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Forum Index : Solar : AGM batteries series parallel thoughts.
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| bob.steel Senior Member  Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Dunno about brains just working on practical experience . You only need a quarter of lead acids capacity if you use LFP , LiFePo4. Your system if I get it right is 48 volts .220 Ah so only a small useage if going down to say 70% DOD. If that's right , LFP would only need to be 50-60 Ah so 4 off 12 volt batteries would cost you about $500.Delivered.(worth a try is'nt it?) You could afford to double that I would say and use a bit more power and get well in excess of 10-15 years(some I know of are 8 years in use and still at 90% capacity when charged and tested) And keep in mind that's when they get down to 80% capacity so they still have a long way to go . As a side note the very expensive LTO cells have a charge/discharge cycles claimed of 40,000 cycles and charge and discharge at 33 times faster than LFP Once a day cycle is 110 years! You would need 24 cells to get to 48 volts system at a cost of probably $100 per 55 Ah cell and have delivery on top . Only feasible in USA atm $2400 + delivery They use them in the big thumping car Audio systems Edited 2022-02-13 09:40 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
God help us with that mind set already Edited 2022-02-13 09:52 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Generally fellas there is a lot of misinformation and bias in this thread . I'm not going to keep going through this rubbish arguing the toss . What I suggest you do is get hold of say a 50 Ah 12 volt LFP battery from ebay. Digi Marker I know and trust. about $190 AUD I think You can afford to try that. It has cylindrical cells of their own make in it ,I've looked . So its discharge rate is constant 30 amps so its a bit limited . I use one to power my rideon . The BMS didn't like the larger current out (Its less as the volts don't sag) so I opened it up with a butter knife and shorted across the BMS so it could output the power I needed . Its lifetime will be less but what the heck I like to experiment . Now when it comes to charging, the internal mower charger works fine and if needed I can put a modern battery charger on it . Check the battery charger is putting out 14 volts . 14.6 is maximum charging voltage. I use one in my 5K generator too to start it and you can run your shed radio or security lights on it too. Wherever you have used that sh*tty little lead acid you can use it directly to replace it . Even in a small gas car. I run a 4 cylinder Pajero with a 135 Ah LFP without any modifications whatever .A 200Ah model handles my 6.354 6 cylinder diesel starting. A 100 Ah starts my 4 cylinder Fiat tractor. So give them a try  |
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
My own personal experience has been pretty much the same as Clockman. Lithium works great until it stops working. And one tiny little accident with Lithium and you have a very expensive dead battery on your hands. Bob has absolute faith in new technology, and good for him. Old age and experience makes me a bit cynical about claims for new products. Lithium manufacturers warn us : Do not overcharge your Lithium cell even once or it will be permanently destroyed. Do not over discharge your Lithium cell even once or it will be damaged. Do not charge your Lithium cell below freezing or it will be damaged. Your Lithium cell may suffer from dendrite formation which will dead short the cell. Even if you have a very expensive battery management system, things only need to go a little bit wrong once, and it could be a very expensive lesson. Lead is multiples cheaper in dollars per stored watt. Get a vastly larger lead battery for the same dollars as lithium. It will hardly ever see deep discharge and will live a very easy life. Its going to be bloody enormous, but for off grid that hardly matters. Lead will require a lot of frequent care and maintenance, but so will lithium if you are going to avoid a very destructive accident. Cheers, Tony. |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
One point no one has made about those pre-packaged 6\12V Lifepo4 packs with BMS fitted is that you can only have 2 in series at best; the electronics in the inbuilt BMS are not designed for multiple series battery connections or placing them in parallel. They seem cheap and are flooding onto the market here in NZ, personally I would not use them as off grid storage where multiple batteries are in series or placed in parallel, you have absolutely no control over the quality of the internal cells, probable one way of the vendors getting rid of "B" grade or worse product to an unsuspecting public. Quality new 3.3V cells are available direct from the main factories in China (like CALB), the EV car club guys here in NZ purchase them in quantity from time to time, getting them that way is not much more than retail Lead Acid prices here in NZ. For our off grid plant nursery I specified sealed Lead Carbon 6v 300AH batteries as they have a life of 20 years and are less susceptible to sulphation. Each 48V 300AH 480Kg bank works out to approx $5200. Second hand reconditioned forklift packs are not available here in NZ; I recently costed a new 48V forklift pack - quality made in Europe - 525AH at 5hr spec or 630AH (20 hr) costs $7130, but then have the hassle of watering, extra ventilation (inside container) ie more maintenance. We don't have the scale here in NZ, so things like batteries are very expensive and are always going up in price, in my life time I doubt I will ever see them dropping. Cheers Mike |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1021 |
