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Forum Index : Solar : AGM batteries series parallel thoughts.
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi My off grid setup uses some over stressed flooded lead acids. There are 8 6v 220Ah batteries in series. They are starting to die, mostly my fault, I left the caps off after topping up the water once, for about 6 weeks, and its dusty here. Looking into options. I can get some LiFePO4 280Ah cells for like $3500 plus delivery, but still need to add a BMS, take the risk of buying out of China, and wait 3 months for them to show up. There's no redundancy in this, if one cell goes bad, I'm in trouble. Or I can go AGM. The Giant 140Ah 12v batteries are about $290 each, and the supplier is 3 hours drive from my place. I've had a pair of these same batteries in the past, they lasted over a decade. I was thinking of 12 batteries ( $3480 ), in series parallel giving a 48v 420Ah battery bank. I'm reading they can be discharged more than a flooded battery, like to 50%, and still give over 3000 cycles ( 8 years ). This would more than double my existing capacity, plus I have redundancy. I can loose a battery and still have two strings to keep me going while the battery is replaced. What are the brain trusts thoughts? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Clockmanfr Guru  Joined: 23/10/2015 Location: FrancePosts: 429 |
Hi Gizmo, I started with AGM.s i mean real AGM's and good manufcatures from the US and Spain, as there are some that say they are but just have wet acid inside. Where true AGM's are just damp plate separators. With true AGM's i was constantly moving them around and matching actual ah ratings as they got old. I had 1200ah at 48v and after 8 years the messing about with them was getting tiring. Eventually all died as they would lose a cell, turned out that the clearance between the cell plates and the main internal bus bars was only 10 mm to 12mm, so when the cell swelled up it shorted it self out. I just found that AGMS, hard work. Below is info gathered around the World on Off Grid batteries, that have actuall modern tech batteries. ......... 1) Lead acid batteries are forgiving, and generally "die" gracefully. Unless you accidentally run them dead one time, then they lose capacity and start dying pretty quick. 2) Li batteries are unforgiving. 1 overcharge or 1 deep discharge, and they are toast. Might get a few more cycles out of them before they die, but either condition damages the battery. Same as lead acid. Many expensive L16s have been run dead by accident. Their 15 year expectancy dropped to 1 or 2 years. That's why I stuck with the 6 volt golf cart batteries. Just in case I screwed up. Been known to happen. 3) LFP / LiFePo / LP4 are the "safer" batteries that tend to just fail, or swell up and stink. Swell up and fail is a 'true' statement. Most LiFePO4s are made in China. They do not advertise that the battery needs to be caged and compressed. But, when push come to shove, they will admit this. All of their test data on prismatic cells are in a test cage with 12 psi applied the sides of the cell. Without a cage and compression, the cell will swell. The swelling causes internal cell damage and drastically shortens cell life. The cage and compression is a 'pain in the neck'. Once you assemble a bank, you don't move them easily. 4) Some Mfg's include the top and bottom 10% safety margins internal their BMS systems. Some don't and you have to program that into your loads and chargers. Your Mileage May Vary. Some rate the full capacity, but only deliver 70% of capacity. Lead acid batteries like 50% -100%, so same protocols will NOT work for each. LiFePO4 batteries operate from 2.5 volts to 3.65 volts. Lead acid battery protocols will not work for LIFePO4 batteries. Totally different chemistry. Totally different characteristics. These cells have proven to deliver 100%+ of their rated capacity between these two voltages. My research and experience shows that they have a very flat charge/discharge curve at 3.2 volts over most of there capacity. When you approach the end of discharge, the voltage drops off quickly from 3.2 volts to 2.5 volts. The same on the charge side. The voltage slowly rises from 3.2 volts to 3.4 volts. Then the last 5% of the charge cycle, the voltage rapidly rises to 3.65 volts. If you limit the operating voltage zone of the battery from 3.0 volts to 3.4 volts, you will get 90% of the rated capacity every cycle AND you will avoid the over charging and over discharging associated with early cell death. These are programmed into the LiFePO4 chargers and BMS. The BMS is the safety device to protect the battery and ensure long life. I also program these charge parameters into my solar charger and inverter. I am still fairly new to LiFePO4 batteries (15 months). I have done a lot of research. So far they are performing well. I will keep you posted as time goes by. I am not afraid to admit I was wrong, if and when they fail. Keeping my fingers crossed. Hopes this helps to understand the LiFePO4 prismatic batteries better. Just a note. The cage and compression does not apply to the round cylinder cells. Only the rectangular prismatic cells. I trust this helps. PS A friend wanted ROLLS lead acid for his installation, 6v 4000 series, However ROLLS in Canada reckons it is having real trouble getting materials it needs, and at present there is a 6 month backlog. I got him sorted with a supplier in Spain that actually has what he wants. I am sorry but my R&D on the PLANTE batteries 550ah 2v cells is still ongoing, and i don't think my latest book on making your own batteries will be ready until late next summer. Everything is possible, just give me time. 3 HughP's 3.7m Wind T's (14 years). 