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Generator failure/ loss of electrical power

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ssvoysky(at)gmail.com
Guest

Posted: Fri May 12, 2017 9:18 am Post subject: Generator failure/ loss of electrical power

Hello all,

Looking for advice on the following situation- everything looked normal on the ground; "generator failure" on idle, but went away with RPM increase, proceeded to take off and got "generator failure" right away on departure. Landed to check on the ground again, all looked normal, departed, light came on. Decided to go for a short flight, started losing all electrical equipment one by one starting with the radio, but got it all back on final approach when power was reduced. Worked fine (no light, charge as usual) on the ground.



I'd appreciate for any help!

YAK52 in NJ



Thanks,

serge

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Viperdoc

Joined: 19 Apr 2014
Posts: 484
Location: 08A

Posted: Fri May 12, 2017 11:16 am Post subject: Generator failure/ loss of electrical power

What was your voltage meter doing? Was it the "GenFault" light that came on and at what %RPM were you getting the light.

Doc

Doc



Sent from my iPad



 	  Quote: 	
		   On May 12, 2017, at 12:16 PM, Serge Svoysky <ssvoysky(at)gmail.com> wrote:

 

 

 

 Hello all,

 Looking for advice on the following situation- everything looked normal on the ground; "generator failure" on idle, but went away with RPM increase, proceeded to take off and got "generator failure" right away on departure. Landed to check on the ground again, all looked normal, departed, light came on. Decided to go for a short flight, started losing all electrical equipment one by one starting with the radio, but got it all back on final approach when power was reduced. Worked fine (no light, charge as usual) on the ground.

 

 I'd appreciate for any help!

 YAK52 in NJ

 

 Thanks,

 serge

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_________________
Viperdoc

cerveirapinto(at)gmail.co
Guest

Posted: Fri May 12, 2017 11:43 am Post subject: Generator failure/ loss of electrical power

Hi Serge



Have you checked the regulator voltage?



Check and register voltage and negative/positive amperes(meaning battery is charging) at diferent settings



Adjust regulator voltage with a srew driver to obtain 25-26 volts

Also check batteries condition

Cheers

2017-05-12 18:16 GMT+01:00 Serge Svoysky <ssvoysky(at)gmail.com (ssvoysky(at)gmail.com)>:

 	  Quote: 	
		  --> Yak-List message posted by: Serge Svoysky <ssvoysky(at)gmail.com (ssvoysky(at)gmail.com)>

 

 Hello all,

 Looking for advice on the following situation- everything looked normal on the ground; "generator failure" on idle, but went away with RPM increase, proceeded to take off and got "generator failure" right away on departure. Landed to check on the ground again, all looked normal, departed, light came on. Decided to go for a short flight, started losing all electrical equipment one by one starting with the radio, but got it all back on final approach when power was reduced. Worked fine (no light, charge as usual) on the ground.

 

 I'd appreciate for any help!

 YAK52 in NJ

 

 Thanks,

 serge

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 List" rel="noreferrer" target="_blank">http://www.matronics.com/Navigator?Yak-List

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 eferrer" target="_blank">http://forums.matronics.com

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 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 rel="noreferrer" target="_blank">http://www.matronics.com/contribution

 ====================================

 

 

 

 	


-- 

Pedro Cerveira Pinto

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dsavarese0812(at)bellsout
Guest

Posted: Fri May 12, 2017 4:07 pm Post subject: Generator failure/ loss of electrical power

25-26 Volts is too low if you want to charge the battery.  Should be set 

to 28.5 volts

Dennis



A. Dennis Savarese

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 5/12/2017 3:41 PM, Pedro Cerveira Pinto wrote:

 	  Quote: 	
		   Hi Serge

 Have you checked the regulator voltage?

