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Old 12-19-2017, 05:45 AM   #21
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Peter, PM sent hope it helps!

Cheers
Thanks. I have initiated contact.
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Old 12-19-2017, 05:53 AM   #22
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Here's someone doing it: https://www.gonewiththewynns.com/sai...hium-batteries

I have just seen on one of their latest videos on youtube where one of their Relion batteries died. The support from Relion appears to be first rate, but that could be because of their number of followers.......
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Old 12-19-2017, 06:23 AM   #23
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Peter
I can't top the suggestions you've received, but have a few questions on system design. First, how important is individual cell monitoring and are the manual rebalancing remedies simple or an aggravating requirement?
The key is that you don't want to over discharge or over charge a cell as it will kill it quickly. One approach is to restrict battery operation to 20%-80% state of charge. The idea is that you stay far enough away from the danger zones to avoid the problem. Slight imbalance between cells doesn't matter because you have stayed far enough away from danger. I have seen recommendations to check individual cells once a month initially to be sure all is working well, then every three months, then every 6 months as you gain confidence that everything is working OK.

For me, I would rather just instrument the battery bank and have per-cell monitoring. Then I can alarm if things start to drift apart, and have the tools to fix it easily. So I am leaning heavily towards per-cell monitoring, especially since this is my first Li battery system and I'll be wanting to keep a close eye on it.

Balancing involves either extra charge for selected cells that have fallen behind, or extra discharge for cells that have gotten ahead. a BMS with balancing capabilities have electronics per cell that can do this. With manual balancing, you need to have an external charger or load that you can apply while carefully monitoring the cell.

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Second, would the land based charging systems be materially different than possible on the water thus affecting commonality in battery design and monitoring?
I don't think so, or at least not in my case. For the land system, I have dual solar chargers, plus an inverter/charger. The charger is powered via an auto-start generator. The charging parameters need to be adjusted for Li, but otherwise I don't expect any difference.

On the boat I have more diverse charging sources. There is solar plus inverter/chargers. In addition, there is the main engine alternator, and shore chargers. Parameters need to be adjusted, but I think that's all.

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Third, is there sufficient user experience to suggest LFP batteries age gracefully and are longer lived than flooded cell?
Yes, there is. Not nearly as much experience as with LA, and they need to be managed properly where LA batteries are very tolerant of abuse.

2000-3000 cycles seems reasonable to expect. That's as much as 10 years with almost daily cycles. But battery life is only one reason to switch to Li, and not the most compelling at least to me. I think the most compelling parts is being able to charge at full rate right up until they are full, getting rid of the annoying absorption stage in charging LA batteries. Plus being able to run indefinitely at a partial state of charge. This means much shorter generator run time with much more effective charging. At the fast charge rate, I could fully recharge on the boat in 1-2 hrs. And at the house I should be able to fully recharge with the generator in around 2-3 hrs vs 5-6 now.

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Lastly, for existing flooded cell systems that are working successfully are existing chargers, inverters, combiners etc - usable in a switch to LFP?
Most modern chargers are able to change, but it does require a careful evaluation. Fully programmable charge parameters are essential. Fixed voltage internal regulator alternators are out, but with an external regulator like a Balmar, it can be adapted.
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Old 12-19-2017, 12:46 PM   #24
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Here is what I think I know, which may be different from what is true.....

Too soon to tell much, but based on my limited experience so far, my Lithionics 24vdc 300 amp LiGFePO4 batteries are very impressive. If charging is limited to 28 volts, balancing is hardly needed, at least based on what I understand Maine Sails experience indicates. The Lithionics engineers I spoke with confirmed that unless you push to 29 volts +, the BMS built into these doesn't have much to do. They thought that perhaps once a month, or once every few months it might be a good idea to push the charging to that level so that top end balancing via shunts will occur, but they certainly weren't emphatic that it was a necessity.

As I've mentioned elsewhere, I find it perfectly convenient to discharge the batteries by 400 amps or so, then charge and when I observe the voltage hitting 28 and the acceptance rate dropping to 20 amps or so, I stop charging. At that point they are around 95% - 99% full. I store them about 50% discharged. Since the acceptance rate is basically a flat line until full, you can divide the amps used by the input amps and that is how many minutes it will take to fully recharge. Pretty simple. I replaced 1600# of AGM Northstars with 270# of Lithionics and what I like most is that the voltage available is 26.4 volts through to the point where the voltage falls off a cliff at 90% discharge, which I would never typically reach, preferring to re-charge at around 70% discharge.

The only area I am not sure of is memory, so I probably will take them down to 90% discharge and then recharge to 29 volts every six months or so.

In my case the installation was pretty much just remove one set of batteries and replace them with the Lithionics. Very simple.

As always, happy to hear from experts if they think I am doing something wrong, but so far, so good.
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Old 12-19-2017, 01:02 PM   #25
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I want something that in the end will be both rock solid reliability, and be maintainable into the future.
I agree but that first is a much higher priority.

If the cells are healthy over decades and better protective devices appear in that time I won't mind upgrading the latter.

