Alisha:
Is this a one-shot product? Is the space within your enclosure not so critical? Is there any available money?

If you answered "yes" to any or all of the these questions I would urge you to purchase a ready made unit to do the job instead of building one up from the chip level. I have used the fine products available from PATCO. They have a small, high quality charger that should be perfect for your battery. They are in stock at Digikey (just guessing where you are located). You can look at the PATCO unit here on Digikey Catalog Page 1006. Look in the lower right hand corner. The part number PATC-04-ND unit will work nicely with a sealed lead acid battery of 12V at 2-4 Ah rating. It also works on larger batteries too....just takes longer to charge. They keep these in stock at about $70 US.

It is also possible to acquire a product called a "battery tender". Here in the USA there is a chain store called "Batteries Plus" that sells several models of these at prices from about $20 to $45 US. These units are designed to be installed on an intermittent use 12v lead acid battery and keep them charged and topped off for extended periods of time. These products are not as high quality as the PATCO unit mentioned above, but may be almost as good of solution for you. A small rating battery tender can be an effective recharger for a small capacity battery.

For your application you could even use a battery tender and break it out of its plastic enclosure and re-mount it inside of your enclosure so that it looks like a real OEM solution.


Michael Karas