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Thread: Cheap LIFEP04 batteries

  1. #21
    Expert Brissieboy's Avatar
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    Quote Originally Posted by the evil twin View Post
    You will risk damage to the device/cable/ after 2 to 3 hours because as the battery supply voltage falls the device will draw more current IE as the battery voltage falls the current draw will increase proportionally (P = E x I ... where P equal power, E equals voltage and I equals current).
    I disagree with that part. The power delivered will not remain constant so the logic of applying that formula is flawed. As the voltage drops, so will the current supplied, so the power delivered will reduce with the voltage. The possible exception to this would be a brushed motor load which will increase the current draw as its speed reduces and be max when it is stalled, but the voltage would be quite low at this point. And that formula still does not apply.

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    10G (31st October 2020)

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  4. #22
    I am he, fear me the evil twin's Avatar
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    For lights, analog loads, leccy motors etc I agree with you 100% and my original wording was a tad poor...
    but...
    DC/DC chargers or Supplies and the Digital Power Supplies associated with or found in a lot of medical or electronics are all examples of devices that often have constant power consumption independant of input voltage.

    The whole idea of these devices is that no matter the input voltage/current they deliver a controlled output to the load.

    DC/DC chargers in particular are notorious for being a source for blown fuses and burnt out wiring or connectors in equipment power circuits.
    When/if the vehicle supply voltage falls due to smart alternators, wiring voltage drops or other loads, the device compensates and pulls more current to get the same power output and a failure can occur especially if connecting a DC/DC into existing wiring.
    Last edited by the evil twin; 31st October 2020 at 03:34 PM.
    Dolphins are so smart that within a few weeks of captivity, they can train people to stand on the very edge of the pool and throw them fish.

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  6. #23
    Patrol Freak
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    Found this here:
    https://www.evergen.com.au/batteryte...gydifferences/

    Thought it was worth putting up ...



    For manufacturers trying to decide whether lithium-ion or lithium iron phosphate will be ideal for applications, consider these key factors:

    Highest energy density: lithium-ion
    Good energy density and lifecycle: lithium iron phosphate
    Stable chemical and thermal chemistry: lithium iron phosphate
    No thermal runaway and safe when fully charged: lithium iron phosphate
    Portability and lightweight characteristics: lithium-ion
    Long life: lithium iron phosphate and lithium-ion
    Low costs: lithium iron phosphate

    Also, take the operating environment into serious consideration as well as any vibration issues that may be experienced. These instances may influence a manufacturer’s choices as the chemistry stability that lithium iron phosphate offers are superior than that of lithium-ion.
    ..

  7. #24
    Expert pollenface's Avatar
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    Quote Originally Posted by pollenface View Post
    Never had experience with the cheap ones but I have 2x50ah 4s propower lithiums ($600 each) running a 24v 3000w inverter in my shed. They run all my power tools bar the welder & compressor. They are rated to 100amp discharge current. They go hard.

    https://www.ebay.com.au/itm/Pro-Powe...xX6YVaIqIWtn5A
    Not long after making this post both of my lifepo4 deep cycles had BMS failures.

    Knowing what I know now, if I wanted to do it cheaply I would buy the individual 3.2v cells and use my own BMS and run important loads straight independent of the BMS.
    Last edited by pollenface; 2nd November 2020 at 11:25 PM.
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    Factory snorkel, flashlube catchcan pro, 3" manta exhaust, hpd boost controller, dyno-tuned & egr deleted

  8. #25
    I am he, fear me the evil twin's Avatar
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    Not being critical just making an observation but a 3000 Watt Inverter can demand a shit load more than 100 Amps so that may have been what cooked the internal BMS.

    A 3kW Inverter running off a 24 Volt supply can draw well over 200 amps momentarily.
    Dolphins are so smart that within a few weeks of captivity, they can train people to stand on the very edge of the pool and throw them fish.

  9. #26
    Expert pollenface's Avatar
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    I agree.

    Live and learn.
    Last edited by pollenface; 4th November 2020 at 11:49 PM.
    2008 CRD Auto Wagon
    Factory snorkel, flashlube catchcan pro, 3" manta exhaust, hpd boost controller, dyno-tuned & egr deleted

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