What's new
Van's Air Force

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

BMS and you?re failure scenarios (Not an EarthX)

humptybump

Well Known Member
Update: I have never said who the battery vendor is. After a good open discussion of several days, a moderator took it upon themselves to change the title of my thread to add “(Not EarthX)”. I did not request that change.



On a recent flight, on a cruise descent, while about 30 minutes from landing, my engine monitor gave an over voltage warning.

A brief diagnostics determined it wasn’t something I’d resolve in flight.

Background: My plane has one alternator, one main battery, and one “minimum essentials” backup battery. The backup battery is “dumb” while the main battery is newer - (a recent replacement) - and has an integrated battery management system (BMS).

No worries I thought. I’ll switch off the alternator and the main battery is more than enough for the last 30 minutes with plenty of power to spare.

Oops.

It appears the undocumented BMS behavior in my situation is to disconnect itself and shutdown for some unknown amount of time.

I landed with my backup systems without incident.

The moral? My redundant electrical system isn’t as redundant as I had thought. I had assumed an alternator failure would leave me with main and backup batteries. The reality is some basic failure scenarios could immediately remove two sources of power, not just one.

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.
 
Last edited:
Glen,

It would be interesting to know what the indicated voltage was when the overvoltage was alarming. Also what is your overvoltage point in the warning settings.

Now the big question. Did the battery go open causing the overvoltage event or open as result of the overvoltage event?

What type of battery (I assume EarthX), type of alternator/regulator, and type of overvoltage protection.

This incident is a good reminder of the unknown consequences that can result from experimental electrical design. What pilot actions were necessary to activate the essential buss, did everything have to reboot, can the buss be left on and remain isolated from other systems, what is on the essential buss.

A lot can be learned from this.

George Meketa
RV8
 
Good post Glen. If you're electrically dependent, be sure your backup power source is available no matter what happens to the alternator and primary battery. We recommend that you can fully isolate these from backup power.
 
Actually,
Rather than assume, please do tell us the battery manufacturer. Not all BMS?s are the same.
 
Let me try to get some answers:

My airplane is basic. Dual mags.

My warning is set at 15.0V. I observed 15.3V while I was attempting to diagnose.

It’s unclear when the battery disconnected.

After shutdown, it reset at some point. The next morning the battery showed 13.1V. The “dumb” battery showed 13.7V.

I’m in the middle of correspondence with the manufacturer to better understand the BMS. Once I have a response, I should be able to answer “which came first?”

I agree that not all BMS are the same. If you’re battery has a BMS and it’s not well documented, then it’s a good idea to contact the manufacturer.
 
Small update:

I?ve attempted to reach out to the manufacturer of the battery I am currently using as my main battery.

Thus far, the manufacturer has not provided any details of how their BMS behaviors - specifically what events will cause the BMS to disconnect the battery from the circuit and how long before it attempts to reconnect.

Until my event, I never thought to ask these questions. I now consider this critical data to have when a BMS is in my electrical system.
 
Glen,
It sounds like your main BMS battery is NOT an EarthX but some other brand. Am I correct?
 
i have an electrically dependant system. 2 batteries, independant of each other and fed by an alternator that will run the system without batteries. these are earth x . i had wondered this exact scenario. i had assumed that the battery would go online again as soon as the overvoltage was removed. if this is not the case i guess i have to dig into this before first flight.
 
I would love to know if this was a EarthX and if not how a EarthX would handle this situation since I am sonsidering the Surefly ignition system.
G
 
I would love to know if this was a EarthX and if not how a EarthX would handle this situation since I am considering the Surefly ignition system.
G

Your comment is apropos. If you have an “electric dependent design or mission” then it’s good to know how it will respond to adverse scenarios of your electrical sources.

If you’re battery has a BMS and it’s not well documented, then it’s a good idea to contact the manufacturer.
 
Last edited:
I respect Glen's desire not to comment on the brand, at least till more info has received from the manufacture.

I know EarthX BMS will shut the battery completely for a period of time if there is a sudden and large draw of power like a short circuit at the battery. But the incident does not seem like a large draw from the battery similar to a short circuit.
 
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.
 
Last edited:
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.

I may have experienced the combination of these two functions.

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.

So tell us whose battery incorporates the above BMS functions.
 
SNIP..

Oops.

It turns out the undocumented BMS behavior in an over voltage situation is to disconnect itself and shutdown for some unknown amount of time.

I landed with my minimal backup systems without incident.

The moral? My redundant electrical system isn?t as redundant as I had thought. I had assumed an alternator failure would leave me with main and backup batteries. The reality is some basic failure scenarios could immediately remove two sources of power, not just one.

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.

This has been discussed in the past, but I fear the implications of such ?Self Protect? batteries are not being considered in electrical designs.

