120 AH, , nominal 12.8V.
12.95V unloaded, 12.8 under 4-5 A load. According to discharge curve 12.8 is 30% (they measured at much higher 0.5C rate discharge): Lynac 12.8V 120 AH .
Quite a bit of sag. Battery is 3 years old. I did bring it to 20% SOC once or twice.
12.95V resting it is only starting at 25%. what are you charging them up to? A flooded deep cycle would be drooping a lot more at that low state of charge if it even works. The one problem with LFP batteries is getting an accurage state of charge from voltage due to the small change from 70 to 30% and every cell will be slightly different so charts will be close. 20% soc won't huirt a LFP battery and expecial in the way your thinking.. the cycle life is based off a 100 to 0 to 100 charge cycle, by limiting the top or bottom end all we are doing is increasing the cycle life. so the battery you have says if you go from 100% to 20% to 100% all the time you will get 6000 cycles so they ignore the standard industry standard of 100-0-100% so you can't compare to other batteries. also they kinda don't tell the truth in their littiture with this statment trying to increase sales.
"battery is truly rated for 12.8V 120Ah (1536Wh)
since roughly 20% of the rated power stored in all Lithium Iron Phosphate batteries is unusable. We
strive to give you more for less - change the game."
a LiFePo4 has 100% of its capacity available at the rated cycle life. at the end of the cycle life you simply have a battery that only is 80% of the original batteries capacity but it can be used for who knows how much longer.
I don't mind that they recomend from 100% to 20% capacity that will increase your capacit and is how they get up to 6000 cycles, and protects then from warenty claims. SO I guess their statment could be true if you look at it like you can only use 80% of the capacity of you want to get 6000 cycles, but even 3500 to 4000 cycles at 100% is a long long lasting battery, I would be tempted to use it as a 120AH battery myself haha. I see it uses celindrical cells so you can pound the charge a bit harder than prismatic as they disapeat the heat a tiny bit better, I would like to see you charge it up to 100% and try it after it sat resting for 30 minuits to get a true 13.6V resting volatage. in the mean time I will continue to look for my volatage chart for LFP under load, I changed laptops a couple months ago so I'm still trying to find a bunch of stuff.... with that chart I will know what a normal drop is if they have a measurment for a 5amp load.
Hi Almot,
Best to bring the Li to 100% state of charge every 30 cycles. Do you have access to the bms on these units?
I don't have access to BMS, sealed unit, don't want to open and wouldn't know what to do if I opened 🙂
The battery is mostly for back-up, there is grid power. I'm trying to find a middle ground btw the popular mantra "Don't keep for long in Absorb, don't float, don't keep it 100% all the time" on the one hand, and the need to keep it near-full in case of blackout on the other hand. Blackouts happen a few times a month.
I would like it to stay at 80% and cycle shallow. What I do now is letting it charge on solar + converter, and then shut converter off for the night to reduce floating time.
Ideally, I would like to store it unloaded at 50% charge for a longer life but this is unrealistic and I doubt that my life will be much longer than 4000 battery cycles (6 months a year = 180 cycles a year = 22 years).
haha ya thats what I meen, I was all worried about getting the most life out of mine, I believe it was an old habbit of the flooded cell days, treat them right and you will only have to buy new ones every 8 years, with the LFP I am finding after two years on my 280AH running at 100% to 10% I havent lost one bit of capacity. well 100% to 10 are my cutoffs, it rarely sees under 50% , because of the extra capacity I built in, but always is charged back to 100%. its kinda funny people are still afrade to go to 100% of capacity for the charge, if you look at all the people running big 48V battery back up systems on their homes they charge to 100% every day with a specified amount of adsorbtion time then they drop off to 13.4 to 13.6V for the float. and these guys are cycling every day, and floating as long as the sun is up. I honestly don't know where half the rhoumors and old wives tails came from in the rv world that we can only use 80% of the capacity, don't float, don't fully charge and so on. most of them are totaly BS and prevent people from using there batteries to the fullest. the one hard one is don't charge below 0C , and don't float at 14.6V if you have a float have it set for 13.4 to 13.6 depending on your school of thought. idealy a 3 stage charger that you can customize bulk, adsorb and float voltage (and time in the case of adsorb) would be ideal.
thats not to say park your rv for the winter and leave it floating for 6 months, thats concidered storage and I take my battery to 90 to 100% and shut it off ( battery disconect that leaves no parasidic loads) and it sits like that till camping season is close. even during camping I don't charge between trips, just charge it to 100% the day before I leave, then the solar handles the charging during the trip which takes it to 100% every day.
As of this morning I have taken my old battery (280AH) out of the camper and it is going to a friend for his camper and I am just working now on the replacment battery for my camper. upgrading to newer larger cells and if they are good I am buying 16 more for the 5th wheel. the biggest advantage, aside from larger capacity, is the ability to run at -35C (discharge only, and only 10 degrees colder than the old cells) and increased cycle life (3500 to 4500. ) at 100% usage
There is some rationale behind charging to 80%, cycle life is longer. Having max available energy is more important for me so I'm going to ignore this. Besides, charging to 100% takes care of cells balancing.
OTH in storage, say unused for more than a week or two, I don't see why not discharge it down to 40-60% as per recommendations. Even if it saves me 5% of capacity in several years. Hot storage is the worst: https://www.uschemicalstorage.com/lithium-ion-battery-storage-requirements/
Thanks for the care of LI link!
Just out of curiosity what size wires do you have that battery wired up with and how long is its run?
