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What thermistor?

  1. Jul 24, 2014 #1
    I'm thinking about buying a tp4056 and I'm wondering what thermistor I should buy. I looked at the data sheet and it said a [STRIKE]new[/STRIKE] NTC but that was it. So I went online to find one and I noticed they have resistance and I don't know which one to get. Could someone help me figure this out?
     
    Last edited by a moderator: Jul 24, 2014
  2. jcsd
  3. Jul 24, 2014 #2
    When I said new I meant ntc.
     
  4. Jul 24, 2014 #3
    consult the tp4056 datashhet.

    basically you need the operation point(s) of thermistor's resistance
     
    Last edited by a moderator: Jul 24, 2014
  5. Jul 24, 2014 #4

    davenn

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    The datasheet isn't specific about the type of thermistor etc

    Actually, all it indicates is that it makes use of the thermistor that is already part of the battery pack

    cheers
    Dave
     
  6. Jul 24, 2014 #5

    sophiecentaur

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    The thermistor needs to be integral with the battery so it knows the temperature reliably. You don't need to buy one; it's there already.
     
  7. Jul 24, 2014 #6
    Where is it?
     
  8. Jul 24, 2014 #7

    sophiecentaur

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    You would expect to find more than two contacts in the battery. The thermistor would be between two of them.
     
  9. Jul 24, 2014 #8
    I don't think we are talking about the same battery. What battery are you talking about?
     
  10. Jul 25, 2014 #9

    davenn

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    show us a pic of YOUR battery and also a datasheet for it would help too

    As I said in my first post, the thermistor is usually incorporated as part of the battery

    Dave
     
  11. Jul 25, 2014 #10
    Datasheet for the battery?
     
  12. Jul 25, 2014 #11

    sophiecentaur

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    Yes. Or at least a picture of the contacts.
     
  13. Jul 25, 2014 #12
    There's the battery and datasheet
     

    Attached Files:

  14. Jul 25, 2014 #13

    sophiecentaur

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    I see, now. We have been at cross purposes. I (/we) were assuming that you were talking of the type of LiIon battery pack you get in cameras, mobile radios etc.. These are in a (8V or whatever) pack with their own protection circuitry included and sometimes have several contacts on the sealed pack which interface with the 'special' charger. They usually cut off when the volts get low and cannot be recharged without opening the case or getting at them in some way.
    Energiser (the company) supply their own chargers which will be their own design and may or may not include your charger IC. The value of the thermistor will probably be difficult to find out without opening up an Energiser charger and trying to read the legend on the side of the thermistor (probably some obscure number) and the IC may well have a similarly unhelpful type marking on it. They probably don't want you to copy their unit.
    The chargers that come with electronic gear are also probably full of components with weird numbers on - and for the same reason. The manufacturers of batteries and chargers are not interested in being helpful - unlike the manufacturers of chips who want to sell them to as many people as possible.
    LiIon batteries are a bit dodgy to charge if you don't have the right information about them. I'm sure it's not really as bad as all that but I would be inclined to do the charging in a suitable box to contain any leaks or explosions, during the experimental stage.
    I just wonder if it's really worth while trying to save on the cost of buying a ready made charger. The Energiser ones are pretty cheap.
     
  15. Jul 25, 2014 #14
    I'm not really trying to save money on a charger in teeing to make a portable cellphone charger. When is out of battery I want it to be able to charge at someone's house with a usb. It's for accessibility not for a cheap way of charging. So you're saying that I cannot charge those batteries with the tp4056?
     
  16. Jul 25, 2014 #15

    sophiecentaur

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    You have a cellphone with those Energiser Cells in it? That's pretty unusual, I think.
     
  17. Jul 25, 2014 #16
    I messed up. Im making a cell phone charger with those batteries in it. Those batteries will recharge the 3.7v li - ion battery in the phone.
     
