9-Volt 150 mAh battery - Page 1
Forum section: electronics / beginners

author: Crockett
author_rank: Contributor
timestamp: May 17, 2013, 01:05:58 pm
content: Does anybody have a schematic or link to a free schematic for charger that will charge this battery?I'm sure some discussion might be necessary, so ....

author: Psi
author_rank: Super Contributor
timestamp: May 17, 2013, 01:20:06 pm
content: na, no discussion needed.Any old switchmode wallwart that's 12-19V + one resistor.Resistor value in ohms = (Vpsu - 9) / 0.0150.015 is 1/10 the battery capacity (0.150) so will take 10 hours to charge.Done.

author: Balaur
author_rank: Unknown
timestamp: May 17, 2013, 01:24:04 pm
content: Safest way is to use a slow, trickle, C/10 constant current charger.(You cannot/should not use a fast (i.e dv/dt, or dT/dt termination) charger.)Basically, use a 15V+ power source, then build a 15mA constant current with a TL431 (figure 31from this datasheet) and let the battery to charge during 15 hours or so.(431s can be easily found everywhere, especially in broken PC PSUs)Best regards

author: Crockett
author_rank: Contributor
timestamp: May 17, 2013, 01:42:56 pm
content: I'm not sure yet how I want the design to go. I'm thinking I'd like to be able to have a 9 volt power supply that I could leave usually plugged in. And then when I want I can unplug it and the battery take over. (Remember, I'm here in the "newbe" section. Also, I have not yet determined the application for this power supply, but I'm sure I've got more parts to play with.

author: Paul Price
author_rank: Super Contributor
timestamp: May 18, 2013, 01:43:22 pm
content: This simple circuit will work with about any wall wart power supply that is unregulated >8V or regulated up to 20V and will not harm the battery and the LED's set the correct charge voltage so will not damaging the battery or your equipment.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 03:17:44 pm
content: I like this, but I have some questions.I've been working with a AD-101ADT (wall wart) that is rated at 10VDC 1A output with 120VAC 60Hz 18W input. (I presume this will work to charge the battery). But, it seems this is an unregulated supply, since in measuring it I get 13.22VDC (unloaded). Applying a simple 5ohm (cement) resister as load I get ~7.7V and 1.53A. (Should this be like that?) I haven't checked the specs on this model wall wart so I don't know if it is supposed to be regulated or not, but regardless of that I want to build into this power supply a regulator for it. (Aside: I was even thinking it might be a good idea for Dave to do a vblog about loaded and unloaded voltage divider circuits with and without control circuit on a "Fundamentals Friday" episode)So, as it is, we have a beefy wall wart to power this thing that as yet still has unspecified application. Bummer.Another question; does it have to be LEDs? How do they control charging. I am assuming the LEDs light up as the battery charge maximizes to keep it from overcharging?

author: Paul Price
author_rank: Super Contributor
timestamp: May 18, 2013, 03:36:24 pm
content: The rather precise voltage of each RED LEDs are added together to set the correct voltage to charge the battery, the red LEDs have the correct voltage and other colors, green or yellow or blue LEDs certainly do not. This charger does not care whether you connect this to an unregulated or regulated power supply, so long as the power supply is working, it regulates the voltage and current.If you have a volt meter you power up this circuit and connect it to a charged NiMH 9V bat and you can measure the voltage at the battery or at the emitter of the power NPN transistor with just a 1k load connected, and you should read between 9 and 10.5 volts, and this is right in the range to charge the battery to full capacity without over voltage. The current itself is limited by the gain of the transistor, and a low gain 1w power transistor (with low beta) is preferred that can handle 25V or more.If you want to gild the rose:If somehow you compulsively think you need to have to so precisely control everything in life, you may want to fine tune this circuit according to the discarded wallwart power supply of your choice and to fit the Beta characteristics of your luck in winning the current gain lottery of the BD139 transistor:Calibration Procedure:(1)Replace the 100K fixed resistor with a 68K resistor in series with a 50K tiny pot connected as a rheostat. Apply wallwart voltage to the circuit and using a 1-ohm resistor as a current shunt in series with your discharged 9V NiMH batter, adj. the 50k pot for 14 to 28mA, whichever level you think you like. I have mine trimmed to 20 mA...a compromise between the two extremes.(2)Replace the 10K fixed resistor with a 20K pot in series with a 1k resistor. Now, with a 10k ohm load at the emitter of the BD139(no battery connected), adj. the Max full charge cutoff (output) voltage to 9.3V or whatever else arbitrary voltage you might think will please you and the almighty god of NiMH batteries.Once you've set these values you can remove the adj. pots and insert the closest value of a fixed resistor or two to match their actual resistance setting...pots are too expensive and handy to keep around the experimenter's shop, why sentence them to a life of neglect???Myths: All NiMH batteries cannot be trickle charged after cut off voltage or charge completed voltage has been reached.A circuit needs to be complicated to work well.A simple circuit cannot work as well as a very sophisticated and elegant design.A NiMH battery such as 9V 150mA type must only be charged so as to achieve a precise voltage at a precise current.A 9V NiMH battery will be damaged by "float charging". Truth: if the charger current limit of the "float charger" is set to the correct charging current and float voltage, then the float charger automatically switches mode from constant current to float charge as the cutoff voltage is reached.The proof of a pudding is in it's tasting.I have been using this charger for 8-years for my two NiMH 9V batteries and they are both still giving great service.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 03:44:57 pm
content: A "glowing" power supply/charger! Cool!