 Check and register voltage and negative/positive amperes(meaning 

 battery is charging) at diferent settings

 Adjust regulator voltage with a srew driver to obtain 25-26 volts



 Also check batteries condition



 Cheers



 2017-05-12 18:16 GMT+01:00 Serge Svoysky <ssvoysky(at)gmail.com 

 <mailto:ssvoysky(at)gmail.com>>:



     

     <mailto:ssvoysky(at)gmail.com>>



     Hello all,

     Looking for advice on the following situation- everything looked

     normal on the ground; "generator failure" on idle, but went away

     with RPM increase, proceeded to take off and got "generator

     failure" right away on departure. Landed to check on the ground

     again, all looked normal, departed, light came on. Decided to go

     for a short flight, started losing all electrical equipment one by

     one starting with the radio, but got it all back on final approach

     when power was reduced. Worked fine (no light, charge as usual) on

     the ground.



     I'd appreciate for any help!

     YAK52 in NJ



     Thanks,

     serge

     ====================================

     List" rel="noreferrer"

     target="_blank">http://www.matronics.com/Navigator?Yak-List

     ====================================

     FORUMS -

     eferrer" target="_blank">http://forums.matronics.com

     ====================================

     WIKI -

     errer" target="_blank">http://wiki.matronics.com

     ====================================

     b Site -

               -Matt Dralle, List Admin.

     rel="noreferrer" target="_blank">http://www.matronics.com/contribution

     ====================================

 -- 

 Pedro Cerveira Pinto

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cerveirapinto(at)gmail.co
Guest

Posted: Fri May 12, 2017 5:04 pm Post subject: Generator failure/ loss of electrical power

Hi Dennis I have my 2x 12V gel batteries for 5 years no problem so far. My opinion is that 28.5V will degrade gel batteries to soon.

Regards 

Enviado a partir do meu smartphone Samsung Galaxy.



-------- Mensagem original --------

De: "A. Dennis Savarese" <dsavarese0812(at)bellsouth.net> 

Data: 12/05/17  21:05  (GMT-03:00) 

Para: yak-list(at)matronics.com 

Assunto: Re: Yak-List: Generator failure/ loss of electrical power 



--> Yak-List message posted by: "A. Dennis Savarese" <dsavarese0812(at)bellsouth.net>



25-26 Volts is too low if you want to charge the battery.  Should be set 

to 28.5 volts

Dennis



A. Dennis Savarese

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 5/12/2017 3:41 PM, Pedro Cerveira Pinto wrote:

 	  Quote: 	
		   Hi Serge

 Have you checked the regulator voltage?

 Check and register voltage and negative/positive amperes(meaning 

 battery is charging) at diferent settings

 Adjust regulator voltage with a srew driver to obtain 25-26 volts



 Also check batteries condition



 Cheers



 2017-05-12 18:16 GMT+01:00 Serge Svoysky <ssvoysky(at)gmail.com 

 <mailto:ssvoysky(at)gmail.com>>:



     --> Yak-List message posted by: Serge Svoysky <ssvoysky(at)gmail.com

     <mailto:ssvoysky(at)gmail.com>>



     Hello all,

     Looking for advice on the following situation- everything looked

     normal on the ground; "generator failure" on idle, but went away

     with RPM increase, proceeded to take off and got "generator

     failure" right away on departure. Landed to check on the ground

     again, all looked normal, departed, light came on. Decided to go

     for a short flight, started losing all electrical equipment one by

     one starting with the radio, but got it all back on final approach

     when power was reduced. Worked fine (no light, charge as usual) on

     the ground.



     I'd appreciate for any help!

     YAK52 in NJ



     Thanks,

     serge

     ====================================

     List" rel="noreferrer"

     target="_blank">http://www.matronics.com/Navigator?Yak-List

     ====================================

     FORUMS -

     eferrer" target="_blank">http://forums.matronics.com

     ====================================

     WIKI -

     errer" target="_blank">http://wiki.matronics.com

     ====================================

     b Site -

               -Matt Dralle, List Admin.

     rel="noreferrer" target="_blank">http://www.matronics.com/contribution

     ====================================

 -- 

 Pedro Cerveira Pinto




	


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dsavarese0812(at)bellsout
Guest

Posted: Fri May 12, 2017 5:41 pm Post subject: Generator failure/ loss of electrical power

5 years is pushing the life expectancy of any battery.  You may just 

want to bite the bullet and replacethem and then see if the problem 

still exists.



