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 <bo...@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 > al...@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/> > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > >
_______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
