[EVDL List]

The schematic I have shows power to the DC/DC and accessory battery on
all the time.
I would like to wire it so it is only powered when the key is on.
Good idea, bad idea ?

Thanks;
Dennis

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[EVDL List]

I'd say check what's connected to the accessory power. Is there
anything that should always have power? For example, if you have a
clock/stereo system, it'll "forget" the time when it loses power.

It should be OK to rig them up to the ignition, but on the other hand,
they should take very little power from the main batteries even if you
leave them on all the time. Even a regular car starting battery can
power accessories for a long time, and you've got a string of deep
cycle batteries. You shouldn't have to worry about the power wasted.

-Morgan

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Hello Dennis,

I have my DC-DC converters disconnected from the main battery pack by use of
the ignition key, that controls two small mini contactors that I got from
evparts.com. I do not like to have any standing voltage in my EV. There is
too much main battery bleed off, no matter how much you clean the battery
and the motor brush dust when every thing is connected to it all the time.
My main battery pack is also disconnected from the controller and main
contactor and also from the battery charger when the ignition key is off.

Only the 12 volt accessory battery provides power to a isolation module that
keeps the E-meter on and to the ignition circuits.

I am using IOTA DC-DC converters, and I found that the problem, is that I
need it adjusted to 14.5 VDC instead of 13.5 VDC, which overcharges the
battery at that rate and boils the water out. So I install a small on board
12 volt battery maintainer or a smart charger will work, that is tap and
circuit breaker to the main input plug.

When I start up the EV and all its 12 volt accessories which can reach about
80 amps or more, it can pull down four IOTA's that are in parallel by about
2 volts.

To reduce this load on the DC-DC converters, I then transfer the DC-DC
converters off the battery and eight 12 volt motors to a alternator, while
the converter provide power the the rest of the 12 volt system.

Roland


Roland


----- Original Message -----
From: "Pestka, Dennis J" <[email protected]>
To: <[email protected]>
Sent: Friday, September 07, 2007 8:16 AM
Subject: [EVDL] Power to the DC/DC


> The schematic I have shows power to the DC/DC and accessory battery on
> all the time.
> I would like to wire it so it is only powered when the key is on.
> Good idea, bad idea ?
>
> Thanks;
> Dennis
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Hi Morgan:

All connections to the traction batteries are disconnected - both sides of the circuit - in my EV.
Both sides of the high voltage tap off the the traction battery pack are fused with two DC cartridge fuses..
Both sides of the high voltage to the DC -DC are disconnected through a double pole relay and there is an additional fuse in each side of that line. It's the same for the other lines to the high voltage power steering pump and heat. Both sides of all the high voltage DC circuits are switched. Both sides of all the high voltage circuits have their own branch fuses.

I use an accessory battery with the DC-DC.

Sometimes switching a DC-DC on can weld the relay contacts, depending on what type of converter you are using. I had a convertor that quite regularly welded the contacts but I ran across one that "soft starts" with a one second delay after the relay switches on and have had no problems.

Dana







-------------- Original message ----------------------
From: "Morgan LaMoore" <[email protected]>
> I'd say check what's connected to the accessory power. Is there
> anything that should always have power? For example, if you have a
> clock/stereo system, it'll "forget" the time when it loses power.
>
> It should be OK to rig them up to the ignition, but on the other hand,
> they should take very little power from the main batteries even if you
> leave them on all the time. Even a regular car starting battery can
> power accessories for a long time, and you've got a string of deep
> cycle batteries. You shouldn't have to worry about the power wasted.
>
> -Morgan
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

M

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I use the IOTA 55amp 220V dc-dc and leave it connected to the pack at
all times. It just goes down to milliamp sleep mode.
Sometimes after 8 hours, I may see that last digit (.01KWH) change after
sitting 8 hours at work, but for the most part, I can't even see the usage.
Since it is plugged in when I get home every nigh and I drive it every
day, this works for me.

The IOTA is an awsome unit

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