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Forum Index : Electronics : SImplest way to use a GTI in stand-alone mode
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| Davo99 Guru  Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
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renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Dave, you live up the coast where you'll rarely get the days of gloomy weather we get in Melbourne. Down here you need to cover a few days load preferably. Having power up your sleeve is very handy indeed. Yes fill the roof with as many panels as you can to charge them in winter too, totally agree with over doing the panels. Having too many panels doesn't make anything go bang, the power simply doesn't get used, so there really is no such thing as too many panels. In the last year I've added more and more, somewhere around 11 or 12 kw now, but not much room left, maybe another 2kw could fit. But if Roger can get batts for scrap metal price that are still decent he'd be bonkers not going big, hell at that price I'd buy 2 800ah units. Self discharge rate isn't anything to worry about. My batt pretty rarely goes below 51v, in normal weather conditions so it does get a very easy time, and it will last very well being looked after like that. Mid winter it sometimes goes below 50v but maybe only once or twice since more panels went up. I started with 5kw, that's more than enough when the sun is shining, but when the clouds hit.........nup, no way near enough, hence it got added to over time. Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That is not how the "C" ratings work. Batteries vary hugely in usage, and the default rating is so many amp hours over a ten hour discharge period. So a 100Ah rated battery would be tested and specified to provide 10 amps for 10 hours, and that would be a C0.1 rate of discharge. That would be a good capacity guide for a fork lift battery that is required to work over an eight hour working shift, or a solar battery that provides power at night. If you ran that 100 Ah battery at only one amp discharge C0.01 it will last a lot longer than 100 hours, maybe 130 hours. Going the other way, at C1 or a one hour discharge you are not going to be able to get that expected 100 amps for an hour. Maybe only 60 amps for one hour tops. Now for some things a ten hour discharge rate is just silly. A watch battery might be expected to last one year plus. For heavy duty batteries C1 or a one hour rated discharge might be about right for a heavy duty lantern battery, for example. C2 would be a half hour rated discharge maybe for a phone or lap top battery. A real extra extra heavy duty application like C20 suggests the battery is rated for only a three minute full discharge! Difficult to imagine what that might be for. A drone ? Some kind of weapon ? But if it was rated by the manufacturer as 10 amp hours at C20, it should be able to produce 200 amps for three minutes. Here is the blurb on a 400Ah Winston. https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP400AHA-LiFeYPO4-3-2V-400Ah.html It is designed and specified to produce 40 amps for ten hours at C0.1 which is the standard way of rating, unless it says otherwise somewhere. It also says maximum continuous rate of discharge C3, which is 1,200 amps. But its sure not going to last for 20 minutes at that high a discharge rate. What they call "continuous" might be only a very few minutes before the thing falls flat on its face. Edited 2019-10-26 06:39 by Warpspeed Cheers, Tony. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
OK, I always understood it like here Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Mark, they have it completely arse backwards. Possibly the best resource for any battery information on the internet is "Battery University". https://batteryuniversity.com/learn/ The topic of what is the "C" rate, is here: https://batteryuniversity.com/index.php/learn/article/what_is_the_c_rate Edited 2019-10-26 08:27 by Warpspeed Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I don't and haven't had batteries but in my head I'm not convinced of having batteries to last days. Completely agree with having all the panels you can. For most people, panels are cheaper than batteries so covering a few days I believe will always be cheaper with a big array than a big battery. If you can't fit enough panels, then go to the generator you are going to need to have anyway. And that's where I am coming from. I don't know your useage but even on crappy days with that many panels you are still going to get decent input. Depends on your draw of course but that will at least extend your run time. Even if you give the batteries a partial top up with a generator, still in my head better than having a big pack sitting discharged for days. Yep, totally agree. If nothing else he would get better life out of the batteries by maybe only hitting them 10-20% instead of 50 or more. The difference between sun and cloud is huge. Not practical to cover it all adding more panels, If you have a week of rain your battery's will need to also be impractically large to cover that so back to the generator. I like the generator option before the Bigger battery pack alternative. Healthy generator output allows one the option of running big loads for long periods and not discharging the batteries to any significant degree no matter what the weather. One has to look at their own individual need however and work out the cheapest and best solution for their circumstances. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Dave ^^^ is spot on !! Mark, The class of batteries we are mostly interested in here, are usually fairly large and are rated for a ten hour discharge rate, as the industry standard. (C=0.1) Smaller batteries used in portable equipment, toys, hand held electronics, power tools and so on, are more commonly rated for a one hour discharge. (C=1) Edited 2019-10-26 08:46 by Warpspeed Cheers, Tony. |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
