I am wondering if a Tec-Marine could charge up Las Cannon power packs from Space Marines armor power backpacks as it is a standard power source and if they are not powerful enough there are up to 5 Space Marines in a team?

I would say that this would have a high probability of offending the power armors machine spirit.

I'd say that from a story point of view it certainly makes sense that a techmarine would have some way of applying power to other machines. Given that a techmarine is in charge of maintaining his chapter's vehicles as well as is equipped with a servo-arm for that purpose, it seems a bit nonsensical that one would be stumped by a Rhino with a dead battery in the field! On the other hand, in game terms, allowing this would probably overlap too much with the Lumein Charge talent and make it redundant. I would personally allow it but impose a significant risk along the lines of a Tech-Use test starting at +30 and -10 for each pack charged. So if you charge the first pack it's a +30, the second pack is +20, 3rd is +10, etc, etc down to -30. Upon failing such a test the power armour suffers the equivalent of reactor damage from being hit in the back and entails a Hellish STR test to move and all that for a period of time (maybe 3d10 minutes or 1d5 hours if you're feeling really cruel ).

Relying purely on fluff I wohld say it's easier than that:

An energy pack can quickly be swapped with another when it runs out of power and each pack comes with an extractable power cord which can be used to recharge it from any standard Imperial power outlet. Also most energy packs have thermal cells which can be used to recharge the power – so a power pack that is exposed to natural sunlight will recharge rather quickly. Even heat will recharge the pack, and a well known guard trick to recharge a pack quickly is to put the pack in an open fire although this kind of treatment tends to shorten the life of the pack.

Or...

The lasgun uses the same basic technology and operates along the same lines as other las weapons, emitting a beam of focused light. It is powered by a small, rechargeable power pack located beneath the weapon, in front of the trigger guard. The pack can be recharged in many ways, including sunlight.

If your GM let's you do that is his choice.

But I have to confess, that this was only described for Lasgun chargepacks, not for those of the mightier lascannon.

How about:

If power armour is active then recharge time is 30 minutes per shot.

If the power armour is 'at rest' then the recharge time is 15 minutes per shot.

If the power armour is shutdown the recharge time is 10 minutes per shot.

Thanks for your idea's! I was thinking for level 1 rank tecmarine could use the backpack power source to charge the lascannon charge packs as the Lumein Charge is not availible till rank 2! Also if there where no other power sources!

Lascannon charge packs are very different to lasgun/pistol charge packs. Charging one of them from power armour woul dbe a significant drain.

Little Dave said:

If we assume a Lascannon shot is about 100kJ (equivalent energy to a 1kg mass travelling at 1000 mph). Then to generate this energy in 1 hour would require 27 Watts. I would assume a power armour generator would be able to handle an extra 27 Watts of output. Even if a Lascannon shot is 1 MJ it is just a question of how long it would take to recharge 1 shot.

As a Lascanon battery pack is attached to a particular type of powerarmour backpack, I would assume there a power connection between the two already. This is an advantage of Las weapons - they do not rely on physical ammunition.

The question should not really be whether it can be done but whather the power from the backpack is compatible without any means of adapting the current. I imagine to power an exoskeleton weighing in at around 200kg you would need and impressive amount of current. that said, a lascannon would need an outrageous amount of juice as well. I would say that a standard marine would be capable of accomplishing the feet with a difficult (-10) intelligence test. I would say a tech marine would be able to accomplish the task with less difficulty. One major caveat being that the cell might suffer reduced shots due to improper energy sources.

Completely out of interest, a while back when I statted up a version of power armour in another system it ended up requiring an RTG of only around 13 kW. I would imagine that a lascannon is getting up into the Mj range, so call it 1Mj, or just over a minute to recharge "one shot." Of course, during that time the armour doesn't have any power...

YMMV, of course.

Kage

Hadriel said:

Err... You seem to be conflating current level for power level. This might work fine in domestic setting where voltage supply is constant. We have no canon to draw on as to estimating what current levels PA requires - not that it really manners. What matters is power requirements - voltage and current can be conditioned as needed. Each sub-system will have its own needs.

Also there appears to be a confusion between Energy in a Lascannon shot with the Power supply needed. Quite how a lascannon draws power from its battery and then delivers it is a seperate topic. We are talking about recharging the battery, not powering the Lascannon directly.

A modern Real World battery pack commonly requires (ideally) a constant current charge, which is achieved by controlling the voltage applied. This sort of control circuit is trival. As I explained above, charging the Lascannon BATTERY over a reasonable period requires no great power source. It is hard to imagine how a space marine PA generator would not have a wide range of well-controlled power outlets capable of recharging a crystal battery also designed for use by Adeptus Astartes Lascannons.

'Improper energy sources'... A battery might suffer reduced capacity (or explode) if mischarged. However, I imagine that an Astartes Lascannon battery pack would be intelligent - its machine spirit would request the properly conditioned power from the spirit of the PA generator and would only accept power within required tolerances.

Fresnel said:

Fair enough, though I'm not certain that during the dark age of technology a battery would have an A.I. to govern its power needs.

Hadriel said:

Well, many Real World batteries do (A.I. is a rather grand term for about 1$ of electronics)... Li-Ion batteries actually need careful treatment in both charge and discharge.

In any case, humanity may have lost a lot of technology, but it's rather stained to suggest recharging batteries is a great mystery. Given that Lasgun crystal batteries can be recharged virtually anywhere from anything, it seems likely that crystal battery technology is basically robust.

N.B. The Luminen Charge talent allows full recharge in 1 minute, so I don't think allowing recharge over the course of hours undermines this talent too much.

In one of the Space Wolf novels, a couple Marines took up a pair of Hellguns when they ran out of Bolters, and it was said they could use them pretty much indefinitely without worrying about their ammo. So might be because of their armor.

Dulahan said:

Its more likely that it was simply more convenient to gloss over such real world concerns.