I think DT is on the right track. We have a relay driver set up at the college. We have it set it for turning lights, alarms and motors on a certain voltages. The students also do a lab with it. It could do exactly what DT mentions.
Jesse Dahl NABCEP PV Installation Professional IBEW Local 292 - Electrician Electrical/Solar PV Instructor - HCC Sent from my iPhone > On Jan 29, 2018, at 9:07 PM, Darryl Thayer <[email protected]> wrote: > > Hi Friends, sorry to be slow. This fits the Morningstar relay driver > exactly. It can look at the battery voltage and activate relays in multiple > fashions. When the battery voltage is low at the recharge point, the relay > driver can be set to start a two wire or three wire generator. This can be > done with the relay driver using a start delay or not. Then when the > generator is running after warm up, the relay driver can close a > relay/contactor to load the generator. The voltage comes up to absorb volts > where the battery will absorb a lot of current. It is possible to use the > relay driver to insert a resistance via a contactor or just let the battery > go to a higher voltage and shut the generator off. For example start the gen > at 50 volts, let it charge to 58 volts, and shut it down. If the generator is > large the battery voltage will rise too quickly and a relay/contactor with > resistor should be used. There are a number of control scenarios. > > I think by the description the generator will overload and depending on > generator field control either stall or reduce speed and keep running. Good > luck > >> 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]/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org >> >> > > _______________________________________________ > 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]/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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