The M14 maintenancemanual clearly states the output voltage should be 

adjusted via the rheostatto to 28 - 28.5 volts.  But you do what you 

want.  You don't have to believe me.  Look it up yourself.



Let me ask you this question.  If it were a 12 volt battery in your car, 

would you want the alternator output to run at say 12.8 volts torecharge 

the battery that should read 12.6-13 volts or would you want that 

alternator putting out 13-14 volts?  How long do you think it will take 

to recharge your 24 volt batteries under load to recharge at 25 volts?



Dennis

A. Dennis Savarese

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 5/12/2017 9:01 PM, Cerveira Pinto wrote:

 	  Quote: 	
		   Hi Dennis I have my 2x 12V gel batteries for 5 years no problem so 

 far. My opinion is that 28.5V will degrade gel batteries to soon.

 Regards



 Enviado a partir do meu smartphone Samsung Galaxy.



 -------- Mensagem original --------

 De: "A. Dennis Savarese" <dsavarese0812(at)bellsouth.net>

 Data: 12/05/17 21:05 (GMT-03:00)

 Para: yak-list(at)matronics.com

 Assunto: Re: Generator failure/ loss of electrical power



 

 <dsavarese0812(at)bellsouth.net>



 25-26 Volts is too low if you want to charge the battery.  Should be set

 to 28.5 volts

 Dennis



 A. Dennis Savarese

 334-546-8182 (mobile)

 www.yak-52.com

 Skype - Yakguy1



 On 5/12/2017 3:41 PM, Pedro Cerveira Pinto wrote:

 > Hi Serge

 > Have you checked the regulator voltage?

 > Check and register voltage and negative/positive amperes(meaning

 > battery is charging) at diferent settings

 > Adjust regulator voltage with a srew driver to obtain 25-26 volts

 >

 > Also check batteries condition

 >

 > Cheers

 >

 > 2017-05-12 18:16 GMT+01:00 Serge Svoysky <ssvoysky(at)gmail.com

 > <mailto:ssvoysky(at)gmail.com>>:

 >

 >     

 >     <mailto:ssvoysky(at)gmail.com>>

 >

 >     Hello all,

 >     Looking for advice on the following situation- everything looked

 >     normal on the ground; "generator failure" on idle, but went away

 >     with RPM increase, proceeded to take off and got "generator

 >     failure" right away on departure. Landed to check on the ground

 >     again, all looked normal, departed, light came on. Decided to go

 >     for a short flight, started losing all electrical equipment one by

 >     one starting with the radio, but got it all back on final approach

 >     when power was reduced. Worked fine (no light, charge as usual) on

 >     the ground.

 >

 >     I'd appreciate for any help!

 >     YAK52 in NJ

 >

 >     Thanks,

 >     serge

 >     ====================================

 >     List" rel="noreferrer"

 > target="_blank">http://www.matronics.com/Navigator?Yak-List

 >     ====================================

 >     FORUMS -

 >     eferrer" target="_blank">http://forums.matronics.com

 >     ====================================

 >     WIKI -

 >     errer" target="_blank">http://wiki.matronics.com

 >     ====================================

 >     b Site -

 >               -Matt Dralle, List Admin.

 >     rel="noreferrer" 

 target="_blank">http://www.matronics.com/contribution

 >     ====================================

 >

 >

 >

 >

 >

 >

 > --

 > Pedro Cerveira Pinto

 >

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mark.bitterlich(at)navy.m
Guest

Posted: Sat May 13, 2017 3:11 pm Post subject: Generator failure/ loss of electrical power

There are a couple of folks that have already commented on the proper setting for the generator voltage, and I want everyone reading this to know that I have high regard and respect for everyone that commented.  They have also said some very nice things about me, for which I am gratified.  This is going to be a long discussion, so be fore-warned.  If you don’t like listening to Mark talk, then just stop right here and discard the message.  OK?  That should stop some of the flak from the peanut gallery.  Be aware that I rarely write up explanations like this anymore, so don’t worry… this is an exception to the rule.



