[ausev] need advice on power management doo-hickey

[jefoy at mindspring.com]

If the concern is making sure the 12V auxiliary battery is getting adequate charge, why not have a parallel circuit connecting the main pack to the DC/DC converter and drive the contactor for that parallel circuit off the main battery charger. This could be logic driven or as simple as a microswitch activated by the physical plug on the charger. A second contactor would be used to power the DC/DC when the switch is in the 'run" position.

You would then be charging the auxiliary whenever the main pack is charging as well as when the vehicle is in use.

Just a thought..

-----Original Message-----
>From: Brian Lasseter <blasseter.cmpe01 at gtalumni.org>
>Sent: Jan 22, 2008 6:03 PM
>To: AustinEV News Announcements and General Discussion <ausev at austinev.org>
>Subject: Re: [ausev] need advice on power management doo-hickey
>
>On Jan 22, 2008 10:24 AM, Sarah & Erik <electricbasset at gmail.com> wrote:
>> You can also just switch the DC-DC on only when the vehicle is on,
>> just connect an additional relay to the keyswitch. You should be able
>> to switch the input or output of the DCDC, unless the DCDC has a high
>> idle load in which case you'll want to switch the input.
>
>I have my DC-DC driven from a contactor that is controlled when the
>key switch is set to "run".   Therefore when the key switch is
>"off"... then the DC-DC is off, so I have very little phantom loading.
>
>Don Carlson ( 800-951-8774 from
>http://www.globalepower.com/DCContactors.htm ) would be happy to sell
>you some small amperage high voltage contactors for your usage.  An
>SW60B is rated for 80A continuous, which is overkill for a DC-DC
>converter, but would work.  I'm not immediately sure of the price of
>the SW60B's, but the SW80B's are $50, so the SW60B's should be less
>than $50.  I am not sure if there are any other high voltage,
>continuous duty contactors or relays that I would trust.   (I
>personally have my DC-DC connected to one of the two SW200B contactors
>that I use to connect the motor controller to the battery pack.  So by
>turning on one of the two SW200B's, I can connect the DC-DC to the
>pack voltage, while still having my motor controller unconnected.)
>
>Creating a device to detect small current flows would likely use more
>current than your detector is trying to prevent.  A timer, as Erik
>suggested, would be a better option.  Have the timer just leave the
>DC-DC connected to the pack for an hour or so after the car turns off.
>
>A KD258 off delay timer would work swimmingly for this purpose.  It
>operates at 12VDC, can have a 1 to 60 minute "off" delay, is plastic
>wrapped for durability, and can drive 500ma of current... which is
>exactly what the continuous duty SW60B contactor will require.
>http://www.ics-timers.com/kdtimers1.html
>http://www.ics-timers.com/pdfile/KD-Timer.pdf
>
>This would work too...
>http://www.airotronics.com/site/product-trueoff_TGMT.php
>
>Or you could build your own...
>http://www.doctronics.co.uk/pdf_files/555an.pdf
>http://people.consolidated.net/fsmyth/pages/555apps.html
>http://www.elecfree.com/electronic/relay-timer-switch-by-ic-555-and-741/
>
>
>> The only worry is if you have a small DCDC charging a small accessory
>> battery, the battery may never get fully charged especially if you
>> drive a lot at night. It would be a medium sized electronics tinkering
>> project to create a timer that started after you shut the car off that
>> would leave the DCDC on for an extra hour or so.
>
>Interesting... I had not thought of this case, but if I were doing a
>lot of night driving, or running the car stereo loudly, then I suppose
>that the 12V accessory battery may never get fully charged.  If I left
>the car in "run" without ever turning the key switch to "start", then
>the DC-DC would be on, and it would charge the battery.  Since the car
>would require the key in the ignition to do that, I hope I would not
>forget about it.  I will think about finding a way to leave my DC-DC
>connected to a timer.
>
>
>-- 
>TTFN,
>Brian "Lasso" Lasseter
>
>  ·  (512)736-1677  ·  AIM:digininja  ·  ICQ:2238123  ·  MSN:azoreg  ·
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>
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