Matronics Email Lists :: View topic - Limiting Current to a Battery

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Limiting Current to a Battery
Goto page Previous 1, 2

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

echristley(at)att.net
Guest

Posted: Mon Jul 08, 2019 8:40 am Post subject: Limiting Current to a Battery

Look for a "poly fuse" in the aviation section of an auto parts store. These will limit current to the rated value

Sent from Yahoo Mail on Android

 

  	  Quote: 	
		    On Sun, Jul 7, 2019 at 10:01 AM, Jared Yates

<email(at)jaredyates.com> wrote:

 

  I have a question that's only somewhat applicable to E/AB aviation, apologies in advance. But I think it points out a hole in my electrical understanding.



The characteristics of the lithium iron battery I'm running allow it to draw lots of current really fast after the engine starts. If it has been a little while since the last flight, the alternator is at max output for several minutes. The alternator puts out all it can give, and it's less than the battery wants to take.

Stepping out of the hangar, my tow vehicle circuitry includes a wire in the 7-pin connector that provides alternator voltage to the trailer, intending to charge a small battery for a breakaway emergency brake. If I install a larger battery for other purposes, perhaps one like what is in the airplane, and connect it to that line coming from the truck, it seems like it would almost certainly open the fuse on that circuit during that initial high-draw stage.

These two scenarios had me thinking, what methods would one have to limit a hungry battery's draw? I'm imagining some type of circuit that takes in 12-14 volts, and puts out almost the same, but only at some specified number of amps. Almost like a DC-powered battery charging circuit, rather than just putting the battery on the bus directly.

Surely this has been solved in some off-the-shelf widget, but I haven't figured out the words to google yet.

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 08, 2019 9:54 am Post subject: Limiting Current to a Battery

At 11:14 AM 7/8/2019, you wrote:

  	  Quote: 	
		  Mr N...as always I am in awe of your immense repository of knowledge...not that others on the group can't challenge you...but I am grateful that you make the time to dispense same on this forum. Often it is a topic that does not really interest me. Yet I find myself drawn inextricably away from the DELETE button! 	


    Thank you for those kind words.

    I am grateful to my teachers

    and constellation of employers who

    offered a great spectrum of

    opportunities.



    Knowledge is like cash . . . the

    value of which grows in proportion

    to how much it CIRCULATES. We

    all have opportunity to stir the

    great stew pot of knowledge. I

    have been gifted with a really

    big pot and spoon to go with it.



    Your participation here goes toward

    refining recipes for success based

    on knowledge and science. Thank

    you for being here! 



 

   Bob . . .

ceengland7(at)gmail.com
Guest

Posted: Mon Jul 08, 2019 11:22 am Post subject: Limiting Current to a Battery

Sent from BlueMail 

 On Jul 8, 2019, at 10:50 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: 	  Quote: 	
		     At 06:16 AM 7/8/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Wayne Blackler <wayne_blackler(at)yahoo.com.au>



 Some current DO-160 qualified Lithium Iron Phosphate batteries often do not limit charge current. A distinct difference in next-gen similarly qualified LFP batteries is to enable the end-user to limit charge current by programming the battery management system. There are clearly implications. Particularly for all electric aircraft.  A large 28VDC 40A-hr lfp battery might be good for 700A continuous discharge and could draw 600A if fully discharged on a charge cycle. If charged with a 400A starter-generator, this could put the generation system into overload, and the limit is reached in seconds. Even a 50% discharged lfp battery of this size draws huge charge currents for not insignificant durations. It would be interesting to see the effect of critical utilisation equipment hung off a bus with this issue. Thoughts? 	


   What goes around . . . comes around . . .



   Had some similar thoughts back in the hey-day

   of wet ni-cads finding their way onto airplanes.

   A number of airplanes suffered battery fires

   due to high rate energy replenishment after engine

   start. The same conditions contributed to

   root cause. Smaller batteries with lower

   thermal mass. Lower internal resistance

   translating into a battery's willingness to accept

   replenishment.



   The 'fix' was to add crew monitored

   battery temperature warning systems to

   the airplane. Here's an example . . .



 [img]cid:.0[/img]



   The idea was that when the yellow light

   came on, the crew would disconnect the

   battery from the bus until the temperature

   fell to happier territory.



   Back in those days, I was participating in

   a series of design programs for alternator

   and/or generator controllers. In numerous

   design reviews I proposed that our product

   included battery temperature monitoring

   that would effect automatic bus voltage

   reduction until such time that the battery

   would again accept replenishment at the

   high rate. Some of the twin turbine

   a/c had DUAL 600A generators!



