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[DPRG] Remedial Circuitry

Subject: [DPRG] Remedial Circuitry
From: . zappepcs at earthlink.net
Date: Mon Dec 8 13:20:01 CST 2003

Just my tuppence worth...

<mantra>google is my friend, google is my friend, google is my friend </mantra>

I found two sites about this particular issue...


Both are interesting enough reading... if you like that kind of thing :)

Google also found several (not too shabby) DIY charger project documents too.


-----Original Message-----
>From: Ralph Tenny <rften at swbell.net>
Sent: Dec 8, 2003 8:16 AM
To: 'Chuck McManis' <cmcmanis at mcmanis.com>, 
	'Earl Bollinger' <earlwbollinger at comcast.net>, 
	'Karim Virani' <karim at compuguru.com>, dprglist at dprg.org
Subject: RE: [DPRG] Remedial Circuitry

I'll have to double-check; at age 72, my memory may not be what it once
Meanwhile, what is the no-load (10k ohms/volt meter or better?) voltage
one of your batteries about an hour after removing from the charger?

-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of Chuck McManis
Sent: Sunday, December 07, 2003 3:27 PM
To: Ralph Tenny; 'Earl Bollinger'; 'Karim Virani'; dprglist at dprg.org
Subject: RE: [DPRG] Remedial Circuitry

Did you really mean 12.8V Ralph or did you mean 13.8V ? My Lead/Acid 
chemistry charger keeps flooded batteries at 13.8 and deep cycle sealed 
batteries at 14.5V


