My charger also has an interlock that requires 12V, and my 12V battery
only holds a charge for 3-4 days due to parasitic loads. My solution was
to install a 12V trickle charger. So while the car's plugged in, the 12V
battery stays topped up. While driving, the DC/DC takes over.
I considered leaving the DC/DC on full-time, but its quiescent current is
too high for my liking. Much cheaper to replace a 12V battery than a whole
pack!
Here are the specs of the charger I used. My main requirement was 120/240
VAC operation. I paid about $35 for mine.
Deltran Battery Tender Waterproof 800
0.8A charge current
"smart" charger
120/240 VAC input
Fully electrically protected
Designed for outdoor use
Comes with alligator clips AND ring terminals
http://batterytender.com/waterproof-800-usa-western-hemisphere.html
-Adrian
On Tue, 08 Jan 2013 11:57:21 -0800, Cor van de Water <[email protected]>
wrote:
I have a charger that does not need 12V to charge the 120V flooded pack,
because I plug the cord directly into the charger's AC input and the
charger's output is directly connected to the pack.
I do use a tap on the charger's transformer to power a small 12V supply
that charges my aux battery and unless that supply dies, I am not afraid
that my 250Ah aux battery runs out of juice.
(The aux is made of 2 spare batteries in case 1 or 2 of the pack's
golfcart batteries die)
The aux battery meter is the only original dash meter that is useful in
my conversion, of course the pack SoC is displayed on a separate meter.
The common item here seems to be that if your EV needs to be "on" to
charge,
even if it is not the key in the ignition, but still contactors need to
pull in, maybe fans are running and other electronics such as BMS needs
to be powered, then you also need to make sure that there is supply to
those critical tasks - the DC/DC needs to supply at least a standby or
float level of power.
If you do not like the idea of having your aux battery on a charger for
long periods of time then you can consider a separate external 15V power
supply running from the AC and powering the critical tasks via a pair of
diodes, one supplying power from the aux battery and one from the
external power supply that you can mount near the charger and run
together. The dual Schottky diodes with about half a Volt drop are
frequently applied for this purpose, for example to separate an RV house
battery and external power or in a car with excessive audio equipment to
power it from a pair of batteries that each are charged by a separate
alternator.
Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of David Ladd
Sent: Tuesday, January 08, 2013 10:41 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Need 12V to Charge?
I've done this too. Not actually with the lights on, just a weak 12v
battery that would die if left unattended too long. Here's a quick tip,
instead of jumping the 12v battery with 4 of your traction pack cells,
just jump the terminals of the contactor that powers the DCDC. In my
case it was controlled by an EV200 contactor, and a quarter jumps the
terminals quite nicely. :-) Once the DCDC is powered, you have 12v to
the battery, and the contactor will now stay on itself as intended.
I did have the same issue where the 12v battery died overnight and shut
down the MiniBMS, which shut off the charger. Bummer, but at least it
happened at home. I just drove another car that day, since I had no way
of knowing how much it had charged before getting cut off.
I now have the DCDC always on, and don't have this problem anymore.
david.
http://www.evalbum.com/4021
________________________________
From: Mike Nickerson <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Monday, January 7, 2013 9:31 PM
Subject: [EVDL] Need 12V to Charge?
However, I was prepared for this. I have been carrying a couple of 10
ga.
wires in my trunk for just this reason. Each cable had an alligator
clip on
one end and a ring terminal on the other end. With the key on, I
connected
the clips to the 12V battery terminals and simply touched the ring
terminals
across 4 of the LiFePO4 cells. That was close enough to 12V. With that
voltage, the main contactor engaged and the DC-DC converter turned on.
After that, I could remove the cables because the DC-DC converter was
keeping the 12V system alive.
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