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Battery or Contactor Issue?

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Paul Valovich

Joined: 11 Jan 2006
Posts: 75

Posted: Fri Jan 03, 2014 10:29 am Post subject: Battery or Contactor Issue?

RV-8A, Z-13/8 architecture with Off-Batt-Batt/Alt switch to get electrons flowing. 380 hours over 3 ¾ years, original Odyssey PC 680 battery. 

  

Flew for 1.3 hours 1 Jan with no problems. On 2 Jan when I turned on Batt/Alt switch, nothing happened. Removed cowl and got out voltmeter – 12.8 volts to hot side of main contactor.  

  

Turned off switch, then back on – same results – nothing. 

  

A couple minutes later as I was digging out the electrical diagrams and references with Batt/Alt switch still on, contactor clicked and system operation was normal with 11.5 volts on the cockpit voltmeter. 

  

I am going to replace the battery, but wonder if there is an issue with the contactor. Tried to search Aeroelectric files for contactor troubleshooting, but couldn’t get system to respond. 

  

Paul Valovich 

IYK  

    [quote][b]

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nuckolls.bob(at)aeroelect
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Posted: Sat Jan 04, 2014 3:48 am Post subject: Battery or Contactor Issue?

At 12:28 PM 1/3/2014, you wrote:

 	  Quote: 	
		  RV-8A, Z-13/8 architecture with 

Off-Batt-Batt/Alt switch to get electrons 

flowing. 380 hours over 3 ¾ years, original Odyssey PC 680 battery.



Flew for 1.3 hours 1 Jan with no problems. On 2 

Jan when I turned on Batt/Alt switch, nothing 

happened. Removed cowl and got out voltmeter – 

12.8 volts to hot side of main contactor.



Turned off switch, then back on – same results – nothing.



A couple minutes later as I was digging out the 

electrical diagrams and references with Batt/Alt 

switch still on, contactor clicked and system 

operation was normal with 11.5 volts on the cockpit voltmeter.



I am going to replace the battery, but wonder if 

there is an issue with the contactor. Tried to 

search Aeroelectric files for contactor 

troubleshooting, but couldn’t get system to respond.



Paul Valovich


	


   Unfortunately, you didn't take enough voltage readings.

   While the battery master was ON but with the contactor

   NOT energized, you needed to know the voltage on the

   ground-side terminal of the coil that goes off to the

   battery switch.



   Had this voltage ALSO been 12.8 volts, then you would

   know that causation for failure to close was downstream

   of the master switch control path either in wiring, the

   switch or it's ground path.



   Had the voltage been zero, then you would know that

   either (1) the battery-master and associated wiring

   was good and (a) the contactor coil had an intermittent

   condition or (b) the contactor's moving parts were

   'sticking'.



   If you could get the problem to duplicate, having

   the extra voltage reading would be helpful. A second

   reading for contactor coil current would be definitive

   too. Put your multimeter in the current mode and use

   it to ground the master switch terminal of the contactor

   with the master switch OFF. This will emulate the switch

   path to ground and will either show about 1 amp of

   contactor coil current (coil good, contactor not

   closing, therefore sticking) or zero current which

   says coil is open. If coil current is good, rap the

   housing of the contactor with a screwdriver handle

   and see if it drops closed with the aid of some

   mechanical encouragement.



   Before you replace the battery, it would be interesting

   to do a load test on it. Do you have a Battery Minder

   or a Schumacher 1562 charger? I would bench charge the

   battery overnight and then load test it at 9 volts

   to see what the engine cranking dump rate is. 200A

   will get you started, 500-700A is what you expect

   from a new battery.



   This is a classic example of opportunity to make

   measurements and KNOW what the problem is before

   turning any wrenches. KNOWING the problem is

   critical to fixing it with confidence. If you

   cannot get it to duplicate for the purpose

   of conducting a detail diagnostic, then there

   are no concrete assurances that you've identified

   and fixed the real problem.

   Bob . . .

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