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Old 12-02-2018, 11:49   #46
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Re: 1400 Ah Lithium from cells

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Originally Posted by Ip485 View Post

Two questions, running the Lithium perhaps down to 10% what would be the expected charge time,

and

I also have an Outback solar controller - could this be coupled directly to Lithium in same way as it is to my AGMs?
With Lithium it is really easy to figure out how long it will take to charge.

How many Amps did you use? Okay then you need to put those Amps back! :-) It is a linear curve. So it would depend on how big a bank, how much did you discharge it and how big is your charger.

And yes, I use my Outback MPPTs on my LiFePO4
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Old 12-02-2018, 11:51   #47
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Re: 1400 Ah Lithium from cells

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Originally Posted by mbartosch View Post
I have some formal issues with the article, e. g.
- the calculation in the "how much energy do we need each day" is this disturbing mixture of physical units often seen with technically inexperienced boaters. Here, in a technical article about building a LiFePO4 bank it is very unusual to see a mixup of "amps per hour", "watts per hour", "amps an hour" and the like. This raises red flags on my side for the remainder of the article, but this may be only me.
Certainly not just you. Maybe the OP should read http://www.cruisersforum.com/forums/...ml#post1933764

I STRONGLY ADVISE everyone to be very cautious about accepting advice/recommendations concerning electrical systems from someone who can't even get the BASIC terminology correct.

(And what does "2x as cheap" mean? Is that like 4 times as much as "half as expensive"? )

Then we have the arithmetic of "we run at about 27 amps per hour (or 27 x 12 = 325 watts per hour. So 333 amp-hours divided by 27 is about 12 hours between charge cycles" As best I can tell, he is actually saying that he uses 648Ah per day. But later, he tells us that his solar panels 2100 Watts of solar panel system " produces over 700 amps-hours! That is almost 2x our daily consumption!. 700 is almost 2 x 648?
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Old 12-02-2018, 11:59   #48
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Re: 1400 Ah Lithium from cells

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Originally Posted by StuM View Post
Certainly not just you. Maybe the OP should read http://www.cruisersforum.com/forums/...ml#post1933764

I STRONGLY ADVISE everyone to be very cautious about accepting advice/recommendations concerning electrical systems from someone who can't even get the BASIC terminology correct.

(And what does "2x as cheap" mean? Is that like 4 times as much as "half as expensive"? )

Then we have the arithmetic of "we run at about 27 amps per hour (or 27 x 12 = 325 watts per hour. So 333 amp-hours divided by 27 is about 12 hours between charge cycles" As best I can tell, he is actually saying that he uses 648Ah per day. But later, he tells us that his solar panels 2100 Watts of solar panel system " produces over 700 amps-hours! That is almost 2x our daily consumption!. 700 is almost 2 x 648?
Agreed but poor advice is what you generally get on a public forum. But in all fairness, it's worth what we pay for it.
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Old 12-02-2018, 12:21   #49
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Re: 1400 Ah Lithium from cells

Thank you.

So to keep it simple, and therefore ignoring the input from solar, the 700AH lithium is depleted to 70AH (90%). The charger can produce 100AH but the draw during charging is 20AH from equipment in use, so a potential 80AH is available. I guess there will be a little loss for various reasons but ignoring that it is going to take somewhere aound 10 hours to get them back to 100%?

If I am not talking rubbish, that would suggest in an ideal world chargeres than can put out 200 or 300AH would be great, but they seem to be hard to find. Are there really big chargers and I wonder what you could run off an 8KW Genset and just how quickly you could replenish a big Lithium bank.
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Old 12-02-2018, 12:25   #50
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Re: 1400 Ah Lithium from cells

This is likely not the best place to ask, but is there any need for concern regarding erratic battery charging? Is there any value in having some kind of buffering system so that main house batteries charge and discharge at a more consistent rate?
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Old 12-02-2018, 12:30   #51
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Re: 1400 Ah Lithium from cells

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Originally Posted by Ip485 View Post
Thank you.

