VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Main > Safety
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #91  
Old 10-20-2017, 11:23 AM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,956
Default

Quote:
Originally Posted by rv6ejguy View Post
In the IR alternators I use, pulling power off the field terminal certainly stops the alternator from charging.
I don't doubt that. But, and it's a big but, there are a lot of older IR alternator designs still out there that don't work that way. If we're depending on the control terminal to shut it down, we need to test to be sure it does what we think.

There are probably rebuilt alts on the market that have the same model number, but different internal regulators. Some will work like yours, but there's a good chance that others will be the old style 'on only' control terminal. And as I mentioned in another post, I'm not comfortable with expecting the regulator that just failed to properly control voltage to then protect the system from that overvoltage. Anyone who's done electronics repair work at the component level knows that sometimes a single component can fail, and other times that component can take multiple others with it.

Charlie
Reply With Quote
  #92  
Old 10-20-2017, 11:29 AM
Kalibr Kalibr is offline
 
Join Date: Aug 2015
Location: St John, Steamboat Springs, planet Earth generally
Posts: 38
Default

Charlie, thank you. It confirms my understanding. If I have a crowbar OVP I see no reason for the need to turn off an alternator manually. As such, I think an internally regulated automotive alternator when installed with a crowbar OVP trigger hooked to a contactor in a B lead circuit provides a safe, reliable and very economical solution compared to "aviation" externally regulated alternators. As icing on the cake, this crowbar B lead contactor hookup makes it sensibly safe (as far as overvoltage protection is concerned) to use common lithium motorcicle/powersport batteries, again saving $$ in the process.
I am in the process of designing an electrical system for my build. I am trying to keep it light, simple and economical without compromising the safety. At this point I am not convinced I should be spending extra $$ for "aviation grade" alternators and batteries, which are generally not only much more expensive, but also heavier, more complicated to install (the need for an external regulator), but provide zero additional safety or utility compared to "automotive" replacements.
But I am very open minded and would be very receptive to being convinced otherwise.
__________________
Building a Panther, but lurking here, like many others

Last edited by Kalibr : 10-20-2017 at 11:35 AM.
Reply With Quote
  #93  
Old 10-20-2017, 11:38 AM
Kalibr Kalibr is offline
 
Join Date: Aug 2015
Location: St John, Steamboat Springs, planet Earth generally
Posts: 38
Default

BTW, the Z-24 figure appears in the current edition of the Bob Nuckolls book. It is marked as "interim", but it is not "pulled" or otherwise recalled. Maybe it was pulled at some point, but it is back in the book now.
__________________
Building a Panther, but lurking here, like many others
Reply With Quote
  #94  
Old 10-20-2017, 12:01 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,956
Default

Yep; it was gone for years, and the most recent revision had it reinserted.

I'm using the IR alt with that circuit on my -4, and my alt engine powered -7 will use a pair (dual IR alts with dual contactor circuits).
Reply With Quote
  #95  
Old 10-20-2017, 12:59 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 4,619
Default

Quote:
Originally Posted by rv7charlie View Post
I don't doubt that. But, and it's a big but, there are a lot of older IR alternator designs still out there that don't work that way. If we're depending on the control terminal to shut it down, we need to test to be sure it does what we think.

There are probably rebuilt alts on the market that have the same model number, but different internal regulators. Some will work like yours, but there's a good chance that others will be the old style 'on only' control terminal. And as I mentioned in another post, I'm not comfortable with expecting the regulator that just failed to properly control voltage to then protect the system from that overvoltage. Anyone who's done electronics repair work at the component level knows that sometimes a single component can fail, and other times that component can take multiple others with it.

