DC/DC voltage output question

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DC/DC voltage output question

Barry Oppenheim
Question to the group:
What are the downsides to leaving a DC/DC converter in the higher voltage output mode all of the time?

Background:
I have a Iota-55 power supply that I have been using as a DC/DC convertor for the last ~4 years. Other than the occasional blown fuse it had been very reliable.

The default output voltage is 13.2-13.4v which is fine for running the EV, but not optimal for charging the accessory battery. The Iota has an option to boost the voltage output to 14+ volts which is what an alternator would normally use to charge the accessory battery.

Thanks,
Barry

www.justanotherEVconversionBlogspot.com
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Re: DC/DC voltage output question

Roland Wiench
Hello Barry,

I have now been running a Iota-45 since 2002 with no problems on the 14.5
volt setting.  It is parallel with a inverter-alternator design to charge a
deep cycle battery up to 15 volts.

Remember that the 14.5 volts is at no-load and if loaded up to about 80%,
the converter voltage will drop below 14 volts.  The alternator is set for a
maximum of 14.5 volts and when the alternator goes off line when the EV
stops, the converter goes on line.

The Iota-45 is fuse for 30 amps output and fuse for 4 amp input using a
Bussman Fusetron which is a slow blow type.

I use a 2-pole contactor that disconnects the DC-DC converters when the
ignition is off.  A 12 volt battery maintainer is use when the main AC is
plug in to the EV.

Roland




----- Original Message -----
From: <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Saturday, July 14, 2012 7:18 AM
Subject: [EVDL] DC/DC voltage output question


> Question to the group:
> What are the downsides to leaving a DC/DC converter in the higher voltage
> output mode all of the time?
>
> Background:
> I have a Iota-55 power supply that I have been using as a DC/DC convertor
> for the last ~4 years. Other than the occasional blown fuse it had been
> very reliable.
>
> The default output voltage is 13.2-13.4v which is fine for running the EV,
> but not optimal for charging the accessory battery. The Iota has an option
> to boost the voltage output to 14+ volts which is what an alternator would
> normally use to charge the accessory battery.
>
> Thanks,
> Barry
>
> www.justanotherEVconversionBlogspot.com
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Re: DC/DC voltage output question

EVDL Administrator
Todds were similar simple switching power supplies that were common as EV
DC:DCs years ago.  They also had those voltage-boosting terminals.  Some EV
builders using them connected a relay to the terminals so that the voltage
was higher when the EV is on and being used, but lower when it was parked.  
This simulated the action of an alternator.  

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: DC/DC voltage output question

Cruisin
This post was updated on .
In reply to this post by Barry Oppenheim
IOTA is a bad choice as it is really just a power supply. Failure will come for sure, when you least expect it. Check around on the forums for the dependability of this product.One person who has used it for a while is NOT a recommendation to use the product. Talk to people who have used them in customer cars and you will get the right skinny. I am sure there are people who disagree, mainly because they bought cheap and dont want to spend more. Get a adjustable DC converter about 150w and leave it on all the time charging a Li-ion 14,5v battery with about 26ah. get rid of the heavy lead acid and convert all lights to LED and headlights to Haligen. Now you have a EV.
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Re: DC/DC voltage output question

Lee Hart
In reply to this post by Barry Oppenheim
[hidden email] wrote:
> What are the downsides to leaving a DC/DC converter in the higher
> voltage output mode all of the time?

A lead-acid battery can be float charged at 13.2-13.8v (the exact
voltage depends on the temperature, type, and age of the battery). A
voltage any higher than this on a continuous basis will overcharge it,
seriously shortening its life.

Normal car alternators aim for about 14v. That's above the optimal float
voltage. But the battery recharges faster at the higher voltage, and
they know the engine won't be running continuously. An hour or so a day
at 14v is "enough" to keep the battery fully charged.

> I have a Iota-55 power supply... The default output voltage is
> 13.2-13.4v which is fine for running the EV, but not optimal for
> charging the accessory battery.

Actually, it *is* optimal for the batter. It's just a bit low for the
rest of the stuff in a car, which assumes an alternator delivering 14v.

> The Iota has an option to boost the voltage output to 14+ volts which
> is what an alternator would normally use to charge the accessory
> battery.

If you want to strap the Iota for 14v, then also wire it to only be on
when the car is actually being driven. Then you are simulating what a
normal car does with its alternator.
--
First they ignore you; then they mock you; then they fight you; then you
win.
        -- Mahatma Gandhi
--
Lee A. Hart http://www.sunrise-ev.com/LeesEVs [hidden email]

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