Wrenches, I answered Richard off-list, but other wrenches may find this information about old SW4048s and batteries useful.
The SW4048 is a solid machine. We've been using one since 1998 and have sold hundreds of them for both on and off grid systems. We would leave what's working alone and replace and expand the battery bank to meet the client's expected grid outage hours. Our system has only 4 kWh of sealed batteries because we live in an area that gets almost no power outages and did not want to bother watering batteries. See info and wiring diagram at http://www.solarsolar.com/oursys.html On the other hand, one of our clients in Malibu on the grid had an off-grid 5 kW PV system for backup power with 75 kWh of IBE flooded lead-acid batteries (2 parallel strings of 24 each 2-volt cells). We installed the system in 1993 but no one maintained the batteries properly. So in 1996 the dead IBE battery bank was replaced with a maintenance-free, sealed Absolyte battery bank that only lasted 4 years because of 40 F to 90 F temperature swings in the equipment room. A few years ago, we upgraded the system with a 31 kW array, 6 Sunny Boys, 2 Sunny Islands, and went back to a new set of 75 kWh of IBE cells like before. Now the batteries are inspected and watered every 2 to 6 months. We are still determining the right service period. I have learned to buy good batteries, install them where the temperature stays 60 to 70 degrees F. as much as possible, inspect and water flooded batteries at least 2 times per year. All things being equal, sealed lead-calcium batteries cost twice as much and last half as long as flooded lead-antimony batteries. Most importantly, batteries are electro-chemical things just like living organisms. Keep them clean, fed (fully charged as much as possible), properly watered, at 70 degrees F, don't over-work them (deeply discharged without fully charging promptly), and they will last 6 to 8 years easily and often 12 years before old-age (high self-discharge) sets in. Battery bank owners that take care of themselves, their families, their animals, and their vehicles carry those good habits over to taking care of their battery banks. It's sad but true that people who are unhealthy and have vehicle problems all the time almost always have battery problems. Best regards, Joel Davidson ----- Original Message ----- From: Allan Sindelar To: re-wrenches@lists.re-wrenches.org Sent: Sunday, November 20, 2011 8:21 AM Subject: Re: [RE-wrenches] Convert Grid Tie SW4048 to Backup System; Add New Inverter, AC Coupled Kirk, I think there are a couple of subtleties that you're missing in your post. All of the SW series that we installed in grid-tied mode prior to Trace/Xantrex losing its 1741 listing - mostly Y2K installations - are still in use legally, as they were grandfathered in. Once Xantrex lost its listing and went to the GTI models (firmware rev. 4.10 and above), only with a GTI were they 1741, and the earlier inverters couldn't be retrofit. So if Richard's customer's SW4048 is pre-GTI and is currently legitimately utility-interactive, it could be argued that it's grandfathered in. Of course, I'd avoid arguing anything that esoteric with any governing body. But it's a moot issue anyway. Reviewing the other Wrenches' suggestions, none advised continuing to use the SW as an interactive inverter, but only as a charging source for a battery bank. One Wrench suggested putting the SW's AC input on a weekly timer, which is a good idea. Jay is correct that the SW was a terrible inverter for grid-tie. One primary weakness of the SW series was that as long as the grid was up, it tried to maintain float voltage to the batteries continuously (this was the "lack of silent sell" issue). This brought overall sell efficiency down to around 55%, as I recall, rather than the 93+% efficiency of today's inverters. But if the inverter is only being used as a charging source, it's not selling and thus neither the poor efficiency nor the lack of a GTI is relevant. Personally, I wouldn't get rid of the SW if the customer wants battery backup. The inverters have proven generally reliable, and this one is likely to last for decades as an occasional battery charger. Plus it's already paid for, and does a good job as both a battery charger and a backup inverter during outages. I'd use sealed batteries to deal with the customer's maintenance concerns. The Honda 3000i is a good choice at sea level, as the SW can hard-limit the AC amp draw from an undersized generator and avoid overloading it (and nuisance-tripping its output breaker). But note that the SW can take up to about 5,200 watts from an AC source, and sealed batteries prefer high charging C/rates, so you might want to use a generator of around 6kW (at 120V) instead for better efficiency and less runtime. Good thing Richard reposted - the second time got a bunch of us responding. Kinda fun... Allan