So with that said, there is a part of me that does not even want to discuss this, but what the heck, I hope I don’t lose any friends.



First of all, EVERYBODY is correct in what they said regarding this topic.  No one is wrong.  That is kind of a unique situation really, but factually it is the truth.



First of all, there was a reference to the Yak manuals, and what they say the proper output voltage of the generator should be set to.  Yes, they all specify over 28 volts DC, and that is for a number of reasons.  All of the equipment in these aircraft, namely engine instruments, voltage inverters for gyro’s, pitot heat, radios, and on and on … ALL of these things were designed to operate at the specified voltage of 28 volts, or 28.5 VDC.  The original battery in these aircraft was typically a Nickel Cadmium design, and the charging voltage for this battery also met the design generator output voltage specified in the publications.



But then these aircraft came to the United States, and people started immediately pulling out the original NiCad battery (which was pretty much impossible to maintain) and started replacing it with two 12 volt gel cell batteries.  Some of the really serious aerobatic types installed two very light weight and minimum capacity batteries, and in my opinion this was a serious mistake.  These batteries combined with the B&C PMG Alternator (the 10 amp version) could combine to cause serious damage to avionics components, and I’ve watched it happen a few times now, regardless of the warnings I have given to a few owners.  Most of them finally learned, use different batteries (yes, Gel Cell too), but larger, and with a better alternator like the B&C SK-35, which is a wonderful design with the LS1A regulator.



Getting back to gel cell batteries.  If you read the fine print that usually comes with these batteries, you will see that they have a MAXIMUM RECOMMENDED CHARGING CURRENT!  Charging current is typically controlled by varying charging voltage on the fly.  One problem …… the YAK and CJ aircraft do not have an inherent system for controlling charging current, voltage yes, current no.



So here we have a conundrum.  We are installing gel cell batteries that typically have smaller inherent capacity than what was originally installed.  This a very important point.  Further, they are a different TYPE of battery than was originally installed, and they are supposed to be charged at a lower CURRENT than what was originally assumed.



So if you leave your voltage set for 28.5 VDC or whatever the Russian manual says, then it is going to result in a little bit too high of a charging current for the gel cell batteries as recommended by the manufactuer.  This will then cause the batteries to gas, and once that happens battery capacity diminishes.  Note:  Causing a gel cell to gas is bad business.  But then to be honest, all batteries die eventually.  You can extend their life by using fancy chargers like Battery Minders (I like these a lot by the way), which will shoot a short blast of HF energy around 3 MHz into the battery to help recombine sulfates back into acid and off the plates but in the end, they all go bad.



The important thing is to know that you need to check them.   Five years is indeed a long time for battery life in these aircraft, but it is feasible if you have spent a lot of effort watching charging current and using chargers like the Battery Minder brand.



What is important to understand is the way generators work.  A generator has a plus and minus connection that outputs voltage correct?  Yes it does.  But when the generator is not turning, the PLUS connection on it is essentially a dead short to ground.  That is a bad bad thing to have your battery connected to.  If you connect a good battery to a dead short to ground, there is going to be a lot of current flowing, and fuses will blow, relays will burn out and wires can melt.  It is a very very bad thing.



As a generator starts spinning slower and slower …. Like when your M-14P engine is coming back to idle, it is not spinning fast enough to deliver a voltage higher than what is in your battery.  At that point, current starts flowing BACKWARDS… or IN REVERSE to your generator FROM the battery.  The slower the generator spins, the less voltage it will then produce and the more current will flow back into the generator from the battery.



The DMR-200 Combined Relay device is put in there to control this situation.  Remember my previous post about the MAIN CONTACTOR RELAY.  This relay is what connects the generator to the main electrical bus of the aircraft, and thus the battery as well.  When current starts flowing backwards into the generator from the battery, there is a special device called THE REVERSE CURRENT RELAY that senses this.  Once that current gets high enough, it will cause the MAIN CONTACTOR RELAY TO OPEN (!!!!)  thus disconnecting the generator from the rest of the aircraft.  TA-DA!  Problem solved!  And yes, that is when the Generator light comes on!



