locked Batteries starting to get weak - MMM - What to do -
|
Steve Bell
There is an interesting detailed article on www.marinehowto.com website on lithium batteries. check it out
|
|
|
|
Porter, That's part of the issue. If you read each manufacturers instructions for how to store their LiFePO4 batteries you will get very different answers. There is some level of commonality between some of them, but the specific recommendations are quite different from manufacturer to manufacturer. See below for the details.
|
|
|
|
Porter McRoberts
Mark. I think your insights are spot on. Both #1 and # 2.
toggle quoted messageShow quoted text
However, It seems to me that with access to solar or other power a charger should be able to be programmed to perfectly care for a battery, so that degradation likelihood is at its lowest potential. I’m sure the lack of data is from your 1 and 2. Interesting the difference in suggestions for parking. Porter McRoberts S/V IBIS A54-152 WhatsApp:+1 754 265 2206Www.fouribis.net
On Sep 19, 2020, at 6:44 AM, Mark McGovern <mfmcgovern@...> wrote:
|
|
|
|
Scott SV Tengah
I used to own and race BMWs and was a big fan of them.
Previously, they recommended oil changes every 3,000 miles. When they started including free oil changes, suddenly their recommendation was that you could go 20,000 miles or more between oil changes. Nothing changed in the engine nor the oil they used. From a business perspective, it makes complete sense. Since BMW started including the oil changes, they rationally, as a business, determined that they could save money by only giving you 2 oil changes before your warranty ran out. Any damage due to extended oil change intervals would probably occur after that. When the customer was paying for oil changes and they wanted to protect their reputation, you were supposed to change the oil 6-7 times as often. If I was a profit maximizing business, I would want my batteries to last the warranty period + 1 day. Or for you to get enough loss of capacity that you buy new ones. They go out of business if their customers only buy once every 10-15 years. For this reason, I rely on statistically valid research from people who are not conflicted to make my decisions. When I leave the boat, I setup a simple programmable relay that drives a load will keep the SOC between 40-70%. Sure, there's one guy who seemed to do ok (in 1 out of 2 tests) when he goes against the non-conflicted researchers' advice...but he also sells lithium related products. It's not much effort and there's very little known downside to doing what the research says. Or you can trust the guys trying to sell you stuff and who have a strong incentive for you to buy from them again once the warranty period ends. -- Scott 2007 A54 #69 SV Tengah http://www.svtengah.com
|
|
|
|
Joerg Esdorn
An interesting tidbit from the manual for my MV batteries. One of the „events“ causing an alarm on the Masterbus system is that the batteries HAVE NOT been fully charged for a period - default 31 days: „ Last time fully charged serves as an event source. To prevent damage the batteries must be charged to the full 100% regularly. It is a common misconception that Lithium- Ion batteries should not be fully charged.“
|
|
|
|
Scott SV Tengah
Joerg,
As I mentioned before, I believe, it is recommended (and I do) charge to full once a month. That resets the battery monitor to 100% and also balances the batteries since for every battery I know, balancing only occurs when nearly full. That has to do with the very flat voltage vs. SOC curve. There's bottom balancing, too, but that's beyond my comfort level. There is a significant difference between charging full once a month and keeping it full. The former is recommended, the latter is generally accepted to be detrimental with no known benefits. -- Scott 2007 A54 #69 SV Tengah http://www.svtengah.com
|
|
|
|
Hello,
During research I found this particular cell balancing technique of FLASH Battery in Italy. Seems to have a lot of industrial applications/ What do you think of this . Regards Denis FLASH BALANCING SYSTEMThe exclusive Flash Battery electronic balancing system is called the Flash Balancing System.Traditional balancing systems apply resistance to the cells with the greatest charge in an attempt to “lower” them to the level of the lowest cell. Although it’s a simple and economical method, it’s also extremely slow: 4 to 8 hours on average are required for balancing alone (in addition to the earlier charging step). OUR FLASH BALANCING SYSTEM OFFERS MUCH HIGHER BALANCING POWER THAT IS APPLIED NOT ONLY AT THE END OF THE CYCLE, BUT ALSO ACTIVELY DURING DISCHARGEThis results in 20 times faster balancing without increasing overall recharge time to a significant extent. Traditional balancing systems require a much longer time, so when they’re interrupted because the battery needs to be used, the result is a gradual reduction in available energy over time: vehicles and machines thus lose range at every cycle. THE ULTRA-FAST BALANCING TIME OFFERED BY THE FLASH BALANCING SYSTEM DURING BOTH CHARGING AND DISCHARGING ELIMINATES THIS PROBLEM AND MAXIMISES RANGE.If unexpected repairs are need, the Flash Balancing System makes it possible to add or replace cells throughout the life of the battery, which overcomes the limits of traditional systems in keeping the higher and lower-performing cells balanced.
