Engines can be started without a charged battery

[DatMeg]

Describe the bug

Despite being essential parts to operating a vehicle, the Car Battery, and Alternator are indeed optional additions! Reduce the weight of your mini deathmobile by cutting out frivolous parts! All you need is an Engine, and a tank of fuel attached to each other. Add some controls and watch the magic happen. If it refuses to function, simply change the engine configuration and give it that little nudge to turn it over!

Jokes aside. It seems the Engine Configuration Menu bypasses checks for a Battery, or Alternator, as long as there is fuel attached to the engine.

Steps To Reproduce

1. Build a vehicle, with nothing but an engine (V-Twin), fuel tank, and controls
2. Fuel the vehicle
3. Try to turn on the vehicle normally, and find that it doesn't work
4. Go to the engine config menu, and toggle it off, then on again
5. Find that it turns on (momentarily)
6. Add an alternator, or generator and repeat 3 & 4. It will turn on, and stay on.
7. Add a dead battery and repeat 3 & 4 once more and find that it will now charge

Expected behavior

Even if I use Magiclysm, there are some things that probably shouldn't feel like magic.

Screenshots

Versions and configuration

• OS: Windows
  • OS Version: 10.0 1909
• Game Version: 0.E-3972-gfd16242 [64-bit]
• Graphics Version: Tiles
• Game Language: System language []
• Mods loaded: [Dark Days Ahead [dda]]

[Alex-Folts]

It is not as simple as it seems:

• old diesel engines do not require electricity while it running, so need power only to start it
• very large diesels do not require electricity even for starting, they use compressed air for start, and can use open flame to preheat intake manifold, but we dont have such big diesels in the game
• steam engine dont need electricity for runing nor start, it starting similar to large diesel but use steam instead of compressed air.
• small motorbikes could have no battery(old style, no electric starter), they have alternator on permanent magnets, and when you crank it with kickstarter it produce enough power for ignition coil
• larger gasoline engine for work require battery or alternator, ofc when battery will dried it will stop if no alternator, for start it ofc need battery.

i think rules should be like:

• if engine large enough it require electric power for start(battery, attached cable to another powered vehicle), and it should consume starting energy from electric source, as for now i think when you start engine it is not consume energy from battery at all
• if engine gasoline it require electrical power while it running(alternator, battery or solar panels, anything)

in both cases above it should require electric power, not certain parts. Alternator and batteries is not mandatory parts as you can provide electric power for start and for continuous work of the engine in alternative ways(solar panels, cable to another vehicle etc), but engine should stop if it have no electric power available, and ofc should not start if no electric power available.

[Alex-Folts]

I did some tests and look in vehicle code - all work as intended, there is no bug.

Small engines like on screenshot(in the description of the issue) can start without vehicle have any battery, it assumed that this is engine with manual starter, for work it require electric energy source(on screenshot it is an alternator, but can also be a battery or reactor), when no electric source available(for example battery got completely discharged) engine will stop. Larger engines work similar but also required electric power to start(so far only battery accepted as starter electric energy source) and consumes battery power even if fail to start, engine wont start if battery have 0 or insufficient charge.

All behavior above realistic and it work as intended.

[Aivean]

@Alex-Folts , there is indeed a bug. I've also stumbled upon it before.

Look here: https://github.com/CleverRaven/Cataclysm-DDA/blob/70028b7295ebaa7a805607295db89157c2f9df34/src/vehicle_use.cpp#L363

control_engines uses toggle_specific_part which doesn't check for any faults. If you have one working engine, using "engine control menu", you can start the second one immediately, no matter how faulty it is.

It should use vehicle::start_engine( int e, bool turn_on ) instead.

[Alex-Folts]

control_engines uses toggle_specific_part which doesn't check for any faults. If you have one working engine, using "engine control menu", you can start the second one immediately, no matter how faulty it is.

Yes i hadnt tested vehicle with 2 or more engines, but it is different bug.

[int-ua]

Please update title to better reflect the issue. Something like "Engines can be started without a charged battery"