But let’s say you have some weak half assed batteries, that you are trying to get the last bit of life out of, because you are too cheap to buy new ones.  Sorry, sometimes I get carried away, but it is the truth.  People have done this all the time, and I have watched them do it.



Now when your generator slows down, you start getting reverse current, but the battery is so darn weak, it cannot supply ENOUGH current to cause the reverse current relay to sense it.  Now you start to have a voltage droop in the aircraft.  Voltage goes lower and lower as the weak batteries discharge more and more.  So now instead of a quick disconnect of the generator, you instead get a lower and lower battery supply voltage to EVERYTHING in the aircraft that is designed to run off 28 volts.  Radios, Transponders, GPS’s, you name it.  They are now all being subjected to a lower voltage than they were designed to operate with.  Sometimes they have had enough and fail.  Who’s fault is that?  Yep… yours, the aircraft owner.



So batteries need to be checked.  The easiest way is to put a fairly good load on the batteries and verify that their voltage does not drop too low.  If you are not up for that, then a good idea is to just replace them every few years and be done with it.



So I took the time to write this.  I hope it was useful to you.  Feel free to write me directly if you disagree, or have a technical input that you feel I missed.  I very well could have.  This whole thing is like a string of Dominoes going down, but you need to keep it in mind.



So yes…, you can lower the charging voltage to try and limit charging current to gel cells, but this is also a two edged sword.  My input is to leave it where the manual says it should be set to, use a Battery Minder charger with a sulfate blaster at 3.4 MHz, and just bite the bullet and replace those batteries on a regular basis, and don’t use itsy-bitsy batteries… dumb move Kemo Sabi.



Mark Bitterlich

Who’s YAK-50 is probably going up for sale.

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Viperdoc

Joined: 19 Apr 2014
Posts: 484
Location: 08A

Posted: Sat May 13, 2017 7:18 pm Post subject: Generator failure/ loss of electrical power

ðŸ‘ðŸ‘

Doc



Sent from my iPad



 	  Quote: 	
		   On May 13, 2017, at 6:08 PM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil> wrote:

 

 

 

 There are a couple of folks that have already commented on the proper setting for the generator voltage, and I want everyone reading this to know that I have high regard and respect for everyone that commented.  They have also said some very nice things about me, for which I am gratified.  This is going to be a long discussion, so be fore-warned.  If you donâ€™t like listening to Mark talk, then just stop right here and discard the message.  OK?  That should stop some of the flak from the peanut gallery.  Be aware that I rarely write up explanations like this anymore, so donâ€™t worryâ€¦ this is an exception to the rule.

 

 So with that said, there is a part of me that does not even want to discuss this, but what the heck, I hope I donâ€™t lose any friends.

 

 First of all, EVERYBODY is correct in what they said regarding this topic.  No one is wrong.  That is kind of a unique situation really, but factually it is the truth.

 

 First of all, there was a reference to the Yak manuals, and what they say the proper output voltage of the generator should be set to.  Yes, they all specify over 28 volts DC, and that is for a number of reasons.  All of the equipment in these aircraft, namely engine instruments, voltage inverters for gyroâ€™s, pitot heat, radios, and on and on â€¦ ALL of these things were designed to operate at the specified voltage of 28 volts, or 28.5 VDC.  The original battery in these aircraft was typically a Nickel Cadmium design, and the charging voltage for this battery also met the design generator output voltage specified in the publications.

 

 But then these aircraft came to the United States, and people started immediately pulling out the original NiCad battery (which was pretty much impossible to maintain) and started replacing it with two 12 volt gel cell batteries.  Some of the really serious aerobatic types installed two very light weight and minimum capacity batteries, and in my opinion this was a serious mistake.  These batteries combined with the B&C PMG Alternator (the 10 amp version) could combine to cause serious damage to avionics components, and Iâ€™ve watched it happen a few times now, regardless of the warnings I have given to a few owners.  Most of them finally learned, use different batteries (yes, Gel Cell too), but larger, and with a better alternator like the B&C SK-35, which is a wonderful design with the LS1A regulator.