   The idea was pushed aside as in the 'too

   hard' pile. We'd have to re-qualify

   a fleet wide array of controllers. Adding

   the 'band-aid' to aircraft carrying ni-cads

   was a much simpler solution.



   In years since, improvements in lead-acid

   technologies lowered cell impedances

   to the point that RG batteries were

   subject to discharge/recharge overheat

   in a/c with large generators. So

   lead-acid batteries began to sprout

   connectors to carry temperature sensor

   data to . . . you guessed it . . .

   the cockpit mounted warning system.



 [img]cid:.1[/img] 



   So here we are again. Itty bitty LiPO4

   cells quite capable of producing engine

   cranking power are similarly at-risk

   for reduced service life from a pair 

   of stresses. (1) high temperature

   induced by extended current flows

   with I(squared)R losses dumped into

   very low thermal mass and (2) over

   discharge below some voltage threshold

   that trashes the chemistry.



   Folks like Earth-X and TrueBlue have

   built protections into their battery.

   Why? Because the primary instigators

   of risk to the battery (charging

   system and battery contactor) have

   no idea as to the battery's condition

   hence not configured to do the

   really simple job of mitigating

   battery abuse.



   In the OBAM aviation world, we have

   opportunity to take the next step

   in power system management and control.

   It would be no big deal to build

   alternator controllers that would

   take battery chemistry and size

   into account . . . totally eliminating

   the need for temperature monitoring.



   Similarly, a battery contactor controller

   could be crafted to simply unhook the

   battery when the voltage dropped below

   some established limit.



   Perhaps its time that the DC power system

   be treated as an orchestra of components

   that play well TOGETHER. Right now, the

   players are marching to their own tunes

   with nary a care for each other's limits

   and needs.



 



 

 

   Bob . . . EarthX doesn't include charge control in their battery management; they force the installer to limit alternator size. That, and the fact that it can 'load dump' if the bat mgmt module fails, keeps me away for now.

Charlie

ceengland7(at)gmail.com
Guest

Posted: Mon Jul 08, 2019 11:24 am Post subject: Limiting Current to a Battery

Don't polyfuses simply open/close? With no regulation, wouldn't you just get a series of pulses?

 Sent from BlueMail 

 On Jul 8, 2019, at 11:44 AM, Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote: 	  Quote: 	
		   Look for a "poly fuse" in the aviation section of an auto parts store. These will limit current to the rated value

Sent from Yahoo Mail on Android

 

  	  Quote: 	
		    On Sun, Jul 7, 2019 at 10:01 AM, Jared Yates

<email(at)jaredyates.com> wrote:

 

  I have a question that's only somewhat applicable to E/AB aviation, apologies in advance. But I think it points out a hole in my electrical understanding.



The characteristics of the lithium iron battery I'm running allow it to draw lots of current really fast after the engine starts. If it has been a little while since the last flight, the alternator is at max output for several minutes. The alternator puts out all it can give, and it's less than the battery wants to take.

Stepping out of the hangar, my tow vehicle circuitry includes a wire in the 7-pin connector that provides alternator voltage to the trailer, intending to charge a small battery for a breakaway emergency brake. If I install a larger battery for other purposes, perhaps one like what is in the airplane, and connect it to that line coming from the truck, it seems like it would almost certainly open the fuse on that circuit during that initial high-draw stage.

These two scenarios had me thinking, what methods would one have to limit a hungry battery's draw? I'm imagining some type of circuit that takes in 12-14 volts, and puts out almost the same, but only at some specified number of amps. Almost like a DC-powered battery charging circuit, rather than just putting the battery on the bus directly.

Surely this has been solved in some off-the-shelf widget, but I haven't figured out the words to google yet.

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Mon Jul 08, 2019 4:13 pm Post subject: Re: Limiting Current to a Battery

The battery manufacturer, EarthX, wrote:

 	  Quote: 	
		  Based on extensive testing, the maximum charge rating will never be exceeded using this simple and reliable diode isolation design. 	


https://earthxbatteries.com/dual-bus-lithium-battery-design

So why not try using diodes first before trying more complicated methods to reduce the voltage and current.  An assortment of diodes with various forward voltage drops could be tried.  Yes, it is trial and error.  But so is finding the ideal voltage output of a DC-DC converter.

  By the way, it is physically impossible to reduce the battery charging current without lowering the charging voltage that is connected to the battery.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 08, 2019 4:53 pm Post subject: Limiting Current to a Battery

At 11:36 AM 7/8/2019, you wrote:

  	  Quote: 	
		  Look for a "poly fuse" in the aviation section of an auto parts store. These will limit current to the rated value

  	
 

   No, these are intended to perform the

   same function as breakers and fuses.

   Placed in series with the power path

   to an electrical load, they present

   a low resistance at or below a certain

   temperature. Should an overload occur,

   they warm past the 'trip point' where

   the resistance rises rapidly thus

   mitigating the fault current.



   See:



  https://tinyurl.com/7vt49mw



  https://tinyurl.com/y2uh3byy



   The TC aircraft world flirted with these

   critters on several occasions where

   I participated . . . and there were

   no doubt others.



   There are several power distribution

   products offered to the OBAM aviation

   community that feature Polyfuses.

   One of the earliest examples is the

   EXPBUS



 [img]cid:.0[/img]

   Greg Richter was a proponent of Polyfuses

   in his designs. One proposal for light

   aircraft power distribution took this

   form:



 [img]cid:.1[/img]



   (We had quite a discussion about both products

   which have been archived on AeroElectric.com

   if anyone is interested. Search on expbus

   or polyfuse.



   But suffice it to say that Polyfuses are not

   well suited for protection of power distribution

   feeders in aircraft. They are well suited to

   protection of circuitry WITHIN an electro-whizzy . . .

   indeed, they're sold by the millions for that

   purpose. They've alos found utility on some

   automotive applications . . . like providing

   electrical limit stops for power windows.

   



 



 

    



 

 

   Bob . . .

9e1a19f.jpg

Description:

Filesize:

67.8 KB

Viewed:

10559 Time(s)

9e1a1ae.jpg

Description:

Filesize:

226.96 KB

Viewed:

10559 Time(s)

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 08, 2019 6:25 pm Post subject: Limiting Current to a Battery

At 02:23 PM 7/8/2019, you wrote:

  	  Quote: 	
		  Don't polyfuses simply open/close? With no regulation, wouldn't you just get a series of pulses? 	


   close . . . the polyfuse maintains a low

   resistance state BELOW some trip point

   whereupon it reverts to a high resistance

   state. Current flow never goes to zero and

   the 'fuse' is held in the high-resistance

   condition at some current value well below

   hazardous.



   To 'reset' a polyfuse, you have to remove

   the current and allow the device to cool

   whereupon the magic molecules re-arrange

   to form the low-resistance matrix.



   



 

 

   Bob . . .

speedy11

Joined: 29 Jun 2015
Posts: 62
Location: Port Orange, FL

Posted: Mon Jul 08, 2019 10:50 pm Post subject: Limiting Current to a Battery

I'm no expert, but Bob's idea seems to have great merit.

  I have noticed, after starting my IO-390 using my two EarthX LiFePo batteries, the amps go to 57 immediately after start.  The alternator is a 60A Plane Power, so it is being maxed out.

  It could be that the EarthX monitor system is limiting the charge so as to avoid exceeding a particular charging limit, but I am not sure of that.  I have little experience with the batteries thus far.

  I am currently installing a complete new panel and the new AFS5800 has inputs available for monitoring the batteries.  I intend to connect them and configure the EFIS.

  Stan Sutterfield

  Spruce Creek Fly-In, FL

  

 

  

 

  Time: 08:44:03 AM PST US

 

  From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

 

  Subject: Re: Limiting Current to a Battery

 

  

 

  At 06:16 AM 7/8/2019, you wrote:

 

  ><wayne_blackler(at)yahoo.com.au (wayne_blackler(at)yahoo.com.au)>

 

  >

 

  >Some current DO-160 qualified Lithium Iron Phosphate batteries often 

 

  >do not limit charge current. A distinct difference in next-gen 

 

  >similarly qualified LFP batteries is to enable the end-user to limit 

 

  >charge current by programming the battery management system. There 

 

  >are clearly implications. Particularly for all electric aircraft.  A 

 

  >large 28VDC 40A-hr lfp battery might be good for 700A continuous 

 

  >discharge and could draw 600A if fully discharged on a charge cycle. 

 

  >If charged with a 400A starter-generator, this could put the 

 

  >generation system into overload, and the limit is reached in 

 

  >seconds. Even a 50% discharged lfp battery of this size draws huge 

 

  >charge currents for not insignificant durations. It would be 

 

  >interesting to see the effect of critical utilisation equipment hung 

 

  >off a bus with this issue. Thoughts?