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When you refer to the primary protection layers, I assume you mean the BMS functions?
Four functions: LVD/OVD and the same for temperature.

Biggest questions are at what level?

cell / block / string or bank-only?

and how much redundancy?

> The idea is that you stay far enough away from the danger zones

Yes, looking at the volts vs SoC curves, stay away from the "shoulders" at both ends.

> 20%-80% state of charge.

At the low end, I think under 10% SoC may be pushing it but IMO 20% is too conservative a sacrifice. Depends on discharge rates and on how expensive/inconvenient your "on demand" charge sources are.

At the top, sticking to "hit 13.8V and stop" I think is sacrificing no more than 3-5% compared to mfg rated capacity, for quality cells.

> 2000-3000 cycles seems reasonable to expect.

That would be true following vendor charging voltage recommendations and BMS settings. IMO triple that and more is likely **if** sub-C discharge rates and avoiding the curves as above. Even 10000 cycles appears possible, but we just don't know yet.

That strategy may also eliminate the need for

> instrument the battery bank and have per-cell monitoring

Besides cost, be **very** wary of the added complexity, actually causing problems and adding failure points.

> I'll be wanting to keep a close eye on it

I think the inconvenience of checklist routines is well worth the greater safety of doing it manually. As you become intimate and no problems arise, then less frequent is OK.

Automated balancing is definitely way too risky for me, even if a robust open-hardware BMS was gifted to me, I would disable that feature.


> existing infrastructure

charger sources and combiners must be fully setpoint and absorb-hold-time adjustable

start spec'ing that in the years before converting, and you won't need to replace as much

load devices like inverters need no changes, but any built-in LVDs setpoints won't be right anymore.

Kombi inverter/chargers with input-output on the same terminals won't be suitable.
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Old 12-19-2017, 05:00 PM   #26
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Have you looked at BYD? Their B-Box systems are targeted at residential use, and they are making a push to enter the market here. They have large production facilities, in China. The link has a North American contact on it.
BYD New Energy-B-box
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Old 12-19-2017, 05:47 PM   #27
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Link to actual product spec sheets and manuals would be great.

From here their website seems content-free
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Old 12-19-2017, 06:15 PM   #28
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Link to actual product spec sheets and manuals would be great.

From here their website seems content-free
Not sure who you were referring to? The link I attached does have spec sheets etc, just scroll down a little.
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Old 12-19-2017, 06:18 PM   #29
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just installed 3 Lithium Battery from Mastervot on sail boat, that totally wonderful, not cheap but very nice product, I have captain friend who have 4 Mastervolt battery on néo-classic sail boat since 9 years never had problem and still working perfectly.

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Old 12-19-2017, 06:25 PM   #30
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Not sure who you were referring to? The link I attached does have spec sheets etc, just scroll down a little.
Not on my phone, just an endless scroll of badly written marketing slogans and background graphics.

Never mind, doubt I'd be interested anyway.
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Old 12-19-2017, 06:34 PM   #31
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I think their web stuff lacks finesse for sure. Not even all that computer friendly, let alone phone friendly. Here is a pdf of a Low Voltage system spec page. You add modules into a cabinet to get the capacity you want.
Attached Files
File Type: pdf BBox LV.pdf (91.3 KB, 36 views)
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Old 12-19-2017, 07:06 PM   #32
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PDF can't be opened here.

Link to the source page?
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Old 12-19-2017, 07:39 PM   #33
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PDF can't be opened here.

Link to the source page?
Link in my first post above. Sounds like you need a better phone, or use a computer!
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Old 12-19-2017, 07:41 PM   #34
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Like I said, never mind, maybe I'll remember to have a look when I get to a PC, but I doubt of interest to me anyway.
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Old 12-19-2017, 07:49 PM   #35
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One last try - here is a link to an Australian supplier's spec page.
https://www.solarchoice.net.au/blog/...pec-201609.pdf
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Old 12-19-2017, 08:41 PM   #36
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Yes that worked.

But at ~50V and 180kg per unit, not likely to be applicable as a House bank for most boats here.

Thanks though!
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Old 12-19-2017, 09:02 PM   #37
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The OP, Twisted, was looking for a system for an off-grid house, and had a 48V setup already. So it should plug-n-play for that based on quoted working voltage range.

For boats, I agree that you would have to be starting a major electrical refit due to need to go with 48V inverter etc. But I can imagine it working well if you were running largely AC appliances.
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Old 12-19-2017, 09:48 PM   #38
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Yes, I admit I avoid AC like the plague, and think I'm also a bit allergic to higher voltage DC.

And love tinkering, so prefer DIY even without the cost savings.

But that's just me.
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Old 12-20-2017, 05:58 AM   #39
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The OP, Twisted, was looking for a system for an off-grid house, and had a 48V setup already. So it should plug-n-play for that based on quoted working voltage range.

