I want to design a charging circuit to charge 2 NiMh AA batteries in series, via a 5V USB Micro cable. I have some basic electronics knowledge but not very in depth, so your help/suggestions would be appreciated.
OPTION 1:
So far, I have looked at TI's BQ2002 chip. Unfortunately, the diagram they have in the data sheet (below) is not very helpful:
The diagram above seems too simple and does not provide enough guidance on how to actually build an application. Then I found a spec sheet but the circuit in there seems pretty complex: http://www.ti.com/lit/ug/sluu007b/sluu007b.pdf I wonder if the diagram in page 3 of that spec sheet with the LM317T is the actual circuit I will have to build for my application?
Here is a diagram for the LTC4060, I wonder if the actual circuit will really be this simple:
OPTION 3:
Finally, there is this very detailed step by step tutorial that does not use any dedicated charger IC: Build a USB Powered AA NiMH and NiCd Battery Charger
But it only uses temperature (thermistor) for charge termination. I feel this is not adequate if one eventually wants to build a charger that's good enough for commercial application.
So basically, option 1 seems to be the most difficult route, and option 2 or 3 seems easier. I feel option 3 is too simple and is more of a toy. My goal is to actually build a charger that is safe, robust, and good enough for commercialization. And in the process, I want to learn.
Which option do you recommend? (in terms of difficulty level for a novice/quality of the charger, etc...)
Thanks
If your developing a 'commercial product' then you will be responsible for it safety wise and thus its hardly appropriate as a project for a 'novice'.
My fee for that commercial advice is a 25% cut of the profits.
A better place for advice on commercial products is probably the 'Gigs and Collaborations' forum.
Thanks, what is the benefit of the MAX charger over the Linear Tech LTC4060? Both requires external components like a PNP transistor, etc... The LTC4060 actually seem to offer more functions and termination modes.
I want to build something in the summer on my own. In Fall, I will be working with a professor and other graduate students on this. I understand the need for the design to be robust for "eventual" commercialization.
However, I just want to pick a chip to use for now, and all future work will revolve around it. So far I'm leaning the LTC4060 since it is easier to design for than the TI BQ2002 (wouldn't you agree?). But I will also investigate the MAX chip.
I'm just curious why you think the MAX chip is better than the LTC4060. Thanks
But has anyone ever implemented something like this before though?
Thanks
If the two devices you have mentioned had no sales, they would have gone out of production years ago. I know the MAX devices have been around for a long time.
srnet:
If the two devices you have mentioned had no sales, they would have gone out of production years ago. I know the MAX devices have been around for a long time.
So someone must be implementing them.
What I meant was, has anyone in this forum actually have designed with either of those ICs and can possibly offer insights or useful advice.
Either way, I need to pick an IC to start designing. All I want to get out of this thread is confirm my belief that the LTC4060 (or the MAX) is easier to use than the TI bq2002 in that less external components (less complex external circuitry) is required, and therefore more feasible for a beginner to tackle.
Guys, I will be working on this as a semester project in Fall. I will have a professor supervise me. But for now, I just want to learn as much as I can first so I won't appear to be a complete noob by then.
I want to start experimenting and building. But I need to decide on a platform first. The LTC4060 is more expensive than the BQ2002, but it seems to be "smarter" and requires less external component. I read the manuals for both carefully. The BQ2002 doesn't offer much info. I then found spec sheet (linked in my original post) for it but the circuit inside contains many external components. I can figure out that circuit myself if it needs to be, but I prefer something simple.
I feel the smarter the chip is, and the less external circuitry I need, the harder it is to mess up. That might make it worth the additional cost. I want to move ahead with the LTC4060 (or the MAX), but just want hear some other opinions to confirm that the BQ2002 indeed would require more expertise to get working than either the LTC4060 or the MAX chip.
Once I decide on a chip, I can study it more in depth so by the time I talk to the professor I can be more productive. thanks
You will get more points with the professor if you ask his/her opinion on the best choice of your two option, rather than telling him/her why YOU chose one over the other.
