[RE-wrenches] DC-DC converter for Sun Frost

[Mick Abraham]

I advise not to "center tap" the 24v battery, with a Voltmaster or any other
"half to half" balancing unit. My own Voltmaster failed to maintain the two
halves at a sufficiently close state of charge. It's hard enough to keep the
cells working well as team without adding possible additional imbalance
issues.

Wattage requirement for a DC SunFrost is small enough that a "not too
expensive" DC-DC converter can be connected in series between battery and
the lower voltage DC load. My $0.02 US.

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675


On Wed, Oct 7, 2009 at 8:11 AM, Bob-O Schultze <bob-o at electronconnection.com
> wrote:

> Allan,First, depending on the age of that Sunfrost, it might be OK to use
> on either a 12V or 24V system directly. The older ones are 12V only, but I'm
> not sure when the changeover occurred. An email to Sunfrost should give you
> that data.
> For over 15 years we've used a Vanner Voltmaster. Don't know if they are
> even available anymore and you need to have a battery system that you can
> tap at 12V into equal sections. Basically, they look at both halves and
> switch from one to the other based on a very small voltage imbalance. In the
> 98% efficient category. The Voltmaster will be way more money than your
> other choices and needs two CBs on it's input rather than one, but if max
> efficiency is more important than initial cost, they are hard to beat.
> Bob-O
>
> On Oct 6, 2009, at 10:04 PM, Allan Sindelar wrote:
>
> Wrenches,
> Simple question, I know: what has worked well as a 24V – 12V DC-DC
> step-down converter for a Sun Frost? I am doing a design to completely
> rebuild/replace an early-90s off-grid 12V system with a new system at 24V.
> The only DC load is a Sun Frost. I think it’s an RF16, so dual-compressor. I
> know of at least three converters: Solar Converters; BZ Products; ICT; and
> I’m sure there are many more. What has worked well, with minimal ghost load?
>
> Thank you,
>
> Allan Sindelar
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> EE98J Journeyman Electrician
> *Positive Energy, Inc.*
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1112
> www.PositiveEnergySolar.com <http://www.positiveenergysolar.com/>
>
>
>
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