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  #1  
Old 10-10-2017, 02:25 PM
EarthX Lithium EarthX Lithium is offline
 
Join Date: Feb 2014
Location: Windsor, CO
Posts: 190
Default Over voltage required for EarthX battery

Dear Van’s Forum readers:

Safety is of top importance to EarthX as we know it is to you too. If you are using an EarthX battery and have an alternator/generator that puts out more than 20 amps, please read.


After careful consideration, as we know this is the experimental community and not the certified aircraft community, we have changed the verbiage throughout our documentations about the importance of having over voltage protection from “strongly recommended” to “require” if you have a 20amp+ alternator/generator charging system on your aircraft.

We also want to stress the importance of also using the fault light indicator by either installing an LED light on your control panel or connecting it to your EFIS. This fault light is a mode of communication to you that something is outside the normal parameters of either your charging system or the voltage of your battery but most importantly, it will also indicate if there is an internal issue within the battery. (We have marked these lights 50% off for the next month to encourage the use of this important safety feature on the website).

The reason for the change in verbiage is for the following real situation that happened to an RV-8 owner/pilot who had a 60 amp alternator charging system. With his permission, we want to share with you what happened so it does not happen again. There will be an article in Kitplanes magazine that will touch on this situation in their November issue, and there will also be an article in EAA Sport Aviation magazine possibly the December issue, plus if you have been to an EarthX presentation at Sun N Fun or EAA Oshkosh, we also discuss this situation as we want to avoid it ever happening.

I will summarize the situation greatly in saying there was a very seasoned, experience pilot and co-pilot, who had recently changed many things in this RV-8 aircraft including wiring and took his plane up for a test run. He had an EarthX aircraft battery in his plane.

Note: He did not have over voltage protection on his plane. He did not connect the LED fault light to his panel or to his EFIS system, and the battery was located with cabin access.

During his flight, his regulator failed and his voltages climbed up and remained at +29V and 40+ amps for many minutes. (After approximately 6 minutes, his alternator failed too). A couple of times the voltage spiked above 60V per the data from the EFIS. The over voltage protection for the EarthX batteries is a maximum of 60V, even though the FAA requires protection only up to 19.8V. When the voltages spiked, it was enough to cause a cell rupture as the pilot smelt a funny electrical smell and with continued high voltages and amps, the battery did go into thermal runaway. As the pilot had just had the new wiring done, he thought it was related to this and immediately started to look for a place to land. In the stress of the situation, the pilot thought he turned his alternator off. He did not. The location of the battery was not sealed outside the firewall so heavy smoke was able to enter the cabin. There was no visible flames and no wiring was melted but there was a lot of smoke inside the cabin. He was able to open the canopy to get fresh air and did land the plane. The pilot’s and the plane were unharmed.

Had his plane had over voltage protection, once his regulator failed, within a millieseconds the overvoltage protection would have been engaged, there would have not been any high voltages or high amps going into the battery (lead acid or lithium), the alternator would not have failed and certainly no smoke or thermal runaway of the battery. This is a very simple, inexpensive safety feature that is very wise to have no matter what battery you use. In a certified aircraft, it is a mandatory safety feature. The pilot was very honest and truthful with us in saying that in a situation like this, you can make mistakes. He really thought he turned the master off. To err is human. Therefore, we have changed the verbiage from “strongly recommend” to “require” as we want to eliminate this situation from happening again.
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Last edited by EarthX Lithium : 10-10-2017 at 03:59 PM.
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  #2  
Old 10-10-2017, 02:50 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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I really appreciate your willingness to share the full story and the new recommendations. Transparency, even when your product was not the cause, leads to increased safety and confidence in your support and products. Bravo.
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  #3  
Old 10-10-2017, 03:41 PM
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ppilotmike ppilotmike is offline
 
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Location: Denver, CO
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Default +1

Bravo, Kathy..
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Old 10-10-2017, 04:28 PM
Fast Eddie B Fast Eddie B is offline
 
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Location: Mineral Bluff, GA
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Am I to understand that overvoltage protection remains optional with the standard 20A alternator in a stock ROTAX 912?

And would these precautions be similarly recommended for another brand of lithium iron battery? Id guess they would.
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Old 10-10-2017, 04:54 PM
sblack sblack is offline
 
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When you say OV protection, it is not just the indicator light, but more importantly the OV breaker tripping to take the alt off line correct?

All new tech has its learning curve. Ask Boeing

sb
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  #6  
Old 10-10-2017, 04:58 PM
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bret bret is offline
 
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Thank you for sharing, so thermal runaway and no flames? that's good to hear, is this normal or odd? I have your 900 series, think I will be installing the suggested items now....
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Old 10-10-2017, 05:02 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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I understand the need for overvoltage protection; any electrical device can be damaged if voltage goes high enough, and there's no reason to expect an EarthX battery (and its BMS) to be any different.


But I have not yet seen an explanation for the alternator's current rating being a factor in any of these discussions about EarthX batteries. An alternator only supplies the current required to maintain the regulator's voltage set point. If there's an insignificant load on the system, there will be insignificant current flowing from the alternator, whether it's a 20A model or a 120A model. If voltage sags below the regulator's set point, the alternator current will continue to increase until it hit's the alternator's limit, or the regulator voltage set point is reached.

Does the EarthX BMS depend on the limited capacity of the alternator to control maximum charging current, or does the BMS control the charge current? If the latter, why the discussion (and limits) to alternator amp ratings?
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Old 10-10-2017, 05:06 PM
EarthX Lithium EarthX Lithium is offline
 
Join Date: Feb 2014
Location: Windsor, CO
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Quote:
Originally Posted by Fast Eddie B View Post
Am I to understand that overvoltage protection remains optional with the standard 20A alternator in a stock ROTAX 912?

And would these precautions be similarly recommended for another brand of lithium iron battery? Id guess they would.
You are correct, overvoltage protection is optional with any charging system that puts out less than 20 amps, which includes Rotax Engines.

As far as other lithium iron battery brands, you would need to confer with them as to their recommendations for this situation. (but I would agree with you that you should have it with not only any other lithium battery, but lead acid too if your charging system can put out more than 20 amps)
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Old 10-10-2017, 05:10 PM
EarthX Lithium EarthX Lithium is offline
 
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Location: Windsor, CO
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Quote:
Originally Posted by sblack View Post
When you say OV protection, it is not just the indicator light, but more importantly the OV breaker tripping to take the alt off line correct?

All new tech has its learning curve. Ask Boeing

sb
When we say over voltage protection, we do not mean a voltage regulator as all engines will have this. The over voltage protection is sometimes referred to as crowbar protection. This is used to protect your plane from over voltages which can damage your expensive electronics in your plane and protect the battery too. It is an automatic shut off of the alternator/generator if the regulator fails and voltages are left unchecked or "regulated."
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  #10  
Old 10-10-2017, 05:15 PM
EarthX Lithium EarthX Lithium is offline
 
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Location: Windsor, CO
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Quote:
Originally Posted by bret View Post
Thank you for sharing, so thermal runaway and no flames? that's good to hear, is this normal or odd? I have your 900 series, think I will be installing the suggested items now....
People associate the "flames" from the lithium batteries you see on the news which are Lithium Cobalt chemistry. It is very rare for a LiFePo4 battery to produce any type of flame but it does produce a lot of smoke, which is not good in the cockpit. This is why we also do not recommend putting the batteries within the cockpit. We will have a new, vented battery for this type of application within the month, it will be the ETX900-VNT.
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