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[DPRG] Robot Pb battery charging question

Subject: [DPRG] Robot Pb battery charging question
From: Paul Bouchier bouchier at classicnet.net
Date: Sun Jan 24 11:50:36 CST 2010

Thank you very much for the ideas Kenneth. It turns out I have a 78ST105H
regulating input to the router, so I can just tap off 5V out of that to run
the Arduino, & run it all off 24V. You've solved my problem - I didn't even
see the possibility. 

Thanks again for all the help.

Paul

> -----Original Message-----
> From: DaKenengineer-meister. [mailto:kmaxon at qwest.net] 
> Sent: Sunday, January 24, 2010 5:00 AM
> To: Paul Bouchier; dprglist at dprg.org
> Subject: Re: [DPRG] Robot Pb battery charging question
> 
> 
> 
> Hi Paul,
> 
> A quick question to chanllenge the statement/assumption about 
> the "normal" 
> way to do it.  Often it can be much more efficent to run both 
> the motors and 
> the electronics from the +24V.  Use a high efficency step down buck 
> regulator such as those produced by National Semiconductor.  
> They make a 
> line of parts called the simple switchers that will take 
> inputs up into the 
> 36~40V range and can operate down into the battery range you 
> are looking 
> for.  These parts can source an amp pretty readily.  The next 
> step from 
> there might be a switching module by TI.  This has the whole 
> switching 
> 'buck' regulator built into a small module, pre-built.
> 
> I mention these due to the efficency.  Efficency is directly 
> related to how 
> long the batteries on your robot will last.  Additionally, it 
> provides two 
> benefits.  1) the batteries can discharge much further before 
> the regulator 
> that would have been on the lower battery only will 
> experience a brown out. 
> Read = longer runing time for the robot.  2) The common type 
> of problems 
> that people have with embedded processor resets when running 
> motors and 
> logic from the primary batteries all but goes away when using 
> a very high 
> frequency buck regulator as the noise in the areas of 
> interest can't pass 
> through the regulators and associated filters...
> 
> -Just something to chew on.  I use this configuration in a 
> good number of 
> the robots I've built over the years and I get some 
> phenomenal run times out 
> of them.
> 
> -Kenneth
> 
> ----- Original Message ----- 
> From: "Paul Bouchier" <bouchier at classicnet.net>
> To: <dprglist at dprg.org>
> Sent: Sunday, January 24, 2010 2:38 AM
> Subject: [DPRG] Robot Pb battery charging question
> 
> 
> > Robot Illuminati - I'm seeking advice on a robot battery 
> > power/charging conundrum. I'm building the electronics for a robot 
> > which has 24V motors but 12V electronics (Mowbot, for those 
> who know 
> > him). The natural way to wire it
> > is to put two 12V batteries in series, tap off the lower 
> one & feed 12V 
> > from
> > it to the electronics, and wire the upper one to the motor 
> power circuit.
> >
> > The concern I seek advice on is charging the two 12V lead acid 
> > batteries. The lower one will discharge faster, especially during 
> > development, because it's running the electronics as well 
> as its share 
> > of the motors. If I just hook up a 24V charger to the two batteries 
> > I'm concerned charging will leave
> > the batteries unbalanced because the upper one will be 
> fully charged 
> > before
> > the lower one.
> >
> > Is this something I should worry about? If it is an issue, 
> does anyone
> > have
> > any ideas on how to address it?
> >
> > I imagine the electric R/C guys deal with this, because 
> they sometimes
> > have
> > separate motor & radio batteries. What are the standard 
> techniques for
> > handling this situation?
> >
> > Thanks for any ideas
> >
> > Paul Bouchier
> >
> >
> > _______________________________________________
> > DPRGlist mailing list
> > DPRGlist at dprg.org http://list.dprg.org/mailman/listinfo/dprglist
> >
> > 
> 
> 

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