4 Sevens
Results 1 to 7 of 7

Thread: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

  1. #1
    Flashaholic* samgab's Avatar
    Join Date
    Aug 2010
    Location
    Auckland, New Zealand
    Posts
    1,096

    Default Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    I'm wondering what sort of burst current a LiFePo4 cell can handle.
    Because I was thinking about voltages of the various chemistries,
    and it seems, regular lead-acid SLI 12V automotive batteries charge at ~14.4V and are nominal 12V using 6 cells.
    LiFePo4 cells charge at 3.6V and work safely down to 3.0V.
    So a LiFePo4 4S battery would have similar voltage properties to a 6S Pb battery.
    14.4V charge rate, and would work down to 12V happily.
    So it would work with standard car charging and electronic and lighting systems.
    So a battery of LiFePo4 cells could be made up, in 4S4P layout or 4S8P or something.
    But would it be able to supply enough of a current burst to start the car?
    How would it cope?

    I'm sure using this technology, if the current supply is up to the task, we could have much lighter automotive SLI batteries.

    And as for LEDs... A lot of very modern cars have LED indicators and brake lights, but it's a very slow advance into the industry.
    It's mostly only top of the line expensive euro cars that have them. Also, strangely, pretty much ALL trucks and busses!
    But they seem like a fairly obvious thing to replace incandescents for brakes and indicator lights.
    They turn on and off much faster than an incan. which is safer.
    They don't blow at the rate of incans.
    They use way less power than incans.
    So why are ANY cars still coming out with incan bulbs, for brake and indicator lights at least?
    It's not like low brightness (I mean, 5mm standard type rather than cree type high brightness ones) LEDs are expensive, or difficult to implement.
    And there are, what, about 2 cars in production with fully LED headlamps? Excluding prototypes.

    I think the automotive industry is behind the times, very backwards.
    In date order, as far as I can remember: Mag 4D LED, LL P14, Fenix LD20 R4, 47s Preon 2 R5 red, 47s Quark Mini AA S2, Fenix TK35 XM-L T6, 4Sevens ReVO SS S2, Maha MH-C808M, Maha MH-C9000, 47s Single Bay Li-ion charger, Zebralight SC600 XM-L U2, Fenix TK70, iCharger 206B, Sunwayman D40A...

  2. #2
    Flashaholic* samgab's Avatar
    Join Date
    Aug 2010
    Location
    Auckland, New Zealand
    Posts
    1,096

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    As far as the possible discharge rates, I found THIS SITE with some discharge specs on one type of LiFePo4 cell.
    These cells are 10Ah and rated for 10C (100A) continuous discharge, and 15C (150A) pulse discharge.
    Charging is stated at 3.65V per cell, but the tech specs state that is +/-.05V, so 3.60V is still within spec.
    So a 4S4P setup would be pretty awesome!
    It would be 40Ah, and could discharge at 400A continuous (WOW!) or 600A pulse!!!
    I'm sure that would be more than enough for any car starter motor draw etc.
    It would charge at 14.4V (14.4-14.8) and could run no problem at 12V.

    As for the size and weight... They are 340g per cell, so just the cells would be 5.44Kg.
    So this battery could be about half the weight (mass) of a traditional lead acid 40Ah car battery.
    Also it's rated for >2000 cycles.
    And in 4x4x1 layout, it could be as small as just over 152x152x146mm

    Wow, I should just buy the cells and make one and see how it works out next time I'm due for a new car battery.
    The initial cost would be more than a lead-acid, $23 per cell for 16 cells = $368 plus shipping etc...

    Anyone already experimented with this?
    Last edited by samgab; 11-07-2011 at 10:21 AM. Reason: typo... have had a few drinks.
    In date order, as far as I can remember: Mag 4D LED, LL P14, Fenix LD20 R4, 47s Preon 2 R5 red, 47s Quark Mini AA S2, Fenix TK35 XM-L T6, 4Sevens ReVO SS S2, Maha MH-C808M, Maha MH-C9000, 47s Single Bay Li-ion charger, Zebralight SC600 XM-L U2, Fenix TK70, iCharger 206B, Sunwayman D40A...

  3. #3

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    I looked into it. Yes, the initial cost would be more than a traditional battery. The biggest issue is that the BMS (battery management system) that SHOULD be used with this setup (capable of high current) would cost as much if not more than the cells. But seriously, that battery would probably last longer than your vehicle would. I built a basic, small version of one here...

    http://www.diyaudio.com/forums/class...y-project.html

    maybe you need something like these...

    http://www.bmsbattery.com/lifepo4-ce...tery-cell.html
    Last edited by lilmarvin4064; 11-18-2011 at 06:01 PM.