 

 Getting back to gel cell batteries.  If you read the fine print that usually comes with these batteries, you will see that they have a MAXIMUM RECOMMENDED CHARGING CURRENT!  Charging current is typically controlled by varying charging voltage on the fly.  One problem â€¦â€¦ the YAK and CJ aircraft do not have an inherent system for controlling charging current, voltage yes, current no.

 

 So here we have a conundrum.  We are installing gel cell batteries that typically have smaller inherent capacity than what was originally installed.  This a very important point.  Further, they are a different TYPE of battery than was originally installed, and they are supposed to be charged at a lower CURRENT than what was originally assumed.

 

 So if you leave your voltage set for 28.5 VDC or whatever the Russian manual says, then it is going to result in a little bit too high of a charging current for the gel cell batteries as recommended by the manufactuer.  This will then cause the batteries to gas, and once that happens battery capacity diminishes.  Note:  Causing a gel cell to gas is bad business.  But then to be honest, all batteries die eventually.  You can extend their life by using fancy chargers like Battery Minders (I like these a lot by the way), which will shoot a short blast of HF energy around 3 MHz into the battery to help recombine sulfates back into acid and off the plates but in the end, they all go bad.

 

 The important thing is to know that you need to check them.   Five years is indeed a long time for battery life in these aircraft, but it is feasible if you have spent a lot of effort watching charging current and using chargers like the Battery Minder brand.

 

 What is important to understand is the way generators work.  A generator has a plus and minus connection that outputs voltage correct?  Yes it does.  But when the generator is not turning, the PLUS connection on it is essentially a dead short to ground.  That is a bad bad thing to have your battery connected to.  If you connect a good battery to a dead short to ground, there is going to be a lot of current flowing, and fuses will blow, relays will burn out and wires can melt.  It is a very very bad thing.

 

 As a generator starts spinning slower and slower â€¦. Like when your M-14P engine is coming back to idle, it is not spinning fast enough to deliver a voltage higher than what is in your battery.  At that point, current starts flowing BACKWARDSâ€¦ or IN REVERSE to your generator FROM the battery.  The slower the generator spins, the less voltage it will then produce and the more current will flow back into the generator from the battery.

 

 The DMR-200 Combined Relay device is put in there to control this situation.  Remember my previous post about the MAIN CONTACTOR RELAY.  This relay is what connects the generator to the main electrical bus of the aircraft, and thus the battery as well.  When current starts flowing backwards into the generator from the battery, there is a special device called THE REVERSE CURRENT RELAY that senses this.  Once that current gets high enough, it will cause the MAIN CONTACTOR RELAY TO OPEN (!!!!)  thus disconnecting the generator from the rest of the aircraft.  TA-DA!  Problem solved!  And yes, that is when the Generator light comes on!

 

 But letâ€™s say you have some weak half assed batteries, that you are trying to get the last bit of life out of, because you are too cheap to buy new ones.  Sorry, sometimes I get carried away, but it is the truth.  People have done this all the time, and I have watched them do it.

 

 Now when your generator slows down, you start getting reverse current, but the battery is so darn weak, it cannot supply ENOUGH current to cause the reverse current relay to sense it.  Now you start to have a voltage droop in the aircraft.  Voltage goes lower and lower as the weak batteries discharge more and more.  So now instead of a quick disconnect of the generator, you instead get a lower and lower battery supply voltage to EVERYTHING in the aircraft that is designed to run off 28 volts.  Radios, Transponders, GPSâ€™s, you name it.  They are now all being subjected to a lower voltage than they were designed to operate with.  Sometimes they have had enough and fail.  Whoâ€™s fault is that?  Yepâ€¦ yours, the aircraft owner.

 

 So batteries need to be checked.  The easiest way is to put a fairly good load on the batteries and verify that their voltage does not drop too low.  If you are not up for that, then a good idea is to just replace them every few years and be done with it.

 

 So I took the time to write this.  I hope it was useful to you.  Feel free to write me directly if you disagree, or have a technical input that you feel I missed.  I very well could have.  This whole thing is like a string of Dominoes going down, but you need to keep it in mind.