I didn't put that well. At the same time as you rely on the battery in cloudy weather it's still getting some charge topping it up, day two it may be down to 90% day three maybe 80% then you get a better day and get a full charge, or maybe up to 90%, then the next day it gets to 100% What I have found with melbourne cloud it's often light density, not like the heavy dark thunderstorm clouds Queenslanders get. We do get nasty ones too but not that often. So our crappy cloudy days can still produce 5-7kw hrs.(on my setup) That won't fully charge it but it cetainly helps. We normally use 10kwhr a day if using the elec oven, so when a crap spell comes on we cook on the stove top more. So what works in Melb may be useless in Brisbane. It's quite cloudy her today but the battery went to absorb at 9.30am or so. Edited 2019-10-26 09:12 by renewableMark Cheers Caveman Mark Off grid eastern Melb |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Cloud is another weird arse aspect of solar. Like so many times before, it was quite hazy here on Thursday and I was making great power. I was outside and noticed the dimmer light and thought to myself, I'll bet the inverters are going Nuts. Sure enough, with noticeably dimmer than normal light, my 5 Kw inverter was reading 5140w. The other inverter which has been reading 2470W quite consistently since I moved a couple of arrays off it was reading a significant 2790W. I get more power out of those hazy days and when the sun breaks through decent cloud than in bright, cloudless sunshine. I can see why they call it cloud edge effect. Yesterday the cloudy was reasonably thick and even from about 2 PM. I did drop about 10 KWh on what I have been averaging generation wise but I thought that was surprising. I'm doing about 10 Kw at that time of day and still doing around 5.5-6Kw at 5Pm so to only drop 10 kwh was a lot better than I expected. I Confused/ educated the Mrs again this morning. She was saying how windy it was outside and what a bugger to hang the washing out. I said put it in the dryer. I got the look and reminded her, spring to Winter is fine, winter hang it out. She said we have plenty of power? I said only too much. Probably shut down the inverters on one phase today so I don't get too far ahead. Meter read is in 2 weeks and wouldn't be good to have used 200Kwh less than we had logged 6 months ago. :0) Other phase still has a little to catch up on the 1600KWh it was behind when the last read was due. Should be caught up tomorrow I think. Pushing up to 11Kw into it atm. |
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| johnmc Senior Member  Joined: 21/01/2011 Location: AustraliaPosts: 282 |
Good Day all, I have always used the discharge rate that Mark refers too, for the last 50 years. Tonys method is the reciprocal to the above method. Take your pick, the battery capacity is always governed by the time rate of discharge. cheers john. johnmc |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I am truly stunned John !!! Never seen anything like that anywhere else from when I was a first year Telecom trainee tech in the mid 1960's to when I was battery applications engineer at Saft Nife for several years. I have never seen any of the battery suppliers do it that way either until today. All the internet sources I can find, including Winston do it the way I have always believed correct. Don't want to start a bun fight, but I am REALLY curious. Even Wikipedia says that a C10 discharge rate is ten times higher than a C1 discharge rate. https://en.wikipedia.org/wiki/Battery_charger Edited 2019-10-26 13:39 by Warpspeed Cheers, Tony. |
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| johnmc Senior Member Joined: 21/01/2011 Location: AustraliaPosts: 282 |
Good Day Tony, The 48v battery pack that I bought from LION batteries ( they have a web site lion batteries ) consisted of 24, 2v cells and they classified their capacity as, C100 900 ah this relates to ah for 100 hrs ( about 9 amps) C5 657 ah and this relates to ah for 5 hrs. (about 130 amps) I had not encountered the system that you are familiar with, until reading the lithium battery specs. The Bosch automotive manual,( My background is automotive repair) refers to 10 hr ah rate for traction batteries and 20hr ah rate for other batteries . Thanks for your insight into the C rating that you are familiar with. cheers john johnmc |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have to go with John and Mark. I always understood the C xx to be the hours a battery would reach end voltage with the specified current draw. The standard as I understood it and was the rating for SLA batters I used to buy a lot of for powering equipment was always C20. Higher C rating gave you effectively more power, Lower gave you less but of course with more current. Always used to size the batteries I needed based on that with a little allowance for incomplete efficiency and never came up short. I also always understood it as on the page Mark linked. That said, having a bit of a google I see most other pages describing the way Tony says. I have seen that before only on Lithium battery's for RC Planes etc. I wonder if there are different understandings of the rating within different applications and industries such as portable applications and Storage use? |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
