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LiFePo4 Battery from 13.2V to 12V (or 11.8V)

124.244.234.206

twlai

In Reply to: RE: cMP - the open source high-end Memory Player posted by twlai on November 27, 2011 at 02:39:46

Hi,

I have recently purchased a pack of LiFePo4 battery which provides 3.3V*4=13.2V. What should be the ohm (R) and watt (w) of the resistor connected in series with the line feeding the CPU (P4) at 12V?

Regards,

Peter

Follow Ups:

RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 03:50:12 11/27/11 (17)
Hi,
What ohm (R) of the resistor depend on what mobo you're using and whether you're powering the P24 12V or P4 12V. For typical 500ma on P4 12V, a 2 ohm 5W resistor will do the job. Or you may plug the battery in directly to the P4 12V and leave it there. Yes, the P4 12V is shut off when the Mobo is powered off, hence no current running and no need for a switch for power on.

Or may be a good idea to use low dropout 3-terminal regulator to stabilize voltage at 11.5V(within 5% Tolerence of 12V).

Edits: 11/27/11
- RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - kclo 03:14:54 12/19/11 (0)
  Hi Jack,
  
  I am planning my next music server, and am also a believer in battery power supply. Would like to get your input on something I found in Taobao:
  
  http://item.taobao.com/item.htm?id=4472332925&ali_refid=a3_420435_1006:1102524038:6:%B5%E7%C4%D4%B5%E7%D4%B4:c31f8980be71f171b0dcf92593006536&ali_trackid=1_c31f8980be71f171b0dcf92593006536
  
  Would something like this be able to simplify the power supply issue?
  
  Thanks for your input, as always,
  KC
  - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - kclo 16:23:02 12/20/11 (0)
    And, jack,
    
    Is it possible for you to sent me an email.
    
    Thanks
    KC
  - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 08:44:37 12/20/11 (0)
    Hi KC,
    
    The product highlighted is very good value for SQ performance. Just slightly more expensive than an ATX PS, you can get a battery switching PS. The good thing is that you will certainly get rid of all power-line noise. The bad is that it's still a switching PS, but at this price I don't think one should ask for more. My comments are that you cannot possible buy a better PS at this price and it can possibly outperform some linear PS.
    
    The choice is very personal. This product offers ease of installation but is not a choice for ultimate performance. If you want better performance, look somewhere else.
    
    The LiFePo4 options are preferred. SQ will benefit from adding some good bypass capacitors and ferrite chokes. Of note, even with this PS, a separate 12V is still needed for the P4 for noise isolation.
    - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - kclo 16:29:08 12/20/11 (0)
      Hi Jack,
      
      Is it possible for you to sent me an email?
      
      Thanks
      KC
    - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - kclo 16:20:28 12/20/11 (0)
      Hi Jack,
      
      Thanks for your input. My intention is to use my existing work bench linear PS for the charging supply.
      
      KC
  - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - theob 03:28:50 12/19/11 (0)
    KC any english translation available? What is jist of article?
    - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - kclo 04:06:40 12/19/11 (0)
      Hi Theob,
      
      This board accepts:
      
      1. Battery input (24V/21V/19V)
      2. Charging input (220V/12V-car lighter/12&24V-car battery)
      
      and output 12V, 5V and 3.3V for the MO and display card
      
      You don't really need the Chinese, just look at the diagram and my description above
      
      KC
      - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - theob 04:32:45 12/19/11 (0)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by kclo on December 19, 2011 at 04:06:40
        
        Thanks
- RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - twlai 04:01:03 11/27/11 (8)
  Any 3-pin LDO regulator suggested?
  
  I also want to use a capacitor bank (http://www.ebay.com.hk/itm/220899802413?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_1522wt_901) and the diodes will be replaced by 2 wires.
  
  Therefore:-
  
  LiFePo4 battery 13.2V --> capacitor bank --> LDO regulator (Belleson?) --> CPU (P4)
  LiFePo4 battery 13.2V --> capacitor bank --> LDO regulator (Belleson?) --> pico-PSU --> MoBo (P24)
  
  I will report whether SQ will improve as compared to Linear PSU.
  