5kW PV on 3 Trackers, (10 yrs). 21kW PV AC coupled SH GTI's. OzInverter created Grid. 1300ah 48v. |
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Technophiliac Regular Member  Joined: 18/12/2020 Location: New ZealandPosts: 92 |
Hi There has also been good promotion of forklift batteries in the forum if you have the room and ability to move said boxes, also Lead Carbon batteries may be worth a look as well. Davo, Wellington. You can have it perfect, on time, and at the best price. Choose any two. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
For that sort of money You should be able to get a forklift pack of around 620 Ah. They are warranted to a DOD of 80%. You should have no trouble with the guaranteed used packs getting 10 years out of them especially with the bigger capacity and what would amount to overall lower DOD anyway. To me the Chyneese lipos are far too bi a risk in too many avenues. Getting them from Chynaah with no real warranty or comeback, no replacement cells and the bottom line is, they can say you did something wrong, prove otherwise and you have no consumer protections either. For me, might be worth the risk with a $300 luxury product I don't need to rely on, for a $3500 product I do.... Not that brave. When Tony here sets up a system as he did and has a 10% failure rate with lipos in 3 years, I know my chances of success are in the single digits so another reason to pass. One small safety net I see with the LA is their scrap price. Even if they do fall over prematurely, from enquiries I have made myself with scrap dealers, they are still worth 25-33% the average purchase price. At this stage I think there are still limited people that will even accept EOL lithiums and who knows in the future if they will even charge to take them off ones hands? |
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| Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429 |
Gizmo, Here below is a copy of what is happening right now in Canada and across the World regards Lead Acid. I asked on a USA Forum what was happening in Canada with ROLLS lead acid batteries, Yes they actually make them there. I have a friend here who wants some good quality lead acid, he wanted the ROLLS 4000 series for his house Off Grid installation. A few years ago he bought Chinese stuff, Batteries, Inverter, Charger, etc, all of which have now failed. His wife came to see me if i could help the family as good facts and good gear are difficult to get in FRANCE. Got him on a temporary installation now, and now the family want to do things properly. Clockman, it's the same here (in Canada). We sell Rolls batteries, and it's been a bear to get/keep supply on the shelves. Their 5000-series is not too bad, 6 - 8 weeks lead-time, but their most popular 4000-series one (S-550, or S6 L16-HC as it's called now) is about 3 - 5 months between orders and actually getting them. We stagger orders with Rolls, so we have something coming every couple months. It's been rough though. By the way, it's not just Rolls, Trojan has the same long lead-times. -'RoB'- Probably, the acid or plastic for the cases may be sitting in a cargo container off the US west coast... 100+++ ships backed up off the port of Los Angeles... 'Mary' And My reply...... Thank you 'Rob' and 'Mary' for the information. That confirms what we here in Europe. Managed to get my Friend sorted out with some 4000 series from Spain, although one up in ah model, but he actually had some stock. According to someone in the UK, Rolls are thinking of dropping their Lead Acid range and start manufacturing LIFEPO types, as it seems they can make 3 times the profit margin than Lead Acid ? Also high price rises coming From Rolls because of the 4 times than normal shipping charges. ? Best get busy with making my PLANTE batteries. I was hoping the family would be here in France for Christmas holidays, with some rolls of lead sheet, but them getting here is becoming a nightmare with these new COVID restrictions and isolation restrictions. 'electrondady1' , "does this have to do with the break down of the supply chains around the world?" Starting to look like that. 'Sparweb', Cheer us up? Gizmo, Sorry for posting over there, but as you can see these are guys are actually in Canada. https://www.fieldlines.com/index.php/topic,150478.0.html So at present, get some good Lead acid as fast as you ruddy can. Best, Leslie. Edited 2021-12-10 17:35 by Clockmanfr Everything is possible, just give me time. 3 HughP's 3.7m Wind T's (14 years). 5kW PV on 3 Trackers, (10 yrs). 21kW PV AC coupled SH GTI's. OzInverter created Grid. 1300ah 48v. |
