I also do not believe the DC genset will be overloaded. It can be used (crudely) in a Bulk-only situation and be fine, as long as it shuts off when its supposed to, probably when charge current drops below a certain threshold (signalling that the batteries are becoming charged) or even on a timer based on bank capacity and load calculation. Its then important for the PV to finish the charging cycle for continued battery health. I know its not optimal, but can work well if set up properly.
Roy Rakobitsch NABCEP Certified Small Wind Installer® Certified Advanced Tower Climbing, Safety & Rescue Wind/PV Design Engineer Windsine LLC 631-514-4166 www.windsine.org On Sun, Jan 28, 2018 at 9:23 PM, Mac Lewis <[email protected]> wrote: > Hello wrenches, > > I'm working on 3 off-grid telecom sites. They are designed to operate > solar only under most conditions but the project manager ordered a > custom-built 48 VDC generators, intended to be used as the battery > charger/backup power for the site. These are ~20 kW generators, and can > probably do about ~350Adc at 48 Vdc at the elevation that these are sited. > The battery banks are 4 x 1000 Ahr GS Nanocarbon 48 battery strings and can > gobble up the 350Adc easily when they are discharged. > > While discussing the generator operation with the generator supplier, we > have found this generator isn't capable of charge control, or limiting its > own output. The charge control functionality isn't necessary at this site > because we really just need it to keep things online until the sun returns, > a simple 54 VDC float voltage would work. However, without the generator > being able to self-limit its output, we expect this generator to stall when > started because it can't regulate its output current and will immediately > become overloaded by the discharged batteries. > > I am trying to come up with some options to rectify this serious design > issue. One idea that immediately came to mind was putting in some parallel > solar charge controllers between the DC generator output and the battery > bank. If the generator output could be dialed up to around 60-70 VDC, > could parallel solar charge controllers be used for charge regulation? It > would be kind of like charging a 48 V battery bank from a 70 V battery > bank. MPPT isn't applicable, could the max current limit in the charge > controller(s) be used to regulate charge rate? Will the charge controllers > blow up? If not, what brand might work. Each site has 8 x Midnite Classic > 150s but I'm open to other manufacturers if it would work. I am open to > blowing up a charge controller in the shop but I thought it best to ask > first. > > What are other ways to put this generator to use, and limit its load? > > > > Thanks for your input/comments > > > > > > > -- > > > > Mac Lewis > > *"Yo solo sé que no sé nada." -Sócrates* > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: http://www.mail-archive.com/[email protected]. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > >
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