  P.S. my LiFePo4 battery is bought in China.
  - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 04:40:54 11/27/11 (0)
    LiFePo4 has very low internal resistance, in mohm, so only very high speed small cap can help them further. The caps on the ebay link do not appear to be high grade ones, I don't think they'll help. LiFePo4 is alread the best choice.
    
    If you want to improve SQ, invest on the 5V rail which is in the audio chain and thus most critical. P4 12V powers the CPU core and graphic etc and has a secondary role. The CPU core is somewhat like the engine of a car but the ram and I/O circut are like a ECU (the brain) which programs and direct how the engine will run.
    
    LDO ICs with 3A or more current delivery capability, such as LT1084, 1085 & 1086 can do the job. You may try using high quality regulators, but I don't know whether they will improve SQ. Please give it a try, as I want to know the result.
  - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - twlai 04:20:14 11/27/11 (6)
    Hi Jack,
    
    I also live in Hong Kong and also a civil servant!!! What a coincidence!!!
    
    May I e-mail you asking more questions about Computer Audio?
    - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 04:47:40 11/27/11 (5)
      Yes. No problem. For general questions about CPLAY/CMP/Computer do share in this forum so that everyone will benefit. We can go out for tea and have a discussion, you might have seen me before!
      - RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - twlai 05:32:43 11/27/11 (4)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by jackwong96 on November 27, 2011 at 04:47:40
        
        Small cap!? You are right as core audio also suggests so: http://www.coreaudiotechnology.com/blog/?p=24.
        
        Therefore, I should use Oscon. What value (Voltage and Farads) should I use?
        
        Is this one OK: http://www.ebay.com.hk/itm/68Pcs-220uF-63V-korea-cap-Power-supply-board-kit-sc-/200619648046?pt=LH_DefaultDomain_0&hash=item2eb5dce42e#ht_2354wt_901? I can replace all cap with Oscon!!!
        
        RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 08:00:42 11/27/11 (3)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by twlai on November 27, 2011 at 05:32:43
        
        Oscon is not good enough, I recommend Siemens Sikorel. 100-220uf 16V will do the job, bypassed by 0.1uf MKP cap.
        I recommend buying from Taobao.com rather than Ebay, cheaper.
        
        The source.
        http://search.taobao.com/search?q=sikorel&searcy_type=item&s_from=newHeader&source=store&ssid=s5-e&search=y
        
        Edits: 11/27/11
        
        RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - twlai 14:42:15 11/27/11 (2)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by jackwong96 on November 27, 2011 at 08:00:42
        
        Thank you, Jack.
        
        I understand that the cap should be connected in parallel. How many pieces do I need?
        
        How should I connect the bypass cap? Should I also connect it in parallel but closest to the load?
        
        Regards
        
        RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - jackwong96 17:44:07 11/27/11 (1)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by twlai on November 27, 2011 at 14:42:15
        
        Battery supply is quite pure and has no ripple. Hence big caps are not necessary. They have noise however. The small caps are for absorbing battery noise and enhancing high frequency response. Therefore, quality rather than quantity matters. 100-220uf + 0.1uf will be fine. I used 22uf 63V Sikorel, just happen to have such value and they work fine.
        
        One suggestion is to connect the caps to the bottom of the Mobo, and in this, beneath the P4 12V socket.
        
        See link.
        http://www.audioasylum.com/forums/pcaudio/messages/7/75904.html
        
        RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) - twlai 04:24:02 11/28/11 (0)
        
        In Reply to: RE: LiFePo4 Battery from 13.2V to 12V (or 11.8V) posted by jackwong96 on November 27, 2011 at 17:44:07
        
        Thank you, Jack.
        
        I now decide to connect in the following way:
        
        LiFePo4 (13.2V) --> 1.5R, 5W resistor in series (later change to Caddock) --> 220uF 16V cap (later change to Simens SIKOREL125) in parallel --> 0.1uF cap (later change to MCap) in parallel --> CPU (P4)
        
        I try to avoid using any IC in the circuit as far as possible.
        
        I have seen your mod on the mobo. Wow, great great work!!! I also wish to have my mobo mod like yours!!! I now use gigabyte 890GPA-UDH3 which is a AMD system as AMD has a lower SMI latency value.
        
        Thank you for the advice again.

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