Matronics Email Lists :: View topic - How do you figure C-Rating of 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

How do you figure C-Rating of a battery?

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 13, 2020 7:58 am Post subject: How do you figure C-Rating of a battery?

At 09:53 AM 9/13/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>



 Hi Group Thank you for replies. Again I want a dual mission total loss battery, one to run a Rotax 914 fuel pump which I'm certain the 5,000mA cells are up to the task and two is to jump start main battery in a pinch. 	


   Is there a history for the failure modes

   you are hypothesizing?  Under what series

   of events would you find it necessary to

   operated a fuel pump from it's own back

   up battery?



   Jump start? Lithium main battery? Going

   airborne with an essentially dead main

   battery after jump starting the engine

   is poor practice. Not recommended in

   any advice I've read or written.



   How hard is it to (1) prevent the main

   battery from becoming depleted while

   parked and (2) maintaining the main

   battery in a manner that guarantees

   availability for alternator-out

   situations?



   I think we're all having trouble

   understanding justification for what

   you propose.



 

   Bob . . .

- The Matronics AeroElectric-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:

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

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 13, 2020 8:08 am Post subject: How do you figure C-Rating of a battery?

 	  Quote: 	
		  I'm pretty 'cheap'; I've been known to expend prodigious effort to save a few $. But from what I think I understand about your goals, I'd find it hard to resist just picking up one of the dozens of lithium 'jump start' packs. They have high current cables for jump starting, and almost all of them now include smaller terminals, adapters, etc that allow connection of devices with lower current demands. $55-$75 will get you pre-packaged cells, cables, a handful of adapters, etc, very close to 'plug&play'. I'll bet that by the time you gather up all the stuff you need to make your idea work, you'll have close to that much money tied up, and a *lot* more work. Way more starting current than you'd ever need, and even the cheapest versions will have more total energy to run the fuel pump than the NiMh cells.



 Charlie

 	




   Sure. If he drops the 'jump start' requirement

   but has an FMEA driven justification for a

   stand-by battery on the fuel pump, these batteries

   connected in series would run the pump for a very

   long time . . . probably duration of fuel aboard.



  https://tinyurl.com/y4oulfy9



   Down side is the legacy stand-by-battery-cost-

   of-ownership for insuring continued air worthiness.

   I'd like to understand what conditions would drive

   the need in the first place.

   



 

 

   Bob . . .

- The Matronics AeroElectric-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:

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

Martymason

Joined: 17 Apr 2009
Posts: 20
Location: Norcross, GA

Posted: Sun Sep 13, 2020 1:34 pm Post subject: Re: How do you figure C-Rating of a battery?

[quote="nuckolls.bob(at)aeroelect"]At 09:53 AM 9/13/2020, you wrote:

 [quote]--> AeroElectric-List message posted by: "rparigoris" <rparigor>

   Is there a history for the failure modes

   you are hypothesizing?  



The Europa with long wings is a motorglider. Hence the need to restart in air. I think Ron is looking for belt & suspenders.



Marty Mason

- The Matronics AeroElectric-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:

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

_________________
Marty Mason
Norcross, GA

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Sun Sep 13, 2020 3:14 pm Post subject: Re: How do you figure C-Rating of a battery?

Hi Bob Here's a few pics of under 2 lb battery: http://www.europaowners.org/main.php?g2_itemId=27335 and  http://www.europaowners.org/main.php?g2_itemId=30614 the batteries are getting old and I want to replace them with 10 year newer NiMh technology. You sent a link for a LiPo battery, true they have great energy density but LiPo is also one active Lithium technology, no place in an aeroplane IMHO. My reasons for wanting a independent battery for a fuel pump is in case main battery stops working for whatever reason. Side note, Europa has a main tank and a reserve just like a motorcycle. Run out of fuel and turn to reserve and you know how long it will last. My reason for total loss battery to run a pump is pretty much the same. If you can no longer supply power to a pump, I'll call on my "reserve battery". Potential things that would cause a failure of E-Bus is a battery that fails opened. Yes yes yes I have read read read read that if you capacity test a battery once a year and replace often that the chance of a failure to occur after the motor is started is very slim. I have had at least 2 failures on a car when driving and battery opened and engine quit. Once on a motorcycle where things went dark but engine still ran. Now I'm introducing a LiFe Earth-X battery that is not a lead acid and as far as I'm concerned unquestionably has the potential to offer up no potential for other reasons besides internal connections going very high resistance. I have a SD20S with LR3C on vacuum pad of Rotax 914, I haven't any experience with SD20S and LR3C, but I did have a Suzuki Samari with a ND alternator, it had a solid state internal regulator, anyway the regulator failed, cooked the battery and I got stuck on the side of the road. True LR3C has over-voltage protection but could it fail and cook my battery? I'm using Eric Jones aluminium clad wire (battery in back), I crimped and soldered and paid a lot of attension to smooth bends and support, but there are several connections that could fail and go high resistance and make my E-bus inoperative. If I take a long and extended flight with additonal fuel onboard, if charging system failed and I was flying off of E-Bus, then engine quit because battery went flat either for flying too long or let's say the fool Rotax TCU decided to draw a lot more power than it normally does and engine quits. I just connect total loss "reserve battery". I haven't tested it yet but if I were on total loss battery, I think I could cycle it on and off and probably double range. Anyway that's my reasons for being able to run a fuel pump. Just recently I figured since I have this battery already, I could use it as a in a pinch jump start pack. This would be just a value added. I agree with you taking off with a battery that's flat is a bad idea. Let's say I'm in the middle of nowhere and camping out. Some load was left on and battery is a bit flat. If I could let the total loss battery charge the main battery for a bit then try a start, if it started I would be gentle and use only the SD20S to charge on ground for a while at reasonable rate before taking off. If I have a choice I don't fast charge. Another scenario is after shutting down motor and soaring for a while, for some reason the engine will not start. If you shut down motor you always want a landing spot at hand assuming that the motor won't start. Let's say for whatever reason the battery can't offer up enough electron flow to do an inflight restart, could be too much a load was left on, bad cell in battery or plain bad luck, true if had enough altitude could go course pitch and do an airstart, kinda hard on a cold engine and you need a reasonable amount of altitude, anyway if I was able to do an inflight jump start, just an added bonus. The under 2 pounds lets me sleep a little better knowing I could keep the motor running if all else fails. Unquestionably belt and suspenders, hope I never need to use it. Ron P.

