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  #21  
Old 10-10-2017, 07:41 PM
scsmith scsmith is offline
 
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Thank you for posting this for everyone's consideration and awareness.

Thank you for mentioning that the only real "last-resort" safety is to have an externally vented, fire-proof battery enclosure.
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  #22  
Old 10-10-2017, 08:00 PM
Chkaharyer99 Chkaharyer99 is online now
 
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Thank you for the informative thread and follow ups Kathy. Great example of transparency.
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  #23  
Old 10-10-2017, 08:05 PM
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Quote:
Originally Posted by AlexPeterson View Post

To answer your question, if the ONLY power supplying the internal regulator comes from the field line, then only a crowbar on this field line is needed.
Pretty sure the ordinary Plane Power is a true crowbar equipped internal.
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  #24  
Old 10-10-2017, 08:32 PM
rv7charlie rv7charlie is online now
 
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Quote:
Originally Posted by DanH View Post
Pretty sure the ordinary Plane Power is a true crowbar equipped internal.
I'd love to see the drawing of the circuit that does that.
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  #25  
Old 10-10-2017, 09:49 PM
jwilbur jwilbur is offline
 
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Default VP-X

If you use a VPX, it will shut down the alternator field if it senses voltage getting too high.
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  #26  
Old 10-11-2017, 07:02 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by rv7charlie View Post
I'd love to see the drawing of the circuit that does that.
Contact 'em and ask:

Hartzell Engine Technologies
2900 Selma Highway
Montgomery, Alabama 36108
Toll Free (877) 359-5355
Phone +1(334) 386-5400
Fax +1(334) 386-5410
sales@plane-power.com

in the meantime, from the "Internally Regulated Experimental Alternator Information" page:

Plane-Power Alternators are the only internally
regulated aircraft Alternators that have built-in
crowbar over voltage protection. The built-in
circuit monitors the regulated voltage and if it
detects a higher than normal voltage will trip your 5-
amp enable circuit breaker and instantly disable the
alternator before any damage can be done to your
expensive avionics. No external relay etc. is
required. The over voltage protection is where it
should be built-in and controlling the alternator not
extra add on devices that add cost, weight,
complexity and reduce reliability!


And see statement, lower right, this page:

http://planepower.aero/pdf/AL12_EI60%20Installation.pdf

For sure, pulling the field breaker shuts down the alternator.
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  #27  
Old 10-12-2017, 11:51 AM
EarthX Lithium EarthX Lithium is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Do you not see the problem with this? More importantly, at least for certified aircraft owners, does the FAA not see the problem with this? Will STCs for your batteries include a requirement for the owner to downsize their alternator to fit battery requirements? What is the battery management system actually managing? Does it not manage the charge current to each cell, in addition to managing the max discharge current? If it doesn't, what prevents overcharging the battery?

An overvoltage event is a potential device-killer, regardless of the current capability of the alternator. The proper way to manage an overvoltage event is to manage the overvoltage event; not limit alternator current.

Again. The current capacity of the alternator is only tangentally related to the output voltage. If the regulator fails, and there's, lets say, 20 volts on the bus, and your battery is fully charged, then the BMS is going to see 20 volts on its input. Are you saying that your battery can handle that 20 Volts at 20 amps indefinitely, but it can't handle 20 volts at 30 amps? Will the current flowing into the battery not vary with charge level?

I'm very confused by the chemistry & physics; apparently I just don't grasp how your battery chemistry works. In a lead-acid battery, the voltage is what delivers the ultimate death blow. Many AGM and flooded cell batteries have been killed by little 1 amp & 2 amp 'trickle' chargers that don't monitor charge level. There is very little current at work, but as the battery becomes fully charged, the voltage rises above the normal ~14V level to 15-16 volts. Charge *current* stays low, but it's relentless, being pushed by the excess voltage. Eventually it boils off the electrolyte, with either battery design.

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*?

