.500 m and a height of 0.167 m. This would make its volume π(0.500/2)² x 0.167 =  0.0328 m³ . With a weight of 0.01 t, or 10kg, that's a density of 10 kg / 0.0328 m³ = 305 kg/m³ , which is about half the density it should be. Maybe we should double this battery's weight to 0.02t

Okay, let's do the same thing with the Z-4K battery. Without the 1.25x scaler,  The Z-4K battery in KSP has a diameter of 2.5 m. A stack of 10 of them equals its diameter, so its height is 0.25 m. π(2.5/2)² x 0.25 =  1.23 m³ . With a weight of 0.2 t, its density is 200 kg / 1.23 m³ = 163 kg/m³ Wow, that's pretty consistently 1/4th the density compared to real life. The devs at least were consistent.

With the 1.25x scaler,  The Z-4K battery in KSP has a diameter of 2 m. A stack of 10 of them equals its diameter, so its height is 0.2 m. π(2/2)² x 0.2 =  0.628 m³ . With a weight of 0.2 t, its density is 200 kg / 0.628 m³ = 318 kg/m³ That's half the density it should be.

So my personal interpretation of these results is that they aren't really too badly off but they do affect some designs more than others. If I quadrouple the weight of my batteries on a landing probe I like to use, my delta-v goes from 3490 to 3145, a ~10% reduction. On a 3-crew manned rocket, however, my delta-v on my upper stage goes from 2842 to 2824, which is insignificant. If you're making an ion powered ship and you have a lot of batteries, a rebalance would affect you a lot, though. But ion thrusters in this game have some thousands of times more thrust than they do IRL anyway, so I'm not sure realism needs to apply anyway.

Edited January 17, 2019 by Xavven
Edited conclusion after looking at some of my ships

[Xavven]

Oh, you know what? I think my numbers don't mean anything because I haven't looked at how much charge the batteries hold. Unfortunately, KSP uses an unknown unit for charge. IRL we use amp-hours for batteries. The Nissan Leaf battery has 48 modules of 4 cells each, and each cell has 32.5 Ah of charge. That's 48 x 4 x 32.5 = 6240 Ah for the whole thing, and with a weight of 294 kg that's 21 Ah/kg.

Without knowing what units of "Electric Charge" are used in KSP, it's hard to draw comparisons. What if we made some guesses? For the Z-4K battery, let's assuming 4000 "Electric Charge" means 4000 amp-hours. It has an energy density of 4000 Ah / 200 kg = 20 Ah/kg. Aha! That's pretty close to the energy density of the Nissan Leaf's battery, so maybe that's the right unit. That means that the weight of the batteries are actually fine, it's just the size that's off, assuming they're using modern battery technology. Maybe Kerbals just pack the cells inefficiently, and/or there's a lot of empty space in the battery's housing.

Edited January 17, 2019 by Xavven
Wait.. I got my conclusion wrong. Fixing that!

[Xavven]

Ah, I fell down the rabbit hole even further. IRL the Apollo program used two silver-zinc batteries for the LEM, weighing 57kg each and holding 296 amp-hours of charge (each). That's an energy density of only 5.2 Ah/kg. So if you assume Kerbals haven't advanced their battery technology past IRL 1960's levels, then you should double or quadrouple their weight.

If you assume they use litium-ion batteries, leave them alone. You could shrink their size but don't change their weight.