 

  

 

     What goes around . . . comes around . . .

 

  

 

     Had some similar thoughts back in the hey-day

 

     of wet ni-cads finding their way onto airplanes.

 

     A number of airplanes suffered battery fires

 

     due to high rate energy replenishment after engine

 

     start. The same conditions contributed to

 

     root cause. Smaller batteries with lower

 

     thermal mass. Lower internal resistance

 

     translating into a battery's willingness to accept

 

     replenishment.

 

  

 

     The 'fix' was to add crew monitored

 

     battery temperature warning systems to

 

     the airplane. Here's an example . . .

 

  

 

  Emacs!

 

  

 

  

 

     The idea was that when the yellow light

 

     came on, the crew would disconnect the

 

     battery from the bus until the temperature

 

     fell to happier territory.

 

  

 

     Back in those days, I was participating in

 

     a series of design programs for alternator

 

     and/or generator controllers. In numerous

 

     design reviews I proposed that our product

 

     included battery temperature monitoring

 

     that would effect automatic bus voltage

 

     reduction until such time that the battery

 

     would again accept replenishment at the

 

     high rate. Some of the twin turbine

 

     a/c had DUAL 600A generators!

 

  

 

     The idea was pushed aside as in the 'too

 

     hard' pile. We'd have to re-qualify

 

     a fleet wide array of controllers. Adding

 

     the 'band-aid' to aircraft carrying ni-cads

 

     was a much simpler solution.

 

  

 

     In years since, improvements in lead-acid

 

     technologies lowered cell impedances

 

     to the point that RG batteries were

 

     subject to discharge/recharge overheat

 

     in a/c with large generators. So

 

     lead-acid batteries began to sprout

 

     connectors to carry temperature sensor

 

     data to . . . you guessed it . . .

 

     the cockpit mounted warning system.

 

  

 

  Emacs!

 

  

 

  

 

     So here we are again. Itty bitty LiPO4

 

     cells quite capable of producing engine

 

     cranking power are similarly at-risk

 

     for reduced service life from a pair

 

     of stresses. (1) high temperature

 

     induced by extended current flows

 

     with I(squared)R losses dumped into

 

     very low thermal mass and (2) over

 

     discharge below some voltage threshold

 

     that trashes the chemistry.

 

  

 

     Folks like Earth-X and TrueBlue have

 

     built protections into their battery.

 

     Why? Because the primary instigators

 

     of risk to the battery (charging

 

     system and battery contactor) have

 

     no idea as to the battery's condition

 

     hence not configured to do the

 

     really simple job of mitigating

 

     battery abuse.

 

  

 

     In the OBAM aviation world, we have

 

     opportunity to take the next step

 

     in power system management and control.

 

     It would be no big deal to build

 

     alternator controllers that would

 

     take battery chemistry and size

 

     into account . . . totally eliminating

 

     the need for temperature monitoring.

 

  

 

     Similarly, a battery contactor controller

 

     could be crafted to simply unhook the

 

     battery when the voltage dropped below

 

     some established limit.

 

  

 

     Perhaps its time that the DC power system

 

     be treated as an orchestra of components

 

     that play well TOGETHER. Right now, the

 

     players are marching to their own tunes

 

     with nary a care for each other's limits

 

     and needs.

 

  

 

  

 

     Bob . . .

echristley(at)att.net
Guest

Posted: Tue Jul 09, 2019 6:10 am Post subject: Limiting Current to a Battery

What he said, Charlie.  I had a part with threaded studs that was a 40amp fuse.  I was under the impression that it acted as a current limiter.  It appears that I was wrong.



                  

                                                                    On Monday, July 8, 2019, 10:26:14 PM EDT, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:                 

                 



                 



                   At 02:23 PM 7/8/2019, you wrote:

  	  Quote: 	
		  Don't polyfuses simply open/close? With no regulation, wouldn't you just get a series of pulses? 	


   close . . . the polyfuse maintains a low

   resistance state BELOW some trip point

   whereupon it reverts to a high resistance

   state. Current flow never goes to zero and

   the 'fuse' is held in the high-resistance

   condition at some current value well below

   hazardous.



   To 'reset' a polyfuse, you have to remove

   the current and allow the device to cool

   whereupon the magic molecules re-arrange

   to form the low-resistance matrix.



