Aux Battery High Amps

This is a public forum for 737 maintenance related questions, requests and experience exchange discussions for every Boeing 737.


Aux Battery High Amps

Postby Navy2010 » 07 Aug 2017, 15:26

We have an issue on one of our Auxiliary batteries. with power off, and standby power on, with the Battery switch in the on position, Aux Battery Amps are drawing high, and with APU power on and the AUX Battery Charger in charge mode its charging the battery at OVER 100 amps (about 107). the battery chargers are rated at average 50 amps in charge mode but will not supply more than 65 amps. this is kinds stumping me as there is a circuit breaker rated at 100 amps that comes off of the charger. Has anyone else had anything like this before. we are currently looking at the RCCB as a possible cause.
Navy2010
 
Posts: 5
Joined: 07 Aug 2017, 15:04

Re: Aux Battery High Amps

Postby maro12 » 09 Aug 2017, 22:21

Hi Navy2010,

Did You perform any troubleshooting?

When You switch power on and observe this +/-100 amps, try to:

-pull "RCCB REMOTE" CB on SPCU (on my diagram it is pos. A4 - check for position of this CB for Your aircraft effectivity), check if current indication changed, if yes -> it might be SPCU (constantly giving ground to RCCB logic);

-if indication did not change, with above CB opened (we make sure that RCCB is not commanded close), have someone in EE bay and ask him/her to pull "AUX BATTERY CHARGER" CB, this one rated 100 amps on J9, and check how current indication change; if there is still charging current, I would suspect RCCB.

Let us know the outcome.

Best Regards,
maro12
maro12
 
Posts: 74
Joined: 05 Oct 2008, 01:51

Re: Aux Battery High Amps

Postby Navy2010 » 16 Aug 2017, 17:29

What i dont understand is how there can be more than 100 amps when there is a breaker C1209 (Aux Batt Charger) is rated at 100 amps. And now we are having issues with Main batt as well. RCCB works as advertised. SPCU works. Standby Power and DC Power checks are good. We swapped with known good parts. The battery chargers are throwing faults. We even swapped them initially to make sure. Only thing we havent done that I have suggest is to read directly off of the terminals of the battery charger to ensure it is giving off as many charging amps as the P5-13 says it is. Is it possible that maybe the P5-13 is wrong and if not then we might be looking at a wiring issue. What related to wiring would cause excessive amps
Navy2010
 
Posts: 5
Joined: 07 Aug 2017, 15:04

Re: Aux Battery High Amps

Postby Navy2010 » 16 Aug 2017, 18:34

If there are any other electricians that want to chime in please do. Also with supplying charging (positive) amps. What determines the rate of charge. Does the battery pull amps or smdoes the charger put out a nominal amount based on current capacity and then trickle charge close to max. I only have about 5 years of electrical and avionics experience its not much. And wmcould there be something else giving us a false reading on the p5 meter panel while the chargers supply their normally rated amount.

Any advice is welcome as this aircraft is hard down.
Navy2010
 
Posts: 5
Joined: 07 Aug 2017, 15:04

Re: Aux Battery High Amps

Postby maro12 » 16 Aug 2017, 22:11

Hi Navy2010,

Did You have a chance to swap P5-13 panel? Maybe there is a problem?

Best Regards,
maro12
maro12
 
Posts: 74
Joined: 05 Oct 2008, 01:51

Re: Aux Battery High Amps

Postby maro12 » 16 Aug 2017, 22:18

For how long amps are so high? Battery chargers cycle is controlled by battery temperature, charging battery with 100 amps... I would think that state would not last long, resulting in some protection to work, and battery temp would go up rather quickly and cut charge.

"During Basecharge mode and Overcharge mode, the maximum battery temperature the charger
will allow is 60 °C. If the temperature of the battery increases to 60 °C, the charger immediately
and automatically changes to the Sustaining mode of operation. In Sustaining mode of operation,
the charger operates as a regulated TRU. If the battery temperature increases to 70 °C, the
charger will stop its operation and set a battery-fault indication. The charger will automatically go
back to Sustaining mode operation as battery temperature decreases to lower than 70 °C. It will
automatically go back to Overcharge mode or Basecharge mode as battery temperature
decreases to lower than 60 °C."
maro12
 
Posts: 74
Joined: 05 Oct 2008, 01:51

Re: Aux Battery High Amps

Postby Electron » 17 Aug 2017, 05:20

FOR GUIDANCE ONLY
==========================================+++==========================================
!!!HIGH VOLTAGE AND CURRENTS. DEATH LIKELY IF NEGLIGENT. PROCEED WITH EXTREME CAUTION!!!
==========================================+++==========================================
QUESTIONS
1)What maintenance or flight crew procedure was being followed that lead to this fault discovery?
2)Have you consulted the applicable FIM if there is one?
3)Have you checked the maintenance documentation for history?
4)What components and LRU's have you changed thus far?
5)What is the voltage and current draw on the Main Battery indications from the overhead panel in the various configurations?
6)What is the voltage and current draw on the Auxillary Battery indications from the overhead panel in the various configurations?
7)What is the voltage and current draw on the INV indications from the overhead panel in the various configurations?
8)Are the Battery Charger LRU lights ON or OFF?
9)Is the ELEC light illuminated upstairs on the overhead panel?
10)How long until the BAT DISCHARGE light comes on?

SUGGESTIONS
1) Yes, you're going to need to compare ACTUAL voltages and currents to INDICATED/SENSED.
2) As you said - THE CHARGER CIRCUIT BREAKER SHOULD POP if it is doing its job properly. You should check here first because it is an *easy check. You need to check the breaker for:
- HOW MUCH CURRENT it is allowing downstream in the different conditions you mentioned in your initial post, and,
- WHAT VOLTAGE IS PRESENT at the circuit breaker.
3) If you are able to, you should measure VOLTAGE and CURRENT at other parts of the circuit AT and UPSTREAM of both batteries, in the normal, and different configurations you mention.
4) Once you have attained all of that, you MUST sit down and analyse that information to make sense of it and diagnose the cause or possible causes. This is best done over a cup of tea, during or after your lunch/dinner break. You should have suggestions 1 thru 3 completed before completing this suggestion. Remember your human factors training and manage your time and effort correctly.

GENERAL SUGGESTIONS
1) To cover your arse, are you able to check on another airplane to see if it behaves the same and make comparisons? You could indeed be chasing your tail.
2) CROSS CHECK PART NUMBERS fitted to the airplane against the AIPC.
3) I suggest you include the Main Battery circuitry in your troubleshooting unless you have conclusive evidence to suggest that part of the DC circuit isn't faulty.

TOOLING
Voltage meter (Recommend Fluke Digital Multimeter 187, an equivalent or better)
Ammeter (Recommend Fluke Clamp Meter 374, an equivalent or better)


COMMENTS
-I'll be back with more suggestions after I have had a proper look at the diagrams and have read the system notes but I really need answers to the above questions.
-Generally (depending on your specific aircraft circuit), the Battery Charger will charge the battery at approximately 38A DC or 50A DC continuously, for a time.
-Generally (depending on your specific aircraft circuit), the Battery Charger will sense an over current at approximately 75A DC.

Edited:
24AUG17 - Changed Recommended Fluke Clamp Meter from 322 to 374 under TOOLING.
24AUG17 - Created COMMENTS title.
24AUG17 - Added Battery Charger charging remark under COMMENTS.
24AUG17 - Added Battery Charger over current remark under COMMENTS.
Electron
 
Posts: 10
Joined: 21 Mar 2015, 14:17


Return to - 737 technical questions & requests -

Who is online

Users browsing this forum: No registered users and 4 guests