I am curious if there is any way to possibly fix NIMH batteries. I saw at http://www.youtube.com/watch?v=L1RxhgFEPSM how a freezer fixes them, but it did not work. It would be great if somebody with dry ice and dead NIMH batteries would try freezing these batteries (safely).

I'm modding something (secret, Instructable later) and there's going to be some integrated NiMH batteries to replace the one 1.5 AA battery that the device use to use. Due to funky space constrictions, I'll be using 7 tiny 320mAh 1.2V NiMH coin cells in parallel (to get a decent amount of maH). How hard is it to charge a bunch of batteries like this? Could I get a chip from a place like Maxim or TI? All of their chips require the batteries to be in series... Thankyou!

I am wondering how I can create a charger for 3 NiMH batteries connected in series for a portable Raspberry Pi build I am creating. I would also need help creating an over discharge circuit for them so I don't damage them too much. I will be powering a Raspberry Pi and Car backup screen with this. Any help would be appreciated, thanks.

I have a laptop battery that was cracked, so i opened it up, and like any other, it had individual NIMH batteries strung together... how to i find out how much voltage the individual batteries can take? I want to make my own battery pack with several of these laptop batteries... battery pack is GP B905 NIMH 12 volt thanks

I want to use solar power to charge batteries to use to charge electronic devices (phone, ipod,etc.), and put it in a backpack.  Is there any way to modify a regular AC NiMH charger to safely charge the batteries?  Or do I have to make my own?  Also what do I have to do to regulate the final power coming form the batteries to charge the device safely.  I know that there are instructables on this, but some contradict the others and most don't include all of the things that I need in one instructable. Thanks in advance

First off I'm pretty expierenced with electronics, but I've not been using rechargables that much. I'm not sure how to build a charger for nimh batteries. I want to charge a 3.6v battery, 70 mah (3x 1.2 volts, 70 mah each, I know, it's a small battery for a small device) as cheaply as possiable. I also want it so that it can still power the circuit (takes about 20 maH to run the circuit) when charging. If possiable, I want to charge like 5 or 6 of these at once. Help please!

I'm looking for cheap rechargeable digital camera batteries online, and 2500mah is the most abundant option. In fact, I haven't been able to find any 1300mah nimh batteries, nor 1600mah(which is what the now-dead ones are). I only have about 6 dollars to spare on this at the moment, as that's all I have in my paypal account, so there isn't much else I can do...

Does anyone have the circuit for these batteries please ? There is a temp overload (bimetalic type) and also a two diode (? zener) + resistor in series that I presume identifies the pack (voltage) to the charger.  I have burnt out pack that I have new cells to rebuild but not certain about the connection / values for those parts. Thanks

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Is a 4 amp charge rate to much for a nimh 6 cell battery with 3000 mah?

I have a powerbook 190 battery, but the batteries are all corroded and have leaked some acid. i was looking online, and i found some batteries, but i don't know the mah value of the original batteries, so i think these ones will work. it originally has 12 batteries in the pb190, so i'll be needing to get 12 of these. they will work, right? http://www.dealextreme.com/details.dx/sku.25496

Hello, I found this schematics on the Instructables. So my question is, will this charger stop charging when the battery reaches voltage of 1.4V? It won't overcharge my NiCd battery? Best regards.

I have tons of NiCd battery packs and tons of (sometimes) corresponding cordless drills. Only with a complicated discipline, involving several chargers, I can count on enough performance for a hard day's work. I did rejuvenate the individual cells by zapping; some packs improved, some packs died. The 'electric hubcap' site : http://members.shaw.ca/Craig-C/, states that a home made NiMH battery battery pack (several chains of 10 cells in parallel) can be charged and re-charged hundreds or thousands of times, and have a better performance than Lead-Acid...  Is it worth the investment???

A project that i am building is going to be powered by 4 NiMh batteries in series, i need to be able to just plug a cable(wall wart) into my project box to charge the battery pack. there will be an arduino clone(with plenty of free pins to spare) available which i could use to control a charging circuit with it. how many volts and amps should i charge the pack with? how do i detect the voltage drop when the batteries are done charging? is heat detection necessary? the batteries are 2000mAh each btw.

What are the risks of using the wrong charger for rechargable batteries?  Can you do it if you don't leave the batteries on too long?  Can you get away with it if you make certain the batteries don't get too hot?  Specificially for my 18V power tools the charger I have is only intended to charge NiCad batteries.  The company that made the tools has also made different types of battery packs that are interchangable in the tools, but each battery pack comes with a different model charger.  What if I used the NiCad charger to recharge a NiMh battery pack?  What if I use the NiCad charger to recharge a Lion battery pack?

