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N6722C avatar image
N6722C suggested N6722C edited

Add battery CGA, and then simulate Battery Internal Resistance based on CGA and charge

If there is a way of simulating Battery Voltage drop on Load, due to its Internal resistance, it is not evident in the SDK.

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IcemanFBW avatar image
IcemanFBW commented

If you're making any sort of complex electrical system, I would definitely encourage you to make it completely custom (using WASM gauges and your own variables), so that you have full control over how deep you want to get the simulation to be, and to make sure it "just works."

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N6722C avatar image
N6722C commented N6722C edited

Please, please consider:

Rather than just requesting that Asobo simulates Battery Internal Resistance, and hope that the need is understood and its simulation figured out, here, very simply, is how to do it, in a way that WILL NOT AFFECT any previous Simobjects that use a battery.

Its literally, adding one indexed A:var, and One line of code in the "Charge to Voltage code"


Currently, Asobo models the CHARGE that the battery has, (as a % of its Total Capacity), and then uses a Curve to create an internal Battery Voltage V:index, that is put into various Battery Voltage A vars

All that is needed to to create a new indexed A:var say : A:ELECTRICAL_BATTERY_RESISTANCE:Index )

and then modify that internal Battery Voltage V:index value that is put into these indexed Battery Voltage A: vars to

Battery Voltage V:index = Battery Voltage V:index - ( A:ELECTRICAL_BATTERY_RESISTANCE:index * A:ELECTRICAL_BATTERY_LOAD:index)

This simple addition with save 1000's of lines of Dev Code trying to FAKE the effect of Battery Internal Resistance on all circuits , and more importantly, not affect any exstiting Simobjects that use a battery, because the new;y added A:ELECTRICAL_BATTERY_RESISTANCE:index will default to zero (if not used and controlled by the dev)

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FlyingRaccoon avatar image
FlyingRaccoon commented N6722C edited

Hello @N6722C

This is already in our roadmap.
No ETA yet, keep an eye on SDK release notes.


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FANTASTIC !!! Thank you ....
1 Like 1 ·

Hi Sylvain,

(Bold and italic used to help emphasize key words, as one might, when verbally communicating)

A Follow on question, associated with road mapped Battery Internal Resistance, .
and the desire for Correct Alternator operation and the concept of an Alternator Voltage Regulator.

With the addition of Battery Internal Resistance, and then hopefully the introduction of a similar A:Var for Alternator Internal Resistance, the correct Alternator Output Voltage (and hence current), can then be simulated, with the addition of adding the Alternator Voltage Regulator "Sense" connection, to a definable bus, and introducing an A:var, for the Voltage Regulator Set-Point, (A:var so it can be dynamically adjusted, and have the possibility of failing high or low). (see, for example , Cessna POH Electrical Diagram)

172r-poh.pngThe existing CURVES, for Alternator Current & Voltage with RPM, should really be "maximum outputs" for a given rpm, with the actual outputs, within these max limits, and based on the Battery's currently external voltage (function of how charged the battery is -- etc etc.).,

The end result would be , that starting off with a fully charged, battery, and starting the engine with the starter motor, the battery get discharged, and when the alternator is turned on (assuming no other load is placed on the electrical system), the battery should charge back up, to the Voltage Regulator set-point voltage, with a current that reduces, and the battery changes up, and a current that is not dependent on the alternator RPM, (provided it is rotating fast enough to provide the required re-changing current & voltage).

Currently, the ammeter incorrectly shows a high current flowing into the battery, all the time, that is a function of RPM, and it does not decrease as the battery chages up to a Voltage Regulator set point. (sure way to overheat and ruin an expensive Aviation Battery !!)


I am hoping your response to thisi will be -- YES - now we are adding Battery Internal Resistance, we will also be adding Alternator Internal Resistance, and thus allowing the realistic addition and simulator of the missing "Alternator Voltage Regulator "..

This stuff is really not that complex, and is almost "Trivial" in detail and complexity, comaipred with the current advances flight modeling !!.


Also, note.(Ref POH Diagram) Currently, in the Asobo C172 , the ammeter is measuring the Bus current at the battery (Pink) , so it incorrectly includes then Starter Motor Current. (150+ Amps)
It should be measuring the Current on the Bus AFTER the starter motor (Green), as in the POH

1 Like 1 ·
172r-poh.png (160.5 KiB)
Is "battery Internal Resistance simulation" on the roadmap for SU10 ( or later ) ?
0 Likes 0 ·
Still no ETA but not SU10 for sure.
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N6722C avatar image N6722C FlyingRaccoon ♦♦ ·

Thanks .. not sure if that is good news or bad, after spending over a week, working around it, and simulating the effects of it. So all that work is not wasted in the short term ...., as none of it will be needed, when the battery resistance is finally there.

ALSO --- Will the Bug in writing to the Battery Charge, and the ability to set it from 0 to 100% be fixed in SU10 ??

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