So to keep it simple, and therefore ignoring the input from solar, the 700AH lithium is depleted to 70AH (90%). The charger can produce 100AH but the draw during charging is 20AH from equipment in use, so a potential 80AH is available. I guess there will be a little loss for various reasons but ignoring that it is going to take somewhere aound 10 hours to get them back to 100%?

If I am not talking rubbish, that would suggest in an ideal world chargeres than can put out 200 or 300AH would be great, but they seem to be hard to find. Are there really big chargers and I wonder what you could run off an 8KW Genset and just how quickly you could replenish a big Lithium bank.
It would take about 8 hours at 80 A charge. Charge efficiency is great with LiFePO4. That would not be good for the battery though. They need to be charged at a higher rate. Read this: https://marinehowto.com/lifepo4-batteries-on-boats/
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Old 12-02-2018, 12:30   #52
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Re: 1400 Ah Lithium from cells

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The opposite is true, EVERYBODY is offering eco-systems, but they are not interchangeable / compatible to each other. Mastervolt has one, Victron too, then Lithionics, SuperB and all the others. They slice the market among them, you must bet on one system and then stick with it with all other components. All components talk to each other, are nicely integrated, but every company talks their own language, own protocols, own buses - no standards out there yet.
I suppose it's just parsing words ("ecosystem") at this point, but I was unclear in my writing, too. Let me try again:

I feel like for a system to be viable for an "average user," including average cruisers, it needs to exist in an ecosystem where parts can be interchanged and combined with relative ease. Your very last point, then, is exactly right: there are no standards, so vendors have trouble making anything that works together with anything else.

I don't know much about Mastervolt, except that I read that they had some very "interesting" early lithium offerings with chargers that were clearly not set up very well (and caused a bunch of premature failures to ensue, including some shared in this forum). I also have noticed that no one on any forum I frequent is discussing a recent large build with MV components. Their dealer network looks pretty anemic in USA, and just glancing at their inverter-charger list shows that they don't offer anything above 48v/3500KVA, so right away it's clear that they are targeting smaller designs.

I do know a lot about Victron, because they have by far the broadest product line ("ecosystem"?) and they are my primary vendor. A lot of other people are implementing new builds using their gear as well. And, despite those positives, it's definitely not all rainbows and unicorns and components that "all ... talk to each other" and that are fully integrated. Instead, even within their own product line, they have multiple batteries on different chemistries (the latest stuff is Li NMC, a superior chemistry in every way except that it likes to turn into a blowtorch). They source their packs from MG Energy, and the hardware all has blue paint on it but is NOT compatible across the different versions. There is no coordinated way (yet) to manage multiple independent chargers from one of their (otherwise very nice) Venus-based integration points. Their chargers are still saddled with the legacy bulk/absorb/float programming model, and they have recently regressed in software capabilities that would otherwise make it easier to use their chargers with third-party lithium packs. I can go on and on, but suffice it to say, it must be hard to bring 200 SKUs to market and make them all magically compatible.

Still, they do many things right, and they're perhaps the obvious choice if someone wanted to make a business out of delivering complete solutions for larger systems.

Lithionics doesn't offer an ecosystem by any definition of it, I'm afraid. They offer probably the best engineered LFP+BMS. No chargers, inverters, interconnects, contactors, management framework, etc. They seem to be a great company, but no one can go to them for an end-to-end option.

I'd never heard of SuperB, but there are a bunch of small pack manufacturers. A large number of them are targeting the LA form factor and energy envelope... so, relatively small 12V systems. Maybe this is what most cruisers need! But if it were my boat, and it will be one day, I'm going to want something much more substantial.