I need a nice, simple charge indicator. I have a battery pack that holds 4 AA NiMH batteries. Normally they charge up to 1.3V per cell or 4X1.3=5.2V total. I have a solar trickle charger on there too and I'd like to have a little charge indicator.   Requirements are: -low part count -under $10 -small (it's on my bike helmet) I was thinking something with a pushbutton an LED or two and a zener diode. Something that turns on the LED at  greater than 5.2 volts. But I don't have experience with zener diodes. Has anyone seen a system like this around? Can you think one up? -Cheers

I would like to build a charger wherein I could specify up to what voltage to charge my nicads and nimh batteries. I'm currently using a la crosse bc-700 smart charger. it usually charges my batteries to 1.44-1.46v. I would like to build a charger that will cut off, say 1.38v.  Is that possible?  Thanks.

My project is a simple portable stereo box - using old USB powered speakers.I put the speakers with their little amp board in a box where I can put a 3-4NiMH rechargeble batteries 1,2V 1100mAh(in series for ~4-5V) to charge the amp board. I really want to make it so I can just plug an USB (5V) to the box to recharge the batteries when its not used so i dont have to take them out to recharge them with a wall charger everytime.I would like it to have LEDs to tell me when its charging and when its done , or even that it stops charging automatically when the batteries are charged. Im fairly new to electronics so I need the easiest way to do this if possible 

Hi I've a 4.8V 180mA NiMH battery i used to charge it with a 6V adapter but now it is broken can i charge with a usb port with directly hooking + terminal of battery to +V of usb and - with -V or do i need a specific circuit

I have a 1.2 V nimh battery and a 3.7V li ion (no protection circuitry) battery, which would add up to 4.9V if put in series. However, I want to turn it into a temporary USB power supply (5V) so ignoring all the things regarding putting 2 batteries of different capacities together, is there a way to kick the voltage up a tiny bit? I was thinking something like filtering the output of a joule thief, possibly. I also have a solar panel (4.5V, ???A) and was wondering if that could help, but I don't want to rely on it too much.

About a year ago I found a project somewhere to turn an old camera flash into a spot welder for small batteries. I found an old flash gun in my spares box and I wanted to have a go at building a spot welder from it but I can't find the weblink. Does anyone have any suggestions ?

Hi all, I want to charge a large number of batteries at one time Say 16 X AA batteries. Can someone please guide me or point to a resource where i can get some information on how i can do this? Many thanks in advance for your feedback.

I want to build a battery charger that is capable of charging 12v (2x6v) of NI-Mh PCB type batteries (varta packs from farnell) . I think the batteries are button types bound together. The input will be from a small 1" diameter motor spun to give 12v out (I assume this is a dynamo). The output from the batteries needs to power : a 12v wireless reciever (6mA standby/66mA switching) a 12v - 24v dc/dc converter powering a solenoid at 25mA@24v. I have seen a 12v charge regulator in Maplins but it is designed for car batteries. If I send the 12v motor/dynamo output to the charge controller and then onto the batteries will they blow up? As I am a mechanical engineer this is new to me so can anyone help ?

Most circuit designs on instructables seem to use NiMH batteries to power up servos (i've been looking at robotic hand projects). I don't see why we can't use a 6 volt power supply to directly power up the servos (assuming weight and portability is not an issue).  Is there any other reason to use those? And is there any other form of batteries we could look into also? Finally if i were to use a 6 volt power supply and  connect it up to a breadboard that powers up the servos, and then feeds into the arduion's 5 volt input. Would that damage the arduino regulator?  Thank you!!!

I have some perfectly good Nokia battery packs from useless 5165 phones (Model "bms-2s"). They are 3.6 - 3.7V NiMH and have 4 flat copper contacts which 'make' with the phones by sliding on. The Phones have matching 'teeth' and happily 'smart' charge either these or the newer LI batteries. (Clear pic here: http://www.jpldisplays.com.au/catalog/images/CPB-BLS2N.jpg ) I want to know if it is OK to simply connect the matching output from the charger across the +/- terminals (the 2 outer ones AFAIK...) and charge them directly ? These work great to power LEDs and I already made a 5165 LED torch, but it was a pain to do and I'd rather just use the batteries naked. Thanks for any info !

I've just got hold of a Union 6V 3W dynamo with lights. I'd like to charge 4/5/6 x AA batteries during the day then switch to the batteries for the lights at night. I'm switching out the old bulbs for LEDs. Any pointers or relevant 'ibles would be great. Thanks in advance people.

Can anyone tell me how to make a smart charger for 9v nimh battery?