What should be the most reliable component in electrical power schemes is perhaps anything but. Now let?s extend this to a two BMS type battery ship, and one over voltage incident turns off both batteries. What will all you with electrically dependent ignitions and/or electronic fuel injections do when all power goes away and you have no option to restore it? I guess you can have a third or more normal chemistry backup batteries but that goes against more common sense options.

A battery design that automatically protects itself on over voltage by isolation violates my design criteria, as does any battery that cannot tolerate a short over voltage condition long enough for the pilot to recognize what is going on and trip the alternator(s). As the OP states, make sure you know how stuff works before you put it in your airplane.

Carl
 
What I’ve learned by reading the available literature is that each vendor implements BMS in their own way.

Some BMS will isolate the battery in an over voltage situation. Other BMS will prevent further charging during an over voltage situation. Most BMS will disconnect to prevent excess discharge and prevent rapid discharge (aka a short). Some have behaviors triggered by temperature.

Based on the vendor’s response, It’s less likely the over voltage condition caused the battery to disconnect in my aircraft.

The key to designing an electrical system is to know the behaviors and assess them against your needs and the systems which rely on electricity.


While I realize readers want to know which battery I have, it is my recommendation that everyone who uses a battery with BMS familiarize themselves with their particular battery and it’s BMS behaviors and then incorporate that information into the operating procedures of their aircraft.
 
Last edited:
Sounds like a good argument for automatic overvoltage protection. And if you're electrically dependent, some kind of isolated feed for your secondary power source.

That said, vendors with BMS incorporated in their batteries should provide better descriptions of the trigger conditions for protection modes.
 
This has been discussed in the past, but I fear the implications of such ?Self Protect? batteries are not being considered in electrical designs.

What should be the most reliable component in electrical power schemes is perhaps anything but. Now let?s extend this to a two BMS type battery ship, and one over voltage incident turns off both batteries. What will all you with electrically dependent ignitions and/or electronic fuel injections do when all power goes away and you have no option to restore it? I guess you can have a third or more normal chemistry backup batteries but that goes against more common sense options.

A battery design that automatically protects itself on over voltage by isolation violates my design criteria, as does any battery that cannot tolerate a short over voltage condition long enough for the pilot to recognize what is going on and trip the alternator(s). As the OP states, make sure you know how stuff works before you put it in your airplane.

Carl

Bingo!, Point taken on the battery designs that automatically protect themselves. I built a aircraft (Rans S-20 Raven) with full Dynon Skyview suite and a battery with BMS. When I turned on my master to start the aircraft, the BMS shut the battery off and threw a fault light. The fault would clear sometimes and sometimes it wouldn't.

It got me thinking. If I was on a gravel bar or beach, or in the backcountry of Idaho and the BMS shut my battery off, I have no way to start my aircraft. I sent the battery back to the manufacturer and they immediately sent me a new one. I asked if they will let me know what had happened to my original battery once the received it and put it on the bench. They said they are not setup to troubleshoot and get back to the customer so I never knew what the problem was or how it is designed. Hence, the BMS system to me is pure friggen magic (PFM).The replacement battery worked as advertised and zero problems and the company was a pleasure to work with.

I am considering building an RV-14 and have been giving the electrical design careful thought. Not sure it will include Lithium Ion battery with BMS. YMMV

Best,
Jim
 
This has been discussed in the past, but I fear the implications of such “Self Protect” batteries are not being considered in electrical designs.

What should be the most reliable component in electrical power schemes is perhaps anything but. Now let’s extend this to a two BMS type battery ship, and one over voltage incident turns off both batteries. What will all you with electrically dependent ignitions and/or electronic fuel injections do when all power goes away and you have no option to restore it? I guess you can have a third or more normal chemistry backup batteries but that goes against more common sense options.

A battery design that automatically protects itself on over voltage by isolation violates my design criteria, as does any battery that cannot tolerate a short over voltage condition long enough for the pilot to recognize what is going on and trip the alternator(s). As the OP states, make sure you know how stuff works before you put it in your airplane.

Carl

+1 here

This is why I stuck with SLA technology on the 10 build. My VR will drop the field voltage on OV condition, protecting the electronics. However, I have good certaintity that my batteries will be there to get me on the ground safely.

Some of these BMS systems are designed to prevent thermal runaway and not necessarily to keep your airplane flying. They are not holistically integrated into a redundant electrical system. If you have a failed VR or alt throwing out 17+ amps, it must be shut down to avoid damage to the electronics. If your batteries magically shut down at the same time, you're gliding to the ground. Most redundant electrical systems I have seen, assume that the battery is a constant. If the battery has an internal switch with logic to control it, you would be wise to design your redundancy around the potential that switch becomes open at the same time you lose an alternator; keeping in mind that many alternators require a battery in the circuit to perform reliably.