Do you not see the problem with this? More importantly, at least for certified aircraft owners, does the FAA not see the problem with this? Will STCs for your batteries include a requirement for the owner to downsize their alternator to fit battery requirements? What is the battery management system actually managing? Does it not manage the charge current to each cell, in addition to managing the max discharge current? If it doesn't, what prevents overcharging the battery? The FAA doesn’t dictate the design only the performance and safety limits. An STC will have to specify an alternator max rating. For our battery, as well as any lithium battery, has a max charge current rating. The EarthX BMS manages many things, for further details please see our manual (can be downloaded from our website, http://earthxbatteries.com/wp-conten..._111017_S2.pdf). As for the over-voltage protection, here is the verbiage out of our manual.
COLOR="Blue"]"]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 1 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).”

An overvoltage event is a potential device-killer, regardless of the current capability of the alternator. The proper way to manage an overvoltage event is to manage the overvoltage event; not limit alternator current. Exceeding the charge voltage rating and exceeding the charge current rating are two separate concerns. Exceeding the charge current rating, stresses the cells beyond their normal operating limits, and will result is a shorter service life (i.e. a slow death). Exceeding the charge voltage limit (greater than 20 volts) of a lithium cell leads to a complete breakdown of cell structures; and thermal runaway (i.e a fast death, within 15 minutes).

Again. The current capacity of the alternator is only tangentally related to the output voltage. If the regulator fails, and there's, lets say, 20 volts on the bus, and your battery is fully charged, then the BMS is going to see 20 volts on its input. Are you saying that your battery can handle that 20 Volts at 20 amps indefinitely, but it can't handle 20 volts at 30 amps? Will the current flowing into the battery not vary with charge level? As stated in the manual and excerpt above, the EarthX BMS completely blocks charge current if voltage is greater than 16 volts. (note, it blocks charge current only, discharge current is still available). So to answer your specific question, yes it can block charge current if the voltage at the terminals is 20V, 30V, 40V, 50V, 60V etc.

I'm very confused by the chemistry & physics; apparently I just don't grasp how your battery chemistry works. In a lead-acid battery, the voltage is what delivers the ultimate death blow. Many AGM and flooded cell batteries have been killed by little 1 amp & 2 amp 'trickle' chargers that don't monitor charge level. There is very little current at work, but as the battery becomes fully charged, the voltage rises above the normal ~14V level to 15-16 volts. Charge *current* stays low, but it's relentless, being pushed by the excess voltage. Eventually it boils off the electrolyte, with either battery design. The same holds true for lithium cells; above the rated charge voltage, even the smallest amounts of current will damage the battery (not from boiling but from irreversible changes in cell structures). So again, if the voltage is above 16 volts, charge current is completely blocked (zero charge current).

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.

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  #28  
Old 10-12-2017, 12:41 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by EarthX Lithium View Post
This design offers charge voltage protection greater than 40V.

As stated in the manual and excerpt above, the EarthX BMS completely blocks charge current if voltage is greater than 16 volts. So to answer your specific question, yes it can block charge current if the voltage at the terminals is 20V, 30V, 40V, 50V, 60V etc.

So again, if the voltage is above 16 volts, charge current is completely blocked (zero charge current).

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.
Kathy, taken all together, it appears the BMS blocks charge current when the level reaches 16 volts...but that built-in ability to block is exceeded by the potential voltage level of an unregulated full size alternator. Put another way, when voltage reaches some unidentified high level (higher than 40 V), it can burn through the BMS protection.

Has to be true, or there would be no need to protect the battery with a crowbar.
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Last edited by DanH : 10-12-2017 at 01:07 PM.
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  #29  
Old 10-12-2017, 12:59 PM
rv7charlie rv7charlie is online now
 
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Quote:
Originally Posted by DanH View Post
Kathy, taken all together, it appears the BMS effectively blocks charge current above 16 volts...but that built-in ability to block is exceeded by the potential voltage level of an unregulated full size alternator. Put another way, when voltage reaches some unidentified high level (higher than 40 V), it can burn through the BMS protection.

Has to be true, or there would be no need to protect the battery with a crowbar.
Or, it operates in a universe where Ohm's Law is written differently.....
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  #30  
Old 10-12-2017, 01:41 PM
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Or... instead of the word blocked at a particular voltage, is the battery going to open circuit internally to protect the cells and by that action allowing the full unrestrained runaway voltage from the alternator to go straight to the main bus and burn everything up?
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