 

 So yesâ€¦, you can lower the charging voltage to try and limit charging current to gel cells, but this is also a two edged sword.  My input is to leave it where the manual says it should be set to, use a Battery Minder charger with a sulfate blaster at 3.4 MHz, and just bite the bullet and replace those batteries on a regular basis, and donâ€™t use itsy-bitsy batteriesâ€¦ dumb move Kemo Sabi.

 

 Mark Bitterlich

 Whoâ€™s YAK-50 is probably going up for sale.

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_________________
Viperdoc

pa3arw(at)ziggo.nl
Guest

Posted: Sun May 14, 2017 12:37 am Post subject: Generator failure/ loss of electrical power

Good story Mark and very true!



BTW: the batteries in my Yak52 were put in there in 2002 when I picked her

up in Lithuania. Until now they have never let me down and have not been

replaced yet. All other things original Russian with the good old dc

generator.



Sad to read y're gone probably sell yr Yak50....so w're possibly gone miss

you here on the net??



Regards,



Hans O.

PH-YAK



Op 14-05-17 01:08, Bitterlich, Mark G CIV NAVAIR, WD

<mark.bitterlich(at)navy.mil> schreef:



 	  Quote: 	
		   

 <mark.bitterlich(at)navy.mil>

 

 There are a couple of folks that have already commented on the proper setting

 for the generator voltage, and I want everyone reading this to know that I

 have high regard and respect for everyone that commented.  They have also said

 some very nice things about me, for which I am gratified.  This is going to be

 a long discussion, so be fore-warned.  If you don¹t like listening to Mark

 talk, then just stop right here and discard the message.  OK?  That should

 stop some of the flak from the peanut gallery.  Be aware that I rarely write

 up explanations like this anymore, so don¹t worryŠ this is an exception to the

 rule.

 

 So with that said, there is a part of me that does not even want to discuss

 this, but what the heck, I hope I don¹t lose any friends.

 

 First of all, EVERYBODY is correct in what they said regarding this topic.  No

 one is wrong.  That is kind of a unique situation really, but factually it is

 the truth.

 

 First of all, there was a reference to the Yak manuals, and what they say the

 proper output voltage of the generator should be set to.  Yes, they all

 specify over 28 volts DC, and that is for a number of reasons.  All of the

 equipment in these aircraft, namely engine instruments, voltage inverters for

 gyro¹s, pitot heat, radios, and on and on Š ALL of these things were designed

 to operate at the specified voltage of 28 volts, or 28.5 VDC.  The original

 battery in these aircraft was typically a Nickel Cadmium design, and the

 charging voltage for this battery also met the design generator output voltage

 specified in the publications.

 

 But then these aircraft came to the United States, and people started

 immediately pulling out the original NiCad battery (which was pretty much

 impossible to maintain) and started replacing it with two 12 volt gel cell

 batteries.  Some of the really serious aerobatic types installed two very

 light weight and minimum capacity batteries, and in my opinion this was a

 serious mistake.  These batteries combined with the B&C PMG Alternator (the 10

 amp version) could combine to cause serious damage to avionics components, and

 I¹ve watched it happen a few times now, regardless of the warnings I have

 given to a few owners.  Most of them finally learned, use different batteries

 (yes, Gel Cell too), but larger, and with a better alternator like the B&C

 SK-35, which is a wonderful design with the LS1A regulator.

 

 Getting back to gel cell batteries.  If you read the fine print that usually

 comes with these batteries, you will see that they have a MAXIMUM RECOMMENDED

 CHARGING CURRENT!  Charging current is typically controlled by varying

 charging voltage on the fly.  One problem ŠŠ the YAK and CJ aircraft do not

 have an inherent system for controlling charging current, voltage yes, current

 no.

 

 So here we have a conundrum.  We are installing gel cell batteries that

 typically have smaller inherent capacity than what was originally installed.

 This a very important point.  Further, they are a different TYPE of battery

 than was originally installed, and they are supposed to be charged at a lower

 CURRENT than what was originally assumed.