author: RPBCACUEAIIBH
author_rank: Contributor
timestamp: May 18, 2013, 05:21:39 pm
content: Well I don't think that circuit ever stops charging... Slowing down yes, but stopping no...Look at my Lithium battery charger (https://www.eevblog.com/forum/beginners/3-6-v-li-ionli-po-battery-switching-and-charging-circuit/), and make it with a little difference. 1. If you need only the charger, loose the entire switching part 2. replace the 7809 with a 7812 or find a suitable 12 V power supply and loose the regulator part. 3. replace the BD 139 with a BC 547 or 847 because you don't need that much current. you find description there about the rest.You will need a Voltmeter to calibrate it. Connect the voltmeter's ground terminal to the ground, and the other to the 555 timer's pin 5 and set the upper limit with R7 where it stops charging. Set it a little bit 0.2 - 0.5 V higher the battery's rated voltage at a 9V battery sized accu is about 8.2 V. Then hook up the voltmeter's positive terminal to R8's middle terminal, and set it with about 0.2 V below the battery's rated voltage, and you're about ready to charge your battery. the LED will be illuminated while it is charging, and will turn off when the battery is charged.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 05:34:13 pm
content: Thanks, RPB... I'm definitely going to study your diagrams. I may build both and compare results. I know I want to regulate the supply to furnish other constant voltage levels and then have the battery take over when it is unplugged.

author: ivan747
author_rank: Super Contributor
timestamp: May 18, 2013, 06:00:56 pm
content: Wait a minute everyone.What kind of battery is this? I assume alkaline, but he mat be using something else like NiCd or NiMH or even Li-ion (charging Li-ion with a resistor will burn your house down without supervision and will burn itself with supervision).

author: RPBCACUEAIIBH
author_rank: Contributor
timestamp: May 18, 2013, 06:39:26 pm
content: Quote from: Crockett on May 18, 2013, 05:34:13 pmWell if your circuit needs to run without interruption when you pull out the plug, then you need to build the modified switching part as well.If you are using 12 V as external power and your circuit is supplied with 9V, you need to replace the 7805 with 7809 at the switching part, eliminate the 7809 at the charger part, and change the C4 with a big electrolitic one. 100 uf I think will do well.if you are not using 12 V as external power, you need to re-calculate the values of R2 and R3, because you can't exceed 5V at the BC's base and GND. You need to replace the 7805 with 7809 at the switching part, and the 7809 with 7812 at the charger part. I advise no less den 12V external supply, and no more then 24 V external because the 78xx ICs supports until 24V.QuoteAlkaline can't be charged, and Lithium can be 3.6-3.7 V/cell which excludes this 2 kind at 9V, so it may be NiCd or NiMH only.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 06:47:50 pm
content: Ok, battery specs are:Name: Power One Rechargable - p7/8h 150mAh8.4 V 150 mAhNo. 5522(IEC 6LR61 size/taille)Charge: 14 h 14 mArapide: 7 h 28 mAup to 1000 timesBlah blahMade in GermanyVARTA Microbattery GmbHThat's it folks!

author: RPBCACUEAIIBH
author_rank: Contributor
timestamp: May 18, 2013, 07:03:28 pm
content: Yeah, I thought so... it's 8.4 V I had one and I remembered 8.2 VPlease note that my design is not tested yet, if you build it than please leave a note there with your modified schematic and if it works well or not. Thanks!

