A dead 12 volt accessory battery has happened at one point or another to
everyone.
We typically run a small DC-to-DC converter to keep the accessory
battery topped up, just to avoid the dreaded flat accessory battery.
You absolutely _must_ have a 12 volt accessory battery, but a DC-DC that
runs whenever the vehicle is "on" increases the reliability a great
deal. Small expense, but is good insurance against forgetting to charge
the 12 volt, which is easy to forget in the excitement of race day. (Ask
me how I know. :-) )
We use a Vicor DC-DC converter module (or more than one in parallel)
like this one:
http://www.ebay.com/itm/201199082834
You might choose a different model, (like a VE-j72-CY) depending on your
main pack voltage and your wattage needs. You should get a 15 volt
output and trim it down to ~13.5 volts (read the data sheet). If you get
one with 12 volt output, it won't charge a 12 volt battery because it
really puts out exactly 12.0 volts.
I don't know who originally said it but, "To finish first, one must
first finish."
I'm guessing, but you probably used a portable "12 volt" battery charger
to recharge your Li-Ion "12 volt" accessory battery. That is likely what
ruined it. Almost without exception, the open circuit voltage of all
portable "12 volt battery chargers" is greater than 15 volts, (often as
high as 17 volts) which is a death sentence for a "12 volt" Li-Ion pack.
Always measure the open circuit voltage, with a voltmeter, on a battery
charger before you use it to charge a Li-Ion battery. Any power supply
or charger that put out over ~14.7 volts open circuit will toast a
Li-Ion accessory battery. Find one, like a laptop power supply, that
puts out the _correct_ voltage.
Also, leaving a switch on overnight accidentally will drain the
accessory battery to zero, which will also result in the demise of a 12
volt Li_ion accessory battery. Good to have an LED tail light or dash
indicator light that lets everyone know that the 12 volts is "on".
Best of luck!
Bill D.
On 6/5/2016 1:20 PM, Casey Mynott via EV wrote:
Hey all!
A historic day for the Shock and Awe racing team from Bothell Washington and
the world of drag racing!
After sitting in gridlock and sweltering heat on the #1 towards Mission
Raceway, I arrived just as the track was doing lunch. All in all it was an
amazing day with some serious excitement (a 9.589 second 152 MPH run) and a
bit of a turn at the end of the day. During run #2 the 16 volt AGM (which
was changed out for a faltering 16v lithium pack of headway cells) ran out
just as the team was pulling up to the line. So, yesterday ended in a somber
moment of reflection. A good reminder, racing is a tough sport, physically,
mentally, emotionally, financially, all of the above!
The team is at the track today hoping to get in another run, depending on
how that goes possibly a second.
For now, enjoy the video! :)
https://www.youtube.com/watch?v=L53JTDnmj_w
Cheers!
Casey
--
View this message in context:
http://electric-vehicle-discussion-list.413529.n4.nabble.com/Shock-and-Awe-Historic-run-9-589-Seconds-152-MPH-tp4682360.html
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.
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