  18. Jul 25, 2014 #17

    sophiecentaur

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    OK. So why not charge those energisers with an energiser charger and avoid a lot of aggravation? The phone will take care of itself as long as you give it some volts. Though, charging as fast as possible needs some cleverness in the USB connector, I believe. I remember getting my knuckles rapped when I referred to USB type charging as a 'trivial' exercise.
    There's more of the black arts than you realise here, I think. You just don't know enough about the battery characteristics to do this safely.

    If you are at someone's house. won't they have mains for a mains phone charger? Personally, I'm all for an easy life and that sounds like the ideal solution. Now, if you were camping in the wilderness . . . . . .
     
  19. Jul 25, 2014 #18
    Well I was hoping to put in a solar panel also and the reason why I want a usb port for charging is because sometimes I'm at a friends house and we go somewhere. So for convenience I want it to charge at my friends house. Not everyone has a battery charger.
     
  20. Jul 25, 2014 #19

    sophiecentaur

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    I know it's up to you and some projects are just fun to do but you could just as easily carry a mains charger as your battery charger. It is true that a nice fat source of DC charge would extend your talk time usefully, at times. I still think the DIY solution for the Energiser charging could be more of problem than you imagine. All the things you need are actually off the shelf (and not very expensive either).
     
  21. Jul 25, 2014 #20
    Ok so I want to build this. Talking to you had put a little doubt in my mind. So my question is if the tp4056 will charge the ultimate lithium batteries safely?
     
  22. Jul 25, 2014 #21
    I personally wouldn't mess with a DIY or e-bay board for a lithium battery charger, ESPECIALLY if I'd be using at at a friends house.
    I know the lithium iron you're using are safer but, I've seen and heard about too many Li/Po fires that might make me a bit paranoid.

    2 personal friends have had major fires.
    One, crashed his plane at the flying field and threw his plane in his trunk to head home. Lipo was damaged enough in the crash it must have shorted in his trunk and set his car a blaze on the highway.
    Friend two, lost his garage, 2 cars, motorcycle, tools, etc. when his son set the charger wrong for an RC car battery that was charging on the work bench.
    Local RC clubs usually require all lithium's are placed in approved fire bags or boxed when charging at their facility. Again, these are Lipo which are a bit more prone to overheat and out gassing when charging.

    If you don't get an answer if your cells are safe to charge with that circuit and still decide to go through with the project. Make SURE you charge them in a safe place the first few times to make sure all is well.

    Good luck with the project!
     
  23. Jul 25, 2014 #22
    Well my box is an altoids tin so I think that will be fine and that's my whole problem. That's my original post question about which thermistor to use. If I put a thermistor then it detects if the batteries overheat and the top 40 is designed to shut off power when the cells overheat. So I'm wondering what thermistor to use.
     
  24. Jul 25, 2014 #23

    jim hardy

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    The Energizer literature for "Energizer Ultimate Lithium" L91 batteries says in two different places that they are not designed to be recharged.
    Is that the battery you propose to recharge? It's the one for which you posted datasheet.

    Product safety sheet here

    http://data.energizer.com/PDFs/lithiumirondisulfide_psds.pdf page 2 of 4
    and Application Manual here
    http://data.energizer.com/PDFs/lithiuml91l92_appman.pdf page 15 of 18

    and from Design Considerations here
    http://data.energizer.com/design_hints/pages/dhints_seriesparallel.html

    What you propose is risky business . I think you should buy rechargeable batteries instead.
    http://www.energizer.com/batteries/rechargeable-batteries/Pages/power-plus-aa.aspx

    http://www.energizer.com/SiteCollectionImages/Batteries/Energizer%20Recharge%20Power%20Plus/tab2-recharge-aa.png


    old jim
     
  25. Jul 25, 2014 #24
    Wow didn't Reed the label. Thanks that would have been bad. So worth these batteries would the tp4056 charge those safetly?
     
  26. Jul 25, 2014 #25

    jim hardy

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    Here's Energizer's doorway to technical information.
    http://data.energizer.com/

    NiMh has different voltage than LiIon so i dont think your 4056 is the right gizmo. Your datasheet says charge voltage is fixed at 4.5, yet also says it's for single cell? I dont understand that.
     
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