I think a lot of people/companies used the hour rate to determine their draw rates. Somewhere along the line someone added the C to it mistakenly thinking it meant draw?? Dunno, just a theory. I have often heard of hour rate, ie 5hr rate, 20hr rate. I am more familiar with this term. Anyway Roger, from what I can see all the fork guys use 5hr rate, so a 600ah 5hr battery will last a lot longer when using it in a solar application where the draw rate will be miles less. Cheers Caveman Mark Off grid eastern Melb |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yup that is definitely right. For as long as I can remember the industry standard for amp hour rated capacity of larger (flooded traction type) batteries has been the ten hour discharge rate. Thinking about that, it follows on from the historic development of batteries in general. The very first commercial flooded batteries were nickel iron which were eventually replaced by lead acid which had much better charging and discharging performance. That then led to nickel cadmium rechargeable batteries which reigned supreme for a short while. All this time, the drive was towards smaller higher energy density batteries capable of higher peak discharge currents. None of the really old batteries were really capable of a one hour discharge while maintaining any kind of useful capacity, the internal resistance was just too high to do that. Today, with Lithium iron and other exotic rechargeable battery technologies, a one hour discharge for rating the capacity is trivial, and now more the general industry standard apparently. So things in the battery world have definitely changed over time. As far as the C "argument" goes, All the reputable sources I have looked up so far (battery University, Winston, and Wikipedia) say C refers to discharge rate and not discharge time. If the Bosch service manual says C is discharge time, that is really significant and cannot be ignored. I would like to see any links to authoritative sources people can find regarding this. Its really interesting. Maybe there really is a parallel universe  .Edited 2019-10-27 07:25 by Warpspeed Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yeah, that was the impression I got from my fork lift mate ... and I don't know enough about this subject to add anything meaningful ... so I'm just observing at the moment. I recognised that 48V @ 500Ah is still pretty substantial ... and seeing the size of the batteries and what they can do installed in a fork lift gives me confidence that experimenting with one will still be worthwhile. I really only want a battery because it seems to be the only way to get an inverter to run off cheap banks of second hand panels ... so at the price (~ $600) I'm more than happy to give it a go. If I can get a few hours of use at night before it kicks back to the mains ... I will still be more than happy as I can get all our major loads taken care of during the day. Just to change the subject ... I've dismantled the first of the Aero Sharp 3kW inverters ... seems such a shame to pull something like that completely to bits ... makes me wonder why it was canned in the first place. Beautifully made and put together ... probably could have been fixed and kept working. How do you get the heatsink off the back ... seems to be stuck extremely well. Is there a trick to it? I had a real job getting the transformer core/glue/glug off the mounting bolt as well. For some reason, when I lifted out the torroid ... the centre mass came out of the torroid and stayed stuck to the back and the bolt. 30 mins with a hammer and chisel fixed it ... but that seemed a bit extreme.  Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I was also going to mention that I came across this article https://www.rjbatt.com.au/tips-on-properly-comparing-flooded-lead-acid-batteries/ It mentions Depth of Discharge rates, Amphour ratings ... but also "Run time Ratings" ... where they give how many minutes a battery will give 25, 50 or 75 amps for example. That seems like a reasonably easy way to compare batteries ... but still all new to me. Cheers, Roger |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Make sure you take off every screw. Get a screwdriver in the edge and start to pry it off. When you get the edge started I get a small tyre lever and gently twist it. You must be very careful to just work on the edge of it, as the mosfets will mount to that and you don't want to scratch up the surface. You can bang in a plastic scraper to help while prying up the edge. When you get it off, spray the thing with windex to make it slippery, and use a stanley blade to clean off all the crap. Cheers Caveman Mark Off grid eastern Melb |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
You were lucky , I had to drill my plug out with a masonary drill and very carefully prize/hammer pieces of the epoxy plug out til it became loose enough to get bigger chunks out .. took an hour. The heatsink , I haven't touched that yet ,I guess it would be some form of silicon adhesive/heat transfer putty. They are nice made stainless steel cases and will make a very presentable enclosure .. I think Oztules joined two together ,? Fork lift batteries-- I've a 48 volt system ,read a lot about fork lift batteries, I'm on the Gold Coast , any ideas where I should start looking -yesterdays search on e-bay came up with just one, I think around $9000. A bit steep ,I thought. and what other clues should I be aware of -like size?, age?,suppose transport is important, and should I look for an assembly that is in a fabricated cage,Etc?. Also, that "inverter junk yard" place in Adelaide -do you think maybe he would have "powerstar W7 " inverter parts ,they were the old inverters that we did the original toroidal modifications on-I'm after the cards from a 48 volt version,6Kw. Thanks, Bruce Bushboy |
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| renewableMark Guru Joined: 09/12/2017 Location: AustraliaPosts: 1678 |
Easiest way to get the torroid out is lay it on the ground with the open side facing down, lift up the heavy end 45 deg and drop it, the torroid will pop out in one or two goes. Do it on carpet or lay down some matt etc. Should take ten seconds at most. The epoxy lump can be twisted off, just get it started with a plumbers wrench. Hang onto the bits inside for now, some you'll re use. Edited 2019-10-27 16:54 by renewableMark Cheers Caveman Mark Off grid eastern Melb |
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