  4. #4
    Flashaholic* samgab's Avatar
    Join Date
    Aug 2010
    Location
    Auckland, New Zealand
    Posts
    1,096

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    Quote Originally Posted by lilmarvin4064 View Post
    I looked into it. Yes, the initial cost would be more than a traditional battery. The biggest issue is that the BMS (battery management system) that SHOULD be used with this setup (capable of high current) would cost as much if not more than the cells. But seriously, that battery would probably last longer than your vehicle would. I built a basic, small version of one here...

    http://www.diyaudio.com/forums/class...y-project.html

    maybe you need something like these...

    http://www.bmsbattery.com/lifepo4-ce...tery-cell.html
    That battery of yours looks brilliant, that's the sort of thing I had in mind, or the beginnings of it...
    I would have thought that the car's charging and battery management system would take car of things pretty well, because as I was saying in the original post, the voltage limits and parameters for a car lead acid battery fall within those for the 4S LiFePo4 battery...
    Thanks for the feedback and links.
    I wonder why LiFePo4 batteries are not commonly coming out premade for cars already?
    Perhaps it's because cost is still prohibitive for most people's usage.
    In date order, as far as I can remember: Mag 4D LED, LL P14, Fenix LD20 R4, 47s Preon 2 R5 red, 47s Quark Mini AA S2, Fenix TK35 XM-L T6, 4Sevens ReVO SS S2, Maha MH-C808M, Maha MH-C9000, 47s Single Bay Li-ion charger, Zebralight SC600 XM-L U2, Fenix TK70, iCharger 206B, Sunwayman D40A...

  5. #5
    Flashaholic* samgab's Avatar
    Join Date
    Aug 2010
    Location
    Auckland, New Zealand
    Posts
    1,096

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    Maybe four of these cells in series would be ideal:
    http://www.ebike-bmsbattery.com/index.php?url=products.php%3Fdid%3D1&did=1

    A
    battery of four of them side by side, wired in series, would be about 220 x 168 x 131 and would weigh about 7.2Kg.
    So you're getting up to the weight and size of a standard car battery.
    And $316 plus shipping.

    It would be good for continuous discharge current of ~150 Amperes, and a peak pulse discharge of 500 Amperes.
    It would maintain 12V under an ongoing 250Amp current draw, according to the data curves.
    It could charge at 14.4 Volts.
    and the minimum voltage is 10 Volts, which a car lead acid battery should never get down to anyway.
    I don't think a third party BMS would be required.
    In date order, as far as I can remember: Mag 4D LED, LL P14, Fenix LD20 R4, 47s Preon 2 R5 red, 47s Quark Mini AA S2, Fenix TK35 XM-L T6, 4Sevens ReVO SS S2, Maha MH-C808M, Maha MH-C9000, 47s Single Bay Li-ion charger, Zebralight SC600 XM-L U2, Fenix TK70, iCharger 206B, Sunwayman D40A...

  6. #6

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    Quote Originally Posted by samgab View Post
    That battery of yours looks brilliant, that's the sort of thing I had in mind, or the beginnings of it...
    I would have thought that the car's charging and battery management system would take car of things pretty well, because as I was saying in the original post, the voltage limits and parameters for a car lead acid battery fall within those for the 4S LiFePo4 battery...
    Thanks for the feedback and links.
    I wonder why LiFePo4 batteries are not commonly coming out premade for cars already?
    Perhaps it's because cost is still prohibitive for most people's usage.
    LiFePO4 cells are commonly used in Hybrid and electric vehicles, as storage batteries; not so common in starting batteries.

    Thanks, I don't think it's amazing but I accidentally over discharged it once already (these cells didn't have any over-discharge protection); that's the biggest thing you should worry about. Aside from reduced weight which can be negligible in a large vehicle, I can't see any benefit by using LiFePO4 vs Lead-acid besides longevity,(get at least a LV cutoff). What if, you are going out of town and you accidentally leave your car door ajar; greatly reduced lifespan.

    How many amps do you need to start your vehicle? I figured most people would need at least 2-3 of these cells in parallel. 4S2P or 4S3P
    Last edited by lilmarvin4064; 11-18-2011 at 06:51 PM.

  7. #7
    Flashaholic* samgab's Avatar
    Join Date
    Aug 2010
    Location
    Auckland, New Zealand
    Posts
    1,096

    Default Re: Automotive technology moving slowly? LiFePo4 SLI batteries? LED headlights?

    Quote Originally Posted by lilmarvin4064 View Post
    What if, you are going out of town and you accidentally leave your car door ajar; greatly reduced lifespan.

    How many amps do you need to start your vehicle? I figured most people would need at least 2-3 of these cells in parallel. 4S2P or 4S3P
    Car lead acids are very sensitive to voltage too, and are damaged by overdischarge as well. If a lead acid drops below 11.89V (OCV) it seriously reduces the cycle life.
    The cells I linked to in the second scenario have a 2.5V per cell, or 10V for the battery (OCV), overdischarge protection.
    My car starter motor might draw about 60-100Amps in normal conditions, and I'd want the battery to be capable of supplying as much as 3-400Amps for worst case scenario cold cranking situations (It's only a 1.8ltr).
    It wouldn't need to sustain those high draw currents, but as long as it can pulse as high as 400Amps, it would suffice.

    The standard SLI lead acid battery in my car is rated for 300 cold cranking amps, and 35Ah capacity. It is 187 x 127 x 226.

    But you got me thinking... Do cars have some kind of built in overdischarge protection to protect the SLI battery? I'm not sure...
    In date order, as far as I can remember: Mag 4D LED, LL P14, Fenix LD20 R4, 47s Preon 2 R5 red, 47s Quark Mini AA S2, Fenix TK35 XM-L T6, 4Sevens ReVO SS S2, Maha MH-C808M, Maha MH-C9000, 47s Single Bay Li-ion charger, Zebralight SC600 XM-L U2, Fenix TK70, iCharger 206B, Sunwayman D40A...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •