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Forum Index : Solar : 48volt flat packs
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
One other thing I should mention. I have blocking diodes in my system. The battery charges from dawn, until fully charged, then no further charging can occur that day under any circumstances. One full charge cycle per day, no constant shuffling of power in and out of the battery. Its either charging during the morning or discharging at night. My inverter runs straight of raw solar power straight from the panels at full solar panel voltage. Nothing at all is drawn from the battery during a typical day. The battery only goes into discharge when solar falls below the battery voltage around dusk. Cheers, Tony. |
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| oreo Regular Member  Joined: 11/12/2020 Location: CanadaPosts: 49 |
FWIW, this is my first experience with LIFEPO4 cells. I find that there is tons of conflicting information on the web, and there are differences between what each manufacturer states, and differences within a particular manufacturer for newer vs older versions of the same battery. I have A123 batteries, and they have published various recommended charge strategies. A few things to note: Shorted cell = overcharging. I have not seen any reference to a shorted cell being caused by anything but overcharging. Similar to what can happen with Nickel cadmium cells, one of the anodes grows and punctures through the insulator. Have you tried whacking one of the failed cells with a large fully charged capacitor, to try to burn out the short and maybe get a the cell working again? -I have not heard of anyone doing this for LIFEP04 but it was common for NiCd cells, so it would be a neat experiment :). For A123 cells, 3.45v is perfectly safe for charging (3.6v is normal so 3.45v will give extended life). This battery should reach full charge by 3.4v, so 3.45 will work. Normally chargers limit the current when they get to the top of the charge cycle. Gives you a better opportunity to balance the cells and ensure that you are reaching full charge. For A123 cells, 2v is good as a low voltage discharging cutoff, so 3.1v is exceedingly safe. Summary: You know what you are doing, and considering you are not float charging, you are using very conservative charge/discharge points. But you are still getting failures, which is disturbing. Here are a couple of articles, which I suggest you scan, to see if anything else jumps out at you. This article is a little old, but if you skip down past the beginning there is some interesting information on charge strategies and memory, which I have not seen on any MFG data sheet. These are boat guys, who have been using Winston cells for a while. Characteristics A123 battery pack design info. Interesting graphs -charge/discharge etc. A123 Are you measuring/logging battery temperature? What current are you charging these batteries at? Greg |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
One thing that sticks out to a Dilettante with no experience, ( me) with these lipo batteries is they seem to be very Complex things with a lot characteristics that need careful management. When the smart and Knowledgeable people have trouble with them, it does not convince me of their quality or longevity nor how successful I would be with the things. Doing everything right with careful management does not seem to assure problem free experiences. I base this on many things I have read, not just here. For a beginner that is likely to make some slip-ups and mistakes, they could prove very costly when people doing everything right have problems. Perhaps they are not quite where we are told they are or hope they would be performance wise? While looking at things related to the battery build thread, I found many recent references to Aluminium based battery's which -seemed- to indicate they would be the next battery technology and appearing in the next couple of years at the outset. I wonder what proclivities they will have? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Batteries always run stone cold, never had them get even very slightly warm to the touch, so its not something that concerns me. Batteries are indoors, never anywhere near freezing either. Charge rate maximum about 0.5C or thirty amps for 60Ah cells. On a fairly typical day full charge within two to three hours. I have researched all this and agree there is a lot of conflicting information, but from what I have read, I have not done anything too terrible to them. Cheers, Tony. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thought I,d show what’s inside a Flat Pak battery pack . Looks like the card of battery management control for equalising and 10 sacks of chemical consisting of the Lithium and other combining ore. Each of 3.2 volts making 32 volts per battery pack ,'3 of these in series for a 48 volt battery. This one is DEAD. .I think ?. The packs are very SWOLLEN aaaand unwrapping them just found each pouch connected to a PCB board which made up the negative and positive connections to the outside world. Not much else , so maybe ,when this is in good working order, it,s purely the container for the 2.5 Kw of battery power. Input and output cables are in parallel ,so maybe one set for charging and the other for powering A load. Don,t know if I can buy the individual packs, will investigate that later. Weighs in at 22 kg. So not very portable ,but for 2.5 Kw it,s probably around half the weight of gel cells or sla,s . It,s a standard rack mount. Lovely connecting terminals and well made SONNEN 2500 LFP2 Australian made. Bruce  Bushboy |
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Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
They look exactly like my RC aeroplane batteries, even down to the orange xt60 connector. Where can we buy them in Australia? |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
Just did a quick search, going by the size of the I think they are 25Ah each cell found these. They are Lifepo4 not to be mistaken with li-polymer, different stuff as far as I'm aware. There are other options, will have to look around some more. @Haxby I have a few of those old flight packs, polymer type they have an enormous discharge rate,but short cycle life, my RC chopper had about a dozen successful flights, then after could only manage a hover. Cheers Aaron Off The Grid |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks for the feedback, Aaron, Yes,they certainly look the same as mine. 30 pouches won,t be cheap,so maybe if I can,t re charge these , then the only thing nice to reuse will be the big terminal posts.,,,, And ,maybe a slim line rack unit for a new inverter,no, too narrow for our Torodials?. Bruce Bushboy |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
It might charge up ok, don't leave it unattended, there could be some bad cells and others good, will see. I just pulled the solar panels out of all the SCC's they are Too many SKY SPARKS ATM, some less than a second between the flash and bang. I bet the grit power is out too. Its heading your way Bruce, Cheers Aaron Off The Grid |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
How would I know If I have some bad cells They all look like new ,like no discolouration, visual breaks , etc.. Lots of lightning and thunder towards Bris and Gold Coast,not much rain. Tanks are overflowing ,nowadays. Not been this way in ,possibly a year or more. Bruce Bushboy |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
The cell might heat up or expand a bit more, or once charged a cell will drop its voltage compared to others. That's what I think anyway, perhaps the control system might not let it charge, don't know yet. It would need the BMS connected by the looks of. Power outage around here, the line out front, can hear the big generators running the chicken farms. No problem for me. Lights on and enjoying it.   Edited 2020-12-20 22:53 by Revlac Cheers Aaron Off The Grid |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 49 |
So I guess the cells were just defective. I will be floating mine, so hopefully things go ok. Here is a factory tour of a China mfg of Lifepo4 cells. More automated than I was expecting. Jump to 2:30 Meritsun Greg |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thank You, Oreo Very interesting tour, my cells or ,pouches, as I called them ,look very similar. I was going to ask if anybody had dismantled one pouch to look at the chemical contents ,but now realise it would be foolish and dangerous . The contents maybe toxic. Would be interested in knowing what actually happens because of mis management in either the charging process or shorting out of the pouch . But , I now realise that any physical or electrical cause would render that singular pouch to die or worse still effect the adajecent and other pouches that are in series. Just my ,Chain of events, thought on the destruction?. Tanks Oreo,you have me much wiser , now. Bruce Bushboy |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
Something I have to clear up, This float charge thing with lithium. By definition if the battery was still taking current and is over its sitting voltage that would be floating.? If the battery is at resting voltage and not taking any current, I think this is what is expected for Lithium. Now with a complete off grid battery there will be cycling during the day, either when there is heavy motor starts or lack of solar due to clouds passing over. Had a lot of cloud and sun this week and countless amount of micro cycles, its unavoidable as fare as I can see. For an on grid battery There should be next to no cycling during the day as the grid (power source) will supply the house/inverter with power until the battery is required, or however that is setup. Our off grid batteries are going to have a lot of mini cycles (or shallow cycles) compared to a house grid battery. Or Am I missing something? Cheers Aaron Off The Grid |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 49 |
Could just be age related swelling, or possibly heat/overcharging. I have seen packs that still output >60% rated power that were badly swollen. Some manufacturers keep the cells under compression using straps or bolted plates. With them being Lifepo4, at least you don't need to worry to much about them burning down your house:). Well, I can only comment on the batteries I have. If I charge them even with a 3.6v constant voltage source, the charge current will go down to 0. But using that high a voltage, will overcharge the cells, and that in combination with the high voltage, will reduce their life. My cells are supposed to be fully charged at 3.37v, and they recommend floating at 3.45v (at 20C IIRC). So just slightly over the charged voltage. I have noticed that recommended floating voltages are going down. I think manufacturers are realizing that the higher voltages were causing damage. Some do not recommend floating lithium at all, but as you say, unless you are pulling power from the grid to back fill clouds and other solar reductions you really need to be floating your batteries (or having a very smart charge controller maybe). Not much tolerance for voltage error here, so need a really accurate BMS and charge controller. So lots of challenges when floating Lithium. (IMO) Greg |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
Yes definitely agree,  As yet I still don't have BMS for the 13s 48v set of Lithium-ion 18650's but there voltage is fairly ridged and they are up to 13 years old now and I have learned a lot from using them, they will be replaced soon with something else, that's another story. Those flatpack batteries could have been drained flat by the BMS, I have found this a few times with laptop batteries and cordless drill batteries, seen it happen with a bunch I had in the shed they were sitting there charged for months, had a storm come though and they got a little damp in the shed with open sides. All the leds on the the BMS circuits lit up and drained the cells completely, later on after circuit boards where clean and dry I charged them all up only to find all of the run flat again (several attempts), cut off the BMS from the cells and charged them again and all the cells were fine, they have been running the house since. So there might be some fault finding to be done if the battery voltage Doesn't hold up after charging, could be the BMS, could be a cell not so good and the BMS goes into protection mode and safely drains the whole thing....This is only a guess at this stage, I would be interested to see how it turns out. Expect the multi-meter to get a lot of use checking each cell's voltage, 15s 2p by the looks of it, in the flat pack. Cheers Aaron Off The Grid |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 49 |
Not sure what you are saying here, but 13yr life sounds really good for Lion. Interesting that you had a BMS drain the batteries due to moisture and then internal failure. Never heard of a BMS intentionally do that though. I have also had Lithium-ion cells go to 0v and have mostly recovered after a few charge/discharge cycles. Not sure if Lifepo4 will do that though. My cells are used, out of an electric bus. They were cheap, and from their current capacity, have probably done ~4k cycles. As the Toyota owner would say, "They're almost broken in". They have good internal resistance though and are at ~80% capacity or so, so it will be interesting to see how long they will last. (assuming I don't break them first) Greg |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
I should have had this on my previous post, might have made better sense I have posted this elsewhere some time ago. These batteries were all used and discarded notebook, medical and cordless packs thrown out due to not working or exchanged out of date, so I have no idea how much of a thrashing they have had or how long they might have been sitting. Best of all they where free, did the fella a favour to get them, unlikely a deal like that will come up again. The have run the house for around 5 years, At the start I had the grid still available in-case, not knowing if they would stand up, but they did well and later when I had time to add some more to it, none left now. Also have a lion camera battery must be 20 years old, still works, just charge it and go, self discharge is a lot higher than normal. I think its not so much the age of them, its how many deep cycles they have had, avoiding deep cycle's seems to be the way to get a little more usable life out of them, For this to happen we would need more capacity to play with as is done with FLA. I do the balancing with charger and some car headlights, haven't done any on that pack for about 3 months, seems to be behaving well. Sometimes I do get asked how many days backup I have, And I find that not really relevant, it depends on the weather and location, as I already have a diesel generator and charger its no problem to give the batteries a bulk charge for an hour or so to avoid running them low Its only a $1 or so in fuel (2 or 3 times a year), much cheaper to do this than buy a lot more battery capacity Would be much different in a place that has less sunlight more bad weather. The phone battery, I think people say 2 or 3 years normal use before they are stuffed, my oppo phone battery is dated 2013, replaced it July 2020 only because of it swelling, it sits on the charge for about 2 weeks straight, a trip to the shop then back on the charger until next time, the old battery would drop 10% on that trip and the new battery is the same, but with some heavy use the old battery would drop its guts before the other. The swelling is likely the battery charging too high, so this tells the same story. My apologies is this Doesn't read all that well....it made sense when it was siting between my ears. I have a bunch old dead 18650 cells, would like to give them the fright of there life (or me if it goes wrong)might try a large capacitor and dump the charge into the cell, providing the cell don't have a high resistance. Sound like your off to a good start with them batteries Greg, be interest to hear more about your setup when your up and running. Cheers Aaron Off The Grid |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
I have watched MANY videos on 18650 Power walls and always wondered how long they would last before a lot of the batteries started Dropping out. They seem like a Lot of time and effort to put together but if one could get 5 years + out of them, that seems a very worth while return. I would like to try this myself But I think now it's become a bot too popular and sourcing sufficient cells could be a real difficulty. Some of the mammoth battery banks people have with created 18650's is impressive as is the level of monitoring they set up. This is a very sensible position to take IMHO. Seems a lot of people get fixated with having huge capacity and solar to charge it. I was reading earlier this morning on another forum a guy wanting a 100Kwh hour battery and a larger array than the 7 Kwh he presently had. Went on like running a generator the 3-4 Times a year he runs short was like having a 6" nail stuck in his rear end and was talking about spending thousands so as not to have to spend Hundred and a few bucks on fuel. | Generators will always be cheaper than batteries for the distant foreseeable future and also a lot more reliable particularly for these people that live where it snows. |
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| Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
I haven't watched any videos but I was reading a post the other day somewhere, someone had build a setup with 5000 of these 18650 cells and is going to upgrade to 10000 and run 3phase, be interesting to see but hell of a lot of work, Must make them into a rack mount or 13-14 flat packs or something. I did 2000 or so cells, just figured today I would have done at least 9000 battery voltage test with the multi meter and went through 2 sets of leads for the meter just to get this lot working, then my mined went blank, forgot what I was meant to be doing, probably something important. The cells would have to cost next to nothing to do it again, just don't know where others are getting them. The generator has been very handy, we had it before going off grid and it had some use when the grid power went out for more than a week due to floods, the house was all ready wired up with a changeover switch. Cheers Aaron Off The Grid |
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