About electricity: how much you consume and how much you need

[gilflo]

Hi

I built an Eve return Lander (10000DV and 105T on take off) for a rescue Mission:

He landed perfectly near the goal, but was unable to depart because battery was depleted and electricity was 0.

Here is the mission report

http://forum.kerbalspaceprogram.com/threads/72103-Rescue-mission-to-Eve

Because he was unable to take off du to this lack of electricity, I stopped the mission and revert to Eve Orbit.

What I do not understand is why it was not able to sustain electricity charge.

There are 2 PB NUK generator that gives 45/mn each that's 90/mn total, and 2 small Z-100 rechargeable batteries.

Consumption is 18/Mn for MK1 lander Can, 18/mn for the Advanced in line Stab, 1.8/mn for the remote guidance, 18/H for Mechjeb2.

I cannot know whether the Kerbal engineer system and protractor use electricity, but the fact is that he total consumption is less than 45/Mn and we got a charge of 90/mn with 2 generators.

So I do not understand why the system seems to deplete as if the generators were not working. They are said to be active all the time.

Once parachutes were deployed, the charge was going down very quickly.

And on the ground charge was going down also, there was no lights on.

Question: Is there an add on to see the needs for electricity?

I am going to launch the same lander but with a giant solar Array, I will lost some DV but i am sure to get 18/sec and that should be far enough....

[Kasuha]

To save electricity, switch off SAS and lights. You should not need them during descent most of the time.

[Jimbimbibble]

Yeah, you're probably burning it with the SAS, especially if you landed on uneven ground. Your design should be working.

[cantab]

If the nuclear generators are still attached, surely it should recharge. And if there's a Kerbal on board and you make sure the lander can's in control of the ship (right click and choose "control from here) you won't need electricity anyway to take off though you might need it to stay in control.

[gilflo]

OK thank's, I'll try to disable SAS as soon as possible. it's a remain control unit. Nobody on board.

[Claw]

OK thank's, I'll try to disable SAS as soon as possible. it's a remain control unit. Nobody on board.

Yeah, that's probably it. SAS on during reentry isn't usually too big of a deal. In fact, you might need it initially to prevent the ship from flipping around. But if you leave SAS on after chutes are out (like you said in the OP), then it's going to drain the batteries very quickly. Same thing after you land.

The reason is because reaction wheels (or pod torque) use more electricity when they are active. They don't use any electricity if SAS (or you) isn't providing input. Unlike lights or probe cores (not the torque part) which draw a steady amount.

So if the chutes are deployed and SAS is on, the SAS tries to turn the craft against the pull of the chutes back to the orientation before chutes were deployed. Hence the rapid battery drain. If you think you need SAS for landing, turn it off after chute deployment to let the craft settle, then turn it back on right before you need it. Turn it off again after you land.

[gilflo]

Ok thank's for advise.

[Pecan]

Question: Is there an add on to see the needs for electricity?

The mod you want for that is Fusebox.

[gilflo]

OJ thank's, mission was a success, I shut down SAS and torque once chutes were opened

See here:http://forum.kerbalspaceprogram.com/threads/72103-Rescue-mission-to-Eve?p=1022393#post1022393

[JiWint]

everytime I just put 2 RTGs and that's it! I (almost) always leave SAS on,but that's not a problem

Edited March 15, 2014 by JiWint