If my ship was VFR and not electrically dependant, I would absolutely have a lithium battery in my plane.

These batteries are being marketed as SLA replacements. However, that simply isn't the case with some of the unique redundancies we have been building into our electrically dependant aircraft.

Larry
 
Last edited:
While I realize readers want to know which battery I have, it is my recommendation that everyone who uses a battery with BMS familiarize themselves with their particular battery and it?s BMS behaviors and then incorporate that information into the operating procedures of their aircraft.

Ok, fine. If true, simply confirm your battery was not an EarthX. If it was not an EarthX, nothing splatters on them, and the actual manufacturer can remain unnamed.

If it was, it illustrates a serious problem with "familiarizing ourselves', given we've been repeatedly told the disconnect you've described cannot happen.

BTW, was there something in you battery's literature stating it might disconnect as it did?
 
... was there something in you battery's literature stating it might disconnect as it did?

There was nothing in the literature that I could find. The BMS features they described spoke mostly of preventing over-discharge. After my incident, I dug deeper and found a description of the BMS protecting against occasional voltage spikes.

I knew it would disconnect in an over-discharge situation.

Update: I did receive an email from the vendor regarding my support question and they explained the BMS would disconnect in an over-temperature situation.
 
Last edited:
Safety issue should not be a guessing game.

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.
 
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.

Sorry for your frustration. Different batteries have different BMS features and behaviors. More important is that any details of a particular product today need to be understood as a “point in time”.

Since this thread will be around for potentially months or years, and any particular battery could well change multiple times in that period, the particular battery is less important than the lesson that we all need to do our homework on what we fly.

As a reference point - In my attempt to better understand my options and to insure I don’t answer questions erroneously, I’ve been reading what I can about the BMS from multiple vendors. I already know there are misunderstandings about more than one vendor’s BMS.
 
Some EFIS systems include an optional backup battery. While that won't help an electronic ignition, it will at least keep the more important parts of the instrumentation alive.

Dave
 
Some EFIS systems include an optional backup battery. While that won't help an electronic ignition, it will at least keep the more important parts of the instrumentation alive.

It’s a good option for “point based backup power”. In my case, I have a “smart idiot light” monitoring my backup battery just like the one I have on my main battery; and my backup can be isolated quickly and easily.

The backup was more than capable of handling my essential equipment for the 30 minutes of flight.
 
Last edited:
It?s a good option for ?point based backup power?. In my case, I have a ?smart idiot light? monitoring my backup battery just like the one I have on my main battery; and my backup can be isolated quickly and easily.

The backup was more than capable of handling my essential equipment for the 30 minutes of flight.

30 minutes is not sufficient, especially for an IFR plane.

Carl
 
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.
 
30 minutes is not sufficient, especially for an IFR plane.

Carl, I agree that 30 minutes of backup is not prudent for an IFR flight.

My description of a “30 minute flight” was not an indication of the system’s limit. As I said, “The backup was more than capable ...”
 
Last edited:
30 minutes is not sufficient, especially for an IFR plane.

Carl

It was sufficient to complete this flight obviously. Reserve capacity needed will depend on your mission and where you fly, along with the proximity of airports to your flight path. The OP said "more than sufficient" which I take to mean more than 30 minutes in this case.
 
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.
 
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.
 
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)."
 
Not an EarthX

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.
 
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. :)
 
Last edited:
Glen,

Previously you stated:

It turns out the undocumented BMS behavior in my situation is to disconnect itself and shutdown for some unknown amount of time.

Then this:

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?
 
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.)
 
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
 
Precise explanation required.

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.
 
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.
2v2ELzPE8xBELK5.jpg


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
 
Last edited:
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 chance in a post or post topic should be clearly identified by the moderator when they make it.- Otis

+1 to both, given Glen refuses to make a clear statement of fact, to wit "The battery in question was not an EarthX"....assuming it was in fact not an EarthX.

As for the actual brand name and battery model...


  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


...future product change by the manufacturer, which may or may not happen, does nothing for current users. What we're asking for is the EAB version of a Service Difficulty Report. Posting the brand and model is the responsible thing to do.
 
Last edited:
Otis - It sounds like you have a well thought out electrical design.

Primarily as a personal query, do you have discrete panel indicators for your batteries and alternator?

I have a smart indicator on each battery as well as my EMS showing bus voltage. I currently do not have an automatic “crowbar” component.
 
Last edited:
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.

Yep, this is the part I trip on.

I had one over voltage incident over the years, and that is when I found out crowbar over voltage protection is great in theory but this time it did not work. It took a few minutes to recognize what was going on, then I tripped the alternator. Voltage got to about 16vdc, not enough to fry anything.

