Battery Charging with Skystreams Forum
Posted by Joshua Janes at 6/15/2009 7:01 AM 
Categories: FORUM
Tags: Southwest Windpower Skystream 3.7
Categories: FORUM
Tags: Southwest Windpower Skystream 3.7
Forum area to discuss - Battery Charging with Skystreams
Does anyone have a good battery charging configuration sorted out for their skystream ? I have an installation off grid with a Sunny Island inverter charging a 24v battery installation. The problems I find is that the system is not designed to cope with variable power from the turbine particularly when the batteries are near full charge. The installers have been working on this issue and have added a diversion load which works by adding a load once the battery volts go above a preset level. We are also planning a trial of the SMA Smartload which works with the Sunny Island inverter controlling the load via frequency shift.
Will be interesting to see if this solves the main two issues I have with teh current system:
1. There are times when the power rises sufficiently that the Sunny Island will overload and briefly cut power shutting down the turbine and all power to the house. (I have seen 4kW at times on the Skyview log - we are in a very windy location).
2. A fixed diversion load cutting in and out does mean the battery volts are not very stable and therefore I believe not optimal for long battery life.
I would be interested to hear others input on this topic.
cheers,
Scott.
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Hi Scott,
I have an off-grid 48V system controlled via a Sunny Island 5048 and supplied by a Sunny Boy managing 1.6kw of PV and a Skystream. Like you we are in a windy area on the Otago Peninsula near Dunedin NZ. Both the Sunnyboy and Skystream are AC connected. Like you we had problems of over-voltage and needed close monitoring to prevent shutdowns. Like you we connected a load dump into the HWS but this was very clunky and was very harsh for battery management. We now have installed a SMA smart load and evrything is operating very smoothly. It is unfortunately the only really manageable option we cold come up with - it works beautifully trickling off every extra watt but the system is expensive. In addition you neeed to ensure you have at least six kW attached to the smart load - it will never need to use it but SMA absolutly insists that the resistanc is mandatory if they are to honour their guarantee.
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Hi Scott, having the same problems adn battery issues. Give me a call to discuss if u like
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I now have the SMA smartload 6000 connected in conjunction with the Sunny Island 3324 inverter. This solves the issue of power cut out due to overloading but it doesn't appear to manage the battery volts too well after a power surge as the smartload maintains a high load for 20-30 seconds after a power surge drawing the batteries down during that time. It then gets back into the proper operating range and does its job again.
Scott.
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Hi,
I came across your response to a situation about Skystream overcharging batteries etc., I have a similar but more complicated problem that I don’t know how to solve, and Outback & Skystream have not been able to provide answers other than, ‘it’s a common dilemma.’
I am an electrical contractor new to renewables. I am located on the island of Saipan, about 150 miles north of Guam. I have limited access to colleagues or inspectors familiar with this technology and equipment. Let me briefly explain the situation.
A local school was the fortunate recipient of a nice solar and wind material package. There was no ‘load’ designated to be operated, other than a critical water pump. The intent is to create some educational curriculum for the students. I was brought in to assist with the installation. I was never provided schematics so I had to do some homework, identify some loads and put it all together. Utility power outages are a regular way of life here, the primary intent of this system was to be able to keep the water pump running during power outages, as after about an hour with no utility, students get sent home because toilets cannot be flushed. I converted some classroom lighting with more energy efficient fluorescents, connected some critical computer and visual aid equipment, put in a small inverter type A/C unit in the inverter-battery room along with the water pump as my loads.
The system consists of 3 small series connected arrays, parallel combined and connected to an Outback MX-60, which is integrally installed on an Outback GTFX-2524-2, grid-tie inverter. There is a 700 amp-hour battery bank connected to the inverter. We have standard 120/240VAC, two phase, 3-wire, with neutral utility power. We also have a Skystream 3.7 turbine.
There is a small load center where all my designated loads are derived. This panel is connected to load side of inverter. The Skystream was initially connected to a breaker in this panel. In the initial testing, we successfully had our PV charging the batteries with Skystream loads on and meter turning backwards when load permitted. We verified that when shutting down the utility, the batteries provided power to the inverter and load center and our Skystream continued to run. We verified the inverter disconnected from the utility and did not back feed.
