Freerails Home 
Home Search search Menu menu Not logged in - Login | Register
Freerails > Model Railroad Forums > R.C. The Future Now If You Desire > Revisiting 1-Cell Versus 2-Cell Li-Po Batteries

Freerails IS ACCEPTING new Members ... To join Freerails ... See how to Register as a Member in the 'Joining Freerails' Forum

Revisiting 1-Cell Versus 2-Cell Li-Po Batteries
 Moderated by: . Page:  First Page Previous Page  1  2  3  4  5  Next Page Last Page  
New Topic Reply Printer Friendly
 Rating:  Rating
AuthorPost
 Posted: Mon Apr 18th, 2016 08:33 pm
  PMQuoteReply
21st Post
Budd
Registered


Joined: Tue Jan 12th, 2010
Location: Adelaide, Australia
Posts: 105
Status: 
Offline
I'm just trying this 1C + step up configuration in an Athearn Mikado and mine was cutting out as well, the Polulu was getting quite warm, so if I use a 2C pack with the step up will it function better, the speed is a bit slow with just 7.2V. I'm using a 9V step up.
I don't know what that engine pulls (in mA's), I set it up tomorrow and see if I can get a reading.

Wayne from Oz.



____________________
Modelling the 3'6" gauge railways of South Australia of course.
Back To Top

 Posted: Tue Apr 19th, 2016 01:32 am
  PMQuoteReply
22nd Post
davecttr
Registered
 

Joined: Sat Nov 9th, 2013
Location: United Kingdom
Posts: 527
Status: 
Offline
The Pololu regulator has a temperature cut off and I think a high current one. These operating might trigger a low voltage cutoff (LVC) in the Deltang RX. I experience these occasionally and have not been able to determine the cause.

A 9V Pololu with a 1S lipo can't handle locos pulling about 0.4A or greater. Some of my locos draw about 0.5A so using a 2S battery means the Pololu can handle up to 0.9A. There are efficiency graphs on the Pololu page.

I determine the amps draw of my locos by running the loco under load and measuring how long the battery lasts. For example the little 70mAh batteries I use for testing will give 1 Amp for 4.2 minutes. If a loco under test hauling 12 coaches at a scale 60mph stops after 10.5 mins the current draw is about 0.4A. This is marginal so I would probably use a 2S battery.

when using 2S batteries I manually set the LVC to 6.8V. this is to ensure a safety margin as my made up 2S batteries are not matched pairs.



____________________
Dave
Back To Top

 Posted: Tue Apr 19th, 2016 02:06 am
  PMQuoteReply
23rd Post
Rod Hutchinson
Registered


Joined: Fri May 8th, 2009
Location: Mooroolbark, Australia
Posts: 521
Status: 
Offline
Wayne,

I am converting my 1S + Pololu to 2S + Pololu. I am doing it because I physically can and because of the electronic theory that has been presented recently.



____________________
Rod Hutchinson
Mooroolbark, Australia
Back To Top

 Posted: Tue Apr 19th, 2016 03:58 am
  PMQuoteReply
24th Post
mwiz64
Registered


Joined: Mon Mar 26th, 2012
Location: Fenton, Michigan USA
Posts: 1330
Status: 
Offline
If you could get 3s to fit you could eliminate the Pololu and your charge would last even longer..... Or you could use smaller cells and maybe have the same duration with but with less heat and complexity. Just sayin....



____________________
Mike
Back To Top

 Posted: Tue Apr 19th, 2016 04:07 am
  PMQuoteReply
25th Post
Rod Hutchinson
Registered


Joined: Fri May 8th, 2009
Location: Mooroolbark, Australia
Posts: 521
Status: 
Offline
Thanks for that.

Yes, plenty of choices.



____________________
Rod Hutchinson
Mooroolbark, Australia
Back To Top

 Posted: Tue Apr 19th, 2016 12:05 pm
  PMQuoteReply
26th Post
davecttr
Registered
 

Joined: Sat Nov 9th, 2013
Location: United Kingdom
Posts: 527
Status: 
Offline
mwiz64 wrote:
If you could get 3s to fit you could eliminate the Pololu and your charge would last even longer..... Or you could use smaller cells and maybe have the same duration with but with less heat and complexity. Just sayin....

