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Earthx - break popping

Clipper1

Active Member
Looking for a little advice/info...

Has anyone experienced a high current draw on Earthx batteries? I've noticed that mine will often pop the alternator breaker. I believe it is the battery as it doesn't appear to pop the breaker on the ground (at low RPM) but once I get airborne with full power the load greatly increases and often the breaker will pop.

TIA!
 
Since Lithium batteries have very low internal resistance, they do not limit alternator charging current. Alternators will put out the maximum charging current that they are capable of. The alternator circuit breaker should be sized to carry that maximum current. The circuit breaker electrical connections should be clean and tight to prevent heat which can cause a breaker to trip at less than its rated current.
 
What is the AMP rating of your alternator and which EarthX battery do you have? EarthX has some specific requirements on which battery is required verses alternator output.
 
Which battery? If you have the 680 max charge rate is 60 amps. A 70 Amp alternator would be to large. The 900 is rated for 80 Amps. From EarthX: 680, This battery is intended for 400ci engine size or less; 60 amp alternator/generator or less. Can be used in experiemental aircrafts or race cars, just match up the alternator output with the correct battery.
 
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Nuisance trip by design

EarthX batteries really demand to be recharged right now after a startup. It's only for a few minutes, but it really wants the amps right now. An alternator is regulated for volts but will provide well over it's rated amps upon demand. Too much demand will pull the voltage down, but it'll put out the amps. This is a prime time to smoke a diode or burn up the internal regulator if so equipped. A breaker on the output at less than or equal to the alternator rating is a designed nuisance trip - just like a Cessna. AeroElectric Bob recommends an ANL instead, which is like a robust slow blow fuse.

Remember - the breaker/fuse is there to protect the B-lead from the battery, not the other way around. If it were not undersized and blew, it would be because of a short to ground in the alternator or the B-lead and resetting a breaker is just asking for trouble. In the case of a nuisance trip of a breaker on the B-lead because the battery is asking for amps, it'll get worse as the other loads on the battery continue to draw amps and the battery is just that much hungrier by the time the breaker is reset.

Ed Holyoke
 
Thanks guys. I think I have my answer now after the info you've given. The EarthX is an ETX900 and the website says it has a max charge of 80A. Probably explains the breaker popping!
 
The good news is you have the right alternator and battery combination. You might need to increase the size of the breaker assuming your wiring is sized to handle it. You should be able to see the amp load. Check it during your runup and again at full power on takeoff.
 
Is the battery not really too large? If it requires 80A on charge and the alternator is only giving out 70A then it will keep popping. Would not the ETX680 be a better fit to keep up with the load?
 
Is the battery not really too large?
No, it is NOT too large. Here is a quote from EarthX website.
"You must use a lithium battery that is designed to handle the current from the alternator or you can damage it, cause premature failure or possible even cell rupture."
That same EarthX website states, "Your fuse, breaker, or current limiting device should be sized approximately 20% above the alternator rating."
In other words, the problem is that the circuit breaker is too small.
 
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No

The battery can ACCEPT 80A for charge; you can use anything smaller, ie 70A, to charge it. The reason it is popping the breaker is because the battery can ACCEPT 80A and 70A is available but it is protected for 60A...so the alternator is putting all 70A into a 60A circuit breaker. What happens? It works as it is supposed to and trips the breaker.
 
The ETX900 does NOT require 80amps to charge. It will accept up to 80 amps without being damaged.
A smaller battery will still accept the full alternator output, but the battery will be damaged.
The circuit breaker is too small.
 
I have a 70A plane power alternator. Breaker is 60A.
I am wondering why you went with the 60A breaker for a 70A alternator. I have been told, to up size the breaker by around 5A from Alternator, in your case it would be a 75A breaker.
 
Thank you Gentlemen. Your advice is very helpful. I think the underlying problem is that the builder initially used a PC680 battery and then he changed it out for the EarthX without doing any swap out on the breaker.
 
Instead of installing a larger circuit breaker, eliminate it altogether. Install a fusible link in series with the alternator "B" lead to protect the battery and aircraft electrical system from a shorted alternator or shorted "B" lead.
 
Instead of installing a larger circuit breaker, eliminate it altogether. Install a fusible link in series with the alternator "B" lead to protect the battery and aircraft electrical system from a shorted alternator or shorted "B" lead.

Or use an ANL. We're not protecting the battery, we're protecting the B-lead and alternator from the battery which will try and melt anything that's shorted.

Ed Holyoke
 
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