Lithium Ion Battery Pack

Discussion in 'General Electronics Chat' started by Andrew Martin_1461983963, Apr 29, 2016.

  1. Andrew Martin_1461983963

    Thread Starter New Member

    Apr 29, 2016
    2
    0
    Hello everyone,

    My wife is an artisan vendor and looking for a battery pack so she doesn't have to pay the exorbitant prices that many of the shows that she goes to want for power. What I have is two deep cycle RV batteries, a battery charger and a 12V DCto 120V AC power inverter.

    What I am wanting to do is tweak it to make it MUCH lighter- the two RV batteries together in the same case is dang heavy and bulky.

    It is powering her booth- about 10 household LED lights (the data sheet says 10W per bulb.) Charge a cell phone or two and charge an Ipad- for her Point of Sale. Any experience in locating couple Lithium ion batteries would be awesome! What type, capacity, number of, voltage, charger/inverter would be helpful.
    I'm also located in Canada as an added twist would like to keep the price of the unit around $500-600.

    Thanks in advance!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,094
    3,033
    Lithium ion does offer a higher energy density (power per kg) than your lead-acid batteries, but they have a lower power per dollar. I believe it's ~3X for the power per weight and ~2-3X for power per dollar.

    Are you willing to pay 2-3X to lighten your batteries by 3X?
     
  3. Scott594

    New Member

    Dec 8, 2012
    1
    1
    The Cheapest Lithium power to be had (to my knowledge) is RC batteries from Hobby King. I like the Zippy Compact Line for power to weight, but there are many good quality ones there. (I fly Giant Scale RC planes, and use some pretty large Lipos) The electrics possible these days rival my 35cc gasoline planes.

    There's quite a lot to designing a SAFE and RELIABLE Lipo system however.

    They CANNOT be overcharged (beyond 4.2v/cell and you can't exceed the rated rate, (fire or worse) and they cannot be exhausted past 3.3v/cell (higher for decent life). They generally should be balance charged (each cell adjusted individually thru a 'balance connector') for life and safety as well.

    They sell computer controlled chargers which help take care of that problem, but don't charge in the house, near anything flammable, or unattended.
    They should be charged and used in a vented metal or similar insulated box in the event of failure. All it takes is typing in the wrong setting and it can get ugly fast.

    Check out a site called "Battery University" they are about as close to the authority on Lipos right now.

    Lipos have made incredible advances as of late (graphite nano-tube electrodes have helped capacity a lot), but anything with that kind of energy density is just downright dangerous if something goes wrong. I had a polarity accident with a tiny (3S 1000mah) one and it produced an instant fireball the size of a basketball. in addition it fused open 14awg stranded leads. I would hate to see a large one go wrong.

    The 18650 cells are a lot more expensive, but due to a more stable chemistry and metal can, are quite a lot safer (these are usually what they use in laptop batteries)

    The problems with the 787 Dreamliner batteries designed to replace the APU illustrate how touchy they can be. If Boeing can't keep them under control, they deserve respect.

    I'm not saying not to do a system, but maybe break it down into several smaller packs, with proper charger, discharge protection etc. Absolutely do the homework, and consult an expert if you're not comfortable.

    A safer, albeit more expensive way may be cordless power tool batteries & chargers. They are consumer 'safe' and the engineering work is done. They have built in overcharge/overdischarge protection (as do SOME 18650 cells, double check if you use them)

    Read, and from reputable sources (Battery U, Manufacturers etc.) beware armchair experts on forums (like me).

    Hope that helps.

    Scott
     
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  4. Andrew Martin_1461983963

    Thread Starter New Member

    Apr 29, 2016
    2
    0
    Thankyou all,

    I like the idea of using power tool batteries- but the cost per battery (would need like 4 for the reserve capacity). But that idea made me think of this PowerAll BPJS 16000R would hooking two of these up with the booster cables to a power invertor work do you think? They are 280 ea CAN and just use USB power to charge.
     
  5. andrewmm

    Member

    Feb 25, 2011
    29
    6
    All the things you mention using are DC power.
    Your taking a low dc voltage ( 24 volts I guess ) changing it to 120 volts AC , then using converters to change that back to low voltage for your leds , chargers.

    VERY in efficient. I'd guess if you have 100 Ah in the batteries, you are only using about 20 Ah.
    Mobile phones / apple pad are usb charged. Look on your favourite web site and you will find pocket power packs for a few dollars, that will re charge your pad and phones a few times.

    As for the lights, look for dc powered caravan lights.
    at most they will need just one heavy battery,
     
  6. crutschow

    Expert

    Mar 14, 2008
    12,993
    3,229
    I agree with andrewmm.
    It's inefficient (perhaps 75%) to step 12V up to 120V just to power some lights and charge a few devices.
    Using ten 10W, 12V RV bulbs would draw about 8A from your battery.
    Thus you would need 64Ah for 8 hours booth time.
    That would require at least 4 of the PowerAll BPJS 16000R packs.

    Edit: If you can get by with lower wattage bulbs, such as one of these, that would lessen the battery requirements, of course.

    The various devices can be charged using an automotive 12V to USB charger plug-in.
     
    Last edited: Apr 30, 2016
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