   



 

 

    Bob . . .

echristley(at)att.net
Guest

Posted: Tue Jul 09, 2019 6:14 am Post subject: Limiting Current to a Battery

Before inserting a diode, I'd add a one ohm "sensing" resistor in the charge line.  You'd get the benefit of having a way to sense the health of the generator/alternator along with never being able to exceed the maximum charge current.



                  

                                                                    On Monday, July 8, 2019, 8:15:11 PM EDT, user9253 <fransew(at)gmail.com> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>



The battery manufacturer, EarthX, wrote:



 	  Quote: 	
		   Based on extensive testing, the maximum charge rating will never be exceeded using this simple and reliable diode isolation design.


	


https://earthxbatteries.com/dual-bus-lithium-battery-design



So why not try using diodes first before trying more complicated methods to reduce the voltage and current.  An assortment of diodes with various forward voltage drops could be tried.  Yes, it is trial and error.  But so is finding the ideal voltage output of a DC-DC converter.



  By the way, it is physically impossible to reduce the battery charging current without lowering the charging voltage that is connected to the battery.



--------



Joe Gores



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=490144#490144





</= the many List utilities such as List Un/Subscription,



http://www.matronics.com/Navigator?AeroElectric-List



http://forums.matronics.com



http://www.matronics.com/contribution[/url]

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Tue Jul 09, 2019 7:22 am Post subject: Re: Limiting Current to a Battery

Suppose the battery charging current is 10 amps.  The voltage drop across a 1 ohm resistor with 10 amps flowing is 10 volts.  That leaves 4 volts to charge the battery.  It will not work.

A resistor of 0.05 ohms times 10 amps equals 0.5 volts dropped across the resistor, which is about right.  A 16 AWG wire that is 15 feet long has about 0.05 ohms.  Maybe the towing vehicle and trailer wires already have enough resistance to limit battery charging current to a safe value.

  Maybe we are trying to solve a problem that does not exist.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jul 09, 2019 3:18 pm Post subject: Limiting Current to a Battery

At 12:02 PM 7/7/2019, you wrote:

  	  Quote: 	
		  Would it be a DC-DC battery charger?



  https://www.renogy.com/renogy-12v-dc-to-dc-on-board-battery-charger/?gclid=CjwKCAjwsIbpBRBNEiwAZF8-z-TrUeFYygbwZh7wrFUpKO_RhdCJkW-vJ-BFwYS_IZjlu9G8uAMNcxoCgBoQAvD_BwE Â Â 



 On Sun, Jul 7, 2019 at 7:05 AM Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:

   I have a question that's only somewhat applicable to E/AB aviation, apologies in advance. But I think it points out a hole in my electrical understanding.



  The characteristics of the lithium iron battery I'm running allow it to draw lots of current really fast after the engine starts. If it has been a little while since the last flight, the alternator is at max output for several minutes. The alternator puts out all it can give, and it's less than the battery wants to take.



  Stepping out of the hangar, my tow vehicle circuitry includes a wire in the 7-pin connector that provides alternator voltage to the trailer, intending to charge a small battery for a breakaway emergency brake. If I install a larger battery for other purposes, perhaps one like what is in the airplane, and connect it to that line coming from the truck, it seems like it would almost certainly open the fuse on that circuit during that initial high-draw stage. 	
 

   Had to come back and review the headwaters

   of this thread. Seems this is a hypothetical

   not yet validated by the actual blowing of

   the cited fuse.



   The WIRE from the ending compartment back

   to the trailer has SIGNIFICANT resistance

   in the battery charging world. As Joe

   pointed out, a 50 milliohm resistance in

   a 10A charging path would drop 1/2 volt.



   This would cause a significant reduction in

   charge current to the second battery.



   Can you offer us a schematic of the trailer

   battery system? Does the battery feeder

   also supply power for electric brakes . . .

   or is that a separate path? What size fuse

   is protecting the current wire . . . and

   what size is the wire?



   10AWG wire is 0.001 ohms per foot. So a

   20' run would 'ballast' your charging

   path to the tune of .02 ohms. A 20A

   replenishment flow would drop 0.4 volts.

   Again, a marked reduction in battery

   recharge current.



   When dealing with batteries having

   sensitivity to 100 millivolt differences

   and charging current in the tens of

   amps, you're working with a rather

   un-predictable set of circumstances,

   difficult to predict without more data

   and perhaps easier to test with empirical

   experimentation.



 

 

   Bob . . .

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours Goto page Previous 1, 2
Page 2 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum