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Forum Index : Windmills : LiFePO4 vs Lead Acid
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Re: battery bank build China Aviation (CALB)LFP's are a little more expensive that Winston LYP's. The larger sizes currently available in Oz winston 200ah, 260ah, 400ah (order), 700ah, 1000ah CALB 180ah, 400ah most are in the $1.35 to $1.50 per Ah range for more than ten units Ex GST 700 and 1000 ah cells would be cheaper If you already have a 48V charger and a controller that can put out 59 or more volts I would say all you need is the Battery management system and some connectors. What about 2 strings of 260's ? That's about 18 Kw @ 70% DOD 5000 cycles if you could knock 2.2kw/day average from your daily use a single string of 400's would do it. That would be my favorite option, I'm not a big fan of parallel strings if it can be avoided, purely for reliability. I'm confused, no wait... maybe I'm not... |
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norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
2 days backup, I thought our grid up north was in bad shape. Yeah I`m thinking of self contained, self installable, just like the PC UPS. Consumer item, purchase at white good store take home plug in on one appliance. Purchase a couple if need be, they`d have to have Li batteries, compact, 10 years life, auto cutout before battery drained too low, charging while on standby auto cut-in on power failure. With this Cyclone bearing down on us today, even with my off-grid system one of the above would be handy to have. I seen one such similar thing at a marine shop but 12v, was only small, fit in your glove box but had the power to start even a V8 according to the gloss on its packing box. Would have to be Li powered. Yeah agree with that about parallel strings, but I wonder because with li charging each cell is balanced independently, parallel wouldn`t be the drama it is with Pb. We come from the land downunder. Vic |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I had a couple of salvaged Toyota Prius cells as starter packs, I didnt think to plate and band them so I used to charge them in the vice with a slab of marine ply on each side. They would start anything! Progress is wonderful. 
photo from Ev power Au I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I am actually very slowly in the process of building such a system like that right now. The basic idea is to rectify the 240v ac mains supply to generate around a 340 volt dc bus. Then PWM that back into a true sine wave voltage a bit less, perhaps 230+ volts, or whatever it turns out to be at fairly high overall efficiency. The idea then is to up convert solar panel voltage to something slightly above 340 volts, say 350-360 volts dc, and feed that into the same PWM inverter. If there is sufficient solar, the diodes in the mains rectifier will never conduct, because the dc voltage at the output will be higher than the peak voltage of the mains supply. My refrigerator would then be running 100% solar, where there is sufficient sun. Any motor startup surge currents will violently pull down the dc bus volts, and the grid will supply the very high inrush for motor starting. Where solar is marginal, solar current will still feed into the inverter, and any shortfall will be made up from the grid. This will all be run off a two axis solar tracker to provide maximum possible hours of solar, and as flat a solar output curve as I can achieve. It will end up as a shoe box sized box, that plugs in between the wall outlet and my refrigerator (like a UPS) but it works the reverse way to a UPS, running of low voltage solar dc whenever available, and reverting to grid power when not available, and for any peak loads such a automatic defrost or motor starting inrush surges. The clever thing about it is, it does not simply switch over between grid/solar like a conventional UPS, but combines two current sources which will add together progressively. So as the sun sets, a gradually increasing proportion of the load transfers to the grid smoothly. And at sunrise, solar gradually takes over the load. In that way I can utilize whatever solar is available to reduce my grid power consumption, without requiring an expensive (and not cost effective at this stage) battery bank. I only have bits and pieces of it in prototype form right now, all the electronics are being designed totally from scratch, so its a long slow job to do properly. Cheers, Tony. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Why not just go to grid tie? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I doubt that a diode would be classed as isolation between the grid and a 340v DC power source.  Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Because grid tie requires either a fully approved installation, or a potentially dangerous system. A smart meter will pick up and permanently record even the smallest amount of export power, which could draw rapid attention to you if you don't have a properly installed and officially recognised grid tie system. My idea is to have something very much like a conventional UPS, and you don't need utility supply approval to plug a UPS in between the wall outlet and any appliance. That is what this is, a UPS that runs on solar, and reverts to grid power if solar input fails. As for diodes shorting, yes they can, and the whole thing will then instantly go *bang* and open a main supply fuse or circuit breaker. Its not the kind of fault that can degrade electrical safety and potentially lurk unseen ready to zap some hapless victim. It follows along with the very basic design philosophy for all safety critical systems, to which there are two very fundamental rules. 1/ ANY fault must cause the system to shut down into a safe condition. (A blown main supply fuse or tripped main breaker will do that). 2/ Any fault must reveal itself in a very obvious way, especially if the equipment keeps on functioning, before it becomes dangerous in some way to the user. (A shorted or open mains rectifier will stop the equipment and be a very obvious fault condition without being dangerous). Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have a 2.4 KW sine wave inverter that I bought on ebay from Taiwan which is designed to act as a UPS also. It has a solar charge circuit built into it as well, there is new version of it now that has MPPT. Cost is under $500 including freight, mine works well. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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electrodacus Newbie  Joined: 30/03/2014 Location: CanadaPosts: 39 |
Sorry I was not participating in the last few days. I'm working non stop to promote my Solar BMS on Kickstarter. The are just a few days left and it did not meat the goal. Solar is extremely inexpensive but battery is still a bit far from grid parity even the best LiFePO4 will not be competitive maybe close in some countries depending on the price/kWh but not enough to make that feasible. Best way is to use solar power directly from PV panels like heating water or cooking and reduce in that way the grid power usage. http://electrodacus.com/ https://www.youtube.com/user/electrodacus |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
