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Li-ion Battery ... ???

Post in 'The Green Room' started by jebatty, Dec 8, 2012.

  1. jebatty

    jebatty Minister of Fire

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    I just started using two 18650's, first because I got one of those high-powered flashlights [wow!! really bright] that uses one of these and second because these seem to be a real advantage where they can work. Who is using them and for what? My flashlight has a Cree XM-LT6 led.

    I might have made a mistake in getting unprotected cells, but when I ordered them, LG 2600 mah, I thought protection related mostly to charging, not excessive drain or over-discharge. I can handle the charging OK with my DC constant voltage/constant current power supply, probably better than most li-ion chargers. I probably will buy only protected cells in the future. Lots of reading on charging, discharge rates, shorting, and over-discharge strongly suggest protected cells are much safer and better.

    Regardless, these are light, pack lots of power, and seem to have lots of advantages over NIMH or nicad, where they work. I also have a led flashlight that takes the typical 3-pack of AAA's, and I found that the case and spring have room to take one 18650 - sweet. I have an RC boat with a nicad battery pack, 7.2V -- two 18650's pack far more power and a lot less weight. I also am making a handlebar mount for the high-powered flashlight so that it can be used as a bicycle light.

    For the high-powered flashlight, I discovered a backup plan using a CR123A lithium primary cell and a spacer made out of 1/2" copper pipe and end caps. Cool.

    Other experience from anyone?

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  2. PapaDave

    PapaDave Minister of Fire

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    Brother has a Li-ion cordless drill. Great unit, until the battery dies. Doesn't give any real indication of low charge....it just quits.
    RC boat or plane might have a bit of a problem with that!!! , unless there's a workaround.
  3. jebatty

    jebatty Minister of Fire

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    The info shows li-ion batteries and packs with protection circuits shut the batteries down at about 3 volts/cell, maybe a little less. Deep discharge can damage li-ions. Yes, a shutdown of the boat out in the water would be a problem.
  4. jharkin

    jharkin Minister of Fire

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    It just quits because this is a low voltage cutoff circuit in the pack. We use lots of lithium battery chemistries in R/C, its not a problem at all really, the speed control units (the electronic "throttle") have a similar cutoff but its usually a soft cutoff that will cut the motor to < 50% power, or sometimes make it pulse power, as a signal to the pilot that your pack is depleted.

    Regular lithium Ion and lithium polymer should never be discharged below 3 volts per cell. If you go under 2.5 volts per cell they get permanently damaged. The A123 chemistry (LIthium Iron phosphate - LiFePO4) is a lot more tolerant in this regard- Ive accidentally drawn them down to zero and they can recover. They also can take ridicolous charge (5C or 12 minute) and discharge (something like 50C)rates and have a nearly flat discharge curve. Also they are easier to direct substitute for NiCD and NiMH, the cells are 3.3volt (vs 3.6v for LiIon) so each cell can directly replace 2 nicads voltage wise. The drawbacks are that those cells are much lower capacity for the same size (the 18650 size cans are only 1100mAh) and they are prety much imposible to capacity check other than recharging due to that flat discharge curve.


    I LOOOOVE the LiIon/LED flashlight that came with my dewalt set...

    For your boats dont bother with the cylindrical metal can LiIon's. They wont last long in high amp discharge use. Pretty much all electric R/C use has gone over to lithium polymer and A123 cells. You can get Chinese made LiPOs at redicously cheap prices these days. A lot of the electric airplane and helicopter guys have good results from the Turnigy brand available at HobbyKing. In the early days of LiPO power we used brands like Thunderpower, Flightpwer, E-Flite, etc. These are very high quality but much more expensive - its cheaper to buy and replace the inexpensive ones more often.

    Right now I use LiPo for motor power, A123/LiFEPO4 for receiver power in my gas models, and Sanyo Eneloop NiMH for my transmitter power.

    Hobby sources for the batteries, charges, etc:
    http://www.radicalrc.com/
    http://www.hangtimes.com/
    http://www.hobbyking.com
    http://www.atlantahobby.com/
    http://www.e-fliterc.com
    http://www.towerhobbies.com/electric/index.html
    http://www.hobby-lobby.com/


    For charging I really like the FMA direct computerized units and the Great Planes Triton series but they are expensive. there are cheaper options out there.

    Most of the hobby chargers are DC to DC. In my shop I made a makeshift 12v DC power supply from a junk PC power supply to power mine.
  5. PapaDave

    PapaDave Minister of Fire

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    How can you tell?
  6. jharkin

    jharkin Minister of Fire

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    On the hobby batteries I check them with a volt meter, or program a low voltage cutoff in the controller. Any cordless tool made specifically for liIon would have a cutoff circuit built in.
    PapaDave likes this.
  7. jebatty

    jebatty Minister of Fire

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    I will check out the lithium polymer and A123 cells. I just started using Eneloops, and I noticed that some of the high power led flashlights come with Eneloops. I've heard an opinion that these should not be used in high drain applications, but the high power led's can have high drain. Any experience on this? BTW, last week the local Costco had 10-pack AA 1900mah Eneloops for $15.

