I have a device that runs off 4 C cell batteries. Was thinking of switching to an internal rechargeable battery. Then the idea cross me to add in a charging port to recharge without removing the battery. Being from the automotive field I now about basic electronics and ohms and volts. But the fine little details are beyond me. Is this even remotely possible or and I doing the proverbial **** in the wind. Any insight would be awesome.

 

It's totally doable, but you need rechargeable cells. The power port is something you can find at Shack.

There are a few things to work out, primarily the charger. You'll also want to think about whether the batteries are switched off when the power plug is attached, and whether the device should be able to run while charging. That's fairly typical but not mandatory.

 

It's totally doable, but you need rechargeable cells. The power port is something you can find at Shack.

There are a few things to work out, primarily the charger. You'll also want to think about whether the batteries are switched off when the power plug is attached, and whether the device should be able to run while charging. That's fairly typical but not mandatory.

as this is a toy for my daughter I don't need to make it fancy. just wanna try to prevent having to disassemble it every time I need to change the batteries. figured internal battery and charging port would be thebest solution. only im not sure how to make that happen. I am very creative with mounting and building whats needed to store the new parts but not about how to build it.

 

If it was me I would aim for a simple design that puts a steady trickle charge into the batteries at a rate they can handle on a continuous charge basis.

Granted it might leave it with a 12 - 20 hour recharge time when run dead but it would prevent the device from over charging and or doing damage to the batteries or itself.

For a basic concept being the device runs on ~6 volts I would go with a common 8 - 12 volt charger that has a simple resistor to limit it's charging current to whatever the batteries are rated for in trickle charge mode.

After that for over voltage protection I would probably use a 7 - 8 volt zener diode across the input circuit just after the current limiting resistor.

 

My preference is an LM317L chip set at the proper float voltage. It self limits at .1 amp until the float voltage is achieved, then it trickle charges forever.

Short answer. I have to go to work now.

 

For a basic concept being the device runs on ~6 volts I would go with a common 8 - 12 volt charger that has a simple resistor to limit it's charging current to whatever the batteries are rated for in trickle charge mode.

After that for over voltage protection I would probably use a 7 - 8 volt zener diode across the input circuit just after the current limiting resistor.

....and you lost me. maybe im gonna need to do some more electrical engineering education before I take on this project. im awesome at building things, putting them together, following directions. but not the planning part.

 

It's not so bad. Start by telling us what you might already have as a power source (got any old wall warts laying around?), and how the toy is used (short play time with long charge time, or used all day and then you want it charged ASAP).

I'm with #12 on the simplicity of using the LM317. But it may depend on what you're starting with.

 

posted a response yesterday, said it was pending approval... still waiting.

basically I have nothing but the toy. a 1985 teddy ruxpin. I actually have two. one was my wife's the other was mine. taking them apart and making one good doll out of them. once I build one good one I can experiment with the other one. on the one the battery tray is old and corroded so I was thinking if I cut out the old tray I can replace it with a more modern power source and possibly a charging system. don't have any parts our anything laying around so I would be staying fresh. was thinking about a 6v r/c car battery but I think that would last long since they don't in those cars.