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Old 10-12-2024, 04:20   #16
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Re: My Experience With Lithium Change Over.

Quote:
Originally Posted by Kristian View Post
Just nine months ago, a scientific paper was published that in depth explains aging characteristics vs. SOC and temperature, both cycle and calendar aging.

It aligns with earlier published papers and lectures from Prof Jeff Dahn about the same things for NMC batteries and of course the latest paper concentrating on LFP batteries is from his laboratory and shows that even this giant researcher has given advice regarding LFP batteries that now have to be slightly expanded and tweaked a bit.

Open source and available here:
https://iopscience.iop.org/article/1...11/ad6cbd/meta
!
Great link, thanks for sharing

Quote:
Based on these results, we would recommend that LFP cells for long lifetime applications operate at low states of charge on average, with charging up to 100% only on occasion. This raises several questions: how practical is it to cycle a battery cell in only low SOC ranges? There is clearly a tradeoff between useful capacity and capacity retention. It is not realistic to recommend cycling LFP cells between 0%–25% SOC only, because that is a waste of capacity. However, we propose that LFP cells cycled between 0%–80% (or 0%–60%) would have a reasonable capacity and a longer lifetime than cells cycled between 0%–100%.
From online chatrooms there seems to be a strong tendency to want to get to 100% every time and stay there for a while, logic usually given that active cell balancers need that high voltage to do their thing. Which imho is probably unnecessary with decent cells, maybe once a month would be more suitable? (guess though)
My cells are nearly 2 years in constant cycling use being balanced just once before put in use & are still within mV of each other.
Which then creates the issue that it's actually impossible to accurately track SOC over time without going into the top knee as a datum. After a lot of logging & tweaking my smartshunt errs slightly on the pessimistic side but the metrics are so small even if the fridge is running or not can change the voltage enough to skew the SOC a tiny bit.

Imho there are a lot of monsters from the Id left over from the ancient tech lead acid we had before.

And of course our inherent multiple big monkey brain biases

Now feel a strong need to get the regulators to switch to float at 80% SOC
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Old 10-12-2024, 09:58   #17
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Re: My Experience With Lithium Change Over.

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Originally Posted by Kerry1 View Post
On occasion I'd had to use my house bank to combine with a flat starter battery to get the engine going. A combiner master switch existed between the house and starter main switches for this purpose. Simple.

Not so with Lithium batteries. Apparently with Lithums and a flat starter Lead Acid battery, such is the strength of the current available to flood the starter battery that things could get mighty hot and it wasn't a good idea.

I still like the idea of using if necessary the house bank to get started.

What to do? !
Just use the combiner switch. Current will be limited to what the start battery can accept.
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Old 10-12-2024, 14:56   #18
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Re: My Experience With Lithium Change Over.

Hi Kristian,
Thank you for your thoughtful response.

I relate strongly with what you've said. I do wonder if my decision to get a second Lithium was not such a wise thing, being more of a spur of the moment decision.

I especially found these comments helpful:
"If your very complicated system can run both batteries in the range for instance 20-80% SOC with an occasional charge to 100% for cell balancing I think you will get the optimum expected life out of your investment and it is a good thing if you believe that the additional cost is offset in overall longer life and even something that will give you a lower unit-cost for the energy you cycle in the system.

If you have a situation where you will have both batteries almost always at 100% and occasionally down to 50% I think the opposite is true, you now have an oversized system resulting in a higher cost per cycled energy unit."

Given this information, how imperative is it that the cells don't stay out of balance? Or how long may they remain in unbalanced state until rebalanced without doing damage, or becoming unsafe? Or - given another punters comment -about not having to re-balance after two years use, and his cells are still very closely aligned, is it more a case of getting to 100% SOC just to recalibrate actual capacity?

I understand that cells do not get balanced unless and until the batteries reach near full SOC. I now have more capacity than ever, so capacity is not an issue, although no doubt I'll use more now that I have it. As you say, with any system, how it is used will decide whether or not I've made best use of the investment.

Given what you say, I see that it appears that using the middle range of cycle, or 20% discharge to 80% charge - in general gives best economy/efficiency/longevity of what I have - and will still meet the daily power requirements. I've heard that once a month is a good aim-for-value to get them to 100% SOC in order to balance cells. Would you agree?

I've heard good things of nordkyn design, and will check out both links, thank you.
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Old 10-12-2024, 15:09   #19
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Re: My Experience With Lithium Change Over.