Charlie
Every Denso alternator I've seen (and that's a lot) with a separate field terminal works this way. I don't use ones without a field terminal on anything, especially aircraft. You're simply complicating your life if something goes wrong.
__________________

Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW since 2003- 422 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm


Reply With Quote
  #96  
Old 10-20-2017, 01:17 PM
EarthX Lithium EarthX Lithium is offline
 
Join Date: Feb 2014
Location: Windsor, CO
Posts: 208
Default

Quote:
Originally Posted by Kalibr View Post
Do I understand correctly that the overvoltage protection of EarthX batteries works only until the voltage becomes really overly excessive? And that a crowbar OVP is required in any case, just like with any other battery?
If that's the case, what does it make an EarthX "aviation" battery any more "airworthy" than any other lithium battery from one of the major brands (for example, Shorai) with comparable Ah and CCA ratings? In many cases, you could get a "motorcycle/powersport" lithium battery with similar ratings for significantly less $ and it would even weight less than the "aviation" battery.
Thank you for the questions. No, you are not correct about the overvoltage protection on the EarthX. The over voltage protection begins at 16V and can continue to protect up to a voltage of >60V. In the EarthX manual this protection is explained in detail.

The crowbar protection is required for alternator/generators that are greater than 20 amps max (non pad mount alternators). This means that if you have a Rotax 912, 914, 915 or 582 engines, you do not need to install an additional crowbar protection as they are 18Ah max output. But if you have a Lycoming IO-360, 60 amp alternator, you do need to make sure that you have over voltage protection. This over voltage protection will also protect all the expensive electrical equipment in your plane too!

You ask, what makes the EarthX aviation battery more “airworthy” than the common motorcycle line brands on the market, which is a great question. The EarthX aircraft batteries are tested to RTCA DO-347 and RTCA DO-160 FAA standards for lithium batteries used in aircrafts (these are the requirements for a certified battery). There is only one other lithium brand out there that test to this standard and that is True Blue. The ETX680C, ETX680, ETX900 and ETX1200 currently in production and soon the ETX900-VNT have a completely different battery management system than the motorcycle batteries EarthX builds with built in redundancy. This is explained in detail in the manual. They also have LED fault light monitoring which is a means of communications to the pilot to the state of health and state of charge of the battery. What is most important about this is the detection of a defective cell. You do not want to use a defective lithium battery. Note: this is what happened with Boeing, they had a manufacturing defect in some of the cells. If you have no issues with your charging system, but you use a defective lithium battery, you can cause a cell rupture. The difference in price from our motorcycle line to our aircraft one with the same performance spec’s is $30 more for these additional design/safety features. We did not want price to be the reason for someone to choose a motorcycle battery over the aircraft version which does costs more to build.

And for your last question, why not use a motorcycle/powersport brand like Shorai because it is cheaper? As you mentioned Shorai, we will focus on them but the same reason will hold true for many of the lithium batteries on the market too. Please read their manuals for specifics on each brand.
First, Shorai itself specifically states on their website to not use their batteries in aircraft and there is no liability or warranty coverage if you do. Second, the EarthX aircraft batteries are designed for aircraft charging systems and are tested to very high quality safety standards set forth by the FAA (RTCA DO-347, RTCA DO-160). Shorai does not do this. Third, Shorai does not offer batteries with enough capacity for aircraft. Their largest sized battery would be a significant decrease in capacity from what aircraft currently use which is a very important consideration in that if your alternator/generator has failed during flight and you are on battery power only, you don’t just pull over in a plane. Fourth, Shorai has no manual listed that has sizing, performance or design limitation for their batteries. It is not enough to match a lead acid or another lithium battery based solely on cranking amps as you also have to consider charging; you must know the maximum charge current the battery is designed to accept. We have a detailed explanation of this on the website. Fifth, Shorai has no protection built in, they have cells in a plastic case. There is no over discharge protection, no over charge protection, no heat protection, no short circuit protection and no cell balancing technology. EarthX has all of this. And lastly, Shorai has no means to alert you to a cell defect such as the LED fault light indicator that the EarthX does. The importance of this was listed previously in this post.

These are the reasons why aircraft manufacturers do not use the “motorcycle/powersport” lithium batteries you mentioned or even some of the lithium batteries that are being marketed to the aircraft market. This is also the reasons why the experimental engine companies do not use them. They are not the same and they are cheaper for a reason.
__________________
Fly Lightly,

Kathy
Reply With Quote
  #97  
Old 10-20-2017, 01:43 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,956
Default

That 20 amp number keeps showing up in your posts, but there is no explanation of the engineering or physics behind it.