My point, as the alternator output voltage increased the standard dumb battery I was using transformed the excess output current into heat. This provided a few minutes of time to figure out what was going on as the battery load kept the buss voltage from spiking. Based on all this discussion, I assume (correct me if I'm wrong) that when a BMS systems protects the battery from over voltage the battery is removed as a load on the alternator. So applying to my incident the buss voltage would have continued to rise.

I wonder how many people flying with such batteries actually test whatever over voltage protection they are using. Considering the critical aspect, perhaps a primary and backup over voltage protection schemes would be appropriate.

Carl
 
Sounds like...

we need to keep in mind how voltage (pressure) works.

If an alternator/regulator in runaway is applying 17 volts of electromotive force across a pair of terminals that are in common with a battery, and said battery has a BMS that will not allow an inward (charging) current at that voltage level, the battery is effectively removed as a load and its float voltage of 13 or 14 volts is irrelevant to what the circuit will see. The impressed voltage from the alternator is all that matters in that case. The alternator/regulator will have to behave as if the battery is not present until the BMS decides to let the battery act as a load again (accept an inflow charging current).

The fact that this taking-itself-offline behavior is temporary and automatically reversible for the EarthX BMS is a crucial point, and seems to be the crux of what Glen experienced when his non-EarthX battery surprised him and went offline for an unquantified period of time even after the bus voltage dropped below overvolt levels.

Just my armchair quarterbacking, here. But I wanted to jump in and clarify that 13V and 17V cannot exist on the same wire at the same time. Voltage is pressure - not flow, not widgets.

This thread has been very helpful in stimulating research and forethought, and in boosting confidence in the EarthX BMS in my planned application (2 B and C alternators and regulators with crowbar OVP).
 
Last edited:
From my reading of different BMS?s behaviors, a key feature of the EarthX BMS appears to be its ability to differentiate a high operating temperature while under extreme load vs under a more normal load. This differentiation means it can shutdown under the condition of high internal temperature from excessive starter time but not shut down from high temperature environmental conditions.

While high environmental conditions are not good for the battery, the BMS has been designed to continue providing electricity. This is important for aircraft but less important for typical ground vehicles.

Assuming my situation was caused by high heat (still not yet determined) I can assume the BMS in my battery does not differentiate the reason for heat and lumps it all under the category of ?battery self preservation? and takes preventative action to protect itself.
 
Assuming my situation was caused by high heat (still not yet determined) I can assume the BMS in my battery does not differentiate the reason for heat and lumps it all under the category of ?battery self preservation? and takes preventative action to protect itself.

Can you tell us where your battery is mounted? FWF or aft? Or is that super secret information also?
 
Can you tell us where your battery is mounted? FWF or aft? Or is that super secret information also?

Nothing here is “super secret information”. I’m not sure why there is an interpretation to the contrary.

I’ve not mentioned the vendor as the situation is still under investigation and it would be inappropriate to suggest anything disparaging without all of the facts.

My RV-8 has the battery on the firewall.
 
Last edited:
your crowbar?

With all this analyzing OP wants us to start doing... this seems like a good time to ask why we don't all have overvoltage tripping devices installed in our airplanes?

B&C and PlanePower alternators have crowbars as standard, and you can buy a standalone crowbar from Bob Nuckolls (plus info on how to implement it), so to me there's really no excuse not to have one, especially if you choose to have a LiFePO battery on board.

Which got me thinking how to test the crowbar in the airplane as part of a maintenance routine: you could connect a variable DC power supply to the B-post of the alternator, turn on the Master switch on the panel (if you don't have an Avionics Master, then pull the breakers/fuses to your expensive electronics), and then increase the voltage until the Field breaker pops. If it doesn't trip by, say, 16V, then you know you have a problem.
 
Last edited:
Otis - It sounds like you have a well thought out electrical design.

Primarily as a personal query, do you have discrete panel indicators for your batteries and alternator?

I have a smart indicator on each battery as well as my EMS showing bus voltage. I currently do not have an automatic ?crowbar? component.

An early description of my system can be found here, but the diagram has an error that is explained in the post but not yet corrected.

http://www.vansairforce.com/community/showthread.php?t=170109&highlight=Dual+batteries

It is absolutely symmetrical, so it matters not at all which battery you choose to act as primary on a given flight, and there are no emergency procedures. The essential loads switches and voltmeters are located in a vertical sub-panel console below the throttle(RV-7A), and the relative voltage readings tell you which is on the main bus and which is on diodes.

If your altetnator has a built-in regulator, replacing it with a B&C and crowbar protected regulator will be a very worthwhile investment.- Otis
 
Back
Top