Allan Sindelar al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com On 11/20/2011 4:33 AM, Kirk Herander wrote: PS - Richard, does it have a Trace / Xantrex GTI interface installed? If not, it's not code-legal to be tied to the grid anyway. Get rid of the 4048 whatever you do. Kirk Herander VT Solar, LLC dba Vermont Solar Engineering NABCEPTM Certified installer Charter Member NYSERDA-eligible Installer VT RE Incentive Program Partner -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Richard L Ratico Sent: Friday, November 18, 2011 6:53 PM To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] Convert Grid Tie SW4048 to Backup System; Add New Inverter, AC Coupled Jay, Marv, Chris, Ray, Joel & Maverick, Thanks tremendously for your input. Each of you provided interesting suggestions, all of which I find thought provoking and helpful. I greatly appreciate your taking the time to share your experience. Dick Solarwind Electric --- You wrote: We redid one in a very similar situation recently. In that case the customer wanted super backup and so we put in Grid tie Outbacks and a new battery bank, added modules, and kept the SWs as battery chargers from the generator. He had the option with bypass switches to use the SWs, if the Outbacks went out. This guy wanted a "keep the power going, no matter what" system, but I can't claim that was optimal. The right answer depends on what the customer wants. I probably wouldn't trash everything though as Jay suggested, since the existing modules are already racked and wired. (unless it's a bogus install, then yep, salvage it all) You could probably easily rewire the parallel 48 v sets of modules all in series in 15 minutes in the combiner box to get the voltage up, and use a small GT only inverter, too. I guess it would also depend on how close the 2 different types of modules are in voltage or current, but it doesn't have to be perfect; as these were modules headed to the scrap heap otherwise. In honor of modules that are well installed and still performing correctly, I do try and reuse them. Being able to brag: "these have been working for 30 years..." is great for the solar industry as a whole, but only if it makes sense. Ray On 11/17/2011 5:51 PM, jay peltz wrote: HI Richard, I'll chime in, although you won't like it. Dump the system and start over with a new battery less system and a genny as back up. Told you, you wouldn't like it. The SW parts are basically gone and it was a terrible grid tied inverter anyway. The modules are usable but why at $1.5 watt keep them? Client doesn't want MX, so that means no batteries. You'll need a genny as back up anyway for long power outages during storms, so get a natural gas/propane unit as back up instead of batteries. OK you asked, jay peltz power On Nov 17, 2011, at 4:03 PM, Richard L Ratico wrote: Hi Wrenches, This is a repost. No replies the first time, so I'm trying one last time. I may be "adopting" an eleven year old, Y2K, grid tie with battery back-up system. It consists of 12 - Astro-Power 120 modules, installed in 2000, 12 - Evergreen EC-110 modules installed in 2004, only one MX60, which controls BOTH sub-arrays, one SW4048 in SELL mode through a dedicated load sub-panel. Existing, seven year old battery is shot (8-Trojan L-16). Initial bank of unknown batteries was replaced after only four years. Recent long, nearby, utility outages have the client requesting a proposal to include a new back-up generator and to restore the system selling to the grid. Client may decide go straight grid tie to eliminate the batteries. They have found the maintenance to be a hassle. My thoughts so far: 1)To take advantage of most of the existing hardware, I wonder if it makes sense to try to improve the system efficiency by relegating the SW to a manual back-up mode only, where, say, by means of a timer controlling grid availability through AC1, it would only charge a smaller battery bank once a week. The battery bank would be small, a single string of either, sealed gel units or T-105s with the new Trojan watering system. 2) Provide new grid-tie inverter/s (appropriate string type or Enphase 190s) to handle the net metering. 3) Provide a way to AC couple the new inverter/s to the SW in the event of an outage. 4) Provide a new Honda 3000 inverter type generator connected to AC2 in the SW. 5)Provide a way to lockout the grid tie inverter/s when the generator is operating. Any thoughts or suggestions would be greatly appreciated. Thanks in advance, Dick Ratico Solarwind Electric Bradford, VT --- end of quote --- _______________________________________________ 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 ------------------------------------------------------------------------------ _______________________________________________ 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
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