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DPRG: 68HC11 Digest V597 #33 (fwd)

Subject: DPRG: 68HC11 Digest V597 #33 (fwd)
From: Eric Yundt eric at sssi.com
Date: Tue Jun 3 11:35:26 CDT 1997

Some nice stuff about battery charging from the 68HC11 list...

owner-mot-68hc11-apps at freeware.mcu.motsps.com wrote:
> Date: Tue, 3 Jun 1997 02:22:38 -0500
> Subject:   68HC11 Digest V597 #33
> 68HC11 Digest          Tuesday, 3 June 1997        Volume 597 : Number 033
>  This is a digest of the M68HC11 Discussion List.
>  The following Subjects are discussed:
> Re: PCBug problems
> RCPT: Battery Charging
> Re: Serial IO in Linux
> Re: Battery Charging
> Re: how to protect program in 68hc711e9
> Re: Serial IO in Linux
> Re: Serial IO in Linux
> Re: Serial IO in Linux
> Re: 68HC11 Digest V597 #32
> Current version of Pink Book
> Re: how to protect program in 68hc711e9
> Re: Current version of Pink Book
> Re: Serial IO in Linux
> RCPT: Battery Charging
> Re: PCBug problems
> Re: Serial IO in Linux
> Re: Serial IO in Linux
> Re: Serial IO in Linux
> ----------------------------------------------------------------------

[ ... ]

> ------------------------------
> From: bobsmith at i2020.net (Robert L Smith)
> Date: Mon, 02 Jun 1997 08:14:39 -0400
> Subject: Re: Battery Charging
>  Message sent by bobsmith at i2020.net (Robert L Smith)
>  to the mot-68hc11-apps Mailing List.
> At 02:26 AM 6/2/94 ARG, you wrote:
> > Message sent by "Pablo" <mocho at einstein.com.ar>
> > to the mot-68hc11-apps Mailing List.
> >
> >Hi!
> >I'm looking for an IC, or app note about charging a lead-acid 
> >battery. I must use the less components I can and to make it 
> >really cheap. I'm using a 68HC68 RTC that can control and manage  
> >switching betwen VCC and battery because it has a Power Sense 
> >circuit. Can I use this feature of the RTC for this application?. 
> >I'll appreciate any help.
> >Thanks in advance,
> >
> Pablo --
> For routine applications it is normal practice to float-charge lead-acid
> batteries with a constant voltage source.  The charger should also be
> current limited according to its capacity.  The float voltage is a 
> function of battery temperature and should be adjusted to produce the
> desired trickle charge rate as the battery reaches full charge.
> For automotive class batteries it was customary to set the float voltage
> to about 13.8 volts at 68 deg F.  This should produce a trickle charge of
> about 2 amps for a battery in good condition.
> If you are using a lead-acid battery for a constant long term load such 
> as a back up to a computer application it is best to select a battery
> specified for deep-discharge service such an an RV battery or one designated
> for deep-cycle marine service.  Automotive types are optimized for short term,
> high amperage starting service and do not tolerate repeated deep discharges
> well.
> The trickle charge rate should be low enough to prevent out-gassing, something
> like 1/100 of the ampere hour rating of the battery.  This is especially 
> critical for sealed types as there is no way to replenish the water lost
> during overcharging.
> I suggest contacting a major battery manufacturer for specific information
> because the float voltage, maximum charge rates and gassing rates vary as a
> function of battery temperature and cell design.
> Try Exide, Gould, or Yausa(sp?).  If you are looking at compact, sealed
> lead-acid types that look like beer cans, contact Gates - Amoung other
> information they publish a very fine small book on the care and feeding
> of their sealed cells which has much fine overall information on batteries.
> I have also recently seen some complex function charge chips intended for
> lead acid designs which detect current battery condition and cycle back
> and forth between a recharge mode and a trickle mode as the cell voltage
> rises and falls.  Sorry, I don't remember the manufacturer off the top of
> my head but will keep my eye open for it.  If I were to search for it I
> would check Maxim, Benchmarq, and speciality chip houses such as Linear Tech.
> A neat trick I saw several years ago was a charger that had 2-3 silicon
> power diodes in series with the output to the battery.  The charger voltage
> was then set to the appropriate number of diode drops above the desired
> float voltage (typically .6 - .7 volts per diode).  The idea of this was
> that as the battery approached full charge float voltage, the diodes would
> drop out of conduction and the charge rate would fall off rapidly and
> vice versa.
> Note that it is essential that the charging supply be current limited to
> prevent burn out of the supply under heavy load and over charging of the
> battery.
> None of this information is useful for Ni-Cad, NmH, or L-ion battery types.
> They have completely different voltage vs. charge relationships and must
> be handled with special charger IC's.  By the same reasoning, do not
> attempt to adapt such a charger chip to lead-acid service.  A lead-acid
> battery does not exhibit the negative dv/dt inflection approaching full
> charge and will not cause the chip to enter trickle charge state.
>   Good luck,  Bob Smith
> >Pablo Mochcovsky
> >
> >
> - -
> - ----  Avoid computer viruses  --  Practice safe hex  --------------
> Robert L. (Bob) Smith			Smith Machine Works, Inc.
> amprnet    wa4ypv at w4za.ampr.org		9900 Lumlay Road
> internet   bobsmith at i2020.net		Richmond, VA  23236+1004
> landline   804/745-1065	
> ------------------------------

- --                                                        .__
Eric Yundt <eric at ytech.com>                       __ ---   ; \_      //    F
                                                  --- -   ("" a\,   // L  I
"HA!" YaTu laughs as he spits into the wind,       -- -    {\_""   // I  N
tryin' t'catch a fox makes da cow's head spin!    --  ooo__{ _}   // N  I
                                                      (O)---(O)  // E  S
YaTu at YTech.COM  --  http://www.dprg.org/yatu (N/A)              //    H



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