12V 7.2Ah rechargeable battery to be used as external supply for arduino

Discussion in 'Power Electronics' started by Gab Cruz, Sep 13, 2017.

  1. Gab Cruz

    Thread Starter New Member

    Nov 16, 2015
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    Hi all. I have a project wherein I need to supply the arduino for a long time so I decided to use the 12V 7.2Ah battery (the bulky one). I am planning to plug it in the dc jack of the arduino. I've read that the maximum input of the arduino is 12V. Is it safe? Thank you very much.
     
  2. Reloadron

    Well-Known Member

    Jan 15, 2015
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    Yes, the suggested external voltage for the Arduino boards is 7 to 12 Volts and actually a higher voltage can be used. The battery should work fine. I have powered my Arduino UNO using 12 VDC and the onboard regulator does not even get warm.

    Ron
     
  3. Gab Cruz

    Thread Starter New Member

    Nov 16, 2015
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    UP-VW1245P1.jpg
    Hi, thank you for replying on my thread. I'm about to use this one. There won't be any problem, right? :)
     
  4. Reloadron

    Well-Known Member

    Jan 15, 2015
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    That battery should work out just fine. All you need is a coaxial plug for the Arduino board, I call them a Size K 5.0 mm OD and a 2.5 mm ID. If you want you can always place a single diode like a 1N4002 in series with the line which will drop about 0.7 volts or two diodes in series to drop about 1.4 volts to the Arduino board but I never had an issue using 12 volts . Actually a 12 volt SLA battery like you have will be a little over 12 volts, with a full 100% charge it should be about 12.6 to 12.7 volts. The diodes I mentioned are rated at 1.0 amp. With or without a few series diodes it will work fine.

    Ron
     
  5. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi Gab,
    In addition to Ron's good advice, when using a SLA battery, fuse the battery positive lead, close to the battery terminal, say 1Amp.

    E
     
  6. Gab Cruz

    Thread Starter New Member

    Nov 16, 2015
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    Hi, is this correct?

    13_Gab Cruz_800x279.jpg
     
  7. Reloadron

    Well-Known Member

    Jan 15, 2015
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    That would be correct and as I failed to mention and Eric points out a little 1 Amp inline fuse would be a wise move. :)

    Ron
     
  8. Gab Cruz

    Thread Starter New Member

    Nov 16, 2015
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    Thanks!!
     
  9. ian field

    AAC Fanatic!

    Oct 27, 2012
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    The SLA battery can go up to around 14.4V while charging, so if you intend to charge in situ; that's the worst case scenario you need to allow for.
     
  10. Reloadron

    Well-Known Member

    Jan 15, 2015
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    That would be a good point. Arduino suggest a external DC voltage between 7 and 12 Volts. The regulator the board uses is a low dropout type having a maximum input of about 15 VDC looking at the data sheet. The thinking with the 7 to 12 volts is to keep the heat dissipation of the on board regulator to reasonable limits. The regulator has a maximum current of about 800 mA out which under normal use the system will never need. That said Ian's message is important and should be considered.

    Ron
     
  11. ian field

    AAC Fanatic!

    Oct 27, 2012
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    A knackered battery can easily be pushed higher than 15V.

    A normal one is just within spec - but sailing close to the edge for dissipation on a linear regulator.
     
  12. Reloadron

    Well-Known Member

    Jan 15, 2015
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    If the battery is charged with a good charger and things kept within reason things should be fine. This is especially true if the Arduino is fused and a few diodes placed in series with it. However, if there are concerns then maybe a better suggestion is in order.

    Just when I thought I had my slang down from the other side of the pond I see a new word, what exactly is a knacked battery?
    "Shortened version of "knackered". When you are so knackered you don't even have the strength to say "knackered" and can only go as far as "knacked".
    The wife made me work out this morning. I'm totally knacked".

    So would that be a worn out battery? :)

    My wife is out of state visiting family on her side. Keeping both dogs fed and the house clean has me totally knacked. This is actually true, she gets home Friday so I started cleaning my mess today.

    Ron
     
  13. MrAl

    Distinguished Member

    Jun 17, 2014
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    Hi,

    Yes i would think that the main concern is with the onboard regulator IC chips that will get warm with significant power dissipation which could result from a higher than normal input voltage.

    Also, some of the Chineses version Arduinos have regulators that ONLY go up to 15v. That is regardless of current. That means sticking to something under 15v is mandatory regardless how much power the regulator has to dissipate.
    You can find this info out by looking at the part number of the ACTUAL regulator chip on your ACTUAL pc board. You cant look at the schematic because the original schematic has a regulator that allows a higher input voltage so that would be misleading. It must be checked on the actual board to be used.

    If you use a good charger it should be regulated to stay under 15v but you should check that too. If you use a wall wart to charge then it may go as high as 17v or more with an aged battery. An aged battery can exhibit an internal resistance of high Ohms like say 1 megohm, so if a charger with an 18v open circuit output is connected it will bang the Arduino with a bit less than 18vdc.
     
  14. ian field

    AAC Fanatic!

    Oct 27, 2012
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    Worn out horses were usually taken to the "knacker's yard" for processing into glue and various other recovered materials.

    Never bothered looking up the origin of the word though.

    Apparently the "rag & bone man" collected exactly that for the war effort and the manufacture of explosives.

    Cockney rhyming slang may have contributed - in an episode of Steptoe & Son (rag & bone men) one of them is trying to flog a violin to a pawn broker, the broker asks; "lacquered?" - he replies; "yeah - I've been hard at it all day".
     
  15. Reloadron

    Well-Known Member

    Jan 15, 2015
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    Ah yes, per MrAl The 'genuino" Arduino. Following the Arduino line came boards from our other friends across a different and much larger pond. Often called Arduino Clones. Our little friends in China have managed to flood the US and other global markets with Arduino boards which are really not Arduino. There are a number of sites, including Arduino which tell us how to tell the difference. Arduino has also taken to using the word "genuino" which translates to genuine. So an Arduino/Genuino Uno Board is what translates to a genuine Arduino board, which has a birthplace other than China and does carry a higher price tag than the Chinese clone version. Like my son the genuine Arduino boards are born in Italy or Italia which is in fact a long way from China.

    Anyway, when referring to an Arduino Uno or any of the Arduino boards my reference is to those made in Italy by real Italians who for the most part are also taller than the Chinese. Additionally I should point out the Italians also make better wine than the Chinese. Anyway, keep what MrAl points out in mind as it is important. As a side note when buying anything like this online always buy from a reputable source as doing anything less becomes a "buyer beware" and good luck on a refund.

    Thank you again Ian for the new term. :)

    Ron
     
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