Would i be able to use a 12v 1.8w solar panel to charge AA NiMh batteries? i built one of the mr16 halogen bike lights with the instructable found here and now have 10 AA NiMh batteries that i would like to charge, and i only have a 4 battery wall charger. A 12v 1.8w solar panel is on sale for $15. its specs are: # Includes quick-connect hardware: connecting wire, DC clips, 12 V socket plug and barrel plug, mounting hardware/accessories # Built-in reverse current protection; won't deplete the power-supply system so can i use this to charge AA batteries? if so how many, 2,4,6,8,10?. i would want to keep it simple so i would just wire my battery holders to the panel if possible.

I have several exhausted NiMH camera batteries, for a camera I rarely use anymore. The batteries (or perhaps the charging system) were awful. But I would like to use it as a backup--maybe by replacing the NiMH cells, or inserting smaller Li-ion unit... Anyone been successful at opening these? I think the seams are welded...

At a thrift shop I found a new 1.8 W (125mA) solar panel with all the parts that is used to trickle charge car batteries. It has three connectors, one a cigarette lighter, pos and neg cable clips and a regular connector for a power pack. Is it possible to use it to build a solar charger for a NiMH battery pack that will power a low end AC item like a cordless phone base or broadband modem during a power outage? If so, what else do I need and can it be done cheaply? Why I want to do this is because I don't want to have lead acid batteries in the house. Answers to this would be much appreciated as I know there are issues with differences in voltage, etc.

Is it possible to built by 1.2 volt 2500mah NIMH batterty. or any other way?

Hi, I am Planning on going airsofting with my echo 1 m4 commando, but do not have enough batteries to make it. The batteries my gun came with were 8.4 1100 mah NIMH rechargable batteries but i have some 7.2 volt , 3000 mah NIMH batteries lying around that i use for my rc car. I would like to know whether using the 7.2 volt batteries will either harm the gun or the batteries.

I need a  VERY powerful battery (4000mah 12V or higher) and don't want to spend more then $30 please help! and i don't want i Puerkerts number lower than 1.2. can anyone help? oh, and the size of it has to fit in a 6V lantern. thats why lead acids bit the dust and (so far what i know) lithium polymer batteries bit the dust because they are way to expensive. with a 35W power consumption, its hard to find a power source that will fit in a 6V lantern, a affordable price (under $30) and powerful enough to power the load for more than an hour. (some calculations i did show i need at least 3500mah for 1 hour of usage ) but i think i might have a solution a 2 laptop batteries from amazon wired in parallel after they have been took apart. a drill battery doesn't even come close to the amount of i need and they suffer from memory effect and just plain out isn't near powerful enough (1.5 AH per cell) OR my second choice is to get many rechargeable AAA batteries and wire them to give 14.4V (BUT HOW DO I SOLDER THEM WITHOUT THE TABS? and what kind of array should i use? [68 AAA])

For charging 6-module packs of NiMh Prius batteries (43.2v) at 1C.

No real details here just though it would be nice to get standard battery sizes in lithium ion rechargeable instead of nimh.

I've been working on this sucker, and I have so far added a battery pack to it that consists of 8X AA NiMh rechargeables and it goes like sh*t on a stick! 13v when it's fully charged! Check it out! Wheel cam:

I'm currently in the process of building a high power LED flashlight from scratch. I've decided to go for AA batteries as a source of power, however, I am not sure as to whether 2 AAs will be enough to drive my LEDs. The LEDs are from a 5W LED bulb putting out ~360lm. I'm assuming the bulb itself has 5 1W LEDs connected in some sort of configuration, but I'm going to run them in parallel. I'm planning on running it on either Alkaline or NiMH. However, I'm not quite sure if there will be some sort of voltage drop with the load I'm going to place on the system (~1A @ 200mA each). Also, 2 NiMH will only have a combined voltage of 2.4v making me a bit skeptical as to whether it would even run. I already have a design for the flashlight for 2 AA batteries. Adding a third battery would complicate the design though, maybe requiring me to make a battery pack or something. So, will a 5x1W LED array in parallel run from a 2.4v NiMH power supply? Or do I have to go with 3 batteries plus a current limiting resistor?

Hi all! I am currently designing a simple electronic device which uses Arduino-software. It needs to be connected to a car (Lead-Acid) battery of 12V and be stepped down to 5V for my ATmega328 to be powered. I read that I must use a "Standard 7805 5V regulator" for this. My question is, will it be able to cope with the heat? Must I put a heat-sink on it and/or is the regulator even "big" enough for this? I figured that using two regulators in parallel, might halve the current and help prevent over-heating. (http://www.sparkfun.com/products/107) Another thing is, how could I go ahead and setup a small NiMH battery charger for this device which works like this: It runs of the car battery at all times and keeps the backup NiMH battery fully charged - as soon as the car battery gets disconnected, it switches over to the NiMH cells. (I will be using 4 of these for my backup-battery-pack http://www.sparkfun.com/products/335) See my attached schematic of what I have in mind, please tell me what you think about it. I have too little knowledge of electronics to solve this problem myself, but if you can point me in the right direction at least, I will try and figure it out from there. Thank you for your time!

