I'm still not clear on why everyone thinks that this is a failure which should be covered under warranty. If Rob or Jean want to give a free cell, then that's above and beyond -- but I don't think we should be blaming the battery in this case. <div>
<br>Let's explore the situation. We've got 6760 AH of battery storage, in four parallel strings. Four strings in parallel would not be my recommendations, but let's leave that aside for now. The solar, if putting out full rated wattage with no degradation due to heat, off-axis, shading, soiling, or any other loss will put out a whopping 100 amps, for a mind boggling C/67. Add normal derates, and we're down to a C/80 charge rate, and we haven't even accounted for daytime loads. The solar is there for show, and to make the owners feel green.</div>
<div><br></div><div>So how about the generator charging? We have 10 Outback inverters -- that should be enough, right? Well, 10x45A each gives us a C/15 charge rate, which should be OK. But is the generator large enough? That's a lot of inverters to drive, this load is pretty reactive, and we've not any information about the background AC loads except that they're probably pretty large. Wait, the generator is only 30kVA, which is only good for 24kVA of continuous resistive load (30*.08). What's the altitude of the installation -- if it's higher than 1,000 feet the generator should be further derated. No inverter is as efficient at charging as it is at inverting, so of that 24kVA of available generator capacity, only 19kVA is likely to make it to the batteries -- that's a likely C/21 charge rate if there were no AC loads, but there are, so it's likely to be lower.</div>
<div><br></div><div>And when do the batteries get charged? Not every day -- the solar can barely keep up with the self discharge. The generator runs every 2 - 3 weeks, so the batteries are <b>in a state of near constant discharge for 14 - 21 days on average</b>. When they get so low they hit the AGS floor, the generator kicks in. However, just as the battery voltage climbs to the beginning of the absorption state, the generator is shut off. </div>
<div><br></div><div>These batteries haven't been full in over six years. They haven't received a proper charge in over six years, either. I'm surprised they've lasted as long as they have. Let me guess the last time they were equalized -- really equalized, not just "I hit the button and ran the generator until I got tired of the noise" equalized -- as in charge until the voltage rises up to 62-64 volts for 3 or 4 hours, and the specific gravity on each and every cell hits 1.265. Was the bank commissioned with an EQ upon installation? </div>
<div><br></div><div>I think that one of the best things that can be done to serve these clients (other than recommend a huge investment in efficiency) is to decrease the time between generator charges by 50-75%. You want to get it to the point where the generator is cycling on at least every 7-10 days. In addition, you really want to extend the absorption time -- 12 minutes is just not enough to do anything but tease. The customer really needs a bigger generator to drive this system, too. Adding vent fans to the power room is highly recommended -- you're dissipating something like 6,000 watts of heat when you're running 10 inverters at full charge. Power the vent fans off the generator output, so they only come on when the system is charging.</div>
<div><div><br></div><div>When it's time to replace this bank of batteries, I'd recommend looking at decreasing the size of the bank by 50%. And investing more in efficiency, of course. </div><div><br></div><div>Hope this helps,</div>
<div><br></div><div>Phil Undercuffler</div><div><br><br><div class="gmail_quote">On Tue, Jun 22, 2010 at 11:14 AM, Jeff Oldham <span dir="ltr"><<a href="mailto:starpower4u@juno.com" target="_blank">starpower4u@juno.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Those HUP batteries are still under warranty and you very well may have a free cell waiting for you, give Rob or Jean a call at NWES and run it past them. They offer 1st rate CS and should take good care of you. You won't get much for used batteries so I would be inclined to keep them in service even though 4 strings in parallel is not ideal. I've had reasonable luck with 4 strings paralleled by getting my battery/inverter cables all over the bank, at the least put 1/2 of your inverters across 2 strings and the other 1/2 on the remaining 2 strings (still parallel all 4 strings).<br>
<br>You never mentioned an EQ cycle either, with that limited Absorption time it should happen at least every 6 weeks. <br><br><br>From the Solar, Wind and Hydro powered office of Jeff Oldham/Regenerative SOLutions
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