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SparWeb Senior Member  Joined: 17/04/2008 Location: CanadaPosts: 196 |
Swapping from flooded lead-acid may have some advantages, depending on what you need to do with your system, but check the charge control regulation that you have to change along with the chemistry, if you did. FLA chargers are pretty basic electronic things. They don't go through "phases" like the types designed for AGM's, which also need to have fine-tuned voltage limits. And nothing's the same when charging any kind of lithium so you'd be starting over for sure. I'm following Clockman's threads about batteries because I sill have no idea what he's doing; waiting to find out.  Steven T. Fahey |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
My charger is a PL20 modified for extra current. With the PL20 I can change all the boost/bulk/float settings, charge current limits, and it also has the temperature compensation sensor installed. I really do want to go for a maintenance free option, bit over the whole topping up of cells, making sure I have enough distilled water on hand, etc. My batteries live in a garden shed attached to the main shed. Mainly to keep the fumes away from my work area and not have to worry about corrosion of the main shed. Be nice to have the batteries inside, and use the garden shed for garden tools. Been chatting with the supplier and got a good deal on the AGM's, think I might go down that path. Be nice to have a battery bank I can just forget about. Interesting to hear about supply shortages. Been a bit of that going on lately, anything out of China. I dont expect that to get better any time soon, and in the back of my head I'm glad I'm replacing the batteries now and not mid next year, who knows what the supply chain will do as tensions rise. Yes always consider the lead value of my old cells when thinking about new batteries. This battery bank still has a little life in it, so might see if any TBS forum members want them for the lead value. Save me taking them to the recycler and someone might get a couple years out of them. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 453 |
Hi Glenn, from what i have read it is not recommended to parallel more than 4 banks of batteries. I would probably add a fuse between each bank just to cover any shorts that may occur. I have VRLA batteries in our bank. I run 24 volt 660 amp hour. The BAE solar batteries I use are doing a great job, mine are only a couple of years old and I do not drain them past 70% full charge. The specs say that the deeper they are discharged the shorter their life. Only using the top 30% of the capacity should mean that I get around 12 to 15 years out of them, which would be great. I found that the batteries struggled with heavy inductive starting loads, so I added a 500 farad capacitor bank in parallel with them. Now things like compressors just start up very fast. Actually they seem to start easier than on mains.(not that I have had mains very often). AGM batteries sound fine if you can get them at the right price. I put some in a few years back for a friend, who also has a 24 volt system. We used 200 amp hour batteries and paralleled 2 banks. Seems to run their system fine. Good luck getting the batteries and getting they system running smoothly. Pete |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Could you give some real world use insight into the maintence requirements you have had to do with your batteries? What size is the pack, do you have an auto watering system, how often you check them, how much water they go through, and what sort of time you need to put into maintaining them? Always good to learn and get first hand real world info. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1020 |
A friend of mine has a motor home with a Plasmatronics PC2410, put a new set of Amaron batteries in it 6 months ago, just found the other day that the charge controller has been dumping 34v into the 24volt battery setup everyday, I disconnected the CC, hopefully the batteries survived that, I have Had Amaron batteries for a long time now and they outlast the century batteries quiet well. For a parallel battery setup I had 4s 2p in 12v volt batteries for a 48v battery setup, the battery was only paralleled at each end, the result of doing that is it can totally thrash anyone of the batteries in series and the others will be ok, to lower the chance of this happening I was told to also parallel each 12v battery as well, helps keep the current a little more even between parallel banks, this is a well known when using eg. 4 x 12v batteries parallel, it is best to take positive and negative from opposite ends so each cell shares a little better, as for cells shorting out????they usually go open circuit. @Clockman Most do not mention strapping the