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View Full Version : On keeping 12v LA batteries "topped up"



shobley
09-15-2009, 12:12 PM
In the app notes for the Sabretooth motor controller they give an example of hooking it up to an ATX psu with a battery in parallel.

http://www.dimensionengineering.com/appnotes/atxguide/atxguide.htm

The battery is to absorb the regenerative braking energy - the guide also says that the ATX PSU will keep the battery charged. Is this reallly the case? I thought that the output from the ATX PSU was pretty much 12V, and I thought you needed more than this to charge a Lead Acid battery.

The reason I ask is that I have a silent 12V switching module that I could use for this purpose in my Dalek, but it's putting out exactly 12V (as far as I can measure) - will this be ok to put in parallel with a battery?

This is to keep the top half of my Dalek running indoors through the winter - he only gets his wheels back when the Spring comes around.

Steve

nagmier
09-15-2009, 12:22 PM
You could run the 12v line through a regulator to get it to whatever voltage you need you would just need to design the proper circuit

Adrenalynn
09-15-2009, 12:51 PM
It would trickle-charge the battery, and you run the risk of overcharging the battery even at the trickle. If you have a flat battery, there's no way it would charge it fully. But yes, you can run it in parallel.

A good name-brand PC power supply should give you _very_ clean and precise 5v and 12v power. That said, even the decent ones aren't all created equal if you need really clean 12v. But that's a whole'nudder topic entirely. :)

shobley
09-18-2009, 08:35 AM
OK - thanks for the replies. I would want to keep it hooked up for several months (not necessarily doing work all the time).