[EVDL List]

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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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: <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
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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[EVDL List]

Todds were similar simple switching power supplies that were common as EV
DCCs 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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[EVDL List]

IOTA is a bad choice as it is really just a power supply. failure will come
for sure, when you least expect it. 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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View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/DC-DC-voltage-output-question-tp4656517p4656521.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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[EVDL List]

[quote]xxx@xxx.xxx 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 xxx@xxx.xxx

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