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-   -   BMS and you?re failure scenarios (Not an EarthX) (https://vansairforce.net/community/showthread.php?t=173586)

rv6ejguy 07-25-2019 06:24 PM

Quote:

Originally Posted by RV8iator (Post 1361949)
I am a little disappointed that here we have a post that identifies a potential safety issue and we can?t identify what product. This dig a little deeper and maybe you can see if you do too is not helpful for what potentially is a life threatening issue.
Just my 02 cents worth.

One other informational battery thread was deleted a couple months back when it was felt that posts strayed over the allowable latitude for the site. Glen is simply saying here to check out and understand how YOUR BMS, regardless of brand, will react to OV, UV, spikes, temperature etc. Certainly important to know.

Hopefully if you ask your vendor, they can supply succinct information in this regard.

scrollF4 07-25-2019 06:36 PM

Quote:

Originally Posted by Bavafa (Post 1361974)
Perhaps this will clarifies this for some of the EarthX users.

Based on my understanding of the EarthX BMS system, in an overvoltage situation (15.2v and up) the battery will blocks the incoming volts but still operates for the voltage out. Of course in such situation, a proper action is to shut down the alternator to protect the $$$$$$ avionics.

Please feel free to set me straight if my understanding of EarthX BMS is incorrect.

Not so sure. EarthX BMS does NOT disconnect for overvoltage and it does NOT began to protect until 16V. That is well documented in their pubs, and discussed WIDELY in this forum (I recall you?re having documentation problems). You do indeed need a voltage regulator in your alternator/charging system for the overvoltage protection function.

What brand battery is it, please. We?re starting to drag a GOOD battery company (EarthX) into the mud of false/uninformed assumptions.

Bavafa 07-25-2019 06:46 PM

Quote:

Originally Posted by scrollF4 (Post 1361983)
Not so sure. EarthX BMS does NOT disconnect for overvoltage and it does NOT began to protect until 16V. That is well documented in their pubs, and discussed WIDELY in this forum (I recall you?re having documentation problems). You do indeed need a voltage regulator in your alternator/charging system for the overvoltage protection function.

What brand battery is it, please. We?re starting to drag a GOOD battery company (EarthX) into the mud of false/uninformed assumptions.

Sid,
You are correct. It looks like the 15.5v is for the non-aviation type battery for EarthX.

reading the manual again (ETX_Manual_111017_X)

ETX Hundred Series - BMS

"In the event of a charging system failure where the voltage increases to above 15.5V, the resistance to charging current increases, and above 16V the charging current is completely blocked. The time delay for this feature is 2 second to allow the aircraft alternator?s over voltage protection (crowbar circuit) to activate first. This design offers charge voltage protection greater than 40V. The discharge current (current out of battery) is unaffected in this situation. EarthX requires having automatic over-voltage protection (crowbar) for alternator type charging systems (not required for <20 Amp pad mount standby alternators)."

EarthX Lithium 07-25-2019 09:32 PM

Not an EarthX
 
Quote:

Originally Posted by humptybump (Post 1361879)
There was not a large or unusual draw on the electrical system. I typically see 6-8 amps of ?usage? when flying VFR day with autopilot.

I have received some details from my battery?s manufacturer regarding the BMS. *
  • The battery?s BMS will attempt to perform its own regulation if presented with over voltage.
  • If the internal temperature of the battery goes above a ?safe level? the BMS will disconnect the battery until the temperature drops.

* the vendor?s statements describe their current BMS design as of this post. BMS technology is changing rapidly and this information may be obsolete to readers at any point in the future.

I may have experienced the combination of these two functions.

One of my next steps is to derive a test for the alternator.


Again, my reason for this thread is to prompt others to fully understand the behavior and scenarios of their own electrical system just as I am developing a better understanding of mine.

