need advice on how to convert power from mains to useable battery voltage

[shyamgenious]

hey guys/gurls
this post is for my upcoming robot and i need to charge some very sensitve li-batteries with steady voltages.
how can i convert the electricity from the mains to useable battery voltage like some 9 volt??
do i use resistors?or do i use transformers??. plz guide me step by step or a circuit diagram will be most welcome as i am a newbie with only a little knowledge.

regards
shyamgeni

[rbtying]

[...] plz guide me step by step or a circuit diagram will be most welcome as i am a newbie with only a little knowledge.

(emphasis mine)

Don't even try to charge lithium based chemistries until you have a thorough grounding in both how the batteries themselves work and the circuits required to charge them properly.  Your life is worth quite a bit more than the ~$20.00 it takes to buy a lithium-ion charger - be well aware that if mishandled, overcharged, overdischarged, or even looked at wrong, lithium batteries might explode - and the lithium inside them is highly flammable. 

Even more so, working with mains electricity is something that is in itself highly dangerous - accidentally touching live wires will leave you in the hospital for weeks. 

I hope that you will redirect your efforts to save your own life =). 

[shyamgenious]

[...] plz guide me step by step or a circuit diagram will be most welcome as i am a newbie with only a little knowledge.

(emphasis mine)

Don't even try to charge lithium based chemistries until you have a thorough grounding in both how the batteries themselves work and the circuits required to charge them properly.  Your life is worth quite a bit more than the ~$20.00 it takes to buy a lithium-ion charger - be well aware that if mishandled, overcharged, overdischarged, or even looked at wrong, lithium batteries might explode - and the lithium inside them is highly flammable. 

Even more so, working with mains electricity is something that is in itself highly dangerous - accidentally touching live wires will leave you in the hospital for weeks. 

I hope that you will redirect your efforts to save your own life =). 

im not that stupid and i correct-i have considerable knowledge about electronics and have made many sophisticated things like a rc boat and automating my lab .i have also built a low cost less energy consuming air conditionor made from...(its a secret) .i am trying my hand in robotics just recently and have researched a lot on the  subject.forget about the li-polymer batteries,just simply tell me how to convert ac to dc (is it the reverse?? ) to fuel my electronic appliances which usually need voltage below 5v.

[Soeren]

[...] plz guide me step by step or a circuit diagram will be most welcome as i am a newbie with only a little knowledge.

(emphasis mine)

Don't even try to charge lithium based chemistries until you have a thorough grounding in both how the batteries themselves work and the circuits required to charge them properly.  Your life is worth quite a bit more than the ~$20.00 it takes to buy a lithium-ion charger - be well aware that if mishandled, overcharged, overdischarged, or even looked at wrong, lithium batteries might explode - and the lithium inside them is highly flammable. 

Even more so, working with mains electricity is something that is in itself highly dangerous - accidentally touching live wires will leave you in the hospital for weeks. 

I hope that you will redirect your efforts to save your own life =). 

im not that stupid and i correct-i have considerable knowledge about electronics and have made many sophisticated things like a rc boat and automating my lab .i have also built a low cost less energy consuming air conditionor made from...(its a secret) .i am trying my hand in robotics just recently and have researched a lot on the  subject.forget about the li-polymer batteries,just simply tell me how to convert ac to dc (is it the reverse?? ) to fuel my electronic appliances which usually need voltage below 5v.

Oh, the experience really shines through in your... colorful... post.

Buy a wall wart if you don't have one already, or buy a lab supply if you want variable voltage and current.

[shyamgenious]

[...] plz guide me step by step or a circuit diagram will be most welcome as i am a newbie with only a little knowledge.

(emphasis mine)

Don't even try to charge lithium based chemistries until you have a thorough grounding in both how the batteries themselves work and the circuits required to charge them properly.  Your life is worth quite a bit more than the ~$20.00 it takes to buy a lithium-ion charger - be well aware that if mishandled, overcharged, overdischarged, or even looked at wrong, lithium batteries might explode - and the lithium inside them is highly flammable.  

Even more so, working with mains electricity is something that is in itself highly dangerous - accidentally touching live wires will leave you in the hospital for weeks.  

