Stand-Alone charger

[-=CrAnSwIcK=-]

i'm building a stand alone charger, before i do my dual-cell, so i can play with it right away what i wanted to know, and couldn't find in a search, was exactly how do you know when it's fully charged?? and is there a way to time it, or add an indicator light, like on the controller?? or do i just guess??

[Softspike321]

tyhe transmitter has a timer circuit and i cant find any shcematics on how to make one, so 4 now, you will just have to time it yourself.........oh well

[Matic]

Timer can easily be build around LM555 chip. It is very simple , just a few resistors and capactoors. search the web for the word "lm555 timer circuit" or something.

If you want a charger which automatically goes off when the battery is full then follow this link
http://www.universalhost.de/html_bit/b-charger.htm
It is not very difficult to build, just follow the schematic.
If you use 12v input then value of R!1 should be 800 ohm
and R4 should be 22k not 33k (error)
Value for RSense is 1 Ohm if you want 250 mA charge current, or 0.5 Ohm for 500mA current (or anything inbeetween ). I don`t recommend using greater charge current than 500mA

You can get free saples of MAX 713 and MAX 712 chips at http://www.maxim-ic.com/

[Softspike321]

Hey, did you build the circuit with the free samples, or did you buy the parts? I need to know more about the "samples program" it seems as if they will ask you to buy more in the future. What's your experience?

Where did they get those nice PCB's? Are they custom?

R4 is 33k in the picture, not 22k.

[SuperFly]

Wow, that peak charger seems pretty cool, but an awful lot of work. Do you really want to charge your batteries to their absolute capacity, or get close with a lot less work? check this out:

Stand-alone charger tutorial

The thing to remember about dual-cells is to charge them at 4.5v or so, and that you will need to charge them for double the amount of time (because there's 2 cells being charged) to get the same run time as a single cell.

The charger in the above tutorial is based on a Motorworks charging base with a button to start new charges. With a multi-voltage adapter, you can charge cars with any number of cells on the same charger. 3 to 4 charges for single cells are perfectly safe, and 6 should be fine for dual cells. Once the cells start generating heat, they are full. I'm sure someone will disagree with me, but these little batteries are easy to come by and are cheap. If I ruin one, I've got a sack full of extras. I've been using the charger above for over a year, routinely get better than 25 minutes of run time and have yet to toast a battery.

[Matic]

Originally posted by Softspike321
Hey, did you build the circuit with the free samples, or did you buy the parts? I need to know more about the "samples program" it seems as if they will ask you to buy more in the future. What's your experience?


R4 is 33k in the picture, not 22k.

I build it from free samples and i prefer using MAX713 chip. My experience is "absolutely worth doing it" it works perfect.

I said that R4 SHOULD BE 22k NOT 33k as in the scheme.

You can (actually is a must) add 2 LEDs for power and charge, there is a diagram in MAX 713 datasheet.