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Seal acid battery equivalent lithium

Discussion in 'Power Electronics' started by Lance0070, Mar 25, 2019.

  1. Lance0070


    Jan 23, 2018
    Hi there can some tell me the equivalent for 12volt 8ah sealed battery to a lithium?
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    You would be looking for an 11.1V 8Ah lipo battery. This will have 3 lipo cells in series.

    Remember that a balancing charger designed for lipo batteries will be required.

    You may be able to get away with a lower capacity battery because more of the capacity of a lipo battery is available than in a lead acid battery.
  3. dave9


    Mar 5, 2017
    A 12V 8Ah sealed lead acid battery is often chosen merely because it is the cheapest cost per capacity and tends to use use a simple/cheap charging circuit.

    It could be very significant what you're trying to power with it, including needed duration (runtime), and "lithium" is just a chemistry family, not specific cells which will determine # of recharge cycles, pack voltage, and drilling down to particular cell construction and size, also max current.

    So, there is no all around lithium equivalent. You could essentially ignore that the widget ever used a 12V, 8Ah and redesign a pack for what the widget needs including the discharge termination circuit and charge circuit.

    Why not just use a 12V, 8Ah lead acid battery? If the size or weight is a factor, you will need to be all the more detailed in the minimum parameters the powered circuit needs instead of just overshooting it and getting the voltage "close enough".
  4. Lance0070


    Jan 23, 2018
  5. Bluejets


    Oct 5, 2014
    I'd be looking at taking something with me to put out the fire if salt water gets anywhere near that Lithium battery.
    Then again, could be safer to pack a good life jacket and then simply jump overboard.

    Curious where your 8Ah came from. The first bit of your link showed 22Ah battery.
  6. dave9


    Mar 5, 2017
    As Bluejets mentioned, I see nothing on that page which takes a mere 8Ah battery. This is beyond what you can power with a single series of 26650 Li-Ion cells so you will need a custom pack of paralleled series and a charger for it as well as either protected cells or a cutoff circuit.

    It would be much easier and cheaper (less than half the cost) to just buy a new lead acid battery. They do wear out eventually. Otherwise it seems like you ought to try to get some motor power consumption specs from the manufacturer and see if there are battery pack builders in your area, for example for electric bicycles/mopeds/etc would be a typical source for a ready made pack and charger for it, though those tend to be more for higher voltage and lower amp hours but it couldn't hurt to ask them what they can build for you.

    You should also be able to get more advice about sourcing components and chargers in an eBike specific web forum, since it's not going to be so simple as merely putting a few 18650 cells in series to power something like that.

    You might even find that the product design factors for the weight of the battery as a ballast and if you put in a significantly lighter Li-Ion pack, you may need to add back much of that weight to retain stability.
    Last edited: Mar 25, 2019
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