That is Exactly right, I have been aware of this for some time and have seen a few failures when this has been done, I haven't seen anyone ask about using these 12V lithium bricks here, The It has been suggested on other sights to just throw out the existing BMS units, wire the cells into the required series or parallel setup and get a single BMS to take care of the whole lot, no more BMS fighting. Quality is another issue. Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If one of those smart fully sealed 12v Lithium bricks does spit the dummy with a dead cell, you have to replace all four cells. If you buy individual cells, at least you get to replace only what is actually dead. Cheers, Tony. |
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| Old Seagull Man Regular Member  Joined: 21/12/2019 Location: AustraliaPosts: 55 |
There are a few 12v Brick type battery's out there that can be configured for 48v. Some allow 4x4. IE 4 in series and 4 in parallel. 16 battery's in the set,But they are few and far between. The idea of breaking up the battery's and adding your own BMS is good at the moment, as the price of "bricks" is far cheaper than the cost of the cells they contain. But this is only valid for prismatic type cells. I would have to go down that road as i need a 60v battery for my application. No Brick type, can handle 60 volts. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1021 |
They say they can, I have read that before. (I should have mentioned this as well) There are flatpacks and others that can be used in parallel, with the condition that the BMS in each is is attached to a com cable as slave's 1 or more, then another unit as a master. Do any of these bricks sold, connect with a com cable? That might be 17s or 18s, for 60v, better off finding single cells, what sort of project? Edited 2022-02-13 19:07 by Revlac Cheers Aaron Off The Grid |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Quite! And it's all coming from one person with an obsessive compulsive disorder. Thank Christ for that! Will you solemnly swear to that please? There are some very experienced, knowledgeable and smart men here you are questioning, insulting and Inferring you know more than all of them put together. That reflects far more on your ( lack) of Credibility than theirs. You are not going to change anyone's mind here so for whatever reason you have to keep pushing this barrow, please push it somewhere else because people here can make up their own minds and your ranting isn't converting anyone to your unhinged obsession. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
+1 Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
The idea of batteries, specifically the Lithium variety's falling is a common claim. I also see no basis for it. The demand for these batteries is Huge. Companies literally can't get enough and the market and applications for them are massive and every growing. There are a whole range of issues relating to their pricing way beyond economy of volume manufacture which has already been hit. There are a LOT of fixed costs in getting any product to market that will not change, Transport, warehousing, distribution, retail markup just to name some very basic ones. Supply of materials is going to be a key factor and due to the limitations in processing more than anything else, I see no basis why this would drop enough to cause a price decrease over all the other elements that would push prices upwards. No product ever goes down in price when demand is huge and supply barely keeps up or does not. Price decreases are usually triggered by market saturation and I also don't see this happening in the foreseeable future. The only way it might is if a whole other technology comes along and that would have to have significant improvements or manufacturing cost reductions and even that is Highly unlikley. Most people seem to think everything is based on the COGS ( cost Of Good Sold) pricing model but in fact these day that is very much the secondary business model. An I phone for instance is cheap as hell to make but sells at a premium price. That's because they are based on the " What the market will stand" pricing model and they know very well what that is and extract every cent from it. Any new battery tech would be the same for at least 10 years and then the lithium may never get cheaper as less people produce it. Nothing to do with batteries, it's just the way things are for any commodity. It's hard, impossible really, to see this demand falling off in the forseeable future and causing a price drop. If the uptake of EV's alone is even a quarter of what is predicted, that will keep prices high for the next 20 years alone. I would hate to own a power lead factory right now because they are becoming a thing of the past as more and more things become portable and the increase in consumerism for short lived products with these batteries is ever growing as well. Maybe the amount of reject B quality cells will increase and become cheaper but then again it is logical to predict that manufacturing will improve and there will be less wastage and better refinement of what is produced so they will become scarce and become closer priced to the A grade cells. Lead acid has been produced by the tens if not hundreds of millions for a long time but they seem to be forever rising in price as well rather than an on an endless slide to get cheaper. I predict with the rush which seems global to get off grid and out of the cities, the demand for batteries across the board in all applications is only going to rise and significantly. |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