I hope that you will redirect your efforts to save your own life =).  

[/quote]im not that stupid and i correct-i have considerable knowledge about electronics and have made many sophisticated things like a rc boat and automating my lab .i have also built a low cost less energy consuming air conditionor made from...(its a secret) .i am trying my hand in robotics just recently and have researched a lot on the   subject.forget about the li-polymer batteries,just simply tell me how to convert ac to dc (is it the reverse?? ) to fuel my electronic appliances which usually need voltage below 5v.
[/quote]
Oh, the experience really shines through in your... colorful... post.

Buy a wall wart if you don't have one already, or buy a lab supply if you want variable voltage and current.

[/quote]
but i have wall warts with adaptors meant only for their specific devices.how can i modify them??i dont even know if a laptop charger is a wall wart.i jus read up the definition in wiki. 

[rbtying]

How to modify a wall-wart:

1) Find a wall wart with an output rating of something like this:
   Voltage: (anywhere from 9v to 16v)
   Current: (more than 500mA, otherwise it's practically useless)
2) Buy a cheap regulator (linear or switching, probably linear for the first time)

3) cut off the ending on the wall wart and use a multimeter to find which one is ground

4) solder the bare wires into a protoboard or use a screw terminal for them

5) Hook up the regulator as required (here's instructions for a 7805: http://www.afreeland.com/node/16)

6) Use the regulated output and have fun.

[Soeren]

but i have wall warts with adaptors meant only for their specific devices.how can i modify them??i dont even know if a laptop charger is a wall wart.i jus read up the definition in wiki. 

Please fix your "quote-fucking" or stop quoting at all!

The point was exactly to stop you from hurting any innocent electronics components (or innocent bystanders) by paying your way to a solution, because, over and over, you sound quite dangerous to yourself and your surroundings.

I'm not trying to discourage you, just trying to get you to not get in over your head - make a simple LED flasher or something and don't move on until you know everything possible about that circuit. Then go a small step further and repeat.


Never mind if the name is "wall wart", adapter, or whatever, just don't break them open, as some of them are switch mode supplies with lots of harmful tracks. Just use them unmodified as rbtying told you, but include a fuse in any circuit you make, until the day that you have enough experience to decide when a fuse is not needed - most power circuits need more than one by the way.

[shyamgenious]

How to modify a wall-wart:

1) Find a wall wart with an output rating of something like this:
   Voltage: (anywhere from 9v to 16v)
   Current: (more than 500mA, otherwise it's practically useless)
2) Buy a cheap regulator (linear or switching, probably linear for the first time)

3) cut off the ending on the wall wart and use a multimeter to find which one is ground

4) solder the bare wires into a protoboard or use a screw terminal for them

5) Hook up the regulator as required (here's instructions for a 7805: http://www.afreeland.com/node/16)

6) Use the regulated output and have fun.

tyvm im gonna convert it rit noow thanks again!!   

[vinniewryan]

You really should take the advice of these people. I've almost blinded myself charging batteries (thank god for safety goggles) simply because a loose ball of solder shorted the battery, all of the sudden acid started shooting out directly at my face! Needless to say it burned and hurt, and ever since then I always configure my charging circuits using capacitors in place of the battery until I'm at the point where I know it won't blow up the cell. There is a lot that can go wrong.

You also might consider purchasing a $4.00 charging chip which will do all of the work for you if calibrated correctly. Charging batteries is something that should never be attempted unless the person doing so knows exactly what they're doing.

All I can do at this point is cross my fingers for you and hope you realize you're basically working with a live bomb. Batteries explode, people get burned, lose vision, even the chemical smell from a shorted battery can make you pass out instantly and DIE!!!

Good luck! Make sure to wear your goggles, lucky underwear, and prepare your fire extinguisher!

[Daanii]

even the chemical smell from a shorted battery can make you pass out instantly and DIE!!!

It's good to be cautious using batteries. But you should not lie to prove your point. This is false.

[vinniewryan]

Battery over heats, chemicals leak out coming in contact with a glass of water (what technician doesn't drink while workin under a lamp), chemical reaction exposes toxic fumes, fumes inhaled, pass out face first on the burning leaking battery, die.