plastic lithium cells together at all, not sure what there idea is, most other's are built with a metal casing and as far as I'm aware do not need any strapping around the cells, however most people put the batteries in a box that is usually a tight fit anyway. I was also told by a local battery seller (supplies 200ah LiFePO4 cells) to charge the LiFePO4 cells to no more than 3.6v instead of 3.65v. Also they say that you don't need big lithium battery capacity, "because you can use all the capacity", that don't sit well with me for an off grid situation, like FLA you need more capacity than you typically use, more headroom and also might last longer if you use less capacity out of them. Also check if you can still buy battery acid in other parts of the would, pretty sure they banned it here, this is what stopped me from making a DIY FLA battery. Edited 2021-12-13 13:27 by Revlac Cheers Aaron Off The Grid |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Davo I would check them once a month. Remove all caps, top up the water to the indicator line, recap, then hose down and remove any splash and dust. I'm guessing 2 to 3 litres of distilled water a month for 8 6v 220Ah batteries. I also have a series of 6 8v 160Ah batteries with I've run in parallel when its overcast for a few days. These I got cheap, they have a leak problem around the terminals, lots of corrosion, copper veins radiating out from the terminal and green fungus. Yeah Aaron I hear you about lithium capacity. I've been told more than once ( usually by a salesman ) that I could replace my 220Ah lead acids with a 100Ah lithium, because I can drain the lithium down to like 10%, and only 70% for the lead acids before damage. But a 100Ah lithium can only supply 90Ah, and its empty. A 220Ah lead acid can supply closer to 200Ah before its empty. Yes it's not good for it, and needs to be recharged ASAP, but its still twice the capacity of the lithium if I need it. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512 |
just a bit of personal experience info... started out with FLA ( ex forklift battery of unknown origin) and agm, 180ah batteries, died in about 3 months, replaced with same as I got a " good deal " on used telecommunications batteries.. never again, they died one by one... the forklift battery dropped 2 cells eventually and I decided to start fresh with a newer, know origin one. .ive got a single 660ah ex forklift battery and 550ah agm in parallel ( these ones are actually cycle rated from different supplier, VERY important as most are rated for " float" why original agms died probably. ) with it, which i " cracked " the seal and filled the cells until i could see fluid then replaced " valves " only reason I kept em was because they in parallel with my forklift battery , the forklift battery is from ceil power in sydney ( other states as well ) 4500 delivered to my door with a 2 year warranty... i use at least 30% out of it every night, for over 18 months now, hasn't missed a beat... in said 18 months, ive topped it up 4 times, solar is incredibly easy on them.. the PITA with topping up agms is mitigated with the forklift cells, most have a central watering system, which WILL have to be done over the life of them if you want to get a decent cycle count.. the forklift batteries are C5 rated, so as I said solar is incredibly easy on them, and if you purchase from a reputable supplier, they will give you a report on them... also, Tap water is perfectly fine for them, if you are a belt and suspenders type of person and need to get distilled water, then please do... but there is no need lithium is fantastic, no argument... but it'll be 3 times the price for the same capacity... and BMS etc... the 2 biggest " problems " with lead acid is weight and venting ... both in your situation mean diddly squat... just some personal experience, if it of any help... I think it works !! |
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InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178 |
I'm just an internet blowhard but I have experimented with storage a bit. My unscientific and recreational chemical adled opinion is that lithium batteries are cool as a general consumer goods power source. But in terms of energy storage for off grid energy needs, they are for the tinkerers. Use lithium if you want to be continuously experimenting and tweaking. But if you want a working system that will keep the wife happy with reliable power for a long time, use lead acid. Everything else is for the mad scientists who don't mind changing out their batteries every few weeks. |
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| InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178 |
I'm just an internet blowhard but I have experimented with storage a bit. My unscientific and recreational chemical adled opinion is that lithium batteries are cool as a general consumer goods power source. But in terms of energy storage for off grid energy needs, they are for the tinkerers. Use lithium if you want to be continuously experimenting and tweaking. But if you want a working system that will keep the wife happy with reliable power for a long time, use lead acid. Everything else is for the mad scientists who don't mind changing out their batteries every few weeks. |
