electric charge - units should not be kV

[avc15]

Hello ksp team! First I know that electrical is not being simulated right now.

I'm an engineer and I've noticed a thing. The units you have displayed in flight for electric charge is kV or kilovolts. There's a better unit! Batteries store charge in AH or amp-hours. (typical average car battery is about 200 mAH or milli amp hours)

The scale doesn't even need realism, so the numbers can be totally arbitrary. It just feels wrong to display kV next to the amount of charge.

Why? A battery's voltage really doesn't change that much as you charge it. Between say 10% and 100% charge, a good deep cycle battery will only change its voltage by around 10%.

[18Watt]

I will second this assessment.  In KSP1 electricity units were called EC.  Which I always equated to A-H units.

[avc15]

correction here - I'm now seeing that the unit in KSP2 is "U". Actually that's good enough for me. I saw it incorrectly as "V".

[18Watt]

1 minute ago, avc15 said:

correction here - I'm now seeing that the unit in KSP2 is "U". Actually that's good enough for me. I saw it incorrectly as "V".

Ah, I'm not actually playing the game right now, teenager has taken over the computer.  But if they're calling it 'U', I would equated that to A-H.

Also, I forgot to say, Welcome to the KSP forums @avc15!

[Nuke]

a game thats trying to get kids into stem should probibly have appropriate units. but then again its not an electronics simulator. i think id put it in terms of watt-hours however, because that is agnostic of the voltages and currents actually used. its also easy to figure out how much power you need for something, if say their power requirements are in watts.

[whatsEJstandfor]

1 hour ago, Nuke said:

a game thats trying to get kids into stem should probibly have appropriate units. but then again its not an electronics simulator. i think id put it in terms of watt-hours however, because that is agnostic of the voltages and currents actually used. its also easy to figure out how much power you need for something, if say their power requirements are in watts.

But amp hours is the correct unit of electric charge. Since it's (C/s)*3600s, an amp hour is 3600 coulombs. Idk which one is more intuitive for a normie, whether it's energy in terms of joules or charge in terms of coulombs, but I think semi-tech-literate people are already used to batteries being in Ah.

Edited February 25, 2023 by whatsEJstandfor

[Nuke]

i suppose it could be either. power distribution people (as well as normal people who pay their power bill) like watts and w/h, while engineering people designing battery systems will want to use ah and c rating and well all the specs from your pack configuration to your battery chemistry. also the units for power requirements on most devices are not in coulombs, but in watts. engineers know this and will therefore design the system to output either a set voltage or a range of voltages (battery voltage does change at different states of discharge, for lithium ion you got 2 volts of swing, multiplied by however many cells you have in series).

a normal people problem would be figuring how much battery you need to keep your ship alive on the night side of an orbit. you will know your target orbital period, say 90 minutes, and so you will need power for 45 of those minutes. say your equipment uses 100w. 45 minutes is 3/4 of an hour, or 0.75 hours, and you just multiply by your requirements to get 75 watt hours. its linear, predictable, and you just need to multiply. also for your solar panels you need double because not only do you have to power the systems, but also charge the batteries. should also point out that solar panels are also rated in watts. its better to think of a battery (and even panels/nuclear reactors) as a black box that supplies power rather than as a complex system that stores charge. 

Edited February 25, 2023 by Nuke

[didkodidko]

5 hours ago, avc15 said:

Hello ksp team! First I know that electrical is not being simulated right now.

I'm an engineer and I've noticed a thing. The units you have displayed in flight for electric charge is kV or kilovolts. There's a better unit! Batteries store charge in AH or amp-hours. (typical average car battery is about 200 mAH or milli amp hours)

The scale doesn't even need realism, so the numbers can be totally arbitrary. It just feels wrong to display kV next to the amount of charge.

Why? A battery's voltage really doesn't change that much as you charge it. Between say 10% and 100% charge, a good deep cycle battery will only change its voltage by around 10%.

Also I didnt notice any power draw!

[Darael]

11 hours ago, whatsEJstandfor said:

But amp hours is the correct unit of electric charge. Since it's (C/s)*3600s, an amp hour is 3600 coulombs. Idk which one is more intuitive for a normie, whether it's energy in terms of joules or charge in terms of coulombs, but I think semi-tech-literate people are already used to batteries being in Ah.

Except generally we aren't talking about electric charge, but about stored energy. regardless of which terminology people use day-to-day. Yes, a lot of batteries are rated in Ah, and that's misleading because two different 200mAH batteries can have wildly different energy capacities depending on their operating voltages. I suppose we could use charge and operate on the assumption that all systems on all craft operate at a standard voltage. If we did that, we'd rate power consumers in amps — well and good, but we'd also rate generators in amps, and I don't know about you but to me that feels deeply wrong. As such, for the unit-combinations that are technically correct (and ignoring any kilo- or milli- prefixes for now), I'd advocate for joules/watts or watt-hours/watts over amp-hours/amps or coulombs/amps.