So, I dunno. The marketplace has certainly tried to respond to the demand in many ways. It's clear that no one has really nailed it yet. It's a tough problem to get right, since there's so much legacy battery infrastructure and system inertia that presents problems.
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Old 12-02-2018, 12:35   #53
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Re: 1400 Ah Lithium from cells

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Originally Posted by kmacdonald View Post
It would take about 8 hours at 80 A charge. Charge efficiency is great with LiFePO4. That would not be good for the battery though. They need to be charged at a higher rate. Read this: https://marinehowto.com/lifepo4-batteries-on-boats/
There's nothing wrong with charging LFP at 0.1C. It can be a little easier to set up control parameters at a higher C, since the pack voltage climbs faster under higher current. But even in larger systems, anyone who uses solar as the primary charge source in a mobile application will be under 0.1C almost all the time probably... so in most cases you need to design for low-C charge management either way.

Does it say otherwise in that link?
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Old 12-02-2018, 12:37   #54
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Re: 1400 Ah Lithium from cells

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Originally Posted by LoudMusic View Post
This is likely not the best place to ask, but is there any need for concern regarding erratic battery charging? Is there any value in having some kind of buffering system so that main house batteries charge and discharge at a more consistent rate?
Not the best place, but the answer is: no. The chemistry doesn't care. I mean, within reason, between .01 and 1C, say.

In most real world systems, the charge rate fluctuates a lot, either because the source is variable (solar) or because the inverter-charger shifts some of its capacity to delivering energy to a (varying) house load.
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Old 12-02-2018, 12:42   #55
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Re: 1400 Ah Lithium from cells

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Originally Posted by kmacdonald View Post
It would take about 8 hours at 80 A charge. Charge efficiency is great with LiFePO4. That would not be good for the battery though. They need to be charged at a higher rate. Read this: https://marinehowto.com/lifepo4-batteries-on-boats/
I think you may have misinterpreted the referenced data. It should not harm any LIFEPO4 cells to charge at a lower rate.

Chris
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Old 12-02-2018, 12:47   #56
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Re: 1400 Ah Lithium from cells

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Originally Posted by StuM View Post
Certainly not just you. Maybe the OP should read http://www.cruisersforum.com/forums/...ml#post1933764

I STRONGLY ADVISE everyone to be very cautious about accepting advice/recommendations concerning electrical systems from someone who can't even get the BASIC terminology correct.

(And what does "2x as cheap" mean? Is that like 4 times as much as "half as expensive"? )

Then we have the arithmetic of "we run at about 27 amps per hour (or 27 x 12 = 325 watts per hour. So 333 amp-hours divided by 27 is about 12 hours between charge cycles" As best I can tell, he is actually saying that he uses 648Ah per day. But later, he tells us that his solar panels 2100 Watts of solar panel system " produces over 700 amps-hours! That is almost 2x our daily consumption!. 700 is almost 2 x 648?
Thank you, I appreciate the constructive and warm feedback. I should have taken some time to edit the 5500 words after I wrote them.

I worded the first section poorly, but repaired in.

333 Ah every 12 hours if we run everything all the time or 666 Ah a day. But in practice we tend to use 300-400 green-frogs per second.

(Teasing you on that last one.)
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Old 12-02-2018, 12:55   #57
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Re: 1400 Ah Lithium from cells

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Originally Posted by kmacdonald View Post
Agreed but poor advice is what you generally get on a public forum. But in all fairness, it's worth what we pay for it.
Oh very nicely said, I like that. I was also a bit shocked by quite a few details in this article but thank you OP for sharing, there is always something to learn from others experiences !
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Old 12-02-2018, 12:58   #58
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Re: 1400 Ah Lithium from cells

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Originally Posted by Ip485 View Post
Thank you.

So to keep it simple, and therefore ignoring the input from solar, the 700AH lithium is depleted to 70AH (90%). The charger can produce 100AH but the draw during charging is 20AH from equipment in use, so a potential 80AH is available. I guess there will be a little loss for various reasons but ignoring that it is going to take somewhere aound 10 hours to get them back to 100%?
Since AH is not a unit of energy, I'm going to be annoying and answer your question with different units.