At 03:05 PM 12/7/2003 -0600, Ralph Tenny wrote:
>One more addition to this thread! The most efficient charge for all
>Lead-acid batteries is to charge from a 12.8 v. source (for a nominal
>12 v. battery). As the battery approaches full charge, the charging
>current tapers off. Leaving the battery connected (float charging)
>replaces any normal self-discharge to keep the battery at full charge.
>-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On
>Of Earl Bollinger
>Sent: Saturday, December 06, 2003 6:42 AM
>To: 'Karim Virani'; dprglist at dprg.org
>Subject: RE: [DPRG] Remedial Circuitry
>Well, that looks pretty good to me at this early in the morning.
>The resistor dividers should be setup for what you expect the maximum
>load voltage to be. But you may need to throw in some reverse biased
>Schottkey fast-switching diodes on the ADC input side to limit the back
>EMF that can be generated off the motors. This may be a problem if your
>ADC's have a problem with negative going voltage spikes. Some ADC's are
>0v to +Vcc and some ADC's can handle -Vdd to +Vcc voltages just fine.
>You need to check your ADC's specs on that. On some ADC's you might
>to use a ZENER diode to limit the maximum voltage a ADC could see, if
>the motors generate a lot of forward voltage spikes (such as braking in
>reverse). Some bypass caps may be needed to smooth out the voltage
>levels on the ADC inputs, to prevent the weird erratic readings being
>caused by the motors.
>Depending on the motors and motor controllers, the back EMF or RFI that
>could be generated, could cause some noise on the ground line that
>get into the computer system logic circuitry. Thus you might need to
>in a diode between the logic ground and the motor ground connection to
>help block the back EMF or RFI off the motors from getting into the
>logic circuits.
>If it is noisier, you might have to run a inductor-capacitor "PI" low
>pass filter on that common ground connection (like the ones in your car
>radio audio systems to filter the engine noises out of the audio
>system). Of course I think it's just us "old guys" anymore that
>the loud motor whine coming out of the radio in the old days, with the
>car's engine running. I remember when my car was OK, but I could pick
>the "unfiltered" car next to me from several hundred yards away on my
>The motor power system and the logic circuit system should only have a
>single common ground point of contact between the two. Usually the
>system has the chassis ground and the logic system floats with only a
>single common ground point of contact. It does get interesting when the
>computer system requires a good shield or box of it's own, and you need
>to keep them separate from the chassis/motor ground.
>A lot of times that simple single common point of contact for ground is
>all that is needed to filter the noise out of the computer system. But
>if it doesn't then it's easy to add in filters as needed.
>I assume your using opto-isolators to isolate the motor system from the
>computer system. I have had motor controllers blow out on me in the
>past. Sometimes the motor controller blows out and allows high voltage
>to appear on the logic lines leading to the computer system, which is a
>definite bad thing to have happen. The computer fuse may pop right away
>but the high amp fuse on the motor side won't pop. Of course, debugging
>is easy, replace all the semiconductors and low voltage caps, reprogram
>and it' back up again. :(
>You can't go wrong having fuses in the system. These larger systems
>start to get downright dangerous. Especially at 3AM and your tired, and
>the probe slips or you drop that screwdriver or bolt, "oops". Of
>it does really irritate you when you blow your last fuse at 5AM on a
>Sunday morning, and now you have to wait for the Radio Shack or Auto
>Parts store to open. I consider it to be very important to try and use
>common automotive type fuses (not the special electronics custom fuses)
>that you can get easily at auto parts stores or Radio Shack, et cetera.
>Although you can "kludge" up a temporary fuse out of many things, such
>as a strand of copper wire, you have to decide how important your
>computer system is if the temporary fuse doesn't pop if you have
>"oops". I almost forgot they just opened the new 24hr Walmart
>SuperCenter, about a mile from my home, they have automotive fuses too.
>:)  I'm saved.
>Isn't it interesting, how it always seems to take three fuses to pop
>before you realize there is something wrong?
>The first fuse pops, maybe it was an old one and went bad.
>The second one pops, humm, maybe it was a fluke.
>The third one pops, drats! Stupid %^#%#^#%#%#% darn #&#&#&#& infernal
>-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On
>Of Karim Virani
>Sent: Saturday, December 06, 2003 2:02 AM
>To: Tom Gralewicz; dprglist at dprg.org; Earl Bollinger; SOLID Corp.
>Subject: RE: [DPRG] Remedial Circuitry
>Thanks Robert, Scott, Earl, Tom and Ralph for your input.  I understand
>now  that reconnecting variously charged SLAs in parallel was the
>primary problem with my concept.  So I'm working from your various
>suggestions to plug 3 chargers into the existing circuit.  Also adding
>couple of voltage dividers to sense battery levels.  Please see the
>diagram (below) that I adapted from Scott's original.
>The chargers are all the harbor freight model that Tom pointed out.
>I went ahead and bought 3 during the post-Thanksgiving sale at the
>Richardson store.  I'll be using them at the 2A setting.  The chargers
>plug into the "O" docking connectors.  From my research, cyclic
>are designed to put out around 14.7v, standby chargers less.  Assuming
>these are cyclic chargers (they don't specify their voltage output),
>rounding up, I'd expect a max of 15v from each charger.  When running
>batteries I'm interested in the region from 12.7v-fully charged to
>12.0v-emergency shutdown.  Thus the voltage divider values for level
>monitoring.  Do these calculations seem right?  I think I went in the
>right direction when figuring worst-case actual resistor values.
>How do I verify the actual voltage from these chargers before hand?
>They're supposed to autosense when to shutoff, and don't show a voltage
>when the circuit is open.  The manual says they need to detect at least
>.7v from the battery before attempting to charge.
>Assuming they shutoff on their own - I should be able to sense the drop
>to 12.8v in the ADC.  Can I have the ADCs monitoring while the chargers
>are active?  I don't know nuthin bout noise and filtering, etc.
>I didn't put much in the way of protection - these chargers are
>to be circuit-breaker protected.  Do I need more fuses?
>I don't understand why the diode is needed - I just copied it from
>Scott's diagram.  On a low battery it'll drop the voltage too much for
>the DC/DC converter down the line.  Can I drop it?
>       motor power
>             |
>            fuse
>      56k    |
>   +-/\/\/---+-------O
>   |         |       |              logic power (dc/dc converter)
>   |        -=-      +                  |
>   |        -=-   charger3             fuse
>   |        -=-      -                  |
>   |         |       |                  -
>   |         |       |                  ^
>   |-ADC.M   +-----O-+                  |  30k
>   |         |       |         O--------+-/\/\/--+
>   |         |       |         |        |        |
>   |        -=-      +         +       -=-       |
>   |        -=-   charger2  charger1   -=-       |--ADC.L
>   |        -=-      -         -       -=-       |
>   |         |       |         |        |        |
>   |         |       +---------+        |        |
>   |         |       |                  |        |
>   +-/\/\/---+-------O---------+--------+-/\/\/--+
>      10k    |                             13k
>           __|_
>           \ \ \
>I'd appreciate any further thoughts,
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