What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

60amp Alternator breaker pops (Question??)

JakeLewis22

Well Known Member
I had the 60 amp alternator breaker pop Saturday after a difficult hot engine start (fuel injected Lyc w/101F OAT). I have a Plane Power 60amp alternator from Van's.

After reviewing the data log in the Advanced Flight Systems engine monitor I discovered that the breaker held at 60 amps for about 10 seconds before it popped. The breaker did its job but at the same time the battery volts never exceeded 13.8v so I didn't have a runaway alternator. I bypassed the breaker and monitored the amps/volts closely and found the the amps peeked at 65 and came down gradually after ten minutes to its normal 10 amps.

I spoke to Stein and Dick at Plane Power and they both agreed that a 70amp breaker will probably solve my problem (before anyone ask, yes the wire will handle 70 amps)

Has anyone experienced this same issue?
 
Last edited:
60 Amp Breaker

I have had the same issue with the breaker tripping.
It was my fault, I had pulled the field breaker and did not see it until the
battery voltage had gotton low enough to set an alarm.
Resetting a coiuple of times while the battery started to recharge then all was well after it had a chance to partially recharge the battery.
 
New question

Has anyone noticed how many amps their alternator is putting out after starting the engine?

After looking at my data log it looks like the average right after the engine starts is 40 amps but within 10 to 15 seconds it's down to 25 amps. After a hot start it gets up to 60 amps and it takes a few minutes to get down to 25 amps. Once the battery charges up the average at cruise is 10 amps.

I've decided to move the breaker from the current firewall forward location to the instrument panel and increase it to 70 amps. I think this should solve my problem.
 
Jake, it all sounds normal to me. Pull the battery down with a hard start and the initial charge rate will be high. It should be more evident in an aircraft with a smaller battery, less so with a big battery.

Rather than extending a high amperage hot lead to a panel breaker, consider a simple fuse link on the firewall:

http://www.bandc.biz/anlcurrentlimiters40athrough130a.aspx
 
Problem solved

In case anyone searches the archives in the future with a similar problem I thought I'd post a closing.

I installed a 70 amp pull-able breaker on the instrument panel and increased the alternator wire to 6AWG. After 3 hours of flying this weekend all is well. No radio noise or popped breaker.

I also changed the audio warning in my Advanced Flight engine monitor to warn me if the battery voltage drops below 12.3 or the Amps reach zero anytime the RPM is above 1500. AFS set the audio warning at 11v and the amps warning was turned off. I just happened to notice that the amps were at zero but at the same time the volts never dropped below 12 so I never received a warning that my charging system was nonoperative. The data log shows that I was running on battery power only for 20 minutes from the time the breaker tripped to the time I was able to land and shut down. Hopefully these new settings will give me a warning as soon as the charging system goes down.

I'd like to give a big thumbs up to AFS for incorporating a data recorder into their product. Every 5 seconds it takes a snapshot of all the engine and EFIS readings which you can export to an Excel spreadsheet. This makes diagnostics very easy.
 
I also changed the audio warning in my Advanced Flight engine monitor to warn me if the battery voltage drops below 12.3 or the Amps reach zero anytime the RPM is above 1500.

At 12.3 your battery will be at about 50%, way too late for a warning.

Set it at about 13.5 if you want to know when your alt. goes off line.
 
mine was popping with a loose connector to the breaker, double check the wiring since this may be an easy fix
 
At 12.3 your battery will be at about 50%, way too late for a warning.

Set it at about 13.5 if you want to know when your alt. goes off line.

12.3 is what mine is set for. Your actual battery OCV is going to be 12.5-12.7, which is plenty of warning. My OCV is 12.8-12.9 after sitting for a week, which is a fully charged battery. I don't want to have to disable a warning for low voltage everytime I turn the GRT on. By load shedding in flight, one will have plenty of time to get on the ground if the battery is in good shape. Buy a load tester from auto parts store and keep a log at each annual.

I have 6 ga wire to alternator going through 60A current limiter from B&C on firewall. I charge two(pc925 & pc680) batteries after startup. I usually wait about 2 minutes to connect aux. Routinely see 55-60A alt load. I believe replacing your 8 ga wire did a bunch to help out. Higher resistance in smaller wire= more heat and less voltage.
 
Back
Top