# Re: [EVDL] Auxillary battery and DC-DC converter...



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

Roland -

Thanks for the response.

The IOTA is 55 amps and my car is very simple - 1974 Honda Civic. The only
12 volt electrical items are lights, wipers, blowers, and a main contactor
relay. I may rig up some sort of defroster later. Thus, there should be no
problem with power. The main pack is 144 volts.

I have a main toggle switch for the 12 volt, before the key switch. Thus,
it seems I can do the following:
1) Connect the car positive to the manual toggle switch as if it were a
battery.
2) Connect the positive HV DC-DC at a point after the breaker, but before
the main contactor.
Then if I turn on the HV and then turn on the 12 volt, I will get power.

So, it seems I do not need a 12 volt battery.

Am I missing something?

John





> Roland Wiench wrote:
> >
> > Hello John,
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

Without a 12V battery, you may be 'stranded' if your DC/DC dies: You
will not have the 12V to keep you contractor pulled in.

Even a small 12V aux bat should be enough for this emergency, but you
should keep it in mind.

In my car, the DC/DC HV+ is after the contactor. I want the HV back
completely isolated when the contactor is closed.

-Nick





> John NLN <[email protected]> wrote:
> >
> > Roland -
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

>
> Roland -
>
> Thanks for the response.
>
> The IOTA is 55 amps and my car is very simple - 1974 Honda Civic. The only
> 12 volt electrical items are lights, wipers, blowers, and a main contactor
> relay. I may rig up some sort of defroster later. Thus, there should be no
> problem with power. The main pack is 144 volts.
>
> I have a main toggle switch for the 12 volt, before the key switch. Thus,
> it seems I can do the following:
> 1) Connect the car positive to the manual toggle switch as if it were a
> battery.
> 2) Connect the positive HV DC-DC at a point after the breaker, but before
> the main contactor.
> Then if I turn on the HV and then turn on the 12 volt, I will get power.
>
> So, it seems I do not need a 12 volt battery.
>
> Am I missing something?
>
> John
> 
Vacuum pump?

I have a 300zx with an IOTA DLS-55 with an aux battery and the same 
loads: Headlights, wipers, blower and vacuum pump.

I have noticed that the blower is the single largest drain and on a 
rainy night with headlights and wipers and need of the blower to defog, 
the voltage sags below 12V if I turn on the blower, especially if the 
vacuum pumps is going. I have not put the boost plug in to raise the 
voltage, that may help.

There is no heat, i have found that just the blower is enough around 
here most of the time.

Nissan did a little overkill on the 300zx, the blower is variable speed 
and powerfull and the headlights are large old style power hogs(1987 
300zx) Maybe the civic has a lighter blower and less headlight current?

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

Hello John,

Lets see, The exterior lights are could be about 10 amps, the radio is 5 
amp, if you have one fan motor for heating, one for controller cooling, one 
for motor cooling, that is about 5 amps each at 15 amps.

The controller may be about 4 amps, and a large main contactor in the 500 
amp size is 5 amps.

So the total is now about 39 to 40 amps. This is about the maximum for a 55 
amp IOTA. If you look at the fuse size that is plug into the IOTA, it is 
less than the 55 amp rating.

This is the same as for a circuit breaker. If a circuit breaker is listed 
for 20 amps, the maximum load should be at least 80% of the rating of the 
breaker and wires in the circuit.

The next problem is that the battery voltage will not be held constant at 
all times. So if you discharge the main batteries lets say to 50% SOC, then 
the converter voltage drops and the ampere goes up in inductive loads like 
motor, coils, and transformer loads.

In resistance loads, the overall power drops as for lighting.

If you use a switch to turn off the 13.5 to 14.5 volt side of the IOTA's 
make sure you have all the independent loads shut off first before you turn 
on this switch. This switch should also be rated at least 125% over the 
maximum load you are going to pull.