Quote:
Originally Posted by donradcliffe View Post
Just use the combiner switch. Current will be limited to what the start battery can accept.
Yes, from the Lead Acid days, that's ordinarily what I've done. I'm not so sure with Lithium house and Lead Starter. My installer actually suggested fairly strongly that I remove the BEP combiner switch handle and put it somewhere safe but handy to avoid any accidental combining of the two banks.

On the other hand I've had pretty flat LA batteries that when put on a charger just won't accept a charge as you have said, so what's the problem with combining to get power to start the engine? My charger at home,(solid state), even cuts out and tells me faulty battery.

I suppose the difference between a battery that is fundamentally shot, and therefore won't accept charge and so the combination switch is safe to use, is quite a different scenario to a start battery that has drained over several days due to circuit leakage, but is still a very much healthy battery is the real issue. Such a battery could take a lot of charge that the Lithiums could pump into it and create issues. Would you agree?

I'd really like more understanding on this point because I'm not comfortable, and in fact disappointed if this new system doesn't allow that combination. There are times when I want my engine to start, and right now!

Thanks.
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Old 12-12-2024, 06:37   #20
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Re: My Experience With Lithium Change Over.

Quote:
Originally Posted by Kerry1 View Post
I'd really like more understanding on this point because I'm not comfortable, and in fact disappointed if this new system doesn't allow that combination. There are times when I want my engine to start, and right now!
We typically wire a 3-switch setup to isolate or parallel an LFP house bank with a FLA start battery in case of a failure of one or the other. Since an FLA start battery will only take so much current, there will be no issue with combining them, although combining them would be an unusual circumstance. It is more typically used to isolate the start battery and start the engine from the house bank, or run critical house loads from the start battery if the house bank failed.

Of course, the usual cautions on selecting the appropriate conductors and fusing apply. And, since you have the possiblity of running house loads from the start bank, it also needs to be fused.
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Old 12-12-2024, 14:17   #21
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Re: My Experience With Lithium Change Over.

Currently my combiner switch does just that, comines both banks. I'd be very interested in isolating either battery and just transferring all loads to on or the other.

Is that what a rotary switch does?
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Old 13-12-2024, 07:42   #22
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Re: My Experience With Lithium Change Over.

Thank you for investing the time to provide this forum with a detailed description of your system. I value this community forum as a searchable database of sailing knowledge.
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Old 13-12-2024, 10:09   #23
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Re: My Experience With Lithium Change Over.

Congratulations on your support from ARCO. I had a similar problem but a very different experience. My problem was that with a fully charged battery, the Zeus would ramp up, throw an internal over-voltage fault, reset, then rinse and repeat. ARCO blamed the 20+ year ABYC certified installer, the Epoch batteries, the Bosch alternator (“we don’t support Bosch alternators”), the shop that modified the alternator for external regulation, the Victron battery monitor that showed that the Zeus was putting out a half volt more than the ARCO app reported, and the Fluke voltmeter that verified the Victron’s reading. We sent them a screen capture of the ARCO and Victron apps side by side showing the problem and ARCO still refused to consider a warranty claim.

The installing shop said that the only way to salvage our season was to buy a second Zeus and see if it fixed the problem. I did – and it did. We sent the faulty Zeus back to ARCO – and they continued to stonewall warranty reimbursement.

It wasn’t until I posted by experience on Rod Collin’s LFP Facebook page that the ARCO CEO intervened and got me a refund.

Since then, the 2nd Zeus has performed flawlessly, balancing battery charging, a power hungry Grunert refrigeration system, voltage, duty cycle, and alternator temperature. A very impressive product when it works – and a nightmare when it doesn’t.
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Old 13-12-2024, 15:00   #24
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Re: My Experience With Lithium Change Over.

Thanks for your “eclectic” discussion! I’ll be switching over next spring and every little bit of information in advance is helpful.

< I know it doesn't sound like economic sense, but in for a penny in for a pound.>

Anything worth doing is worth overdoing! 😂!
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Old 13-12-2024, 16:59   #25
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Re: My Experience With Lithium Change Over.

Wow, what a different response.

I'm glad with persistence they came around. And that you still recommend the product now it's sorted is comforting.
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Old 13-12-2024, 17:00   #26
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Re: My Experience With Lithium Change Over.

Thanks, I like writing and can touch type.
It helps.
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