This is getting closer. But it probably still uses grid power in preference to battery when grid power is connected to it, and uses solar just to recharge the battery. What I am proposing to do is use solar 100% when available. On an overcast day, still use all the solar that is available plus a bit of supplementary grid power only to make up any shortfall. Something like maybe 70% solar 30% grid power for example. This should all be able to work without having any battery which is a bit radical, but not requiring a battery is a huge cost saving. And not feeding any power back into the grid under any circumstances which makes it completely invisible to a smart meter. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You described what you want as a UPS, never seen one without a battery. The inverter I have has several different modes, grid priority, solar priority and another where it will use solar and battery until the batteries draw down to a set voltage. I have bought a heap of used golf cart batteries that still have plenty of life in them for scrap price. But if don't want batteries you may as well go grid tie, unless you are renting it is a easy option. Solar companies are fighting for business around here in QLD. Anyhow this is hijacking a battery thread, why not start your own thread? There are only 10 types of people in the world: those who understand binary, and those who don't. |
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KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
missed a few key features here 18650 cells are 2-2.9Ah you need a SHED LOAD of them for a reasonable capacity. All Lifepo4 / other lithium batts achieve good numbers on their own but even with BMS dont achieve same numbers when in series / parallel with other cells. CALB / Thundersky most other large format inexpensive lithium batts have small footprint in aus as they are not imported by big wholesalers as they are yet to see the required quality and consistency to be able to warrant them in the market. 3000Cycles to 80% dod is realistically as good as it gets for Lithium at reasonable $$ AND Lead such as BAE offer less upfront cost and same 3000 cycles to 80%DOD hence Lithium for stationary applications not necessarily there yet. Needs to happen -manufacturers in Aus as suppliers (even if they are made in China) -better warranty -better technology to monitor SOC/ DOD -wider input voltages on equipment to accommodate as PB <10V on a 48V bank vs >16V on a 48V bank with lithium Luck favours the well prepared |
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| electrodacus Newbie Joined: 30/03/2014 Location: CanadaPosts: 39 |
Actually for LiFePO4 18650 has a smaller capacity of 1Ah to 1.5Ah but for LiCoO2 you are right around 2 to 2.9Ah. In series with a BMS they will get really good numbers in therms of battery life cycle. Can you let me know what Lead Acid can do 3000cycles at 80% DOD? Maybe some of the best can do 3000cycles at 20% DOD (80% SOC) That is quite a difference. Not to mention a Lead Acid battery charged in the top 20% has an efficiency of around 50% do to equalization and absorption stage. The way you monitor SOC for LiFePO4 is more complicated since you need a Ah counter can not say the aprox SOC based on battery voltage. So you are right is a bit more complicated. As for wide input voltage that is not the case with LiFePO4 3V to 3.6V/ cell. 16 x 3.6 = 57.6V high and 16 x 3V = 48V so also 10V max but most of the time is at around 16x 3.2V = 51.2V As for LiCoO2 (I will not recommend necessarily) 14 x 4V = 56V and low 14 x 3.4V = 47.6V so again less than 10V. There is also not less upfront cost with Lead since you need a way larger capacity with Lead batteries so the upfront cost will be the same or probably better for LiFePO4. For long therm LiFePO4 is a few times better. LiFePO4 is quite different form LiCoO2 that you know from phones and Laptops it contains a lot of Iron by weight and way less lithium than LiCoPO4 for the same battery capacity. Also it is much safer to use and lasts for 2000 - 7000 80% DOD cycles vs 300 to 800 for LiCoO2. http://electrodacus.com/ https://www.youtube.com/user/electrodacus |
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marcwolf Senior Member  Joined: 08/06/2009 Location: AustraliaPosts: 119 |
A little off topic here but. One thing I have always puzzled about is this. If an on Grid system needs a 240v 50Hz supply to synchronise with then why should not a small UPS work at triggering it. i.e. a 12v DC to 240v AC invertor at approx. 50w is pretty cheap. Take your system off grid and then apply the output of the small invertor to the Solar one. After 90 sec the Solar one should start and output 240v. Just a though Dave Coding Coding Coding.. Keep those keyboards coding.. RAW CODE!!!!! |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Dave, Your theory is correct and it can work, its known as a "Micro grid" but there is issues with this system. Example...... what happens at startup if the demand is greater than the cheap 12v inverter can supply (overload), what happens if cloud cover stops the PV system supplying enough power to match demand (overload), what happens if PV supply is greater than demand, it can back feed through the 12v inverter H-bridge and fry the 12v battery as there is no charge control, thats just to name a few problems, there is more. Some systems are designed around this method and use AC coupling of inverters, but they are designed to prevent the above problems etc. Pete. Sometimes it just works |
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| marcwolf Senior Member Joined: 08/06/2009 Location: AustraliaPosts: 119 |
HI Pete and thanks for answering that. It's something that has always made me wonder.. You know - end of civilisation and all I got is my Grid Connect solar system. yes - I can guess there be problems but with use of such things like fuses, circuit breakers, and isolation switches (PV system from house circuit) some of these can be fixed. But it was mainly my curiosity re how one could fool a Grid Connect system into thinking there was a grid there. Not that I would try this in practice - barring end of civilisation issues. And on that note - I have an excellent small library of Log books, slide rules, and how to make a workshop with no motive power available. Many thanks Dave Coding Coding Coding.. Keep those keyboards coding.. RAW CODE!!!!! |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Dave, A bit of smart electronic design and a picaxe that you are very adapt with could solve most of the problems i listed, its just needs a little intervention with a smart mind level to bring the package together, and not a plug and play solution to a general thought of connecting A to B and C to D ect. Pete. Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Solar is the primary power source. Backup is grid power. Yes you can build a UPS without a battery. I just requires a bit of lateral thinking. Cheers, Tony. |
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