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 07:22:16 pm
content: Will do

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 08:19:27 pm
content: Quote from: Crockett on May 18, 2013, 06:47:50 pmLooks like NiMh with 7 cells in series (7 x 1.2 = 8.4).The charging current is given (14 h at 14 mA). Or 7 h at 28 mA if you feel lucky.Quote from: Psi on May 17, 2013, 01:20:06 pmThis. This. This. This. This.Forget fancy charging circuits with current transistors, LEDs and voltage regulators.A battery like this has simple needs. Feed it a constant current of about 15 mA for about 12-16 hours. Measure the voltage from time to time if you like while it's charging and when it reaches somewhere over 10 V and stops rising the charge is done.If you try to charge it at higher currents like 30 mA or more you will increase the risk of damaging the battery by overcharge.If you try to use any kind of voltage controlled circuit at 9 V you will fail.Read the good advice from Psi and follow it.

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 08:33:41 pm
content: Quote from: Paul Price on May 18, 2013, 01:43:22 pmI disagree. This circuit is not suitable for charging NiMH batteries.

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 08:42:57 pm
content: Quote from: Crockett on May 17, 2013, 01:42:56 pmUnfortunately this is not simple to do with NiMH batteries. You can't successfully "float" them as you can with lead acid batteries for example.There are generations of cordless phones out there that have routinely run their batteries into an early grave by trying to keep them on charge when the handset is in the base station. The underlying issue is that putting NiMH batteries on permanent trickle charge severely shortens their life.Charging NiMH batteries has special requirements. You can't use a constant voltage based charger because the battery voltage is not stable. It changes with age, battery temperature and manufacturer. Therefore applying a constant charge voltage will overcharge the battery in the worst case, will undercharge it in the best case, or will subject it to constant trickle charging in the middle case. None of these results are optimal.What you need a circuit to do is to charge the battery, detect when the battery is fully charged, and then completely disconnect the charger until the battery is discharged by some significant amount before trying to charge it again. It will involve some kind of voltage window comparator (see Dave's latest video), a charge control circuit with full charge cut off, and some logic to drive the thing. It is not the simplest thing to put together for a beginner.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 08:53:32 pm
content: Cool! That's why I'm here. Good to see the viewpoints... And I don't mind the challenge. I think the other post on building a charger makes sensè for this one since it cuts off charging at a designated level

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 08:59:56 pm
content: Quote from: Crockett on May 18, 2013, 08:53:32 pmBut "cutting off charging at a designated level" is not appropriate, and does not work, for NiMH batteries. (That other post with the LEDs is a bad design.)To charge NiMH batteries you need to feed them a constant current and then measure parameters like voltage, temperature and time while charging.For batteries with one or two cells (1.2 V or 2.4 V) the charging circuit can use a large charging current (from 1 to 4 hours) and look for a drop in voltage at the end of charge.But for batteries like yours with 7 cells this is not as suitable. It is necessary to use a smaller charging current (the 10 hour rate) and charge for a measured time like 12-16 hours.So to repeat the advice above: you should construct a constant current supply of about 15 mA, you should charge the battery for 12-16 hours, then you shoulddisconnectthe battery from the charger until it is used and needs charging again.Of course, if you have a large supply of batteries and you don't mind replacing them when they fail, then you can use some other poorly designed charging arrangement.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 09:21:38 pm
content: I was actually referring to RPB...'s thread on battery switching and charging circuit. I don't know if it can be modified to achieve the points you address or not, but it does cut off charging and does not trickle charge

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 18, 2013, 09:24:26 pm
content: There are plenty of charger chips for NiMH.

