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Battery drain

Radomir

Radomir

Well Known Member
Starting to troubleshoot a battery drain issue... after a few weeks of being away, I found the battery completely dead (it won't even charge now..). First thing that caught my eye is VP-X showing around 3.5Amps on "Alternator field" circuit... with the engine shut down... That doesn't sound right??

I believe the total draw (with most of the stuff shut down via VP-X) was showing a little over 7 amps and that just sounds way wrong.. No idea where the rest was going.,. only one HDX screen was on.. nothing else was supposed to even be powered...

Any ideas why alternator field may be showing such draw w/ engine off?

PS. Did not build the plane so still getting familiar with what it even has let alone how it's wired up.. (have some documents, but still need eyes on each part to really understand everything)
 
Radomir said:
I believe the total draw (with most of the stuff shut down via VP-X) was showing a little over 7 amps and that just sounds way wrong.. No idea where the rest was going.,. only one HDX screen was on.. nothing else was supposed to even be powered...
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If 7 amps was your VP-X total draw, then reviewing each circuit should give you the total. My summary is very accurate of the total of each of the circuits.

Hopefully not a Earth X battery.
 
No, not EarthX... just a good old PC680 (that apparently managed to live for about 60 hobbs hours).

Anyways, I could not see where the rest went.. in either case, I am puzzled by that 3.5 or so amps on alt field.. did not expect anything there.. Should there be some draw on that when engine isnt' running? I wouldn't think so...
 
Electrical schematic would be very helpful obviously.

Main alternator field resistance is ~4 ohms... good reason to have alternator off when engine is not running... regulator will see low V and apply max field current.
 
Heh.. there isn't much in the way of schematics.. it's just VP-X and PPS.. all wired into that.. I do have pinout "diagrams" for VP-X but that isn't telling me much..

But I will pay more attention tomorrow when I go out... and especially alt on vs off (I do not even remember which way I had it today when I was looking at this stuff).
 
Have u found the VPX display on your EFiS? That will show where the amps are going. Posting a picture would assist those with possible knowledge.
 
I learned the expensive way a long time ago about parasitic loads and also about self discharge rates, from experience with my non-aviation toys (boats, campers) to always install a negative post disconnect on the batteries, and use it religiously. Even if storing for a day or two.
Since I've ever owned an aircraft I've never thought about this application. How's it 'supposed' to be done in aircraft?
 
majuro15 said:
USB charger on hot bus?
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Hmmm.. that's a good one! Didn't think of that as nothing is plugged in.. Yes there are USB ports for charging and even a cig lighter plug.. no idea where they are wired.. as they were added later on.. but nothing is directly wired into the battery.. does VP-X even have "always hot"

I'll take a look to see how they are wired..
 
Radomir said:
Hmmm.. that's a good one! Didn't think of that as nothing is plugged in.. Yes there are USB ports for charging and even a cig lighter plug.. no idea where they are wired.. as they were added later on.. but nothing is directly wired into the battery.. does VP-X even have "always hot"

I'll take a look to see how they are wired..
Click to expand...

Are you sure?

Depending on which vpx you have, many of us run out of circuits. I have a pro, but still put in extra circuits. I.e. EBus that has a keep alive circuit for the EFIS.
 
rleffler said:
Are you sure?

Depending on which vpx you have, many of us run out of circuits. I have a pro, but still put in extra circuits. I.e. EBus that has a keep alive circuit for the EFIS.
Click to expand...

Original VP-X pinout diagram shows a few "not used" on J8 (it's a Pro version) but yeah not very many choices.. A few things were added later on that aren't on the diagram (4 things were added that I can think of)

Anyways, I just found USB on VP-X screen (and it is not showing any draw there).. seems to be sharing the circuit with some LED panel light.. and found third thing on separate circuit.. so the only thing left (that isn't showing on VP-X) is that cig lighter plug.. nothing is plugged into it at all, though..
 
Mine was connected right to the battery, a battery tender cigar socket, if you leave a usb outlet plugged into that cigar lighter socket it will drain the battery even with nothing plugged into it
 
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