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Charging different types of batteries ?

Discussion in 'General Electronics Discussion' started by Richard_Electronics, Sep 26, 2019.

  1. Richard_Electronics

    Richard_Electronics

    18
    0
    Oct 31, 2017
    I think this is my fault.. I have never tought about battery tipes.. i just didn't care.. Sorry don't get mad im just a amateur..

    Inglish not rili gud :p

    ~~ I used to charge 12v Lead battery with a big, old and heavy car battery charger (output 11.6v but when is connected to charged battery 13.7v it gives around 16v (measuring when connected) wich i don't understand is it ok?) but i have some lead acid batteries with 4Ah so for me there is no sense to carry that big charger for those such a small and light batteries and i used to make portable speakers with 12v lead acid battery and pass them to other people who does not have big 12v car battery chargers at home so i started to search for alternative. and i found some like wall adapters that i don't know what where they for but i tryed to use them and sh*t happend... ~~

    1. Can a car lead acid battery be charged with something like this charger: charger one
    if not what is difference between charger one and charger two other than price ?
    2. What voltage shoud that charger output to charge 12v battery propertly ?
    3. Is there some datasheet for needed charger voltage to charge specific voltage rated batteries

    Lets get to the point.
    I have this 5.7v 3A charger wich i think caused those problems but im not really sure how and why so im asking you guys...

    I measured its output voltage and it was 5.881v so pretty close and it was stable
    I have bought electric screwdriver and got this charger with it so it makes sense to charge screwdriver with that charger wich i did. After some time i smell something and i saw that screwdriver was melting the batteries got hot and died.. there where 3x 1.2v NiMH batteries in series, its 3.6v so i replaced them with 3.7v li-on battery wich was not really good idea, that battery got warm too and almost blew up (thankfully didn't) than i connected 4v lead acid battery and everithing was fine (expect size of lead acid battery) but when i charged it with that same 5.7v charger true screwdrivers protection circuit it was fine. battery was 5v but next day it dropped to 1.5v.

    Just to mention charge state indicator on screwdriver was never turning off to sign that battery is full or something..

    Im trying to understand.. i know it is deeper than just Voltage and Amps..

    There are some images. Charger voltage, charger, battery voltage, battery, tool
    Sorry for rotated image.
    Thanks for any kind of reply! <3
     
  2. Alec_t

    Alec_t

    2,686
    710
    Jul 7, 2015
    I suggest you check out the Battery University site for all you need to know about charging different battery types safely.
     
    davenn and JMW like this.
  3. Audioguru

    Audioguru

    2,598
    586
    Sep 24, 2016
    Charger One is a 12V, 2A power supply, not a battery charger. Its voltage is too low to charge a "12V" lead-acid battery with 14.5V and its 2A of current is so low that charging a battery the size of a car battery will take a very long time.

    Charger Two is designed to charge a "12V" large car battery fairly quickly with 20A (10 times the current of the cheap little power supply).

    Your problem with using the wrong charger for Ni-MH and Li-Ion batteries is very dangerous so you should stop fooling around and buy a proper charger for each battery. The cordless screwdriver probably came with the wrong or a defective charger.
     
  4. Richard_Electronics

    Richard_Electronics

    18
    0
    Oct 31, 2017
    Yea i understand that it will be very slow charging if i charge car batterys with 50and more Ah..
    but i have got lot of 12v 4Ah lead acid batteries wich will take 2 hours in perfect conditions to charge with 2A charger (if is not just power supply 12v)

    Problem is that battery is much smaller than charger for it and cheaper too so lets say finished prject with that battery in it, what ever it is, is smaller and lighter and cheaper than just a charger for it.. that is just mindblowing there has to be some smaller charger like wall adapter and 2Ah is good enought for my needs. If i find power supply wich outputs 15v will that be able to charge 12v lead acid battery.

    Just don't tell me that i have to buy those bulky chargers that are actually heavyer than a batteries.

    Thanks for reply!
     