After initial programming of the inverter and a day of battery charging, I noticed that my battery bank voltage was about 30VDC. I verified the set-points on the MX-60 to be set at 28.6VDC. This confused me, so I called Outback. They explained that if I did not install the Skystream charge controller device, the turbine would overcharge the batteries by back-feeding through the inverter. I had the charge controller but I did not initially install it as I wrongfully assumed the MX-60 handled all the charging needs.
So I installed and set the charge controller and put the Skystream back on-line. I did not
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Hi Joe,
I am not experienced in this other than what I have seen on my installation. My understanding is that the skystream does not regulate its output power and so the power must either all be absorbed by the batteries OR if the batteries are fully charged then the power must be diverted into a dump load (or the turbine switched off). My Sunny Island inverter using the Smartload for this purpose controlling teh amount of load depending on power out from the turbine and the state of battery charge. If the Outback can't suppor tthis I believe you would need an intelligent load that monitors battery voltage and regulates a diversion load accordingly. I am not familiar with the "skystream charge controller".
rgds,
Scott.
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I am now trialling the use of SMA's Smartload 6000 together with the Sunny Island Inverter. The inverter controls the amount of diversion load through frequency shift. It basically works but doesn't seem to reduce the load quickly enough after peaks of power from the Skystream. Hopefully this can be tweaked to work better. Still it does handle the peaks from teh Skystream (sometimes over 4kW) without overloading the SunnyIsland 3324 which is good !
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I have recently had feedback from SMA Australia that they have an issue with a software setting in the Sunny Island inverter causing the above issue. I am now waiting for the fix and hopeful that this may provide the solution I have been looking for !
cheers,
Scott.
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I have an Outback grid tied battery backup system and I want to be able to charge the batteries with the turbine. It's my understanding that the turbine would be run through a 240/120v transformer and then to the AC in on the inverter and the Skystream battery charge controller turns the turbine on and off. Is this correct?
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SWWP has a published consumer guide, a short 4-page pdf document, that says for the battery charging system you need a wireless battery voltage sensor and Skystream communications kit. I wonder if some of these issues are addressed by those components. Otherwise I see no reason for having them...
Any thoughts?
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I am a renewable contractor and have installed a couple of Skystream systems on battery banks. I use Outback inverters and diversion loads, typically through multiple Xantrex C-40 charge controllers to regulate battery voltage. They seem to work well for me but during an equalization they do need to be switched off. Since they are PWM style controllers they don't let the voltage spike too bad and cycle the batteries unnecessarily.
The "battery charging kit" is a voltage controlled relay that when the voltage reaches the set voltage the turbine is disconnected from Line voltage, causing it to immediately brake itself. When the battery voltage lowers to below the setpoint the relay allows the the turbine to reconnect to Line voltage.
Then wait for the timer to run and start producing again. It works, but it is a fairly rough design. Although I do incorporate it into the system in some applications as a last resort in case some diversion loads fail or controllers fail it is not normally used in my systems.
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I maybe wrong but my understanding was that SWWP stopped selling their battery charging offering...
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That is probably true. There is a more elegant solution. I beleive that the PWM style of diversion charge controllers with a simple resistor element is the easiest choice. If you were into circuit design you could look at using Triac with a cheaper 240 vac diversion load to limit the amperage being forced through the inverter into the batteries.
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The "battery charging kit" you speak of...is this the old charge controller style box, or the wireless sensor device that they now have out?
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That was inspiring,
Keep up the good work,
Thanks for writing about it
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Update: I now have the updated SMA inverters (SI2224 x 2) with the SMA smartload (SL6000). The smartload is basically a diversion load controller with 6kW of load dump resistors using a PWM to continuously vary the load applied to keep the battery volts at the right level. The inverter charger (SI2224) tells the smartload how much load is required by varying the frequency of the AC supply. I have solar too which is also controlled via frequency change, and have things setup so that the solar contribution is derated (cut out) first, progressively from 51 to 52 Hz and then the smartload starts sinking power if the frequency goes up beyond 52Hz. This way I dont have the smartload having to sink power from the solar as well as the wind since the solar controller can manage that. By the way, our nominal frequency of AC supply here in Australia is 50Hz, for the US add 10Hz to all figures.
This setup is so far working really well, the batteries are now performing really well and have recovered significantly in performance from where they were for the first two years of their life ! Even in sudden wind gusts (and therefore power surges from the skystream) the battery volts are being well regulated and battery equalisation works too.
regards,
Scott.
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