I'm building a very simple lighting circuit involving a red LED. The specs give a typical Vf of 2.2V and a Vmax of 2.6V. If I use two NiMH cells to power it (giving a total of 2.4V) does that mean I can get away without a series resistor? Will that degrade the life of the LED by running it at that voltage? vik

Is there a simple way to build a charge indicator for 4 AA NIMH 1.2V 2000 mAh batteries? I thought a small 1-10 volt indicator would do it, but was told it would depend on battery type, etc...

Hi i was wondering if there was any electrically reversible battery chemistries that can be made from around the house materials like copper wire, iron nails, galvanized nails, graphite rods, aluminum foil, and other items like those.

Setup: 330mAh@6V solar panel charging 4xAA Nimh batteries (series connected). Iphone is connected to the batteries. Can I simultaneous charge of nizn battery and iphone? what is the direct source of power charging the iphone? Do the batteries act as voltage regulator??  Any ideas to prevent iphone from drawing more then 500mah?? Thanks, Huzefa

I connected 7 NiMh batteries in series. I connected another set of 7 NiMh in series. Then, I connected the 2 sets together in parallel. A voltage check of the battery pack reads 9.4V. I want to build a miner style light out of it. I'd like to put the battery pack on a belt, and have a control box, also on the belt, with an on/off switch, a dimmer, and a battery recharging connection. I know how to solder and have a basic understanding of electricity. What type dimmer, bulb, etc. would be best? I'd like the light to be as bright as possible, without continually blowing bulbs. Something like this is what I had in mind, but I'm not sure what size/type components to use. Also, am I missing anything? http://i1114.photobucket.com/albums/k522/ALcoonslammer/lightcircuit.jpg

I have a 24V Panasonic rotary hammer drill, model EY6813. It came with two 3.0 amp-hr NiMh batteries, both of which had a problem with one of the contacts almost welding itself to the contact in the drill, and also in the charger. I stopped using those batteries. Now, using an external 7.0 amp-hr NiCd, it's worked fine until recently. The drill began to intermittently shut-off, then quit working altogether. I then noticed that the battery, the wire running to the drill, and the contacts in the drill were hot (battery was very warm, the wires & contacts were VERY hot). Any ideas about the problems with the NiMh or NiCd? Could it be the drill and not the batteries? The hot batteries/wires occurred after minimal runtime, so I don't think its a matter of overdrawing the battery, but I'm just not sure. The vent holes on the drill are not blocked.

I have a robot on wheels that uses 7.2v battery. The battery runs it for good amount of time it is a 2000mah nimh vex battery. I want to supplement and charge it during peak hours. I bought 4 solar panel that can produce 2 V near my window and 3 volts outside. They produce 200mah at full sun. I want to series the solar panel up and have voltage regulator that can regulate it. I was told that the current also needs to be constant and so I ordered a LM317T. Here is the datesheet of lm317t How does the lm317t react when my solar panel hit shade and current goes under 200mah. What voltage should I put on my voltage regulator that I will connect to LM317T. Should I make it 10 V or 9 V? I really am new to this and want to use solar energy to charge my battery while it is connected to my robot in parallel. What current should be held constant to charge 7.2v 2000mah nimh?

I am building a r/c tank and i am using 30 1.2v 3A rechargeable nimh batteries. now i have tried charging them individually in my energizer battery charger, but they seem to get extremely hot (75 celcius) when i charge them for 2 hours. now in the tank i have these batteries in 3 battery packs that hold 10 batteries each and i want to know, if i put a 12 volt 400-500ma current through the battery pack, will that safely charge them without damaging them? recently i tested one of the hot nimh batteries out of the charger with my multimeter, and it read that the battery had 10.28 amps in it and had1.2 volts which is anbormal (exept for the voltage).also i was wondering, is it posible tocharge these packs which once run in parrell give a voltage and current of this (10X 1.2 =12 volt 3A) X 3 packs in parrell =12v 9A can i chareg all of those at the same time, or must i charge one pack at the same time now before you say anything ill just add that these are individual batteries that i have placed inside a battery holder pack, also ill add that i wont buy a sla battery as ive used quite alot of money on these batteries already and lastly, i am not going to go buy a 10 battery charger as they cost way too much, unless sopmeone can find one online that costs under $25