So if the maximum load is about 40 amps, then 40 A x 1.25 = 50 amp switch. I 
use one of those RED FLAG 500 amp @ 12 volt switches that can be dash or 
console mounted. You insert the large RED FLAG key into the switch and turn 
it which then locks it in. Turning it off, you can remove the key.

Without this shut down key, turning on any ignition, light, or any other 
systems that require the 12 volt power, will not work. There is a auxiliary 
normally close contacts on this switch, so it can keep a security alarm 
system running while this key is remove.

I got one of these from my auto parts store for about $15.00. This unit 
also becomes the emergency shut down for me. I use it to open up the main 
accessory 12 volt battery to the EV controller, main contactor, and main 
battery safety contactors.

Roland




----- Original Message ----- 
From: "John NLN" <[email protected]>
To: <[email protected]>
Sent: Thursday, March 05, 2009 8:49 PM
Subject: Re: [EVDL] Auxillary battery and DC-DC converter...


>
> Roland -
>
> Thanks for the response.
>
> The IOTA is 55 amps and my car is very simple - 1974 Honda Civic. The 
> only
> 12 volt electrical items are lights, wipers, blowers, and a main contactor
> relay. I may rig up some sort of defroster later. Thus, there should be 
> no
> problem with power. The main pack is 144 volts.
>
> I have a main toggle switch for the 12 volt, before the key switch. Thus,
> it seems I can do the following:
> 1) Connect the car positive to the manual toggle switch as if it were a
> battery.
> 2) Connect the positive HV DC-DC at a point after the breaker, but before
> the main contactor.
> Then if I turn on the HV and then turn on the 12 volt, I will get power.
>
> So, it seems I do not need a 12 volt battery.
>
> Am I missing something?
>
> John
>
>
>


> > Roland Wiench wrote:
> > >
> > > Hello John,
> > >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

You can check the archives about accessory batteries or not. The
consensus seems to be that at least a small battery is advisable.
Power available if the DC/DC fails and to balance the load on the
DC/DC.

I have the Iota set on the 14.5v setting to keep the lights bright.
Therefore, the DC/DC is only on when the vehicle is on. I am not sure
why, but this is not enough to keep the auxiliary battery charged.

Some have reported that the Iota takes juice from the battery when it
is off, but I don't detect any milliamps into mine. This is currently
a work in progress for me. I just put a charger on the battery every
week or so. Perhaps if the car was used for longer trips it wouldn't
be a problem. I am told it isn't good for the battery to be on float
charge all the time.

One other caveat. If you are contemplating controlling the DC/DC with
your main contactor, be sure to have a resistor (60 watt light bulb?)
on the precharge circuit of your controller. It is dreadfully easy to
end up powering things through the precharge which causes very
expensive smoke.

it seems I can do the following:
>> 1) Connect the car positive to the manual toggle switch as if it were a
>> battery.
>> 2) Connect the positive HV DC-DC at a point after the breaker, but before
>> the main contactor.
>> Then if I turn on the HV and then turn on the 12 volt, I will get power.
>>
>> So, it seems I do not need a 12 volt battery.
>>
>> Am I missing something?
>>
>> John
>>
>>
>>


-- 
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*



> Jeff Shanab wrote:
> > Vacuum pump?
> >
> > I have a 300zx with an IOTA DLS-55 with an aux battery and the same
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

I forgot the power steering pump that I have, which is circuit breaker for 
100 amps and a 70 amp contactor which is a CanEV or is it EVCan unit.

If I am during straight line driving then the 12 volt ampere is about 5 to 
10 amps, but if you do a hard locking up turning where the wheel may be 
pushing against a curve or something, then I see it peg up to around 50 
amps.

I have for years ran the alternator, vacuum pump, power steering, water pump 
for heating right off the pilot shaft of the main motor which puts a lot of 
drag of the motor, but in this mountain area, helps to keep the EV at a 
constant speed going down icy hills.