|
|
|
|
Hi Dennis,
This is one of the problems I have with many BMS systems, if not all. They use passive top-balancing, meaning they can only balance the cells when full and do this by dissipating the energy of the fullest cells. It seems that the one you found is more clever. It does not say if it uses active balancing as far as I can see. Some time ago I found this system that does it all: https://enerstone.fr/en/ However this also needs some additional logic to protect the batteries for under/over voltage. I sort of gave up on the Lithium stuff because if you want to do this right it is immensely complex and you will have to come up with a bespoke solution that I find undesirable on a sailing yacht. Fact is that the market for lithium systems on yachts is quite small compared to other markets so not many companies develop specialized solutions for it. Regards, Arno Luijten SV Luna, A54-121
|
|
|
|
Hi Arno,
The Kaiken Flash seems to be permanent equalizing. That said sometimes I have the same feeling as you about Lithium. The maturity for the cruising yacht market doesn t seem that established leading to complex not fail safe systems probably impossible to fix in remote places. For the moment we have a system that works with Gel batteries (9 years old) religiously maintained and strangely still working. I haven t excluded the possibility of replacing them by the same brand and model. I was also attracted by the Firefly carbon foam AGM. And spending the money saved on a high quality Solar installation that would be ready when Lithium will be at maturity for our specific needs. I know the industrial research on energy storage by Lithium batteries is very active now and the results will pass one day to our little niche market. Robust, reliable and easy to fix systems have there attraction.... Regards Denis
|
|
|
|
I looking into this BMS which I will probably go for, expensive but I got confidence in my contact, he provided a lot of valuable information
http://www.bestlithiumbattery.com/ Paul on sykerpa SM 259
|
|
|
|
Hi Denis
i agree with you , the last 8 weeks have been dealing with Licium batteries , but it was not happy that too many complex questions are still open to me , then I have co2 and carbon batteries are busy, not matured on sailing boats at the moment Now the decision is probably on AGM Victron super cycle with it I get to the SM battery compartment about 580 AH /24 V ich hoffe damit die nächsten 5-10 Jahre zu überstehen und dann schaue ich mal neu Greetings Elja SM Balu 222 Von meinem iPhone gesendet
|
|
|
|
Thank s Paul,
|
|
|
|
Hi Paul,
This Best Lithium BMS still uses passive balancing and it does not say if it only does top-balancing. So from that perspective it's not a great BMS. Arno
|
|
|
|
Hello,
Just had Flash battery Kaiken that does continuous cell balancing... but they don’t do batteries for yachts and private owners just for industrial companies. so that s out for us. regards Denis
|
|
|
|
Scott SV Tengah
Does anyone understand "continuous cell balancing", because I don't?
When I have had unbalanced batteries, the batteries are look perfectly balanced until you get to 90% + SOC. This is because of the flat voltage curve of lifepo4. Above that, the imbalances show up. How does an active balancer reliably detect an imbalance continuously when things look perfect below 90%? Through coulomb counting to determine amps out to see if the imbalance shows up during discharge? That wouldn't be reliable as cells age at different rates. Note that imbalanced batteries generally just reduce your total capacity until the imbalance is corrected. This is because if one of the 4 cells in the battery see an overvoltage condition, the BMS should stop charging altogether, even though the other cells could still accept more charge. Charging is restarted once the overvoltage cell drops below the high voltage threshold, either through a resistor to draw charge from it or a method to transfer that excess voltage to the other cells. Then the charging resumes. The charging will start and stop multiple times as during the cell balancing process. I have seem this before on my Victron setup and have been assured by Victron techs and my own research that it is totally normal. The desire for active cell balancing seems a bit misplaced. Even if somehow they detect cell imbalances when there is no voltage difference, you still need to fully charge once in a while to reset the battery monitor as I believe all battery monitors use (amps in - amps out) to determine SOC and as batteries age, that needs to be recalibrated if you want any sort of accuracy. So solving the former problem still leaves the latter. -- Scott 2007 A54 #69 SV Tengah http://www.svtengah.com
|
|
|
|
Hi Scott,
Typically good BMS-es can measure at 0.01 resolution. So even at lower SOC you will be able to see differences. Charging up to 100% can be postponed longer with continuous balancing. Active balancing means you are using the charge of the fuller cell to charge the less full cell. That improves the speed of balancing and prevents useless heat generation. Obviously it's not as world of difference all together but if you design a BMS for lithium you may as well make it top notch. The system is expensive enough to push it to the limits of longevity. Your battery-monitor has a easier life with lithium as the charge/discharge losses are far less so it will keep an accurate reading longer, especially if you can set the Peukert value yourself. If you are less concerned about those things than I think the Battle Born 24V batteries are a good choice, just do not expect 10-15 years of life. If you do achieve 10-15 years you can always celebrate at that time, but at least you will not be disappointed. As said before and as said by others as well; there is still so much development in this area that I prefer to wait a few years to see what the next best will be. I just read something about a person managing 9 years on some Gel batteries so it's not that all other chemistries are useless. Regards, Arno Luijten SV Luna, A54-121
