Thursday, April 20, 2017

Spaceships Quickie: Power Cell Energy Banks


If you ever built a ship in GURPS Spaceships there's a good chance that you've run into the frustration of trying to balance how many Power Point using systems you have and how many Power Point generating system you can cram into he hull with out compromising something. This can especially become a problem for warships were you usually have to cut something armor to stuff in another power plant or have to cut the number of weapons systems.

Well frustrate no more my most awesome readers! For in today's post I give you guys the one system I think we can all agree should of been in at lest on of the Spaceships supplements:

Power Cell Energy Banks!

In practice Power Cell Energy Banks give you a "pool" of one use Power Points. They store a good deal more Points then any power system generates letting you power far more energy dependent systems for the same amount system spaces, at lest for the short term. They can also be recharged by power generating systems letting you get away with fewer, or with multiple power point system, smaller systems freeing up more room. Of course you are still going to have to think about how many Power Points to spend at any given moment in high risk situations. It may seem like you got a lot of  Power Points to play around with but if you spend them to quickly you might find yourself with to short of a supply on hand if a crisis crops up before you can recharge!

So as you can see this system gives you a good bit of flexibility when it comes to managing high power systems. It can also help give some character to your ships if want to put a little extra detail into it. For example let's say you want to have your ship use a jump drive that needs a charge time before it can be used. Lets say you install three Jump Gate Systems needing a total of 3 Power Points to power. You could then install a Fission Reactor system that only generates 1 Power Point a 2 size smaller system TL9 Power Cell Energy Bank system that gives you only 3 Power Points of storage giving you a three round charge time for it.

Alrighty, now on to the system itself. Hopefully you guys find it useful! 

Power Cell Energy Banks (TL9) [Any]
A series of large, high capacity, power cells arrange in a bank to store and rapidly discharge power when needed. Each system stores up to 30PP at TL9, 120PP at TL10, 480PP at TL11 and 1,920PP at TL12. Keep in mind that this is only a storage system, each power point used deplete the total stored and can only be replaced by excess power being diverted to it from a power plant or reactor. If you are ok with a little extra note keeping, power plants and reactors that produce less then 1PP can still recharge a Power Cell Energy Bank, it will just take longer. A half sized system will take two turns to charge 1PP, a 1 size smaller system will take 3 turns to charge 1PP and a 2 sizes smaller system will take 10 turns to charge 1PP. You can also choose to use non-rechargeable power cells. These double the amount of Power Points stored but in turn they can not be recharged. 

Power Cell Energy Bank Talbe
SM             +4     +5      +6     +7      +8       +9     +10    +11    +12     +13      +14      +15
Workspaces 0        0        0        0        0         0       1        3         10       30      100       300
Cost ($)    81K   270K  810K  2.7M  8.1M 27M  81M  270M  810M  2.7B   8.1B     21M
Repair Skill:  Electrician

Available as half, 1 size smaller, and 2 sizes smaller systems. A half sized system hold half as many PP, a 1 size smaller system holds 1/3rd as many and a 2 sizes smaller system holds 1/10th as many. 

 For those using my optional system that let's you deign spaceships of any size, just multiply how many PP a systems worth of Power Cells store for your ships TL by how many pounds or tons of power cells the ship is going to hold divide by the mass of 1/20th of the ships weight. 

Example: At 1,000,000 tons, 1 ship system weighs 50,000 tons. If you were going to use 10,000 tons worth of TL11 Power Cell Energy Banks, the system would store 480×(10,000/50,000) or 96PP. 

Cost is $100 per pound or $200,000 per ton. 

Thanks to Tamahori for inadvertently making me realize I forgot to mention you can choose to have non-rechargeable cells as well. 



  1. You have no idea how much I've wanted something like this, and I've always been amazed something like this wasn't in the core rules. It seems to be a must have for fighters in reactionless-driver era games as it gives them a reason to have to have a carrier along, especially if they have mostly energy weapons.

    When you say 'turn' you're meaning the basic 20 second turn and if you're running at 'one minute per space combat turn' then you'd burn 3 PP per system per turn ... and at TL9 if you're playing the 10 minute turn game power cells are no better than a fuel cell or fission reactor (which seems perfectly fine to me).

    As it is in some of my designs I've been using fuel cells or even MDH as a kind of 'battery' by assuming if it has another power supply then you can convert the water back into fuel at the same rate the power generator could burn it in the first place.

    (I'm wondering if something like this might be the 'long duration battery' of TL9-10 societies as compared to the super-capacitor that power-cells seem to act like. At higher tech levels pocket fusion reactors are totally a valid thing.)

    1. Sweet, as corny as it may sound, getting this kind of feed back is what makes this all worth it.

      I was kind of clumsy with my wording but what I meant was that whatever the turn length, however many power points your ship can generate on any given turn can all be put towards recharging you power cell energy bank. If you got 4PP, you can choose to have them all go to your banks.

      I did think of also giving the option to having a battery bank instead but dropped the idea both do to the fact it would add more complexity in that you could only discharge so many power points at a given time as well as the fact that unlike with power cells, I don't know the official numbers for ultra-tech batteries and I wanted to keep this as RAW as possible.

      I also like the idea of power cell bank powered reactionless fighters, maybe even make them use non-rechargeable banks to double their endurance. I kinda like the mental image this gives me of the fighters landing and flight crews scrambling to replace their power cells like giant firearm magazines. In fact... it just dawned on me that I forgot to add that you could have non-rechargeable cells... I'm gonna go do that now!

  2. The issue I have with the variable turn length is that it means that it requires one PP out of a powerbank to keep something that needs one PP running for one turn, regardless of turn length.

    So say at TL 9 one power bank will keep your 1PP laser fully powered for 30 turns. Let's also assume the fight is using 1G as the reference acceleration (see page 48 of Spaceships).

    If you're engaging at close range, that power bank will keep your laser running for 30 turns, or half an hour (1 minute per turn). If you're engaging at distance range, that's still 30 turns but now means it's good for 5 hours (10 minutes per turn).

    I was thinking they 'how fast do you chew though power' should be modified with turn length the same way RoF gets modified at the top of Page 58 of Spaceships. So I'd therefor been assuming 20 second turns (as it's the 'base' number that RoF starts at) so '30 PP bank means it can keep at 1 PP system running for 10 minutes (20 seconds times 30)'.

    I'll admit I also like the idea of fighters landing to have their batteries replaced, along with whatever munitions they use ... though them having massive power cables connected (or as part of their launch rack) is also a fun image ... and the carrier's role is mainly to be a giant reactor and resupply craft.

    Hell, if they also have short range FTL, the carrier could be a light-year out and part of space combat is trying to find where the enemy are staging from. I could see Star Trek (who tends to be my go-to for what TL12 looks like) carrier operations looking like that.