    I ran one unprotected 18650-2600mah down to just over 3V, 9 five minute "on" cycles with the flashlight on maximum output. The battery was fairly close to full charge at the start. I then charged fully with the DC constant current/voltage power supply, following the charging guidelines in Battery University: charge 0.7C to 4.2V and then saturation charge at 4.2V down to 0.03C. The 18650 did not get noticeably warm to the touch.
  8. jharkin

    jharkin Minister of Fire

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    The LED flashlight should not be a problem. If its, say, a 1 watt LED, on a 2 AA setup (2.4v) that's pulling 400mA. For a 2000mAh Eneloop AA cell thats a C/5 discharge rate, which isnt too bad.

    When they warn against high discharge they are typically talking rates over 1C. Those lithium polymer cells can typically handle up to 30C, and the A123s can do that and burst up to 60C.
  9. begreen

    begreen Mooderator Staff Member

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    I'm going to get a Li-Ion LED flashlight for my Makita 18v battery packs. These packs sit idle most of the time, unless I'm using the drill. Might as well put them to work in power outages.
  10. Seasoned Oak

    Seasoned Oak Minister of Fire

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    I was blown away by craftsmans LED flashlight for the C3 series tools. Even more surprised to learn its only 1 Watt. Shines VERY bright and more towards a spotlight than a floodlight. Im equally impressed with their C3 Li-ion battery pack. I cut a whole tree down(about 6" diameter)and chopped it in pieces with my C3 reciprocating sawzall and a single LI-ion battery pack. Had at least 4 charged backup batteries but didnt need any of them.
  11. begreen

    begreen Mooderator Staff Member

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    Yes, this latest generation is a huge improvement.
  12. jebatty

    jebatty Minister of Fire

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    I believe the C3 battery packs are nicads, sub-C's, about 700 mah. Price on replacement packs has come down a lot. When the price was high not so long ago, it was less expensive to make up a replacement pack with much higher capacity NiMh batteries, but had to use a different charger. The new li-ion battery pack tools are really light and compact compared to the nicad tools, but replacement battery packs are expensive. I took a look at the inside of the li-ion pack for my Hitachi 18V. It has 5 cells, and the wiring appears to include charging and balancing for each cell, along with protection, which doesn't make it too easy to makeup your own replacement pack with new cells.

    You can buy replacement LED lamps for most flashlights in the familiar PR bulb format. I bought one for my Maglite C-cell flashlight, also impressive on light output. I would guess for equivalent lumens the LED uses about 1/5 the current that the incandescent bulb uses, meaning much longer battery time. I haven't seen specs showing lumens for each type of bulb.

    Many of the LED & li-ion flashlights publish lumen output, which is relatively useful. Also lots of reviews on these flashlights which truth-check the claims and provide reliability and use guidance.
  13. woodgeek

    woodgeek Minister of Fire

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    While a drop in LED bulb is a clear upgrade over the previous bulb, the result is often inferior to buying an 'as engineered' LED flashlight. The drop in LED bulbs throttle down when they heat up (to keep from getting fried), and this causes performance after the first 10 second 'wow' to taper off, often significantly. Regular LED flashlights have enough heat sinking on the emitters to keep running at high power.
  14. jebatty

    jebatty Minister of Fire

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    Very much agreed. I did not want to get rid of the Maglite; thus the conversion to an LED bulb. In this case, good enough was good enough.

    While an engineered LED flashlight with high output, up to about and maybe exceeding 1000 lumens, starts at around $10 and nearly the sky is the limit beyond that, the lower priced ones (mine was $9.99) usually do not come with li-ion batteries or a charger; any of them supplied with li-ion batteries may have inferior batteries; and the chargers, except for high end and expensive chargers, likely do not charge the batteries to full capacity. There are many reports of li-ion batteries not having the advertised capacity, which may relate to inferior batteries, intentional mislabeling, and/or inferior chargers. I bought quality unprotected 18650's because of the lower price point vs protected cells, did not buy a charger because I can charge from my DC power supply at a proper rate, not exceed the specified voltage, and then taper down with a saturation charge to the specified cutoff current to obtain a fully charged battery. After lots of reading I cannot recommend unprotected li-ion rechargeable cells except for those who have the knowledge and ability to use and handle them safely.

    A quality LED flashlight, with high quality batteries and charger easily gets quite expensive. Also, not all of the engineered LED's, even expensive ones, have sufficient heat sinking to operate on the highest output for an extended period of time without automatic shift to a lower output or frying the LED. Mine has reports of fried LED by other users, and I limit highest output operation to 5-10 minutes. I don't really want to test the limit and have a worthless, nice looking flashlight. While limited time output on the flashlight is OK, I am starting a search for a bicycle light which can operate continuously on the highest output. For anyone interested in getting one of these high output, engineered flashlights, I recommend lots of research on the brands and models of interest so that your needs will be met without disappointment.
  15. maverick06

    maverick06 Minister of Fire

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    If you are looking for 18650 cells, tear open an old laptop battery pack.

    I had one sittin gin the basement, at least 10 years old, 10 years of no use. Figured it was trash, so why not try. If you jump the cells (i used 12vdc) for a second or two then pop them in the charger it would charge them right up. I am sure that sitting dormant for that long hurt them, and their capacity isnt anything like the new ones I have. BUT they are probably 15 year old tech. Cheap batteries!

    On the flipside, you can rebuild laptop battery packs with new 18650 cells if the current ones are dead.

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