Hi Glen,

Glad you are safe and sound after your incident here. We are currently at EAA Oshkosh so please forgive the brief response here but just to set the record straight here for everyone on the question to if this is an EarthX battery: this is not an EarthX battery. If you would like to review the documented BMS functions of the EarthX, please go to www.earthxbatteries.com. If your here at Oshkosh, please stop by and see us in Hangar C. We would love to meet you.

humptybump 07-26-2019 01:10 AM

Hi Kathy, hope you guys are having a great Airventure (now that it’s dried out a bit).

I’d like to commend EarthX on having some of the best documentation I’ve read as I investigate my situation.

I’ve been reading the documentation of several vendors, comparing how each vendor’s battery technology might have dealt with it. Having it written down and published is more comforting (and quicker) than the sometimes protracted back-and-forth of e-mail support.


If you fly with an EarthX battery or are considering it, RTFM. You will learn something. Their documentation clearly details how their battery technology works.

EarthX also has a current advantage with its inclusion of a discrete output indicator. It’s level of information would have dramatically reduced my “head scratching”.

This has been one of those “you don’t know what you don’t know” experiences. My backup system worked as designed ... and now I know more about battery management systems than I thought I’d ever care to. :)

DanH 07-26-2019 07:05 AM

Glen,

Previously you stated:

Quote:

Originally Posted by humptybump (Post 1361336)
It turns out the undocumented BMS behavior in my situation is to disconnect itself and shutdown for some unknown amount of time.

Then this:

Quote:

If you have a BMS associated with your battery it’s a good idea to know it’s response to all of the situations it’s design to protect.
If the issue is undocumented, how are readers expected to know?

humptybump 07-26-2019 07:16 AM

Quote:

Originally Posted by DanH (Post 1362071)
If the issue is undocumented, how are readers expected to know?

Ideally, I would have read my battery?s manual *before* purchasing. Had I thought this deeply about the issues and potential scenarios, then I could decide to either contact the vendor or go with a battery who has good documentation.

(My personal opinion is that EarthX has very good documentation. My battery does not.)

The value of the discussion is to open up readers to a level of detail that may not have otherwise considered. (At least, that is what it has done for me.)

humptybump 07-26-2019 08:01 AM

It appears one of the moderators took it upon themselves to change the title of this thread to exclude EarthX.

I have no control over what moderators do on these forums.


I will repeat two points:
  1. It’s important for users to do their own homework
  2. Technology changes fast and any product statement made today may well be outdated a month from now

BillL 07-26-2019 08:56 AM

Precise explanation required.
 
Quote:

Originally Posted by Bavafa (Post 1361974)
Perhaps this will clarifies this for some of the EarthX users.

Based on my understanding of the EarthX BMS system, in an overvoltage situation (15.2v and up) the battery will blocks the incoming volts but still operates for the voltage out. Of course in such situation, a proper action is to shut down the alternator to protect the $$$$$$ avionics.

Please feel free to set me straight if my understanding of EarthX BMS is incorrect.

With a DC voltage perhaps you can explain exactly how this can happen. Until explained it sounds like magic.

Like it will not accept 17 volts input but sends out 13 volt power on the same wires.

Hartstoc 07-26-2019 09:04 AM

This entire thread highlights the importance of having a regulator with crowbar protection like those offered by B&C Specialties. This will kill the alternator within a few milliseconds of an over-voltage event. Regardless of the BMS installed, the event will not likely even be noticed by the battery.

I have that, AND fully redundant, twin EarthX batteries, either of which can be selected as main via an On-Off-On master switch. That causes the other to be automatically isolated by and charged through a diode array. The diode array has an approximate .25V drop from main bus voltage. Even if the main battery were to shutdown prior to crowbar-activation, the “secondary” battery will not see the OV event before the crowbar shutdown. One ignition and the critical fuel pump are always operated off the secondary battery, so a distracting loss of power will not complicate the pilot’s reaction.


The EarthX BMS includes a delayed response to OV events precisely for the purpose of allowing time for a crowbar shutdown.

I for one applaud the moderator’s action in clarifying without doubt that the described failure did not involve an EarthX battery, but I think any such change in a post or post topic should be clearly identified by the moderator when they make it.- Otis


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