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  #101  
Old 10-20-2017, 04:23 PM
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DanH DanH is online now
 
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Quote:
Originally Posted by cjensen View Post
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.
Thanks Chad.

Did you catch what Ross said about alternators? A list of inexpensive alternators which absolutely shut down following a field power disconnect would be one heck of a sales tool for VPX.
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  #102  
Old 10-20-2017, 04:29 PM
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Quote:
In post #76 Kathy writes:
All products have limitations and the EarthX BMS is no exception to this. We can protect up to 60V and no more. We are trying to be very clear on this subject by saying this is above the limitations of the BMS design.

Kalibr asks:
Do I understand correctly that the overvoltage protection of EarthX batteries works only until the voltage becomes really overly excessive?

Kathy responds:
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.
Kathy, may I humbly suggest the best answer would have been "Yes, that's correct, we cannot guarantee the BMS will protect the battery if bus voltage exceeds 60v".

It would be consistent with the evidence, your previous statements, and your desire to see separate alternator OV protection used with your product.
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  #103  
Old 10-20-2017, 04:39 PM
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For those people who are concerned about whether a 20 amp alternator can product excessive voltage, just put crowbar OV protection on it and then you dont have to worry. I know crowbar OV protection is sold by B&C for their PM alternators.
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  #104  
Old 10-20-2017, 05:31 PM
EarthX Lithium EarthX Lithium is offline
 
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Quote:
Originally Posted by rv7charlie View Post
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.
Of course, there is many different combinations, builds, set ups in the experimental aircraft market.



Quote:
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 see our manual or previous posts concerning this.

Quote:
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.
We can appreciate you trying to understand how the BMS works and the MOSFET technology that is used within the BMS, which is definitely in the newer realm of technology advancements.

We have spent years developing the BMS, (9 to be exact) and we not only have the electrical and mechanical engineers at EarthX, but we have also the expertise of the engineering departments from companies such as Vans Aircraft, Rotax Engines, and the engineers of the many aircraft companies that have implemented using the EarthX brand into their aircraft builds that have helped us design a robust BMS for aircraft. Plus we design to the FAA certified aircraft requirements and commercial product certifications as previously mentioned.
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Last edited by EarthX Lithium : 10-21-2017 at 02:19 PM.
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  #105  
Old 10-20-2017, 05:56 PM
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Quote:
Originally Posted by EarthX Lithium View Post
...expertise of the engineering departments from companies such as ... Viking Engines...
Really!? I feel like I just fell off of a turnip truck.
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  #106  
Old 10-20-2017, 07:08 PM
Kalibr Kalibr is offline
 
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Enough said, I guess
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  #107  
Old 10-20-2017, 07:19 PM
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Quote:
Originally Posted by rv7charlie View Post
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.
Of course, there is many different combinations, builds, set ups in the experimental aircraft market.

OK, I guess I should be more explicit. Those installations will not be limited to 20 amps by low rpm, yet your blanket statements ignore that fact.

Quote:
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 see our manual or previous posts concerning this.

OK, so it is blocking the voltage. What controls voltage rise?
Quote:
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.
We can appreciate you trying to understand how the BMS works and the MOSFET technology that is used within the BMS, which is definitely in the newer realm of technology advancements.

I guess it is relatively new; It invented over a decade after transistors (transistor in 1947 to MOSFET in 1959)
https://en.wikipedia.org/wiki/MOSFET

We have spent years developing the BMS, (9 to be exact) and we not only have the electrical and mechanical engineers at EarthX, but we have also the expertise of the engineering departments from companies such as Vans Aircraft, Rotax Engines, Viking Engines, and the engineers of the many aircraft companies that have implemented using the EarthX brand into their aircraft builds that have helped us design a robust BMS for aircraft. Plus we design to the FAA certified aircraft requirements and commercial product certifications as previously mentioned.
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As a corollary to what scard posted, I might have just fallen off the turnip truck, but I didn't land on my head.

I missed the answer to this one; was it in there?:
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?


If you'd like to get above that 40V (or 60V) limit, here's a link to some 150V+ MOSFETs:
https://www.google.com/search?q=150+...hrome&ie=UTF-8

;-)
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  #108  
Old 10-20-2017, 07:20 PM
Kalibr Kalibr is offline
 
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Seriously though, Kathy, thank you for clarifying the difference between EarthX and Shorai and similar batteries. That gives additional food for thought at least.

Also, I think it is clear that EarthX provides no overvoltage protection above 60v or thereabout and a crowbar OVP is needed.

Regarding the PM alternators and the 20 amps, in fact I am thinking about putting a PM alternator on the other end to be belt driven, so I share Charlie's concern and, unfortunately, I am still confused where this 20 amp threshold is coming from. But it's irrelevant as if a battery has no OVP protection above 60v it may as well have none. So, crowbar OVP is required in any case and it will deal with any overvoltage situation whether it is under or over 60 volts and regardless of whether it is a traditional or a PM alternator.

I just got burned with the NavWorx fiasco, and i am accutely aware that the experimental market is strictly builder/owner beware, and that the vendor assurances are not worth much as the buck stops with me. Which, btw, is Just the way I like it. But at the same time, please forgive my scepticism and please understand my efforts to educate myself as it is my life that's on the line.
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  #109  
Old 10-20-2017, 08:41 PM
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I'm curious. Anyone on the forum ever fried avionics with an AGM battery installed for whatever reason- load dumping, switching the field on/off, OV event?
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  #110  
Old 10-21-2017, 01:03 AM
Bevan Bevan is offline
 
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Quote:
Originally Posted by scard View Post
Really!? I feel like I just fell off of a turnip truck.
I was thinking the same thing!

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