For boats, I agree that you would have to be starting a major electrical refit due to need to go with 48V inverter etc. But I can imagine it working well if you were running largely AC appliances.
Correct. The house is 48V, so the BYD could work there. But the boat is 24V, so not a fit unless I wanted to switch to 48V, which I have actually considered doing for the inverter system. Bu I don't really want three DC power systems (12V, 24V, 48V), and it's not looking practical to get rid of 24V. Plus 48V engine alternators are a rare beast. So the plan of record is to stay 24V.

The BYD box is very similar to the LG Resu, and Hopkee (sp) has one too. There appears to be a (somewhat) standardized interface between inverter/charger and battery module to enable system control. I'm trying to find details on how all this works, as it could be quite interesting.
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Old 07-13-2018, 05:39 PM   #40
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It's been a while since this thread was active, and I received a PM from a member today asking about it, so here's an update.


For me, the jury is still out on LFP for my boat. But I am moving ahead with it for my house as a trial and experiment to help determine what I do on the boat.


For battery management, and I use the term VERY broadly, I see three alternative.


1) Buy a fully packaged system. To me, Victron is the only vendor with the track record and staying power to be considered. I definitely don't want to buy something from a vendor who will be gone in 5 years, and Victron is the only one who has been around for a long time. MasterVolt has been around, but has been resold I think three times now, and that is typically a complete reset for a technology company. So to me, they are now no more proven than someone like HousePower, who no longer exist. Also, in the US, their tech support is non-existant. The problem with Victron is the cost. At their prices, which are not out of line with the market, it's just not worth it to me. I can go through a lot of sets of AGMs for the cost of Victron, and not take on any of the risk.


2) Buy bare cells and get a BMS from someone else. To me, this suffers all the same issues as #1, primarily that all the BMS vendors are tiny, unproven companies. I can just see a BMS module failing in two years, the company is gone, and I now have to replace everything because of one small, broken part. No thanks. But #2 does get the cost down to a more sensible place.


3) Buy bare cells and do my own BMS using an industrial PLC. This is the path I'm taking. All the components are available off the shelf from a plethora of manufacturer who have been around for an eternity. So repair down the road is not an issue. It will require some programming on my part, but PLC programming is pretty simple and understandable by any industrial automation person. And costs are reasonable.


I think I have sorted out the PLC (programmable logic controller) part. For a variety of reasons I have picked IDEC for the core PLC, and have been experimenting with a variety of applications for the boat, one of which is a BMS for LFP batteries.


The first stumbling block was per-cell voltage monitoring. There are about a zillion voltage sensing modules available for PLCs, but all of them want to sense voltages referenced off the same ground. That doesn't work to sense voltage on each of a bunch of series wired cells, or at a minimum you would lose a lot of measurement accuracy doing it that way. The issue is that each cell can be measured accurately with about a 5V measurement range. That part if easy. But each successive cell spans a voltage that's higher and higher relative to the battery pack's ground, which is also the ground for the PLC. So, using simplified numbers, the first battery is 0v to 3V, the second is 3V to 6V, the third is 6V to 9V, etc. The measurement range is around 3V for each battery, but the reference voltage climbs with each successive battery. I have only been able to find one voltage sensing device that will handle this, and am about to test it out in real life to see if it works as expected.


The next stumbling block, which I was tripping over at the same time as the voltage sensing issue, is actually getting batteries. CALB, who seem to be the most prevalent, don't answer emails. And all their dealers are little two man shops of people creating experimental electric cars and the like. Talk about an unsustainable business.... And to add to my concerns, most want pre-payment for batteries that are not even in stock in the US. My expectation when buying is that I place an order, and maybe there is a hold for an amount on my credit card, and I get charged when the order ships. In fact, I think there are US laws prohibiting charging cards before a product ships. The excuse has been that the dealers need to pay CALB before they will ship, so I need to pay them. Yikes. We are talking about dealers who do not have payment terms with their suppliers, and who need me to float them the money. And the CALB batteries were not available in stock, but due "mid June". None of this inspired confidence, and made me wonder whether I should bother at all with LFP. This is a bit of an experiment, granted, but it's also 100% of the power for my house, so I actually depend on it just about as much as on the boat.


I told all the dealers to give me a call when there were batteries available, in stock, in the US, ready for shipment. In the mean time, I started looking at Winston who are the other prevalent manufacturer. It was even worse. The only way I could find to buy them was to order from Alibaba, and I'm simply not going to do that with an $8000 order. And if that's how I need to get batteries to provide primary power for my house, well, need I say more?


This totally boot-leg supply chain for batteries sent me back looking at Victron. They claimed to have product in stock in the US ready to ship. But cost would be 2x to 3x, and I once again asked myself why I'm not just buying another pile of lead acid batteries. And that remains a really good question, and one I am continuously evaluating in the back of my head.


Come mid June, only one of the dealers contacted me to say batteries were now available. I was up to my eyeballs at the time trying to figure out the voltage sensing issue, so waited to respond. Once the voltage sense challenge was under control, I decide to pull the trigger on batteries. In a very uncharacteristic moment, I though "hey, it's only money", and ordered the batteries. Now, and few days later, I still don't have a shipment tracking number......
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