Yes, it is all down to how much space you have. I am lucky in that all my passenger locos can achieve at least a scale 60mph with a 9V Pololu. The smaller freight types have a single battery because of space problems and the larger freight locos run on a simple 2S battery without Pololu. The nominal 7.4V is enough to give over a scale 25mph and most freights in my modelling period were restricted to about 25mph top speed!.

I have one mixed traffic loco that generates a lot of LVC cutoffs and I am going to try that one with a 3S battery and disabled LVC.



____________________
Dave
Back To Top

 Posted: Tue Apr 19th, 2016 12:25 pm
  PMQuoteReply
27th Post
Budd
Registered


Joined: Tue Jan 12th, 2010
Location: Adelaide, Australia
Posts: 105
Status: 
Offline
davecttr wrote:
mwiz64 wrote:
If you could get 3s to fit you could eliminate the Pololu and your charge would last even longer..... Or you could use smaller cells and maybe have the same duration with but with less heat and complexity. Just sayin....

Yes, it is all down to how much space you have. I am lucky in that all my passenger locos can achieve at least a scale 60mph with a 9V Pololu. The smaller freight types have a single battery because of space problems and the larger freight locos run on a simple 2S battery without Pololu. The nominal 7.4V is enough to give over a scale 25mph and most freights in my modelling period were restricted to about 25mph top speed!.

I have one mixed traffic loco that generates a lot of LVC cutoffs and I am going to try that one with a 3S battery and disabled LVC.


I am getting a bit of track here but I have had the discussion at a couple of DC and DCC railways where I operate (with my BPRC engine) about how big a BPRC railway can become before it is too big to manage, my comment was that you may become limited by the amount of battery charging you would have to manage (assuming you don't have some form of auto track charging).
Out of interest Dave, how many engines do you have?

Wayne from Oz.



____________________
Modelling the 3'6" gauge railways of South Australia of course.
Back To Top

 Posted: Tue Apr 19th, 2016 12:29 pm
  PMQuoteReply
28th Post
Budd
Registered


Joined: Tue Jan 12th, 2010
Location: Adelaide, Australia
Posts: 105
Status: 
Offline
mwiz64 wrote:
If you could get 3s to fit you could eliminate the Pololu and your charge would last even longer..... Or you could use smaller cells and maybe have the same duration with but with less heat and complexity. Just sayin....

So you are saying that a 600mA 3C pack will last longer than a 600mA 2C pack + Polulu?

Wayne from Oz



____________________
Modelling the 3'6" gauge railways of South Australia of course.
Back To Top

 Posted: Tue Apr 19th, 2016 03:05 pm
  PMQuoteReply
29th Post
davecttr
Registered
 

Joined: Sat Nov 9th, 2013
Location: United Kingdom
Posts: 527
Status: 
Offline
Out of interest Dave, how many engines do you have?

Wayne from Oz.


I have 20 converted and another 10 to do. An operating session on my layout will use about 15 locos with over 20 batteries. My locos do not have an on-off switch and I use freshly charged ones at each session. I use an E-flite 4 battery charger and am going to buy 2 USB chargers. With these I can charge 24 batteries in under 4 hours. This is easy to do in an evening. I also have three Tx-22, One handles the main line passenger locos, the second freight locos including a consist and the third branch line and mixed locos. I have not populated this one yet.



____________________
Dave
Back To Top

 Posted: Tue Apr 19th, 2016 04:58 pm
  PMQuoteReply
30th Post
fallen
Registered
 

Joined: Wed Apr 3rd, 2013
Location: United Kingdom
Posts: 197
Status: 
Offline
Budd wrote:


So you are saying that a 600mA 3C pack will last longer than a 600mA 2C pack + Polulu?

Wayne from Oz


That's right Wayne, If the Polulu steps the voltage up it must also draw more current than is being supplied to the loco, by at least the same factor as the voltage is increased. If the Polulu draws more current, the 600mAhr cells in the 2S battey will run down faster than those in the 3S battey which just supplies the loco current direct.

Frank

Back To Top


 Current time is 11:49 am
Page:  First Page Previous Page  1  2  3  4  5  Next Page Last Page  

Freerails > Model Railroad Forums > R.C. The Future Now If You Desire > Revisiting 1-Cell Versus 2-Cell Li-Po Batteries
Top



UltraBB 1.172 Copyright © 2007-2016 Data 1 Systems