 

 So if you leave your voltage set for 28.5 VDC or whatever the Russian manual

 says, then it is going to result in a little bit too high of a charging

 current for the gel cell batteries as recommended by the manufactuer.  This

 will then cause the batteries to gas, and once that happens battery capacity

 diminishes.  Note:  Causing a gel cell to gas is bad business.  But then to be

 honest, all batteries die eventually.  You can extend their life by using

 fancy chargers like Battery Minders (I like these a lot by the way), which

 will shoot a short blast of HF energy around 3 MHz into the battery to help

 recombine sulfates back into acid and off the plates but in the end, they all

 go bad.

 

 The important thing is to know that you need to check them.   Five years is

 indeed a long time for battery life in these aircraft, but it is feasible if

 you have spent a lot of effort watching charging current and using chargers

 like the Battery Minder brand.

 

 What is important to understand is the way generators work.  A generator has a

 plus and minus connection that outputs voltage correct?  Yes it does.  But

 when the generator is not turning, the PLUS connection on it is essentially a

 dead short to ground.  That is a bad bad thing to have your battery connected

 to.  If you connect a good battery to a dead short to ground, there is going

 to be a lot of current flowing, and fuses will blow, relays will burn out and

 wires can melt.  It is a very very bad thing.

 

 As a generator starts spinning slower and slower Š. Like when your M-14P

 engine is coming back to idle, it is not spinning fast enough to deliver a

 voltage higher than what is in your battery.  At that point, current starts

 flowing BACKWARDSŠ or IN REVERSE to your generator FROM the battery.  The

 slower the generator spins, the less voltage it will then produce and the more

 current will flow back into the generator from the battery.

 

 The DMR-200 Combined Relay device is put in there to control this situation.

 Remember my previous post about the MAIN CONTACTOR RELAY.  This relay is what

 connects the generator to the main electrical bus of the aircraft, and thus

 the battery as well.  When current starts flowing backwards into the generator

 from the battery, there is a special device called THE REVERSE CURRENT RELAY

 that senses this.  Once that current gets high enough, it will cause the MAIN

 CONTACTOR RELAY TO OPEN (!!!!)  thus disconnecting the generator from the rest

 of the aircraft.  TA-DA!  Problem solved!  And yes, that is when the Generator

 light comes on!

 

 But let¹s say you have some weak half assed batteries, that you are trying to

 get the last bit of life out of, because you are too cheap to buy new ones.

 Sorry, sometimes I get carried away, but it is the truth.  People have done

 this all the time, and I have watched them do it.

 

 Now when your generator slows down, you start getting reverse current, but the

 battery is so darn weak, it cannot supply ENOUGH current to cause the reverse

 current relay to sense it.  Now you start to have a voltage droop in the

 aircraft.  Voltage goes lower and lower as the weak batteries discharge more

 and more.  So now instead of a quick disconnect of the generator, you instead

 get a lower and lower battery supply voltage to EVERYTHING in the aircraft

 that is designed to run off 28 volts.  Radios, Transponders, GPS¹s, you name

 it.  They are now all being subjected to a lower voltage than they were

 designed to operate with.  Sometimes they have had enough and fail.  Who¹s

 fault is that?  YepŠ yours, the aircraft owner.

 

 So batteries need to be checked.  The easiest way is to put a fairly good load

 on the batteries and verify that their voltage does not drop too low.  If you

 are not up for that, then a good idea is to just replace them every few years

 and be done with it.

 

 So I took the time to write this.  I hope it was useful to you.  Feel free to

 write me directly if you disagree, or have a technical input that you feel I

 missed.  I very well could have.  This whole thing is like a string of

 Dominoes going down, but you need to keep it in mind.

 

 So yesŠ, you can lower the charging voltage to try and limit charging current

 to gel cells, but this is also a two edged sword.  My input is to leave it

 where the manual says it should be set to, use a Battery Minder charger with a

 sulfate blaster at 3.4 MHz, and just bite the bullet and replace those

 batteries on a regular basis, and don¹t use itsy-bitsy batteriesŠ dumb move

 Kemo Sabi.

 

 Mark Bitterlich

 Who¹s YAK-50 is probably going up for sale.

- The Matronics Yak-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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