You just explicitly stated that no overvoltage protection is needed if the alternator is 20 amps or less. You also state that your battery can't protect itself if voltage gets above ~60 volts. Consider this very real scenario:

VFR a/c with minimal electrical loads & 18A alternator (to keep it lower than your spec'd current limit). The regulator fails, and voltage starts climbing. At some point, your battery will be fully charged. There are minimal or no other loads on the alternator. How high will the voltage go? (Hint: pretty good odds, higher than 60 volts.) What happens to the battery?
Reply With Quote
  #98  
Old 10-20-2017, 02:11 PM
EarthX Lithium EarthX Lithium is offline
 
Join Date: Feb 2014
Location: Windsor, CO
Posts: 208
Default

Quote:
Originally Posted by rv7charlie View Post
That 20 amp number keeps showing up in your posts, but there is no explanation of the engineering or physics behind it.

You just explicitly stated that no overvoltage protection is needed if the alternator is 20 amps or less. You also state that your battery can't protect itself if voltage gets above ~60 volts. Consider this very real scenario:

VFR a/c with minimal electrical loads & 18A alternator (to keep it lower than your spec'd current limit). The regulator fails, and voltage starts climbing. At some point, your battery will be fully charged. There are minimal or no other loads on the alternator. How high will the voltage go? (Hint: pretty good odds, higher than 60 volts.) What happens to the battery?
Please see post#27 which did address these questions.
__________________
Fly Lightly,

Kathy
Reply With Quote
  #99  
Old 10-20-2017, 02:13 PM
cjensen's Avatar
cjensen cjensen is offline
 
Join Date: Jun 2005
Location: Milwaukee, WI area
Posts: 2,960
Default

Quote:
Originally Posted by DanH View Post
The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?
Wanted to be sure an answer this as soon as I could, 30ms at or above 15.9v or 31.9v before the VP-X shuts off the alt field.
__________________
Chad Jensen
RV-7, 5 yr build, flew it 68 hours, sold it, miss it.
Vertical Power - Support, Astronics/Ballard Technology
920.216.3699

chad.jensen@astronics.com
Reply With Quote
  #100  
Old 10-20-2017, 03:05 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,956
Default

Quote:
Originally Posted by EarthX Lithium View Post
Please see post#27 which did address these questions.
I assume that you're referring to this:
So what's different about lithium iron chemistry that makes it able to handle a 20 amp alternator in an overvoltage situation, but not handle a 30 amp alternator in the same situation, meaning the same level of over-*voltage*? Our manual may be causing the confusion when we say over-voltage protection is not required on “<20 Amp pad mount standby alternators”. The confusion is that it has nothing to do with it being a < 20 amp alternator. The real reason is the “pad mount standby alternator”, for a pad mount alternator RPM is much lower and as such the unregulated voltage (in the event of a regulator failure) will be much lower. Low enough that Earth’x BMS can block any charge current at those voltages.

You do realize that PM alternators are being installed on the other end of experimental engines, too, driven by belts at their original design rpm? This is most likely to be done by those obsessing over weight; the same people that will be drawn to lithium chemistry batteries.

For the wound-field models that B&C & others sell for the vacuum pad: Are you saying that your engineering dept has spun one at vacuum pad rpm with the output feeding the field, minimal-to-no load, and the voltage never rises above your 60V threshold?

Oh, and it didn't answer the question....

I ask the above question because if the BMS is *blocking* the voltage, it's removing the load, which will allow voltage to rise (probably a lot). On the other hand, if it's *shunting* the current to ground, it's *supplying* a load to hold the voltage down. So, which?

Please understand that I'm asking these questions because I can't get some of the earlier answers to line up with a couple of careers worth of experience herding electrons. I want the new tech to work, but we need to understand all the differences from the old tech to have confidence in it.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:23 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.