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| InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178 |
I'm just an internet blowhard but I have experimented with storage a bit. My unscientific and recreational chemical adled opinion is that lithium batteries are cool as a general consumer goods power source. But in terms of energy storage for off grid energy needs, they are for the tinkerers. Use lithium if you want to be continuously experimenting and tweaking. But if you want a working system that will keep the wife happy with reliable power for a long time, use lead acid. Everything else is for the mad scientists who don't mind changing out their batteries every few weeks. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
My experience with Lithium is that they are expensive for the capacity, but work wonderfully well until they stop. I have had three cells suddenly without warning fail dead shorted in three years, and the cost of that makes the whole exercise uneconomic. Lithium makes more sense where you require a small light weight fully sealed battery, such as in a vehicle or a boat. But for home use, the massive size and weight of lead is of no real consequence. I will not be replacing those dead lithium cells, but will going to a fully reconditioned fork lift battery that has a five year pro-rata warranty. The smallest available cell size is 340Ah and 24 of those costs about $2.5K Many larger sizes available of course. I will be getting 48 of the small cells for my 100v system. The automatic watering feature is expensive, but probably well worth it. If the battery is protected from accidental over voltage, and under voltage, and equalized on a shedule, it should be more robust. Slow degradation over time is to be expected, but that is arguably better than very sudden unexpected failure. Cheers, Tony. |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
The Irony of reading things here and then they happen never ceases to astound me. 2.5 hour blackout this morning. Brought home the effect of having no power. Mrs Couldn't work as she has been from home but that wasn't a Big problem, she didn't want me to get a genny going for a while anyway. I wonder how many more we will get over summer? Not really wanting to jump to batteries even for backup just yet but everything I am reading everywhere I look related or not tells me putting it off may be a case of waiting too long. Supply isn't generally a problem now but time it is, might be too late. Supply chain issues and other planned " Interference" makes me think next year may make the last 2 look like a picnic. Friend in logistics told me on the weekend there is a shortage of Adblue now,the Urea solution trucks inject into their exhaust for emissions. If it runs out, the engines throttle back to half power and if you have ever driven one like that, you know how virtually non viable that makes them. I believe some only allow that for a while then will ultimately shut down all together. The other problem with this is Urea is a fertiliser so the impact on that for food production is also serious. I'm not wanting to spend money before I need to but I'm also thinking time I need to everything will be double the price or simply Unobtanium. Hadn't heard of the 360Ah batteries Tony but they sound good. I have plenty of Generation so outright capacity is something I can pull back on.... and if I do find I need to add more that's not a problem. I'll look into them and one of those MSB inverters. I think those of us whom are thinking of getting something might be better to jump sooner rather than later though interested to hear the Voices of the less paranoid... if that is what I'm being. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I think that is the whole point Dave. Many things we take totally for granted may suddenly no longer be there. The power grid goes down. The internet goes down. The ATMs stop working. Supermarkets cannot get supplies. Petrol becomes unavailable. Etc, etc.... A bit of extra cash in the cookie jar, some extra supplies of essentials, and planning alternative ways of doing things may not be totally wasted effort. Cheers, Tony. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1020 |
I agree Davo, Don't leave it too late, Have a friend that is putting up a new shed, told him to get the sparky in and put in a change over switch and generator input....your going to find it very useful, your going to need it.  He has some panels already, but no batteries or inverter yet. Cheers Aaron Off The Grid |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512 |
I'm a big fan of " I'd rather be looking at it, than for it "... having a bit in reserve is not a bad idea, nothing stupid... but also things you use and can rotate etc... I think it works !! |
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