Roland


----- Original Message ----- 
From: "Josh Wyatt" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, March 06, 2009 8:02 AM
Subject: Re: [EVDL] Auxillary battery and DC-DC converter...




> > Jeff Shanab wrote:
> > > Vacuum pump?
> > >
> > > I have a 300zx with an IOTA DLS-55 with an aux battery and the same
> ...


----------



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*



> John NLN wrote:
> > If one has a DC-DC converter, is a large 12 volt auxiliary battery
> > really necessary?
> 
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

Some more questions on this topic:

1. With the Iota 12v out permanently connected to the auxiliary battery,
and the HV removed by a contactor or SSR, does the Iota draw any current
from the aux battery? Otmar indicates that a Zilla permanently connected
(for example) will draw 70-80ma from the 12v, which can discharge the
aux battery within several days. It would be easy to put in a 12v
"planned non-operation" switch for the controller, since the current is
low. But what about the Iota?

2. For the auxiliary battery, can the same type of battery used in the
HV pack be used as the aux battery, as a spare for the HV pack? Or will
the charge/discharge profiles be so different that the aux battery will
drift farther and farther from a matched set? Take for example a 144v
pack of 12 Odyssey PC1500 AGMs, with a 13th for the aux battery. Could
that extra cost be justifiable for the availability of a potential spare
and the deep-cycle nature of an AGM?

Best Regards,

- Gene




> John NLN wrote:
> > If one has a DC-DC converter, is a large 12 volt auxiliary battery
> > really necessary?
> 
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*



> Lee Hart <[email protected]> wrote:
> 
> > There are basically two options:
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

Also you need to add the inrush protection as Lee
recommends WITHOUT removing the input bridge rectifier. 


Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

Please consider the environment before printing this e-mail.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Peter Gabrielsson
Sent: Tuesday, March 10, 2009 3:42 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Auxillary battery and DC-DC converter...



> Lee Hart <[email protected]> wrote:
> 
> > There are basically two options:
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

There is a fourth option:

I running four DC-DC IOTA as per Lees modification but use a fifth one or I 
am using a Schumacher Smart Charger that float charge the 12 volt accessory 
battery at 13.3 volts using commercial power while the converters are switch 
off with the ignition switch controlling a 2 pole contactor that is between 
a 15 amp limtron main fuse and main battery and a bank of four 4 amp 
limitron fuses to the IOTA's.

As soon as I plug in the main power plug, the onboard 12 volt charger comes 
on which is fed with a 20 amp C/B. Normally in with 5 seconds, the charger 
readouts indicated 100% SOC and the voltage ramps down to 13.3 volts.

Before I made this change, the old system was a DC-DC rotary converter which 
also had a pilot shaft that also power the power steering unit and a vacuum 
pump. The on board battery charger was a custom made unit that could float 
charge the 12 volt accessory battery at the same time it charge the main 
battery pack while the charger was on or off.

The problem with the DC-DC rotary converter, it was more of a 12 volt power 
supply, that would only furnish about 12.5 volts to the 12 volt system. The 
onboard 12 volt charger would then only charge the battery when the main 
plug was connected.

Roland


----- Original Message ----- 
From: "Peter Gabrielsson" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Monday, March 09, 2009 3:12 PM
Subject: Re: [EVDL] Auxillary battery and DC-DC converter...


>


> Lee Hart <[email protected]> wrote:
> >
> > > There are basically two options:
> > >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*

>> Third Option, Connect the DCDC so it is powered from the pack when
>> you're driving and powered from the utility when you're charging.



> Cor van de Water wrote:
> > Also you need to add the inrush protection as Lee recommends WITHOUT
> > removing the input bridge rectifier.
> 
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Auxillary battery and DC-DC converter...*



> Gene Stopp wrote:
> > 1. With the Iota 12v output permanently connected to the auxiliary battery,
> > and the HV removed by a contactor or SSR, does the Iota draw any current
> > from the aux battery?
> ...


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