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I have learned from experience that small inverter-generators can have
problems in this application, depending on the inverter. For instance,
with an Outback inverter, you need to size the gennie large enough to
handle loads and surges larger than the programmed battery charging
rate, as the Outback lacks the full inverter support we had with the SW
series. Other inverters have this same issue. The inverter isn't fast
enough to control a surge load and can trip the gennie's output
breaker. We have seen that the 3000W Yamaha inverter-generator will lug when overloaded before tripping its breaker, but the Honda has a very sensitive breaker that will trip on even a slight overload. The tripping often goes unnoticed if the engine noise isn't audible in the house. The problem is exacerbated by the need to charge the batteries at the highest rate available from the generator/inverter combination, both for decent C/rate and to minimize runtime. So setting the inverter charge amps way back in order to leave some surge headroom defeats these objectives. All of this is exacerbated when the generator is small. We install at 6-8K' elevation, so we need to derate 25% +/- anyway. But in one system the customer had a 3000W Honda inverter-generator, and we installed a VFX3524 inverter, which maxes out at 19A AC charging input. After numerous nuisance trips, we told the customer to leave everything off while AC charging, plus pay attention to the charge rate to notice if the output breaker trips. Allan Sindelar Darryl Thayer wrote: The system is way short on PV, and I would think that it is already a Gen with PV support. I agree with everybody more PV is the way to go but the batteries must be cooked by now with this many Deep cycles. BTW C/10 is not important, in fact I feel better if I charge slower. I know fast charging is a good way to kill batteries. Operating cost needs a high efficiency engine. So until you can get the PV up to become the dominant source, a gen is probibly in order. I tend to use smaller generators than most people, and the fuel efficency of a Honda inverter gen is hard to beat.--- On Thu, 12/3/09, wind...@wind-sun.com <wind...@wind-sun.com> wrote:From: wind...@wind-sun.com <wind...@wind-sun.com> Subject: Re: [RE-wrenches] Off-Grid Sizing Case To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> Date: Thursday, December 3, 2009, 12:18 PM Off-Grid Sizing Case The rate of charging is not the real problem in most undersized systems, it is the fact that the batteries seldom, if ever, get fully charged. Given the ratio of PV vs battery capacity, I would suspect that their batteries have been chronically undercharged for ages. We usually recommend around 1 watt of pv per AH for a 12 volt system, 2 watts for 24 volt etc. A generator is not usually the answer, because it may have to run for hours to get that final 5-15% of charge into the batteries. Generators are good for equalizing, not so much for general charging. .................................................................................................. Northern Arizona Wind & Sun - Electricity From The Sun Since 1979 Solar Discussion Forum: http://www.wind-sun.com/ForumVB/ .................................................................................................. ----- Original Message ----- From: Mark Frye To: 'RE-wrenches' Sent: Thursday, December 03, 2009 10:56 AM Subject: Re: [RE-wrenches] Off-Grid Sizing Case So being able to achieve C10 charging from the PV is not so important? Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 www.berkeleysolar.com From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of wind...@wind-sun.com Sent: Thursday, December 03, 2009 9:51 AM To: RE-wrenches Subject: Re: [RE-wrenches] Off-Grid Sizing Case I would go with #1. The solar is obviously undersized for the battery bank he has. Another panel + MPPT should give him about 25-40% more, depending on temps etc. -
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