|
|
|
|
Scott SV Tengah
Arno, My Victron BMS reports cell level voltage down to 0.01v. I can view it via bluetooth and have seen it vary by 0.01v. I can attest that when I had an imbalance, up to 90% SOC, the cells had the exact same voltage, down to 0.01v. Above that, the variance reared its ugly head. This is not theory - this is my experience living with this system fulltime for 2 years. So I would be very skeptical of any active balancer that has the same resolution as you may be unknowingly exacerbating an imbalance by relying on marketing promises. If I haven't stated before, I do agree that if you want a system that requires no planning and very little monitoring aside from making sure you don't go below 50% SOC, then lead batteries are fine. If I were in your position and spent most of my time plugged into marinas, I would probably NOT get lithium even if someone paid me to take it. One guy may have had his gel batteries last 9 years, but longevity is not the main reason we got lithium. As we speak, I am running the dishwasher and washing machine and the admiral just turned on the microwave - all on battery/inverter. The continuous draw is around 160amps and the voltage is quite stable. Because of the huge boost in charge efficiency compared to lead, I won't be running the genset to recharge the batteries, either. Our solar is more than enough. But as economists like to say - there is no free lunch. Lithium requires planning and thinking prior to implementation and if you plan it right, it is set it and forget it. I am not quite there but moving in that direction slowly. The same thing applies if you compare roller electric in-mast furling vs. manual stacking mainsails. The former requires some thinking but, at least to me, is well worth the effort. For my use case, lithium is the same. I hope my contribution to this forum is useful in that those who are off-grid and would rather not run the genset all the time are given some useful info that they can use to plan their systems. It is beyond my risk tolerance to try to assemble battery cells and rely on them in the middle of the ocean, so I went with a mostly-one-brand solution that allows me to monitor every single of the 24 cells via bluetooth and if a cell fails, quickly remove that battery pair and continue on with my trip. Luckily I haven't had to do that yet.
On Wed, Sep 23, 2020 at 9:34 AM Arno Luijten <arno.luijten@...> wrote: Hi Scott,
|
|
|
|
Hi Scott,
Don't get me wrong. I'm not against Lithium. I'm just trying to bring some nuance to the many über-happy stories about Lithium. These things are bloody expensive and people should know what they are getting into. Actually I'm really happy that you bought Lithium because that means you can tell me about how this works in the long term 😎. In the electric car world you see similar discussions about charging speed and charging level. People are now starting to find out that these batteries are degrading much faster when you are a super-charging junkie and keep pushing it to 100% SOC So if you buy a used Tesla from a predominately home charging person that doesn't use his car as racing vehicle you are much better off then when you buy a mostly supercharged race-car. There is a reason Tesla keeps all these metrics on their cars. Latest EV cars are charging with more then 2C (250 kW) using water cooled charging cables. I really wonder how that will work out on the long term. Anyway I don't want to talk anyone out of Lithium and if my use case was different I probably would have bough an all singing and dancing Lithium pack by now. But I would expect a 8-10 year lifespan of it. Regards, Arno Luijten SV Luna, A54-121
|
|
|
|
Oliver Henrichsen, SV Vela Nautica
Hello, Good BMS systems measure 0.001 Volt with +/- 2 exact. Balancing is over evaluated in the thread. A good batterie setup stays balanced for years after initial balancing if needed at all. You may check on it from time to time but a good system will hand a banalce Alarm anyway. Active balancing has no real advantage agains passive balancing. It only reuses a tiny bit of energy instead of dissipating it. Oliver from Vela Nautica A54#39 Martinique
On Wed, Sep 23, 2020, 18:18 Arno Luijten <arno.luijten@...> wrote: Hi Scott,
|
|
|
|
Scott SV Tengah
Oliver, that has not been my experience. Perhaps Victron makes bad internal cell-cell connections but I surmise it might have to do with my keeping the Amel configuration of 12v batteries paired up in serial to create 24v and paralleled to create the total AH. This is useful in case your starter battery dies and you need to borrow a 12v battery to start engine/genset. I opted to retain that redundancy.
To my knowledge, BMS systems do not typically balance between serial pairs of batteries. As such, I've had a few cases of meaningful imbalance in the last 2 years of operation. By meaningful, I mean high enough to cause a cell to go over the cutoff threshold and cause the BMS to tell the chargers to stop charging. Note that these voltage imbalances didn't show up unless I charge to 90% SOC or greater, because of the shape of the lithium voltage curve. I agree that active balancing doesn't seem to provide any benefit and is of questionable utility. -- Scott 2007 A54 #69 SV Tengah http://www.svtengah.com
|
|
|