No its often exactly wrong. The examples I have shown you can be 4 in series and 4 in parallel if you wish so thats just a bit more wrong dis-information . Logically there is no difference in putting 6 lead acid batteries in parallel except if or when one goes wrong it will likely put a heavy drain on its peers and do damage to them too if you are not around . Electrically there is no difference with LiFePo4 and their BMS's except if one cell dies that battery turns off and protects the other ,say 3 cells inside . With lead acid in old days the cells were joined outside on the top with lead bridges . We did not have BMS's then but if we did they could have been used the same way. Sadly they hid the decreasing size of joiners inside the plastic. I used to break them apart to get acid and lead in bulk volumes and I saw the physical reductions in lead used in Taiwanese batteries for years. Electrically speaking though , and we have some experts here , why do you think they cannot be paralleled ? or seriesed? Id like to know apart from what manufacturers might say (read SELLERS might say). Edited 2022-02-14 15:56 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Edited 2022-02-14 16:24 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
UMM,Ummm, NO! thats totally wrong again . The top is sealed with rtv silicon . Working carefully with a butter knife and a chisel you can lever the top off gently and get at it all . When finished stick it down the same way. Now its very interesting you say this because EVERY set of cells I have bought , I have bought at least on extra to pull apart for my facebook page members to see. So they don't have to do it and they know whats in them . As with all batteries with cells in them, each cell can be separated out and charged or discharged individually as you wish . The BMS is always on the negative line and can be disconnected and replaced if you want to . One problem has developed with some dropins, generally the foil pouch cell types . One cell can get to top voltage first and cut the entire battery. Then it can't be discharged because its not connected . It can't be charged because its disconnected ,so you sit there for as long as it takes with no power until the self discharge brings that cell back into spec. Voltage drop is very fast up at the top charge knee so its usually pretty quick . Its easy to overcome by putting in a direct negative connection point between the terminals. Facebook Page It means however getting into it as explained to drain some power off it with a bulb or resistor pack. Here's one I did earlier . "PRO POWER" terrible reseller . bad construction . Fixed and still running my shed radio. https://www.facebook.com/photo/?fbid=2428382970766074&set=g.271980786862023</a> Edited 2022-02-14 16:51 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Interesting problem hey. 5 off 12v nominal = 60 v , but top voltage is 5 x 14.6v = 73 volts . Too much no doubt but the ideal charge on LFP is 3.4v tops so 5 x 3.4v x4 = 68 volts ...No good? If not is there a way to buck the DC voltage . There is a buck converter I use for 30 amps or so but it costs $30 and is probably way too small. So depends on how much current you use? 90 amps you might parallel 3 of them. I just received 16 cells of 310 Ah at a delivered cost of $2300. 18 of these cells would give you a nice 18 x 3.4v =61.2v tops So 310 Ah @ 60 volts would cost you say $2300 + $288 = $2588. ? Edited 2022-02-14 17:09 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
Edit got me again . Here is the Pro Power I first opened up. I had the zero voltage cel out for the dendrite treatment. Can't work out what the admin is doing with these pictures . Ive never seen so many ridiculous restrictions Admin . Its time you took another look at this . Everyone wants to edit there posts so they are coherent and errors are removed . You don't allow it? This silly little picture that comes up here ,you cant see a thing . Pointless posting it!  Edited 2022-02-14 17:22 by bob.steel |
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| bob.steel Senior Member Joined: 27/02/2020 Location: AustraliaPosts: 188 |
200Ah droppins https://www.ebay.com.au/itm/384683511144 https://www.aliexpress.com/item/1005003494764090.html?spm=a2g0o.productlist.0.0.40fc22dcjqWAU5&ad_pvid=202202132341223034015037376440023022766_4&s=p Mine I watch for selling deals . It can make a big diff as you see above . PWOD is a store I have used successfully but its a 3 month wait. They send by sea. 310 cells at Ali Edited 2022-02-14 17:52 by bob.steel |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512 |
please listen to this old mate, the other people that have years of PRACTICAL experience are wrong... this blokes on facebook so must be ligit.. bob, if you want to use / promote lithium, best practice is not insult well respected members of a forum with information that contradicts even manufacturer claims, insulting people's intelligence in the process.. lithium has its place, and many on here have used / use and thoughly tested them, many have even documented how they had preformed.. dare I say most have moved BACK to fla for ease and life expectancy as, has been stated several times , is a much more forgiving chemical and when its your ONLY source of power that is far more important when something goes wrong (and it WILL)... however if you / anyone wishes to use lithium for a stationary off grid system, go hard , in fact I'm pretty sure I speak for most when I say document it and post it up... but, as I say again, the people you keep saying are wrong have built up a reputation on here for being both honest and experienced with what this forum stands for solar/electronics etc.. oh and a side note, to think that china will only sell you stuff ( be it anything) because its the " only way to sell it legally " is a incredibly naive statement, again practical experience will tell you, many would sell your grandmother if it made them a buck, just like ANY country.. heck, how would a lowly AFP official / china customs official know that these cells were legally aquired in the manna you described ?? how many low grade cells fall off the proverbial " back of the truck " and end up here .. there are literally hundreds of threads in various forums testing various brands of batteries because soooo many dodgy ones end up everywhere.. I think it works !! |
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