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 10:36:42 pm
content: Quote from: NiHaoMike on May 18, 2013, 09:24:26 pmAnd that is a point well suited for this area of the forum,"beginners." It is good to see advice from some that points out fire hazards. It's good to see the various concepts like red LEDs being used to set a voltage level. (I still want to play with this circuit). And all in all I'm just exploring what I can do with an old 9-volt Rechargable I found in one of my boxes of parts

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 10:42:59 pm
content: Quote from: Crockett on May 18, 2013, 09:21:38 pmRight, but that circuit still has a problem because it is still trying to use an adjustable voltage to stop charging:Quote from: RPBCACUEAIIBH on May 18, 2013, 05:21:39 pmNiMH cells read about 1.2 V open circuit when discharged and they reach a peak voltage somewhere between ~1.45 V and ~1.50 V when under a low charge current (say C/10 rate). The voltage profile is very flat, so the peak voltage is very difficult to pin down; it varies by battery and it varies with temperature.If you set the full charge threshold at the lower end, about 1.45 V, then your 7 cell battery would reach a voltage of 7 x 1.45 = 10.15 V at this point. It might be a little less than fully charged, but this only matters if you want the absolute maximum run time afterwards. The lower you set the threshold voltage the more sure you are that charging will switch off, but at the same time you are leaving more unused capacity in the battery.

author: IanB
author_rank: Super Contributor
timestamp: May 18, 2013, 10:45:13 pm
content: Quote from: Crockett on May 18, 2013, 10:36:42 pmIf it's an old battery it might not even perform very well, so that adds another layer of uncertainty to your enterprise. You would probably want to analyze the battery to see how well it works before devoting time to making a charger for it. And building a battery analyzer is a whole new kettle of fish...

author: Crockett
author_rank: Contributor
timestamp: May 18, 2013, 11:41:41 pm
content: Quote from: IanB on May 18, 2013, 10:45:13 pmOh, there's a lot of layers of uncertainty, IanB, but I don't want to be analyzing the battery. So, I'll just presume it is ok enough to give me some cool levels of hands on practical electronics experience with trying to design something. And of course Dave himself hopes it won't work, which I completely see why he says that. I just don't want to blow the thing up, you know!?!?!

author: Paul Price
author_rank: Super Contributor
timestamp: May 19, 2013, 01:17:49 am
content: A precision 9V NiMH charger,Both end of charge voltage and charging current are precisely set for optimal charging a 9V 150mA NiMH battery.This charger turns the charge current completely off at full charge.Both of these charger circuits can be turned off at any time and this doesn't upset your circuit at all, the circuit will switch to just battery operation automatically.Take a look at this circuit that even lights a LED when charge is complete.=======================================================The truth is,I've been using the simple 6 LED circuit shown below to charge the 9V NiMH battery in my Fluke multimeter for about 8 years now and the two batteries I have are still working well after many, many charges.I often run down the batteries because I leave my multimeter on many hours on my work bench, so I charge one and switch between the two batteries about once or twice a week. Both of the batteries were used when i got them. One came with the used Fluke I bought at a flea market and the other I found in a battery disposal box a year later (a tiny bit of battery dumpster diving.)

author: RPBCACUEAIIBH
author_rank: Contributor
timestamp: May 19, 2013, 06:24:29 am
content: Quote from: IanB on May 18, 2013, 08:42:57 pmWell my design doesn't include trickle charging but otherwise it would be just as you said... has 2 limits one which turns on the charging if it is low enough, the other one which stops completely, but you can add an extra 555 timer in astable mode after the existing one, and connect the existing one's out pin(3) to it's reset pin(4) to make it trickle. Now I don't really know what you really mean by "trickle charging", I mean what kind of waveform, but if square is not good, then it's pretty easy to make it a triangular of some kind as well... with 2 more trimmer, 1 cap and an o-scope(which I don't have).

author: Crockett
author_rank: Contributor
timestamp: May 19, 2013, 08:50:33 am
content: If I'm correct, trickle charge refers to current. The battery reaches full charge and the charger continues charging at the same charge voltage but at a much reduced current.Trickle charge is actually a good topic, I think, for us newbies to learn about... Even though I've heard the term used alot.