  5. dave9

    dave9

    795
    186
    Mar 5, 2017
    The first charger is regulated to output 12.0V. A lead acid battery is called "12V" for convenience sake but is really a 12.6V battery comprised of 6 x 2.1V cells in series.

    In order to put charge in a battery you must input more than it's (present charge state) voltage, so to fully charge a 12.6V battery the charger must be capable of a fair amount above 12.6V to overcome the battery internal resistance, the more it is over (providing it has the current capacity) the faster it can charge, but then you want the charger to terminate charge or maintain a float charge level so it does not overcharge and product excessive gas, electrolysis will produce explosive hydrogen and breach the battery vent and waste away the electrolyte. This means you cannot charge a lead acid battery with a voltage regulating charger unless it has further charge termination circuitry meant for lead acid charging, or to very carefully monitor the battery voltage and time elapsed (unless the charge voltage is carefully mated to the battery full charge voltage like very old linear battery chargers were) so you can manually terminate the charge, which is not practical and a recipe for damage.

    The ebay battery charger you linked is called a 12V charger but that is just to tell you it's for so-called 12V lead acid batteries and maintains a charge voltage above 12.0V. It's an overly simplified way to try to get across what the intended purpose of the charger is, rather than listing specs for the customer to determine that.

    There are smaller lead acid battery chargers than what you linked, but I don't know what is available in your country. Here is an example:
    https://www.ebay.com/itm/Car-Motorc...tomatic-Smart-Power-Charger-B4K6/223274435101
     
    Last edited: Sep 26, 2019
  6. dave9

    dave9

    795
    186
    Mar 5, 2017
    Now about your other battery... escapades :eek:

    The screwdriver was built to a low price point with little care for battery preservation. It was not all that uncommon years ago before Li-Ion batteries, with their more demanding safety requirements, caused manufacturers to make more elaborate chargers. The point is that type of charger typically was just a volt-amp output that was a medium charge rate with no charge termination so if you didn't guess or measure when the batteries were done (some had an LED indicator) and manually terminate the charge, it would overcharge the cells with a primary byproduct being heat.

    As mentioned above, Li-Ion has more demanding safety requirements so you should never substitute a Li-Ion rechargeable for 3 x NiCd or NiMH in series unless you have a charge controller/termination board designed for Li-Ion between the supply and battery. This is crucial to prevent damage to cells and possibly prevent fire.

    The charge state indicators on cheap old NiCd/NiMH screwdrivers was often nothing more than an LED and resistor in parallel with the supply line so the LED lit up based on the amount of current flowing. Such a charge indicator design requires a careful mating of the battery type/chemistry, and # of cells, versus the specific charger type (regulated vs unregulated) and voltage. It was a poor design that ended up leaving many people hating NiCd/NiMH batteries and creating some false assumptions about (one of the use/abuse reasons) why the batteries had poor life.

    Regardless, NiMH, and lead acid (besides the hydrogen venting issue) are much safer to overcharge without risk of a fire compared to Li-Ion. You could use a Li-Ion battery of sufficient current rating in the screwdriver but must get a different charger meant for charging a single 3.7V Li-Ion cell, or a more involved setup with a current limited PSU and charge controller, and discharge limiter since the screwdriver brushed DC motor would drain a Li-Ion cell down to a damaging voltage level quite easily.

    To clarify, even if you use a charger meant for a Li-Ion cell, your screwdriver must have a discharge protection circuit in it between the battery and the motor. Some cells have this built in and are called "protected cells", but sometimes what they can fit in the available space, built-on to the end of a battery is not enough for the high current of power tools and an external (to the battery wrapper, still in the tool itself) protection circuit with "unprotected cells" is needed instead.
     
    Last edited: Sep 26, 2019
    hevans1944 likes this.
  7. Audioguru

    Audioguru

    2,598
    586
    Sep 24, 2016
    Since a "12V" lead-acid battery needs about 14.5V to charge quickly then a 14.5V or 15V power supply would probably melt because it would have nothing to limit the current. The battery might try to take 10A or 20A without a current limiter. A cheap 2A power supply will have nothing in it to limit the current to 2A.
     