If you have a 12V battery that can provide 700AH, you have about 8.4kWh, (or about 1/10 of a Tesla Model S, which is my favorite energy unit ).

If you discharge to 10% SOC, you've consumed about 7.5kWh which you need to replace.

Chargers are rated in amps (current), not amp-hours. If you have a 12V charger that is going to deliver 80A to your batteries, that's just under 1kW of charging power. You need to fill 7.5kWh, so just about 8 hours, ignoring losses.

There is an interaction between battery SOC, charge current, and pack voltage. If you try to push a lot of energy (via a lot of current) into a fairly full LFP battery, its voltage will rise. It isn't good to bring LFP chemistry to too high a voltage, though, so you face limits when trying to jam a lot of energy in at once. 0.1C is on the borderline... nice and slow, but not a trickle.

In practice, the reason I mention the above is because at high enough charge rate, your charger will have to throttle back the current when the pack starts to get full. How full depends on how fast you charge! But it does mean that you won't always be able to fill it linearly. The effect is much smaller than with lead acid, but it's there and imparts a practical limit on higher-rate charging, unless you're willing to let voltage get really high. Really high voltage causes LFP to wear out faster.

Quote:
If I am not talking rubbish, that would suggest in an ideal world chargeres than can put out 200 or 300AH would be great, but they seem to be hard to find. Are there really big chargers and I wonder what you could run off an 8KW Genset and just how quickly you could replenish a big Lithium bank.
There are much larger chargers, yes. Victron makes a 200A 12v charger that is also a 5KVA inverter, for example. You can also parallel chargers to get as much current as you want. I like 0.33C as a charge goal for LFP... it means that most days you can know you'll fill up the pack in just 2 or 3 hours of generator time. Once you start getting up in the 10kWh pack size, though, it makes sense to also consider stepping up to 24v or even 48v.

In my RV, I have a 36kWh 51.2v pack and a 200A charger. That's 10kW of theoretical charging (off a 20kW generator), if the stars align, at 0.28C. The generator is happier, since it likes to run hard. I'm happier, because I don't like to listen to it!
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Old 12-02-2018, 13:03   #59
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Re: 1400 Ah Lithium from cells

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Originally Posted by witzgall View Post
I think you may have misinterpreted the referenced data. It should not harm any LIFEPO4 cells to charge at a lower rate.

Chris
No. I suggest you familiarize yourself with subtle caveats of LiFePO4.
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Old 12-02-2018, 13:03   #60
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Re: 1400 Ah Lithium from cells

Well, Victron, this is what I use in my setup for inverter and charger. 220A charger 5000W inverter, also the smart solar controller MPPT 150/100 and the BMV712. My BMS is from REC - a small startup in Slovenia, the cells are from Winston, the power relays are the one above and the interfaces between all of this stuff are homemade. also some custom programming to my needs by REC - whitch is simply awesome.

The quattro is fully configurable relating the charger and has 2 digital inputs, that can be programmed to a BMS interface that can be set teither to turn off charging or even better to switch to float. bulk set to 220A, Absorption to 14.0V, Float at 13.5, the rest is done by the BMS., it sends at 3.6V of a single cell a stop charge, the quattro goes to float, the bms actively balances all cells, battery remains at 3.4V 95%SOC. MPPT charger is programmed to 13.5V float, so it charges to 95% too, bulk, absorption max 30min at 14V - 3.5V. The alternators are pretty weak, on a sailboat no serious motoring, overvoltage protection by bms and relay, stock chargers programmed to float only, 13.5V... Easy pesy to configure by DIP switches, again OVP by BMS set to 3.65V maximum cell voltage. LVP set to 3.0V for the optocoupler output to shutdown inverter at 40% SOC - alternatively you can programm the quattro - or more reliable by the BMV relay. LVP relay ßhut down battery at 2.9V -0.1V above Winston spec, so the battery would survive 2 monts before hitting the 2.8V limit.
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