author: Psi
author_rank: Super Contributor
timestamp: May 19, 2013, 09:07:51 am
content: Quote from: Crockett on May 19, 2013, 08:50:33 amYes, trickle charge just refers to charging at low current. You can pretty much leave the battery on charge permanently at trickle charge current.Charging for 2,3 or 4 times longer than needed won't damage your battery.Note: There are some variations on what C rating trickle charge is.Some define it as 0.05-0.1C while others say it's just enough current to stop self-discharge. (probably 0.0001C or something)

author: IanB
author_rank: Super Contributor
timestamp: May 19, 2013, 09:21:11 am
content: Trickle charging generally means continuous charging at a low charge current without end. This is mostly a bad idea with NiMH batteries and is to be avoided. The trickle charge causes constant chemical reactions to occur inside the cell which over time will cause the electrodes to deteriorate and the battery to lose capacity. When a NiMH battery reaches full charge it should be taken off the charger and used.The key thing about NiMH charging circuits is that using voltage to detect the state of charge is inherently unreliable. The exact voltage is not well determined as it is with Li-ion, it varies battery by battery and according to how long the battery has been off the charger.That said, with most NiMH cells they will be more or less charged when they reach a charging voltage of 1.45 V. So for a 7 cell 8.4 V battery, this would be 10.15 V. After reaching this voltage you would disconnect the battery from the charger and stop charging. As soon as you disconnect the charger the voltage will drop, soon going below 1.40 V. But this is not a signal to start charging again. The battery should be taken off the charger and used before putting it back on charge.In a post above there is mention of charge being complete at 9.3 V. However, for a 7 cell battery this would be 1.33 V per cell and at this voltage charging is far from complete. At that voltage the battery would be less than half charged. It won't harm the battery to stop charging at that point, but neither would you get anything like the full run time from it before needing to recharge.

author: IanB
author_rank: Super Contributor
timestamp: May 19, 2013, 09:24:19 am
content: Quote from: Psi on May 19, 2013, 09:07:51 am2, 3 or 4 times longer at trickle charge rates may not be a problem, but leaving a battery charging like this for weeks or months at a time most probably is. It is tempting to leave a battery sitting in the charger permanently "so it is ready to use when needed", but this is also a surefire way to ruin batteries.

author: Crockett
author_rank: Contributor
timestamp: May 19, 2013, 09:51:25 am
content: It seems then that the battery's properties are going to limit the application possibilities.To use it for instant supply voltage when the power/charging source is removed (like a mini UPS) doesn't seem so reasonable; still possible, just not so much a good choice. And yet still something to play with.Building just a plain charger where you remove the battery after it is charged is probably the way to go.

author: IanB
author_rank: Super Contributor
timestamp: May 19, 2013, 09:57:27 am
content: Remember anyway that a 150 mAh battery has a rather small capacity. There is not much it can power except tiny electronics.

author: Psi
author_rank: Super Contributor
timestamp: May 19, 2013, 10:10:39 am
content: Quote from: IanB on May 19, 2013, 09:57:27 amNonsensecapacity wise its enough to start a car once or twice~150A @ 9v for ~3.5seconds

author: Crockett
author_rank: Contributor
timestamp: May 19, 2013, 10:22:51 am
content: I hope I don't ever have to try to start a car with it... Attaching the jumper cables sounds a pretty tricky endeavor.

