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  #1  
Old 11-20-2017, 06:53 PM
gfb gfb is offline
 
Join Date: Jul 2014
Location: Madison, WI
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Default Self-discharge or parasite drain?

I've had an EarthX ETX680 in my project for many months now. Usually it is on the Optimate charger they recommended. A few months back I unplugged the charger to move some things around. I went to start avionics today and the battery was dead, showing 7v. I charged and it came back to 13.65v but I'm trying to figure out what could be causing this.

This happened over maybe 3-4 months unplugged. The battery is in the plane and everything is wired up but the master is off. There should be nothing draining the battery, and if I put an ammeter in-line with ground I see 0.000A going through it.

What am I missing? Their install doc claims a discharge at ~3%/month so it should not have been a self-discharge problem.

Here is my wiring diagram:
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Last edited by gfb : 11-20-2017 at 07:00 PM.
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  #2  
Old 11-21-2017, 09:41 AM
gfb gfb is offline
 
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Voltage drop so far:
11/20 17:00 - 13.65v
11/20 21:00 - 13.50v
11/21 08:30 - 13.36v

BMS light is on solid indicating a fault per the manual. This is the second ETX680 that I have had trouble with after it discharges. Is there something wrong with my electrical system or is over-discharge protection not quite as sturdy as we think? I'm open to the idea that I'm doing something wrong here, I just don't see where and hoping for some pointers.
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  #3  
Old 11-21-2017, 09:56 AM
vic syracuse vic syracuse is offline
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Make sure you are turning off the ALT 2 field. Yes, it's a PM, and not much field current, but with that switch closed you are operating a relay which should take a long time to deplete the battery, like 3 months.
The easiest way to check for parasitic drain is to disconnect the positive post on the battery and put an ammeter in series with it. If you have no parasitic drain, then get ahold of Earthx.

Vic
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  #4  
Old 11-21-2017, 11:02 AM
gfb gfb is offline
 
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Thanks Vic. I don't think I've ever turned the PM "field" on I'll double-check my wiring to ensure I don't have it on by mistake. I'll also re-run my in-line amperage check on the positive side to be certain.
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  #5  
Old 11-22-2017, 02:28 PM
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rgodsy rgodsy is offline
 
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Circuit looks good, assuming all swithches are open. I'm planning to use and EarthX for backup so interested in what you find. I'm using a Lead Acid for primary to help provide a load for a runaway alternator.

You also want to keep your batteries on float charge when not in use, using the correct charger for the correct chemistry of course. They will drain super slowly over time with no use and lose performance. At least this is what they guys that sell fancy chargers claim.
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  #6  
Old 11-22-2017, 03:24 PM
Richard Connell Richard Connell is offline
 
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You don’t mention what type of alternator your main alt is but you have a B&C standby.
If you have an externally regulated main alternator - make sure the voltage sense is connected to the main buss not the battery (or always hot buss).
I had a similar problem to you. With everything turned off the regulator was still drawing 20milliamps or so.
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Last edited by Richard Connell : 11-22-2017 at 03:27 PM.
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  #7  
Old 11-22-2017, 03:31 PM
EarthX Lithium EarthX Lithium is offline
 
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Quote:
Originally Posted by vic syracuse View Post
If you have no parasitic drain, then get ahold of Earthx.

Vic
We have been troubleshooting this problem for the past couple of days with this customer and the first battery was returned due to excessive shorting of the battery, it had nothing to do with being over discharged. We do protect up to 1,000 amps but if the short is over this or has been done repeatedly, it can damage the BMS. This battery currently has been charged and it is holding the charge which indicates the cells are fine but the solid red light means something is wrong with the BMS, such as possible damage due to shorting again. We have requested this battery back to see what is wrong with it as we can not trouble shoot further without checking the battery out. The big question is how and why is the battery being shorted?
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  #8  
Old 11-23-2017, 09:24 AM
gfb gfb is offline
 
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EarthX support has been impressively responsive and helpful with troubleshooting. The battery seems to be holding charge once it stabilized at 13.3v but the Fault light is lit solid. I'll be pulling it to send to them for evaluation soon and will report back.

This is my second battery from them as the first one discharged all the way and then would no longer charge. The diagnosis was a large short damaged the battery. I'm hoping that I don't have an electrical miswire or design problem.

It's been suggested to me by a couple people that we use a non-lithium battery during electrical install to avoid damaging the more expensive battery with initial miswiring, etc. This sounds like a reasonable idea.
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  #9  
Old 11-23-2017, 09:36 AM
gfb gfb is offline
 
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Quote:
Originally Posted by rgodsy View Post
You also want to keep your batteries on float charge when not in use, using the correct charger for the correct chemistry of course. They will drain super slowly over time with no use and lose performance. At least this is what they guys that sell fancy chargers claim.
Yup, using the Optimate charger I purchased together with the battery.

Quote:
Originally Posted by Richard Connell View Post
You don’t mention what type of alternator your main alt is but you have a B&C standby.
If you have an externally regulated main alternator - make sure the voltage sense is connected to the main buss not the battery (or always hot buss).
I had a similar problem to you. With everything turned off the regulator was still drawing 20milliamps or so.
I have the PlanePower 60amp that came with the Van's FW FWD kit, and the SD-8 you mention. I'll double-check the wiring for the PP, the SD-8 relay Com pin is connected (via a fuse) directly to the battery so that it can provide power with the master solenoid off (per AEC Z-25.)

As a side, I have the SD-8 relay NC pin connected (via a fuse) to an EMS discrete in pin, and I notice a 10mA drain on that when connected but with everything off. The NC pin is connected to the battery via the Com pin as the alternator relay is open. Note that I disconnected this a few months back once I noticed the 10mA drain and contacted Garmin to understand whats up.
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Last edited by gfb : 11-23-2017 at 09:51 AM.
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