  8. ChosunOne

    ChosunOne

    321
    73
    Jun 20, 2010
    Actually, a "12V" lead-acid battery is really a 13.2V, comprised of 6X2.2V cells in series. I've worked with Sealed Lead-Acid (SLA) batteries for decades. The 2.2V/cell is for new factory-fresh batteries. As they age with use, the volts/cell decreases and will eventually read 2.1v/cell. The battery is usually still usable at that point (depending on the application), but its capacity (Ah) is diminished.

    The only simple way that I know to read the state-of-charge of a lead-acid battery with a DMM is to wait about 5 days with no activity after you take it off the charger (to give the chemistry time to settle down) and read the open-circuit voltage. A new and freshly-charged (within a few days) 12V battery will read about 13.2 volts. You can read the voltage earlier than 5 days, but with less accuracy. After about 2 days, the reading will be within about 20% of the actual state of charge, IIRC.

    @Richard_Electronics, ideally you would charge your lead-acid battery at a 10-hour rate, i.e., for a 4 Ah battery, you'd charge it at .4 Amps.
    There is some inefficiency in the charging process, so from a completely discharged state, it would actually take about 16 hours for a completely discharged battery to fully recharge. You can get away with charging it faster, but that reduces the cycle life, i.e., the number of times it will recharge before it just won't take a charge any more.

    HOWEVER--you shouldn't usually be charging the battery from a completely discharged state. Completely discharging the battery kills the cycle life even faster than charging it too fast. For optimum cycle life, recharge the battery after using 20% of its capacity, or .8Ah. Again, the battery will work fine if you discharge it deeper than 20%, but the price is a reduced cycle life. If you use it to its full capacity before you recharge it, you aren't going to get many charge cycles out of it---you'll find it just won't recharge after a few cycles.
    Rule of thumb is to charge it, at the 10-hour rate, for 1.6 hours for every Amp-hour that you discharge it.
     
  9. dave9

    dave9

    795
    186
    Mar 5, 2017
    ^ No, No, and No.

    The moment you wrote "actually" it was clear you were deluded. Don't use that word unless you want people to scrutinize what you wrote because all by itself that is a sign of delusion.

    The cells are 2.1V over the nominal lifespan. What some peak is when brand new is irrelevant because that peak will discharge down to 2.1V quite fast, like, right away (but you mentioned 5 days, how crazy is that?).

    No, you do not have to wait 5 days. That's ridiculous. A few hours if not minutes is enough to see if it's holding capacity or here is a vDrop.

    No, it will not read 13.2V. Unless your multimeter is off that much. 12.6V.

    No, you do not need to charge at a 10 hour rate. There is nothing ideal about that. I'm not suggesting that bad per se, just that there is no particular benefit to that strategy. We could as easily say charge it at C/5 or C/20 and the difference would be trivial but for the sensitivity of the charging circuit.

    There is no "rule of thumb" to charge at C/10. Practically nobody does that. Typically there is slow-median rate with voltage termination or voltage with current limiting. Either works as long as it doesn't overcharge and doesn't get too deeply discharged which is not a charger function.
     
    Last edited: Sep 28, 2019
  10. ChosunOne

    ChosunOne

    321
    73
    Jun 20, 2010
    I'm down with some kind of bug today and don't feel up to a proper response. I've been brain-flatulating all day and I don't want to do it on this forum. Hopefully I"ll be on my game tomorrow.
     
  11. WHONOES

    WHONOES

    723
    147
    May 20, 2017
    Good grief. So much tosh written about lead acid batteries.
    The voltage of each cell is 2.25V To charge one you will need at least 2.3V per cell. This will provide a trickle / maintenance charge. For a faster charge. you will need 2.35V per cell no higher or else you will boil the electrolyte.
    Sealed lead acid batteries should follow the same regime, charging at 2.35V per cell but, when charging is complete the charge voltage should be reduced to 2.3V per cell.
     
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