- The Matronics AeroElectric-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:

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

user9253

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

Posted: Sun Sep 13, 2020 6:38 pm Post subject: Re: How do you figure C-Rating of a battery?

Can a dead battery be recharged by a fully charged battery?

- The Matronics AeroElectric-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:

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

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 13, 2020 7:09 pm Post subject: How do you figure C-Rating of a battery?

You've stacked a bucket load of suppositions

   and hypotheticals for which I perceive no

   foundation. Most of the things you're worrying

   about are the same things we've been working

   to mitigate for the last 100 years or so.



   Worried about crimped AND soldered connections?

   Why? No, LR3s have no failure modes that would

   cook a battery.



   LiFEPO4 has an excellent design history and

   track record when packaged with a BMS. AeroVolz,

   EarthX, TruBlue and others have done their 

   homework.



   AeroVolts has a BMS fitted battery right

   at 2 pounds and proofs out at 4.5AH . . .

   it will even crank an engine.



   What kind of charge/maintenance protocol

   are you proposing for your home brew array?

     

  	  Quote: 	
		   Unquestionably belt and suspenders, hope I never need to use it. Ron P.

 	
  Ron, of all the electrically involved

   accidents I've worked, the vast majority

   had root cause in inattention to mechanical

   or architectural design details. I.e. poor

   FMEA and/or craftsmanship. When component

   failure was part of the script, it was almost

   never due to manufacturing defect . . . in

   fact I cannot now recall a single instance.



   Consider sharing your architecture drawing

   with the List . . . let's run it under the

   FMEA microscope before you pile on Band-Aids

   more likely to produce complexity induced

   risk. Better to prevent the injury than to

   carry tourniquets and field dressings.



 

   Bob . . .

- The Matronics AeroElectric-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:

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

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 14, 2020 1:24 am Post subject: How do you figure C-Rating of a battery?

At 09:38 PM 9/13/2020, you wrote:

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



 Can a dead battery be recharged by a fully charged battery? 	


   Think about it. What voltage does the alternator put

   out to charge the battery? What voltage does the

   battery put out while being discharged?



   Exception: Those glove box 'chargers' for dead battery

   recovery are much higher than 14v. Further, they

   obviously don't have the energy to fully charge

   their rescue battery . . . just put in enough snort

   to crank the engine.



 

 

   Bob . . .

- The Matronics AeroElectric-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:

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

rparigoris

Joined: 24 Nov 2009
Posts: 792

Posted: Mon Sep 14, 2020 9:55 am Post subject: Re: How do you figure C-Rating of a battery?

Hi Bob Thank you for your review. I will post schematic when it's completed. A few points: I'm not too worried about LiFe batteries getting thermal runaway, but I am about LiPo batteries getting to a thermal runaway. You posted a link to: https://tinyurl.com/y4oulfy9 As far as LiFe batteries go, I think mfg has done a reasonable amount of homework but fact is there is potential for problems that Lead Acid does not have and they can still fail opened. Good enough for me to use. I'm not worried about soldered and crimped connection to aluminium wires, but the terminal connections can get a high resistance. Keeping connections clean and tight mitigate majority of problems, but not all. As far as keeping NiMh pack charged, using one of my AstroFlight delta peak chargers (110D or 112D), once or twice a year will give them a C/10 for ~ 15 hours to balance, then delta peak charge the rest of the times. Unless battery is very flat, peaking at 1C takes less time than a pre-flight. 1x a year will capacity test down to 1V per cell and fuel pump equivalent load. BTW have you ever used an AstroFlight Whatt Meter (Whatt is correctly spelled)? Pretty slick meter that shows volts, amps and watt hours. Pricey though, here's an alternative that works pretty good: https://hobbyking.com/en_us/turnigy-180a-watt-meter-and-power-analyzer.html?queryID=7b349d17e0c87dff11877b2ea51342de&objectID=42854&indexName=hbk_live_magento_en_us_products Ron P.

- The Matronics AeroElectric-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:

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

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

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