author: Paul Price
author_rank: Super Contributor
timestamp: May 19, 2013, 11:05:39 am
content: There are two charge circuits shown below. The first circuit I designed is precise but not so easy to build because of its many parts, the second (LED circuit) is what I use today.Theory of operation of the 6-LED circuit:The rather precise voltage of each RED LEDs are added together to set the correct voltage to charge the battery, the red LEDs have the correct voltage and other colors, green or yellow or blue LEDs certainly do not. This charger does not care whether you connect this to an unregulated or regulated power supply, so long as the power supply is working, it regulates the voltage and current.If you have a volt meter you power up this circuit and connect it to a charged NiMH 9V bat and you can measure the voltage at the battery or at the emitter of the power NPN transistor with just a 1k load connected, and you should read between 9 and 10.5 volts, and this is right in the range to charge the battery to full capacity without over voltage. The current itself is limited by the gain of the transistor, and a low gain 1w power transistor (with low beta) is preferred that can handle 25V or more.If you want to gild the rose:If somehow you compulsively think you need to have to so precisely control everything in life, you may want to fine tune this circuit according to the discarded wallwart power supply of your choice and to fit the Beta characteristics of your luck in winning the current gain lottery of the BD139 transistor:Calibration Procedure:(1)Replace the 100K fixed resistor with a 68K resistor in series with a 50K tiny pot connected as a rheostat. Apply wallwart voltage to the circuit and using a 1-ohm resistor as a current shunt in series with your discharged 9V NiMH batter, adj. the 50k pot for 14 to 28mA, whichever level you think you like. I have mine trimmed to 20 mA...a compromise between the two extremes.(2)Replace the 10K fixed resistor with a 20K pot in series with a 1k resistor. Now, with a 10k ohm load at the emitter of the BD139(no battery connected), adj. the Max full charge cutoff (output) voltage to 9.3V or whatever else arbitrary voltage you might think will please you and the almighty god of NiMH batteries.Once you've set these values you can remove the adj. pots and insert the closest value of a fixed resistor or two to match their actual resistance setting...pots are too expensive and handy to keep around the experimenter's shop, why sentence them to a life of neglect???Myths: All NiMH batteries cannot be trickle charged after cut off voltage or charge completed voltage has been reached.A circuit needs to be complicated to work well.A simple circuit cannot work as well as a very sophisticated and elegant design.A NiMH battery such as 9V 150mA type must only be charged so as to achieve a precise voltage at a precise current.A 9V NiMH battery will be damaged by "float charging". Truth: if the charging current limit of the "float charger" is set to the correct charging current and float voltage, then the float charger automatically switches mode from constant current to float charge as the cutoff voltage is reached.All NiMH batteries will be damaged and their service life will be severely shortened if you trickle charge or do not stop charging at a precise cutoff voltage.All NiMH batteries must be fully charged to be serviceable. Truth: If the cutoff voltage of a charger is set to low, then the charger cannot force current into to the battery to charge it, if it is set very much too high(>10.5V), it might damage the battery. I have charged 9V batteries of this type to a voltage limit of 10.5V and left them at this level in this other charger circuit that I built even for weeks and the batteries were still functioning well after 2-3 years of service.The proof of a pudding is in it's tasting.I have been using the 6-LED charger circuit for more than 8-years to charge my two NiMH 9V batteries and they are both still giving great service.

author: Psi
author_rank: Super Contributor
timestamp: May 19, 2013, 11:09:53 am
content: Quote from: Crockett on May 19, 2013, 10:22:51 ami could start mine, its got supercaps instead of a battery.If my supercaps were dead and i had a constant current dc-dc psu i could discharge a 9V over say 10 hours and recharge my supercaps

author: Crockett
author_rank: Contributor
timestamp: May 19, 2013, 01:28:52 pm
content: Well, I do want try out as many of the circuit diagrams offered here as I can for charging the battery.AND, I'll leave the car starting using 9-volts to Psi. Hopefully I won't need that sort of application.

author: ivan747
author_rank: Super Contributor
timestamp: May 19, 2013, 02:53:07 pm
content: Quote from: Psi on May 17, 2013, 01:20:06 pmWe have never been so wrong...Have you looked at ready-made chips? It's yet another alternative.

author: Crockett
author_rank: Contributor
timestamp: May 19, 2013, 04:57:46 pm
content: I think there was some mention (maybe not exactly to ready made chips) to pre designed circuit. I'll have to read back through the thread to see exactly what I am remembering, though.

author: IanB
author_rank: Super Contributor
timestamp: May 19, 2013, 06:15:35 pm
content: Ready made chips are typically designed for fast charging with negative delta-V detection and possibly temperature monitoring. This can work for single cells and for well balanced multi-cell batteries, but it is not a good approach for a tiny 9 V consumer battery. The best way to charge these is a slow timed charge.

author: RPBCACUEAIIBH
author_rank: Contributor
timestamp: May 20, 2013, 04:45:03 am
content: Quote from: IanB on May 19, 2013, 06:15:35 pmI agree... Fast charging will damage the battery in very short time... Slow charging is the best for a battery, this is true in case of any kind of battery.

author: Crockett
author_rank: Contributor
timestamp: May 20, 2013, 05:10:06 am
content: I'm sure it is best to slow charge! It may also be best to physically remove the charger from the battery; but there are options to accomplish this while not actually having to take the battery out. Maybe not any very good options, yet!Anyway, I like all the posts responding to my query. And I like the circuit suggestions. And I hope to explore each of them... at least for the educational value in them.Everybody have a good week(seven)!!