Big Negative Battery Amps on Acclaim

[exM20K]

So this happpened a couple times on both batteries.  It's intermittent and goes back to normal -1 or 0.  Any ideas on how to troubleshoot?

 

[milotron]

I had a broken main alternator lead that was doing something similar to me. The rubber boot over the termination on the alternator was holding the cable together, but it had in fact burned right off. It looks like it was a sloppy crimp and wire stripping job from the onset.

 

Took a while to troubleshoot as it looked just fine until I gave it a tug and it came right out!

[carusoam]

The circuit is usually not too hard to follow...

The Ship's electricity is all flowing through one supply line through a very low resistance device called a shunt.  Shunts are often mounted on the firewall supplied by the generator/battery.  Depending on which way the current is actually flowing...

A voltage meter in the G1000 or JPI, reads the voltage drop across the shunt and presents the results calibrated in amps.

The presentation on a G1000 or any electronic device gets a bit fuzzy when it adds logic and filtering to the reading.

Probably a loose wire losing contact from the shunt.  Possibly a burnt or compromised fuse...?

There are some inline fuses related to this as well because the wires connected to the shunt have access to high voltage with no resistance.

basically you are looking to track down two smaller wires off the shunt to see if the fuses are still there and see if a loose connection shows up on its way to the display...

hoping this helps some...

PP ideas only, not a mechanic....

Best regards,

-a-

Edited January 22, 2017 by carusoam

[DonMuncy]

1 hour ago, carusoam said:

1 hour ago, carusoam said:

 

There are some inline fuses related to this as well because the wires connected to the shunt have access to high voltage with no resistance.

 

 

On my K model, they are not "inline". They are mounted under the dash, and they are expensive until you locate a good source for them.

[exM20K]

Update - sorry for not doing this earlier: i hate squawk posts w/o resolution...

 

It was the #1 battery shorting out.  Apparently one battery shorting is sufficient to show this sort of draw even when the faulty battery is not selected and receiving only a trickle charge.  Anyway, one new battery and 35 trouble-free hours since.

-de

[carqwik]

What brand battery was shorting out? 

[carusoam]

Nice follow-up.

Any additional details on the battery shorting would be greatly appreciated. 

Best regards,

-a-

[exM20K]

It was a Concord RG24-15, and I believe it was original to the aircraft (2009), so I can't be too upset about that lifespan.  My A&P said there was one or more cells shorting out - don't know much more than that, and it failed a load test miserably.  Basically, it was done.

-de

[carusoam]

A lost cell will fail the test...

That many years seams pretty good to me.

Great Pirep too.  Something interesting about the large negative amps when selecting the other battery. There has got to be an explanation for that effect.  The alternator was still working and the other battery was still viable.  

Not sure why negative amps shows...?

Best regards,

-a-

Edited May 22, 2017 by carusoam